RESULTSAND DISCUSSION - Shodhgangashodhganga.inflibnet.ac.in/bitstream/10603/72660/4/... ·...

33

RREESSUULLTTSS AANNDD DDIISSCCUUSSSSIIOONN

In the present work, removal of Methylene Blue (MB), Methyl Violet (MV), Acid Blue

(AB) and Acid Violet (AV) dyes are carried out using a bio waste, Blue-Green Algae (BGA)

as an adsorbent by adsorption technique. The adsorption studies are performed by

conducting batch mode experiments by varying the parameters such as initial concentration

of the dye solution, pH, adsorbent dosage, agitation time and temperature. The

experimental data obtained and the findings of the present study are interpreted and

discussed in the light of the objectives set forth. The results are used to evaluate the

optimum conditions for the removal of these dyes from aqueous solution and to examine

the efficiency of the low cost adsorbent BGA for the treatment of dyeing industrial effluent

containing these dyes by adsorption.

4.1 Characteristics of the Adsorbent BGA

The characteristics namely Moisture Content, pH, Surface Area and Pore Diameter of

the adsorbent Blue-Green Algae (BGA) used in this study are given in Table 2.

Table 2

Characteristics of the Adsorbent BGA

S.No. Physical Characters ForAdsorbent BGA

1. Moisture Content (%) 5.4

2. pH 5.7

3. Surface Area (m2/g) [Appendix II] 479

4. Pore Diameter (µm) [obtained from SEMAnalysis] 10.39 -10.98

The Surface Area of the adsorbent, Commercial Activated Carbon (CAC) used in this

study is 1021m2/g (Appendix III).

4

34

4.2 Effect of Initial Concentration of Dye Solution on Dye Removal

The study of the distribution of the dye between the adsorbent and the dye solution at

equilibrium is important to assess the adsorption capacity of the adsorbent for the

dyestuffs. The initial concentration of the dye solutions are varied from 60 to 120mg/l and

batch mode experiments are performed at 32 ± 2ºC and at pH 7.0 ± 0.2 to study the effect

of initial concentration of dye solutions on the removal of dye from aqueous solution and

from dyeing industrial effluent with 500mg of the adsorbent BGA by varying the agitation

time from 10 to 180 minutes.

The study reveals that the percentage removal of all the dyes (MB, MV, AB and AV)

from aqueous solution and from dyeing industrial effluent decreases, whereas the amount

of dyes removed increases with the increase of the initial concentration of the dye

solutions. The results obtained shows that the percentage removal of dyes from aqueous

solution used in this study decreases from 94.9% to 80.3% for MB (Table 3), from 81.25%

to 74.42% for MV (Table 4), from 77.78% to 60.72% for AB (Table 5) and from 75.56% to

61.77% for AV (Table 6), when the initial concentration of dye solutions varied from

60 to 120mg/l in 180minutes of agitation time. The results are graphically depicted in

Figures 1– 4.

The results obtained shows that the percentage removal of dyes from dyeing

industrial effluent used in this study decreases from 45.07% to 34.44% for MB (Table 7),

from 76.74% to 69.39% for MV (Table 8), from 61.7% to 52.2% for AB (Table 9) and from

68.75% to 60.38% for AV (Table 10), when the initial concentration of dye solutions varied

from 60 to 100mg/l in 180minutes of agitation time. The results are graphically depicted in

Figures 5 – 8.

The results depicted in Tables 3 –10 and Figures 1– 8 indicates that the removal of

dyes increased progressively with the contact time for all the concentration of the dye

solutions used in this study. In addition, perusal of the results indicated that with increase in

dye concentration the percentage removal decreased, but the amount of dye adsorbed/unit

weight of the adsorbent increased for all the four dyes used in this study suggest that, the

dye removal using adsorption technique is concentration dependent. Further, it was

observed that the rate of adsorption was higher in the initial stages, because of the dye

uptake onto exterior surface, after that the dye molecules are entered into pores (interior

surface), relatively slow process (Ahmad and Kumar, 2010). This is due to an increase in

the driving force of the concentration gradient, as the initial dye concentration increases,

mass transfer driving force became larger and the interaction between the dye and

35

adsorbent was enhanced, hence resulting in higher adsorption capacity (Hameed et al.,2008; Aksu and Balibek, 2010; El-Syed, 2011; Han et al., 2011). The results obtained in

this study are in good agreement with the results reported on the extent of removal of

methylene blue dye on activated carbon (Sharma and Uma, 2010), on rice husk (Sharmaet al., 2010), on oak (Abd El-Latifa et al., 2010), on carbon nanotubes (Shahryari et al.,2010), on water weeds biomass (Tarawou and Horsfall, 2007) and on cashewnut shell

(Kumar et al., 2011).

This may be explained as, at a given constant adsorbent dosage, the decrease of the

adsorption with increase in initial concentration of dye solution may be due to the lack of

adsorbent surface area and the available sites for the adsorption becomes fewer for

adsorption and also due to nearly complete coverage of binding sites of the bioadsorbent

(Aksu and Balibek, 2010; Abechi et al., 2011; Satish Patil et al., 2011). In addition, the

formation of second layer of the dye molecules is highly hindered at higher initial

concentration of the dye, due to the repulsive interaction between adsorbed and

unadsorbed dye molecules present on the solid surface and in solution, respectively.

The curves were found to be continuous and smooth, leading to saturation, indicating the

possibilities of formation of monolayer coverage of dye on the outer surface of the

adsorbent (Theivarasu et al., 2010; Venckatesh et al., 2010).

36

Table 3

Adsorption of Methylene Blue Dye from Aqueous Solution with Variation ofInitial Concentration of Methylene Blue Dye Solution

Conditions:

Adsorbent Dosage : 500mg

pH : 7.0 ± 0.2

Temperature : 32 ± 2˚C

Time inminutes

Removal of Methylene Blue Dye in Percentage

60mg/l 80mg/l 100mg/l 120mg/l

10 83.8 78.3 75.7 51.6

20 88.0 79.1 77.7 56.1

30 88.9 84.5 82.4 57.3

40 89.8 86.5 86.2 61.8

50 90.7 88.4 87.2 64.3

60 91.5 89.2 87.8 66.9

90 92.3 89.9 88.5 70.1

120 93.2 90.7 90.5 74.5

150 94.0 92.2 91.2 78.9

180 94.9 93.0 92.6 80.3

37

Table 4

Adsorption of Methyl Violet Dye from Aqueous Solution with Variation ofInitial Concentration of Methyl Violet Dye Solution

Conditions:


pH : 7.0 ± 0.2


Time inminutes

Removal of Methyl Violet Dye in Percentage


10 59.38 45.71 43.90 41.86

20 62.50 48.78 48.57 44.19

30 65.63 57.14 53.66 46.51

40 68.75 60.00 58.54 48.84

50 71.88 65.71 63.41 55.81

60 74.47 68.57 65.85 60.47

90 75.38 71.43 70.73 62.79

120 78.13 74.29 73.17 67.44

150 78.46 77.14 75.61 72.09

180 81.25 80.00 78.05 74.42

38

Table 5

Adsorption of Acid Blue Dye from Aqueous Solution with Variation ofInitial Concentration of Acid Blue Dye Solution

Conditions:


pH : 7.0 ± 0.2


Time inminutes

Removal of Acid Blue Dye in Percentage


10 53.33 45.83 38.46 37.50

20 55.56 47.92 40.39 39.29

30 57.78 52.08 44.23 41.07

40 62.22 54.17 46.15 42.86

50 64.45 56.25 50.00 46.43

60 66.67 60.42 53.85 50.00

90 71.11 64.58 57.69 51.79

120 73.33 70.83 63.49 53.57

150 75.56 72.92 67.31 57.14

180 77.78 75.00 69.23 60.72

39

Table 6

Adsorption of Acid Violet Dye from Aqueous Solution with Variation ofInitial Concentration of Acid Violet Dye Solution

Conditions:


pH : 7.0 ± 0.2


Time inminutes

Removal of Acid Violet Dye in Percentage


10 37.78 35.72 34.21 29.42

20 42.22 39.10 38.47 32.35

30 46.67 42.48 40.10 35.29

40 53.33 44.86 42.74 41.18

50 57.78 47.62 47.37 44.12

60 60.00 52.38 50.00 47.06

90 66.67 57.14 52.63 50.00

120 71.11 61.91 55.27 52.94

150 73.33 66.67 57.89 55.88

180 75.56 69.05 63.16 61.77

40

Figure 1

Figure 2

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Perc

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Time in minutes

Adsorption of Methylene Blue Dye from Aqueous Solutionwith Variation of Initial Concentration of

Methylene Blue DyeSolution


40

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Perc

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Time in minutes

Adsorption of Methyl Violet Dye from Aqueous Solution withVariation of Initial Concentration of

Methyl Violet Dye Solution


41

Figure 3

Figure 4

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45

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65

75

85

0 20 40 60 80 100 120 140 160 180 200

Perc

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Time in minutes

Adsorption of Acid Blue Dye from Aqueous Solution withVariation of Initial Concentration of

Acid Blue Dye Solution


20

30

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60

70

80

0 50 100 150 200

Perc

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Time in minutes

Adsorption of Acid Violet Dye from Aqueous Solution withVariation of Initial Concentration of

Acid Violet Solution


42

Table 7

Adsorption of Methylene Blue Dye from Dyeing Industrial Effluent withVariation of Initial Concentration of Methylene Blue Dye Solution

Conditions:


pH : 7.0 ± 0.2


Time inminutes


60mg/l 80mg/l 100mg/l

10 35.21 31.36 26.11

20 35.91 32.00 27.78

30 36.62 32.64 28.33

40 38.03 33.28 29.44

50 38.73 33.92 30.00

60 40.14 36.48 31.11

90 41.55 37.76 32.22

120 42.25 40.60 32.78

150 43.66 42.24 33.89

180 45.07 43.52 34.44

43

Table 8

Adsorption of Methyl Violet Dye from Dyeing Industrial Effluent withVariation of Initial Concentration of Methyl Violet Dye Solution

Conditions:


pH : 7.0 ± 0.2


Time inminutes



10 44.19 43.78 42.86

20 46.51 45.65 43.46

30 48.84 47.83 46.93

40 51.16 50.00 48.98

50 60.47 58.87 53.06

60 63.28 61.04 57.14

90 65.12 63.22 60.26

120 72.09 69.57 65.31

150 74.42 71.74 67.35

180 76.74 75.10 69.39

44

Table 9

Adsorption of Acid Blue Dye from Dyeing Industrial Effluent with Variation ofInitial Concentration of Acid Blue Dye Solution

Conditions:


pH : 7.0 ± 0.2


Time inminutes



10 38.5 35.3 28.6

20 41.0 37.2 30.8

30 43.2 38.8 34.2

40 45.2 40.7 36.6

50 47.4 42.9 40.0

60 49.6 45.5 43.5

90 53.1 47.9 45.9

120 55.8 51.0 47.4

150 58.9 53.2 49.1

180 61.7 56.0 52.2

45

Table 10

Adsorption of Acid Violet Dye from Dyeing Industrial Effluent with Variationof Initial Concentration of Acid Violet Dye Solution

Conditions:


pH : 7.0 ± 0.2


Time inminutes



10 40.39 39.62 37.12

20 43.75 41.51 39.62

30 45.83 44.10 43.75

40 50.00 49.02 45.28

50 52.08 50.94 47.17

60 58.33 54.90 48.56

90 60.42 56.86 50.94

120 62.50 58.82 52.83

150 64.58 60.78 56.60

180 68.75 62.75 60.38

46

Figure 5

Figure 6

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Adsorption of Methylene Blue Dye from Dyeing IndustrialEffluent with Variation of Initial Concentration of

Methylene Blue Dye Solution

60mg/l

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Adsorption of Methyl Violet Dye from Dyeing IndustrialEffluent with Variation of Initial Concentration of


60mg/l

46

Figure 5

Figure 6

60 80 100 120 140 160 180 200

Time in minutes

Adsorption of Methylene Blue Dye from Dyeing IndustrialEffluent with Variation of Initial Concentration of

Methylene Blue Dye Solution

80mg/l 100mg/l

60 80 100 120 140 160 180 200Time in minutes

Adsorption of Methyl Violet Dye from Dyeing IndustrialEffluent with Variation of Initial Concentration of


80mg/l 100mg/l

46

Figure 5

Figure 6

200

200

47

Figure 7

Figure 8

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0 50

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Adsorption of Acid Blue Dye from Dyeing Industrial Effluentwith Variation of Initial Concentration of


60mg/l

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Adsorption of Acid Violet Dye from Dyeing Industrial Effluentwith Variation of Initial Concentration of

Acid Violet Dye Solution

60mg/l

47

Figure 7

Figure 8

100 150 200Time in minutes

Adsorption of Acid Blue Dye from Dyeing Industrial Effluentwith Variation of Initial Concentration of



100 150 200Time in minutes

Adsorption of Acid Violet Dye from Dyeing Industrial Effluentwith Variation of Initial Concentration of

Acid Violet Dye Solution


47

Figure 7

Figure 8

200

200

48

4.3 Effect of pH on Dye Removal

The pH of the dye solution plays an important role in the adsorption process,

particularly in the adsorption capacity, influencing the surface charge of the adsorbent, the

degree of ionisation of the dye present in the solution and the dissociation of functional

groups on the active sites of the adsorbent (Aksu and Balibek, 2010; Saeed et al., 2010;

Chakraborty et al., 2011). The hydrogen and hydroxyl ions are adsorbed quite strongly,

and therefore, the adsorption of other ions is affected by the pH of the solution. The anions

are adsorbed by the adsorbent at lower pH due to the presence of H+ ions and at higher

pH, cations are adsorbed due to the negatively charged surface sites (Emrah Bulut, 2008).

The role of hydrogen ion concentration is studied for the adsorption of the dyes used

in this study by varying the pH (from pH 5 to pH 9) using 0.1N H2SO4 or 0.1N NaOH.

To study the effect of pH, 100ml of the dye solutions containing 100mg of the dye are taken

in Pyrex bottles containing 500mg of the adsorbent BGA at 32 ± 2ºC and batch mode

adsorption experiments performed. The experimental results observed for the effect of

variation of pH on percentage removal of dyes from the aqueous solution are shown in

Tables 11 – 14.

The percentage removal of Methylene Blue dye (from 86.4% to 92.6%) and Acid

Violet dye (from 54.76% to 69.05%) increased, when the pH is varied from 5.0 ± 0.2 to

7.0 ± 0.2 in 180minutes of agitation time and then decreases with increase in pH above

7.0 ± 0.2. The graphical representations of the adsorption of Methylene Blue and Acid

Violet dyes from aqueous solution with the variation of pH are shown in Figures 9 & 10

Lower adsorption of Methylene Blue and Acid Violet dyes at acidic pH, may be due to

the presence of excess H+ ions competing with dye cations for the adsorption sites

(El-Sayed, 2011; Guimaraes Gusmao et al., 2012). At alkaline pH, the surface of the

adsorbent acquires negative charge due to the adsorption of OH- ions and the negatively

charged surface of the adsorbent repelled the dye species and thus adsorption of the dyes

decreases.

In the case of Methyl Violet and Acid Blue dyes, the percentage removal of the dyes

increased from 70.73% to 78.05% for MV and from 51.92% to 69.23% for AB with the

increase in pH of the dye solution from 5.0 ± 0.2 to 7.0 ± 0.2 in 180minutes of agitation

time. Further increases of pH from 7.0 ± 0.2 to 9.0 ± 0.2, adsorption of the dyes are

49

insignificant and almost kept constant. Similar results were observed by Aksu and Balibek,

(2010); Yi Liu et al., (2010); Deng et al., (2011); Chakraborty et al., (2011). The graphical

representations of the adsorption of Methyl Violet and Acid Blue from aqueous solution with

pH variation are shown in Figures 11 & 12

As pH increases from 5 to 7, the charge density of the dye solution decreases,

so that electrostatic repulsion between the positively charged dye molecules and

the surface of the adsorbent is lowered. It results in an increase in the adsorption of the dye

(Mittal et al., 2010; Saeed et al., 2010; Yonghui Lin et al., 2011; Yu et al., 2012).pH is, also, known to affect the structural stability of the dye and therefore, its colour

intensity also affect. It is obviously observed that the dyes MV and AB dyes used in this

study are not stable to combine with hydroxyl ion in the solution and generate emulsion

precipitate when pH > 7, thus, original pH 7 for MV and AB dyes are considered as

optimum pH for the dye adsorption. Similar results were observed by Unuabonah et al.,(2009); Saeed et al., (2010); Abd El – Latifa et al., (2010); Han et al., (2011); Ma et al.,(2012).

50

Table 11

Adsorption of Methylene Blue Dye from Aqueous Solution with pH Variation

Conditions:


Concentration of dye Solution : 100mg/l


Time inminutes


pH 5 pH 6 pH 7 pH 8 pH 9

10 66.2 73.3 75.7 67.6 63.5

20 68.9 76.4 77.7 75.7 76.8

30 69.6 80.7 82.4 81.8 80.7

40 73.7 82.7 86.5 84.5 82.2

50 75.0 83.4 87.2 85.8 83.4

60 76.4 84.7 87.8 86.5 84.7

90 81.8 85.3 88.5 87.8 85.9

120 84.5 86.7 90.5 88.5 86.6

150 85.8 87.3 91.2 89.2 87.3

180 86.4 88.5 92.6 91.6 88.5

51

Table 12

Adsorption of Acid Violet Dye from Aqueous Solution with pH Variation

Conditions:


Concentration of dye solution : 100mg/l


Time inminutes



10 26.19 33.33 35.72 33.33 19.05

20 28.57 35.72 38.10 35.72 21.43

30 30.97 38.10 40.48 38.10 23.81

40 35.72 42.86 45.24 40.48 26.19

50 38.10 45.24 47.62 45.24 28.57

60 42.86 47.62 52.38 47.62 33.33

90 45.24 49.03 57.14 52.38 35.72

120 47.62 52.38 61.91 57.14 38.10

150 52.38 54.76 66.67 54.76 40.48

180 54.76 57.14 69.05 64.43 47.62

52

Figure 9

Figure 10

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Adsorption of Methylene Blue Dye from Aqueous Solutionwith pH Variation

pH 5 pH 6

10

20

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10 20 30

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Adsorption of Acid Violet Dye from Aqueous Solutionwith pH Variation

pH 5 pH 6

52

Figure 9

Figure 10

40 50 60 90 120 150 180Time in minutes

Adsorption of Methylene Blue Dye from Aqueous Solutionwith pH Variation

pH 6 pH 7 pH 8 pH 9

40 50 60 90 120 150 180Time in minutes

Adsorption of Acid Violet Dye from Aqueous Solutionwith pH Variation

pH 6 pH 7 pH 8 pH 9

52

Figure 9

Figure 10

180

180

53

Table 13Adsorption of Methyl Violet Dye from Aqueous Solution with pH Variation

Conditions:




Time inminutes



10 39.02 41.46 43.90 43.90 43.90

20 41.46 43.90 48.78 48.78 48.78

30 43.90 51.22 53.66 53.66 53.66

40 51.22 53.66 58.54 58.54 58.54

50 53.66 58.54 63.41 63.41 63.41

60 58.44 60.98 65.85 65.85 65.85

90 60.98 63.41 70.73 70.73 70.73

120 65.85 68.29 73.17 73.17 73.17

150 68.29 70.73 75.61 75.61 75.61

180 70.73 73.17 78.05 78.05 78.05

54

Table 14

Adsorption of Acid Blue Dye from Aqueous Solution with pH Variation

Conditions:




Time inminutes



10 30.77 36.54 38.46 38.46 38.46

20 32.69 38.46 40.39 40.39 40.39

30 34.62 40.39 44.23 44.23 44.23

40 36.54 42.31 46.15 46.15 46.15

50 40.39 44.23 50.00 50.00 50.00

60 42.31 46.15 53.85 53.85 53.85

90 44.23 48.08 57.69 57.69 57.69

120 46.15 51.92 63.49 63.49 63.49

150 48.08 53.55 67.31 67.31 67.31

180 51.92 57.69 69.23 69.23 69.23

55

Figure 11

Figure 12

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Adsorption of Methyl Violet Dye from Aqueous Solutionwith pH Variation

pH 5 pH 6

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Adsorption of Acid Blue Dye from Aqueous Solutionwith pH Variation

pH 5 pH 6

55

Figure 11

Figure 12

40 50 60 90 120 150 180Time in minutes


pH 6 pH 7 pH 8 pH 9

40 50 60 90 120 150 180Time in minutes

Adsorption of Acid Blue Dye from Aqueous Solutionwith pH Variation

pH 6 pH 7 pH 8 pH 9

55

Figure 11

Figure 12

180


180

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4.4 Effect of Adsorbent Dosage on Dye Removal

Adsorbent dosage is an important parameter that strongly influences the adsorption

process by affecting the adsorption capacity of the adsorbent (Chakraborty et al., 2011).The effect of adsorbent dosage is investigated for the removal of Methylene Blue, Methyl

Violet, Acid Blue and Acid Violet dyes from aqueous solution by varying the dosage of the

adsorbent BGA from 200mg to 500mg. Batch mode experiments are carried out by using

100ml of dye solution containing 100mgdye/l at 32 ± 2ºC and at pH 7.0 ± 0.2 by varying the

adsorbent dosage. It is observed that the percentage removal of dyes increased, when the

adsorbent dosage is varied from 200mg to 500mg (for Methylene Blue from 85.1% to

92.6%, for Methyl Violet from 63.41% to 78.05%, for Acid Blue from 51.92% to 69.23% and

for Acid Violet from 42.86% to 69.05%). The results obtained are shown in Tables 15 – 18

and graphically represented in Figures 13 – 16.

The increase in the percentage removal of the dyes with adsorbent dosage could be

attributed to an increase in the surface area of the adsorbent, augmenting the more

number of adsorption sites available for adsorption (Subha and Namasivayam, 2009;Renugadevi et al., 2009b). Similar reports were observed for the adsorption of Direct Red-

28 onto Punica Granatum Carbon (Venckatesh et al., 2010) and for the adsorption of

Methylene Blue onto biomass material Lotus Leaf (Han et al., 2011).

57

Table 15

Adsorption of Methylene Blue Dye from Aqueous Solutionwith Adsorbent Dosage Variation

Conditions:


pH : 7.0 ± 0.2


Time inminutes


200mg 300mg 400mg 500mg

10 57.8 66.2 69.6 75.7

20 63.4 68.9 73.7 77.7

30 67.6 69.6 75.0 82.4

40 68.9 73.7 75.7 86.5

50 69.6 75.0 81.8 87.2

60 73.7 75.7 83.8 87.8

90 75.0 81.8 85.8 88.5

120 75.7 83.8 86.5 90.5

150 81.8 85.8 87.8 91.2

180 85.1 86.5 88.5 92.6

58

Table 16

Adsorption of Methyl Violet Dye from Aqueous Solutionwith Adsorbent Dosage Variation

Conditions:


pH : 7.0 ± 0.2


Time inminutes


200mg 300mg 400mg 500mg

10 36.57 39.02 41.46 43.90

20 42.73 43.90 46.34 48.78

30 46.34 48.78 51.22 53.66

40 48.78 53.66 56.10 58.54

50 51.22 58.54 60.98 63.41

60 53.66 60.98 63.41 65.85

90 56.10 63.41 68.29 70.73

120 58.54 65.85 70.73 73.17

150 60.98 68.29 73.17 75.61

180 63.41 70.73 75.61 78.05

59

Table 17

Adsorption of Acid Blue Dye from Aqueous Solutionwith Adsorbent Dosage Variation

Conditions:

Concentration of dye solution : 100 mg/l

pH : 7.0 ± 0.2


Time inminutes


200mg 300mg 400mg 500mg

10 30.77 32.69 36.54 38.46

20 32.69 34.62 38.46 41.39

30 34.62 36.54 40.39 44.23

40 36.54 40.39 42.31 47.15

50 40.39 42.31 44.23 50.00

60 42.31 44.23 46.15 53.85

90 44.23 46.15 48.08 57.69

120 46.15 48.08 51.92 61.49

150 48.08 51.92 53.55 65.31

180 51.92 54.17 57.69 69.23

60

Table 18

Adsorption of Acid Violet Dye from Aqueous Solutionwith Adsorbent Dosage Variation

Conditions:


pH : 7.0 ± 0.2


Time inminutes


200mg 300mg 400mg 500mg

10 17.00 19.0 26.19 35.72

20 19.05 21.43 29.00 38.10

30 23.81 24.57 30.95 40.48

40 24.57 26.19 33.33 42.86

50 26.19 28.57 35.72 47.62

60 33.33 35.72 38.10 52.38

90 35.72 38.10 42.86 57.14

120 38.10 42.86 47.38 61.91

150 40.48 47.38 52.38 66.67

180 42.86 52.38 54.76 69.05

61

Figure 13

Figure 14

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200mg

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200mg

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Figure 13

Figure 14

60 80 100 120 140 160 180 200Time in minutes


300mg 400mg 500mg

60 80 100 120 140 160 180 200Time in minutes


300mg 400mg 500mg

61

Figure 13

Figure 14

200

200


62

Figure 15

Figure 16

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Adsorption of Acid Blue Dye from Aqueous Solutionwith Adsorbent DosageVariation

200mg

0

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Adsorption of Acid Violet Dye from Aqueous Solution withAdsorbent Dosage Variation

200mg

62

Figure 15

Figure 16

60 80 100 120 140 160 180 200

Time in minutes

Adsorption of Acid Blue Dye from Aqueous Solutionwith Adsorbent DosageVariation

300mg 400mg 500mg

60 80 100 120 140 160 180 200Time in minutes


300mg 400mg 500mg

62

Figure 15

Figure 16

200

200


63

4.5 Effect of Temperature on Dye Removal

The effect of temperature on adsorption of Methylene Blue, Methyl Violet, Acid Blue

and Acid Violet dyes are studied by varying the temperature 22˚C, 32˚C and 42˚C. Batch

mode experiments are carried out by using the 100ml of dye solution containing 100mg dye

per litre at pH 7.0 ± 0.2 using 500mg of the adsorbent BGA. It is observed that the

percentage removal of dyes increased, when the temperature is varied from 22˚C to 42˚C(for Methylene Blue from 87.8% to 93.4%, for Methyl Violet from 73.17% to 85.37%, for

Acid Blue from 51.92% to 75.00% and for Acid Violet from 54.76% to 73.81%).

The enhancement in adsorption with temperature may be due to the increase in the

mobility of the dye molecule with increase in their kinetic energy (Renugadevi et al.,

2009b; Ahmad and Kumar, 2010). The results obtained are shown in Tables 19 - 22 and

graphically represented in Figures 17 - 20. Similar results have been reported for the

adsorption of Crystal Violet on grape fruit peel (Saeed et al., 2010) and on oak saw dust

(Abd El – Latifa et al., 2010).

64

Table 19

Adsorption of Methylene Blue Dye from Aqueous Solutionwith Temperature Variation

Conditions:



pH : 7.0 ± 0.2

Time inminutes


22˚C 32˚C 42˚C

10 69.6 75.7 84.5

20 71.0 77.7 85.8

30 73.7 82.4 86.5

40 75.0 86.5 87.8

50 75.7 87.2 88.5

60 81.8 87.8 89.1

90 85.1 88.5 90.5

120 85.8 90.5 91.2

150 86.5 91.2 91.9

180 87.8 92.6 93.4

65

Table 20

Adsorption of Methyl Violet Dye from Aqueous Solutionwith Temperature Variation

Conditions:



pH : 7.0 ± 0.2

Time inminutes


22˚C 32˚C 42˚C

10 41.46 43.90 48.78

20 43.90 48.78 51.22

30 48.78 53.66 56.10

40 51.22 58.54 60.98

50 53.66 63.41 65.85

60 56.10 65.85 73.17

90 60.98 70.73 75.61

120 65.86 73.17 78.05

150 70.73 75.61 80.49

180 73.17 78.05 85.37

66

Table 21

Adsorption of Acid Blue Dye from Aqueous Solutionwith Temperature Variation

Conditions:



pH : 7.0 ± 0.2

Time inminutes


22˚C 32˚C 42˚C

10 30.77 38.46 50.00

20 32.69 40.39 51.92

30 32.69 44.23 53.85

40 34.62 46.15 55.77

50 36.54 50.00 59.62

60 42.31 53.85 63.46

90 44.23 57.69 65.39

120 48.08 63.49 69.23

150 50.00 67.31 71.15

180 51.92 69.23 75.00

67

Table 22

Adsorption of Acid Violet Dye from Aqueous Solutionwith Temperature Variation

Conditions:



pH : 7.0 ± 0.2

Time inminutes


22˚C 32˚C 42˚C

10 23.81 35.72 38.10

20 26.19 38.10 40.40

30 28.57 40.48 42.86

40 33.33 42.86 47.62

50 35.72 47.62 52.38

60 40.48 52.38 54.76

90 42.86 57.14 61.91

120 47.62 61.91 64.43

150 52.38 66.67 69.05

180 54.76 69.05 73.81

68

Figure 17

Figure 18

50

60

70

80

90

100

10 20 30

Perc

enta

ge re

mov

al o

f dye


22◦C

0

20

40

60

80

10 20 30

Perc

enta

ge re

mov

al o

f dye


22˚C

68

Figure 17

Figure 18

40 50 60 90 120 150 180

Time in minutes


32◦C 42◦C

40 50 60 90 120 150 180Time in minutes


32˚C 42˚C

68

Figure 17

Figure 18

180


180

69

Figure 19

Figure 20

0

20

40

60

80

10 20 30

Perc

enta

ge re

mov

al o

f dye


22◦C

0

20

40

60

80

10 20 30

Perc

enta

ge re

mov

al o

f dye


22˚C

69

Figure 19

Figure 20

40 50 60 90 120 150 180Time in minutes


32◦C 42◦C

40 50 60 90 120 150 180Time in minutes


32˚C 42˚C

69

Figure 19

Figure 20

180

180

70

4.6 Adsorption of Dyes from Dyeing Industrial Effluent

The textile dye effluents are collected from a common effluent treatment plant in

Tiruppur, the texcity of Tamilnadu, India. Batch mode experiments are carried out at pH

7.0 ± 0.2 and at 32°C using 500mg of BGA and the contact time is maintained as

180minutes.

Blue-Green Algae was found to be efficient in the removal of the dyes from the

dyeing industrial effluents and the experimental work reported lesser percentage removal of

dyes from the effluents, compared to that of aqueous solutions. This may be due to the

adsorption of other pollutants (Sharma and Kaur, 1997) present in the dyeing industrial

effluent on the surface of the adsorbent BGA. The data for the adsorption of dyes from

aqueous solution and from dyeing industrial effluent using BGA are given in

Figures 21 - 24.

Pollutants present in the Dyeing Industrial EffluentName of the dyeingindustrial effluent

Organic Pollutants InOrganic Pollutants

Methylene Blue,Methyl Violet,Acid Blue andAcid Violet Dyes

Detergents, phenols, organic matterand cellulose fibres

Hardness, alkalinity, Iron,suspended solids, cyanide,thiocyanate, sulphates,carbonates and chlorides,

10 20from aqueous solution 75.7 77.7from effluent 35.21 35.91

20

40

60

80

100

Perc

enta

ge re

mov

al o

f dye

Adsorption of Methylene Blue Dye from Aqueous Solutionand from Dyeing Industrial Effluent using BGA

70





180minutes.







Figures 21 - 24.






20 30 40 50 60 90 120 150 180

77.7 82.4 86.5 87.2 87.8 88.5 90.5 91.2 92.635.91 36.62 38.03 38.73 40.14 41.55 42.25 43.66 45.07


70





180minutes.







Figures 21 - 24.






180

92.645.07


71

Figure 21

Figure 22

Figure 23

10from aqueous solution 43.9 48.5from effluent 42.8 43.4

20

40

60

80Pe

rcen

tage

rem

oval

of d

ye

Adsorption of Methyl Violet Dye from Aqueous Solution andfrom Dyeing Industrial Effluent using BGA

10

from aqueous solution 38.4from effluent 28.6

20

40

60

80

Perc

enta

ge re

mov

al o

f dye

Adsorption of Acid Blue Dye from Aqueous Solution andfrom Dyeing Industrial Effluent using BGA

71

Figure 21

Figure 22

Figure 23

20 30 40 50 60 90 120 15048.5 53.6 58.5 63.4 65.8 70.7 73.1 75.643.4 46.9 48.9 53.0 57.1 60.2 65.3 67.3

Adsorption of Methyl Violet Dye from Aqueous Solution andfrom Dyeing Industrial Effluent using BGA

10 20 30 40 50 60 90 120

150

38.4 40.3 44.2 46.1 50 53.8 57.6 63.4 67.328.6 30.8 34.2 36.6 40 43.5 45.9 47.4 49.1

Adsorption of Acid Blue Dye from Aqueous Solution andfrom Dyeing Industrial Effluent using BGA

71

Figure 21

Figure 22

Figure 23

150 18075.6 78.067.3 69.3

180

67.3 69.249.1 52.2

72

Figure 24

4.7 Efficiency of Blue-Green Algae in the Removal of Dyes by Adsorption

The percentage removal of Methylene Blue, Methyl Violet, Acid Blue and Acid Violet

dyes from aqueous solutions and also from dyeing industrial effluents using the adsorbents

Blue-Green Algae and Commercial Activated Carbon are investigated. Batch mode

experiments are carried out by using the 100ml of dye solution containing 100mg of

dye/litre at 32 ± 2º C and at pH 7.0 ± 0.2 with 100mg of the adsorbents. The obtained

results are given in Tables 23 - 26 and Figures 25 - 28.

Removal efficiency of the adsorbent Blue-Green Algae (BGA) is an important

aspect, as it needs to be compared with the Commercial Activated Carbon (CAC).

Commercial Activated Carbon has greater percentage removal of the dyes from aqueous

solution and also from dyeing industrial effluents, compared to that of Blue-Green Algae,

which could be attributed due to the greater surface area of the adsorbent CAC (Surface

area of CAC is 1021m2/g). However removal of dyes by adsorption using Commercial

Activated Carbon is quite expensive. Though the percentage removal of dyes from

aqueous solution and also from dyeing industrial effluents using Blue-Green Algae by

adsorption is less compare to that of CAC due to its lesser surface area (Surface area of

BGA is 479m2/g), it is advantageous, since BGA is available in large quantities as natural

biowaste and cost effective.

10from aqueous solution 34.2 38.4from effluent 27.1 29.6

20

30

40

50

60

70

Perc

enta

ge re

mov

al o

f dye

Adsorption of Acid Violet Dye from Aqueous Solution andfrom Dyeing Industrial Effluent using BGA

72

Figure 24



















20 30 40 50 60 90 120 15034.2 38.4 40.1 42.7 47.3 50 52.6 55.2 57.827.1 29.6 33.7 35.2 37.1 38.5 40.9 42.8 46.6

Adsorption of Acid Violet Dye from Aqueous Solution andfrom Dyeing Industrial Effluent using BGA

72

Figure 24



















150 18057.8 63.146.6 50.3

73

Percentage removal of dyes from the dyeing industrial effluents, compared to that of

aqueous solutions are lesser with both the adsorbents CAC and BGA, this may be due to

the adsorption of other pollutants present in the dyeing industrial effluents on the surface of

the adsorbents CAC and BGA.

Table 23

Adsorption of Methylene Blue Dye from Aqueous Solution and fromDyeing Industrial Effluent using Blue-Green Algae and

Commercial Activated Carbon

Conditions:


pH : 7.0 ± 0.2


Timein minutes

Removal of MB Dye inPercentage using

BGA

Removal of MB Dye inPercentage using

CACFrom Aqueous

SolutionFrom

EffluentFrom Aqueous

SolutionFrom

Effluent

10 31.1 19.7 66.2 38.0

20 33.1 20.4 68.9 38.7

30 33.8 21.1 69.6 40.1

40 35.1 21.8 70.9 41.5

50 41.2 23.2 73.6 42.3

60 42.6 25.4 73.9 43.7

90 43.2 26.8 77.0 45.1

120 43.9 27.5 77.5 47.2

150 44.6 28.9 81.1 51.4

180 45.3 31.0 82.4 54.2

74

Table 24

Adsorption of Methyl Violet Dye from Aqueous Solution and from DyeingIndustrial Effluent using Blue-Green Algae and

Commercial Activated CarbonConditions:


pH : 7.0 ± 0.2


Timein minutes

Removal of MV Dye inPercentage using

BGARemoval of MV Dye in

Percentage usingCAC

From AqueousSolution

FromEffluent


FromEffluent

10 36.6 19.5 41.5 26.8

20 41.5 22.0 43.9 29.3

30 43.9 24.4 48.8 31.7

40 46.3 26.8 51.2 34.1

50 48.8 29.3 53.7 36.6

60 51.2 34.7 56.1 41.5

90 53.4 36.6 60.9 46.3

120 55.0 39.0 65.9 51.2

150 56.1 41.5 68.3 53.7

180 58.5 43.9 70.7 56.1

75

Table 25

Adsorption of Acid Blue Dye from Aqueous Solution and from DyeingIndustrial Effluent using Blue-Green Algae and



pH : 7.0 ± 0.2


Timein minutes

Removal of AB Dye inPercentage using

BGA

Removal of AB Dye inPercentage using

CAC


FromEffluent


FromEffluent

10 7.7 3.8 26.9 13.5

20 9.6 5.8 28.8 15.4

30 13.5 7.7 32.7 17.3

40 19.2 11.5 34.6 21.2

50 23.1 13.5 38.5 23.1

60 26.9 17.3 40.4 26.9

90 32.7 21.2 44.2 28.8

120 34.6 23.1 46.2 32.7

150 38.5 25.0 50.0 36.5

180 40.4 26.9 53.8 38.5

76

Table 26

Adsorption of Acid Violet Dye from Aqueous Solution and fromDyeing Industrial Effluent using Blue-Green Algae and



pH : 7.0 ± 0.2


Timein minutes

Removal of AV Dye inPercentage using

BGA

Removal of AV Dye inPercentage using

CAC


FromEffluent


FromEffluent

10 9.5 4.8 23.8 9.5

20 11.9 7.1 28.6 11.9

30 16.7 9.5 31.0 16.7

40 19.0 11.9 33.3 21.4

50 21.4 14.3 35.7 23.8

60 26.2 16.7 38.1 26.2

90 31.0 19.0 42.9 28.6

120 35.7 21.4 45.2 31.0

150 38.1 23.8 47.6 35.7

180 40.5 26.2 50.0 38.1

77

Figure 25

Figure 26

Removal of Dyes from Aqueous Solution using BGA

Conditions:

Adsorbent Dosage : 100mgpH : 7.0 ± 0.2Temperature : 32 ± 2˚CConcentration ofDye Solution : 100mg/lContact Time : 180minutes

Removal of Dyes from Aqueous Solution using CAC

Conditions:


77

Figure 25

Figure 26

Methylene Blue45.3%

Methyl Violet58.5%

Acid Blue40.4%

Acid Violet40.5%

Removal of Dyes from Aqueous Solution using BGA

Conditions:


Methylene Blue82.4%

Methyl Violet70.7%

Acid Blue53.8%

Acid Violet50.0%

Removal of Dyes from Aqueous Solution using CAC

Conditions:


77

Figure 25

Figure 26

78

Figure 27

Figure 28

Removal of Dyes from Dyeing Industrial Effluentusing BGA

Conditions:


Removal of Dyes from Dyeing Industrial Effluentusing CAC

Conditions:


78

Figure 27

Figure 28

Methylene Blue31.0%

Methyl Violet43.9%

Acid Blue26.9%

Acid Violet26.2%

Removal of Dyes from Dyeing Industrial Effluentusing BGA

Conditions:


Methylene Blue54.2%

Methyl Violet56.1%

Acid Blue38.5%

Acid Violet38.1%

Removal of Dyes from Dyeing Industrial Effluentusing CAC

Conditions:


78

Figure 27

Figure 28

79

4.8 Kinetics of Adsorption

The study of adsorption kinetics is significant as it provides valuable insights into the

reaction path ways and into the mechanism of the reactions. The adsorption process is

usually demonstrated by four steps:

1. Transport of adsorbate from bulk solution to the liquid film or boundary layer

surrounding the adsorbent.

2. Transport of adsorbate from the boundary film to the external surface of the adsorbent

(surface diffusion).

3. Transfer of the adsorbate from the surface to the intraparticle active sites (pore

diffusion).

4. Adsorption of dyes by the active sites of adsorbent.

The slowest of these determines the overall rate of the adsorption processes. The

first step is not involved with adsorbent and fourth step is a very rapid process, they do not

belong to the rate controlling steps. Therefore, the rate controlling steps mainly depend on

step 2 and step 3 either surface diffusion or pore diffusion (Theydan et al., 2012).

4.8.1 Lagergren Rate Equation

The Lagergren rate constant for the adsorption of the Methylene Blue, Methyl Violet,

Acid Blue and Acid Violet dyes from aqueous solution and from dyeing industrial effluent on

the adsorbent BGA is determined using Lagergren equation (Lagergren, 1898;Renugadevi et al., 2010).

log (qe- q) = log qe – (Ka / 2.303) x twhere

q - amount of dye adsorbed (mg/g) by the adsorbent at time ‘t’

qe - amount of dye adsorbed (mg/g) by the adsorbent at equilibrium time

Ka - rate constant of adsorption in time-1

t - agitation time in minutes

Batch mode experiments were carried out by varying the concentration of the dye

solutions at 32 ± 2ºC and at pH 7.0 ± 0.2 for all the dyes used in this study. The data

obtained from Lagergren equation for the adsorption of the dyes from aqueous solution in

terms of variation of initial concentration of the dye solutions with the adsorbent BGA

80

are summarised in the Tables 27 - 30 and the corresponding Lagergren plots are shown in

Figures 29 - 32.

Attempts are made for the adsorption of the dyes used in this study from dyeing

industrial effluent onto BGA. The data obtained in this study are summarised in the

Tables 31 - 34 and the graphical representations are shown in Figures 33 - 36.

The linear plots obtained show the applicability of Lagergren rate equation for the

adsorption of the dyes used in this study and suggested the formation of monolayer of dyes

onto the surface of the adsorbent (Geetha et al., 2008). The rate constants Ka are

calculated from the slope of the plots of log (qe- q) vs t and are shown in Tables 27 - 34.

The values of correlation coefficient (r2) obtained, show good correlation. The rate

constant Ka decreases with increasing initial concentration of the dye solutions used in this

study. The reason for this behaviour can be attributed to the high competition for the

adsorption surface sites at high concentration which leads to lower adsorption rates

(Sen et al., 2011).

Similar types of kinetic model were reported for the adsorption of Rhodamine-B

using cocoa shell (Theivarasu et al., 2010) and for the removal of methylene blue onto

pine cone biomass (Sen et al., 2011).

81

Table 27

Lagergren Rate Equation for the Adsorption of Methylene Blue Dyefrom Aqueous Solution onto BGA

Time inminutes

log (qe – q )


10 0.8235 1.0712 1.2098 1.5366

20 0.6128 1.0477 1.152 1.4632

30 0.5551 0.8338 0.9759 1.4397

40 0.4871 0.6794 0.7324 1.3458

50 0.3118 0.5705 0.6075 1.2813

60 0.1875 0.4914 0.6075 1.2058

90 0.1875 0.3945 0.5289 1.0874

120 0.0086 0.2695 0.1303 0.8382

150 -0.0292 -0.2076 -0.1739 0.1847

180 _ _ _ _

Intercept (log qe) 0.7089 1.0917 1.2315 1.6932

Slope (-Ka / 2.303) 0.00568 0.0082 0.0093 0.0085

Ka in min-1 x 10-22.2962 2.146 1.8885 1.3081

CorrelationCoefficient (r2) 0.9312 0.9677 0.9750 0.9582

82

Table 28

Lagergren Rate Equation for the Adsorption of Methyl Violet Dyefrom Aqueous Solution onto BGA

Time inminutes

log (qe – q )


10 1.1179 1.4314 1.5315 1.5911

20 1.0414 1.3979 1.4624 1.5563

30 0.9542 1.2553 1.3802 1.5185

40 0.9031 1.2041 1.3010 1.4914

50 0.7782 1.0414 1.1761 1.3424

60 0.6021 0.9542 1.0792 1.2304

90 0.6021 0.8451 0.8451 1.1461

120 0.3010 0.6990 0.6990 0.9031

150 0.3010 0.3010 0.3010 0.4771

180 - - - -

Intercept (log qe) 1.1233 1.4918 1.6226 1.7314

Slope(-Ka / 2.303) 0.00616 0.00754 0.00847 0.00759

Ka in min-1x10-2 1.984 1.951 1.736 1.418


83

Table 29

Lagergren Rate Equation for the Adsorption of Acid Blue Dyefrom Aqueous Solution onto BGA

Time inminutes

log (qe – q )


10 1.664 1.3679 1.4881 1.4449

20 1.1252 1.3359 1.4599 1.4103

30 1.0792 1.2632 1.3979 1.3724

40 0.9704 1.2219 1.3632 1.3310

50 0.9031 1.1761 1.2840 1.2343

60 0.8247 1.0671 1.1870 1.1092

90 0.6021 0.9207 1.0622 1.0302

120 0.4265 0.5224 0.7612 0.9330

150 0.1271 0.2227 0.2833 0.6325

180 _ _ _ _

Intercept (log qe) 1.4198 1.5290 1.6929 1.5182

Slope (-Ka / 2.303) 0.00887 0.00818 0.00847 0.00552

Ka in min-1 x10-22.279 1.951 1.884 1.772


84

Table 30

Lagergren Rate Equation for the Adsorption of Acid Violet Dyefrom Aqueous Solution onto BGA

Time inminutes

log (qe – q )


10 1.288 1.365 1.522 1.656

20 1.247 1.278 1.491 1.602

30 1.201 1.227 1.456 1.540

40 1.092 1.168 1.418 1.426

50 1.025 1.102 1.331 1.329

60 0.945 1.023 1.222 1.270

90 0.849 0.925 1.076 1.027

120 0.724 0.801 0.854 0.728

150 0.548 0.624 0.377 0.427

180 _ _ _ _

Intercept (log qe) 1.3214 1.3147 1.6848 1.7810

Slope (-Ka / 2.303) 0.00522 0.00502 0.00775 0.00881

Ka in min-1 x10-22.0299 1.7844 1.2014 1.1553


85

Figure 29

Figure 30

0.0

0.4

0.8

1.2

1.6

2.0

0 20 40

log

(qe

-q)

Lagergren Rate Equation for the Adsorption of Methyl VioletDye from Aqueous Solution onto BGA

60mg/l 80mg/l

85

Figure 29

Figure 30

40 60 80 100 120 140 160Time in minutes

Lagergren Rate Equation for the Adsorption of Methyl VioletDye from Aqueous Solution onto BGA


85

Figure 29

Figure 30

160

86

Figure 31

Figure 32

87

Table 31

Lagergren Rate Equation for the Adsorption of Methylene Blue Dye fromDyeing Industrial Effluent onto BGA

Time inminutes

log (qe – q )


10 0.9206 1.0849 0.9936

20 0.8235 1.0615 0.9619

30 0.7860 1.0366 0.9267

40 0.6990 1.0103 0.8476

50 0.6474 0.9823 0.8021

60 0.5224 0.8476 0.6929

90 0.3464 0.7604 0.5465

120 0.2201 0.2833 0.4502

150 0.2596 0.1072 0.1492

180 _ _ _

Intercept (log qe) 0.9094 1.2626 1.7856

Slope (-Ka / 2.303) 0.00519 0.00735 0.00585

Ka in min-1 x10-2 1.693 1.347 1.195

CorrelationCoefficient (r2) 0.9600 0.9698 0.9913

88

Table 32

Lagergren Rate Equation for the Adsorption of Methyl Violet Dye fromDyeing Industrial Effluent onto BGA

Time inminutes

log (qe – q )


10 1.291 1.416 1.424

20 1.259 1.386 1.351

30 1.224 1.354 1.309

40 1.186 1.319 1.264

50 0.9899 1.085 1.213

60 0.9232 1.018 1.088

90 0.8439 0.939 0.788

120 0.4456 0.718 0.611

150 0.1461 0.542 0.309

180 _ _ _

Intercept (log qe) 1.4430 1.4968 1.5499

Slope (-Ka / 2.303) 0.008208 0.00648 0.008056

Ka in min-1 x10-2 1.49 1.86 1.89


89

Table 33

Lagergren Rate Equation for the Adsorption of Acid Blue Dye fromDyeing Industrial Effluent onto BGA

Time inminutes

log (qe – q )


10 1.3655 1.3159 1.3729

20 1.3159 1.2742 1.3304

30 1.2672 1.2355 1.2553

40 1.2175 1.1847 1.1931

50 1.1553 1.1173 1.0864

60 1.0828 1.0212 0.9395

90 0.9345 0.9085 0.7993

120 0.7709 0.6989 0.6812

150 0.4472 0.4472 0.4914

180 _ _ _

Intercept (log qe) 1.4565 1.4094 1.4236

Slope (-Ka / 2.303) 0.00623 0.00611 0.00643

Ka in min-1 x10-2 1.479 1.4345 1.407


90

Table 34

Lagergren Rate Equation for the Adsorption of Acid Violet Dye fromDyeing Industrial Effluent onto BGA

Time inminutes

log (qe – q )


10 1.243 1.253 1.317

20 1.176 1.237 1.276

30 1.138 1.149 1.229

40 1.051 1.041 1.179

50 1.000 0.895 1.121

60 0.796 0.798 1.121

90 0.699 0.673 0.975

120 0.374 0.469 0.878

150 0.398 0.196 0.578

180 _ _ _

Intercept (log qe) 1.4072 1.3574 1.3215

Slope (-Ka / 2.303) 0.0061 0.00762 0.0079

Ka in min-1 x10-2 3.43 3.31 2.64


91

Figure 33

Figure 34

92

Figure 35

Figure 36

0.3

0.7

1.1

1.5

0 50 100 150 200

log

(qe

-q)

Time in minutes

Lagergren Rate Equation for the Adsorption of Acid Blue Dyefrom Dyeing Industrial Effluent onto BGA


0.0

0.4

0.8

1.2

1.6

0 20 40 60 80 100 120 140 160 180

log

(qe

-q)

Time in minutes

Lagergren Rate Equation for the Adsorption of Acid Violet Dyefrom Dyeing Industrial Effluent onto BGA


93

4.8.2 Intraparticle Diffusion Rate Equation

There is a possibility of transport of dye molecules from the bulk into pores of the

adsorbent as well as, adsorption at the outer surface of the adsorbent. The rate limiting

step in the adsorption may be either film diffusion or intraparticle diffusion. As they act in

series, the slower of the two will be the rate determining step. The possibility of the dye

species to diffuse into the interior sites of the particles of adsorbent was tested with Weber-

Morris equation given as follows (Weber and Morris, 1963; Lalitha et al., 2011):

q = Kpt1/2

where,

‘q’ is the amount of dye adsorbed (mg/g) by the adsorbent at time ‘t’Kp is the intraparticle diffusion rate constant and

‘t’ is the time (agitation time) in minutes

In order to study the diffusion process, batch mode experiments are carried out with

the adsorbent BGA at 32 ± 2ºC and at pH 7.0 ± 0.2 by varying the initial concentration of

the aqueous dye solutions used in this study. The results are given in the Tables 35 – 38

and graphically shown in Figures 37 - 40.

Adsorption of the dyes (Methylene Blue, Methyl Violet, Acid Blue and Acid Violet)

from dyeing industrial effluent onto BGA is also carried out at 32 ± 2ºC and at pH 7.0 ± 0.2

by varying the concentration of the dye. The data obtained are summarised in the Tables

39 – 42 and the graphical representations are shown in Figures 41 - 44.

The rate constant for intraparticle diffusion Kp for various initial concentrations of the

dyes are determined from the slope of the linear equation drawn between square root of

time (t1/2) and the amount of adsorbate adsorbed (q). Values of Kp increased with increase

in initial dye concentration which shows that the adsorption rate is governed by the diffusion

of the dye within the pores of the adsorbent (Vucurovic et al., 2012).

If the intraparticle diffusion is the rate controlling step, the plot should be linear and

pass through the origin. It can be noticed from the Figures 37– 44, the plots are linear but

not passing through the origin and this deviation from the origin or near saturation might be

due to the difference in mass transfer rate in the initial and final stages of adsorption

(Theydan et al., 2012). It also indicates that there is an initial boundary layer resistance

and intraparticle diffusion is not the sole rate controlling step, but other kinetic models may

simultaneously control the adsorption rate (Ma et al., 2012).

94

Similar results were reported in the literature for the adsorption of crystal violet onto

Opal (Ma et al., 2012), adsorption of methylene blue onto sugar extracted spent rice

biomass (Rehman et al., 2012), on sugar beet pulp (Vucrovic et al., 2012), on rice husk

(Safa and Bhatti, 2011) and on teak tree bark powder (Satish Patil et al., 2011).

Table 35

Intraparticle Diffusion Rate Equation for the Adsorption of Methylene BlueDye from Aqueous Solution onto BGA

Conditions :


pH : 7.0 ± 0.2


Timein minutes √t

Initial Concentration of Methylene Blue Dyein mg/l

Amount of dye adsorbed (q) in mg

60mg 80mg 100mg 120mg

10 3.1623 50.3 62.4 75.7 79.6

20 4.4721 52.8 63.3 77.7 78.3

30 5.4772 53.3 67.6 82.4 83.8

40 6.3246 53.9 69.5 86.5 87.1

50 7.0711 54.4 70.7 87.2 89.2

60 7.7460 54.9 71.3 87.8 90.3

90 9.4868 55.4 71.9 88.5 92.1

120 10.9545 55.9 72.6 90.5 93.4

150 12.2474 56.4 73.8 91.2 94.8

180 13.4164 56.9 74.4 92.6 96.3

Intercept 49.89 56.16 72.85 50.99

Slope (Kp) x10-3 0.543 1.596 1.683 3.569

Correlation Coefficient (r2) 0.918 0.869 0.912 0.996

95

Table 36

Intraparticle Diffusion Rate Equation for the Adsorption of Methyl VioletDye from Aqueous Solution onto BGA

Conditions :


pH : 7.0 ± 0.2


Timein minutes √t

Initial Concentration of the Methyl Violet Dyein mg/l

Amount of dye adsorbed (q) in mg60mg 80mg 100mg 120mg

10 3.1623 35.63 36.57 43.90 45.32

20 4.4721 37.60 38.86 48.78 50.23

30 5.4772 39.68 45.71 53.66 55.81

40 6.3246 41.25 48.00 58.54 58.60

50 7.0711 43.13 52.57 63.41 66.98

60 7.7460 44.68 54.86 65.87 72.56

90 9.4868 45.23 57.14 70.73 75.35

120 10.9545 46.88 59.43 73.17 80.93

150 12.2474 47.08 61.71 75.61 86.51

180 13.4164 48.75 64.00 78.05 89.30

Intercept 33.7865 29.3078 34.681 34.901

Slope ( Kp) x10-3 1.1779 2.8544 3.608 4.1997


96

Table 37

Intraparticle Diffusion Rate Equation for the Adsorption of Acid BlueDye from Aqueous Solution onto BGA

Conditions :

Adsorbent Dosage: 500mg

pH : 7.0 ± 0.2


Timein minutes √t

Initial Concentration of Acid Blue Dyein mg/l


60mg 80mg 100mg 120mg

10 3.1623 32.00 36.67 38.46 45.00

20 4.4721 33.33 38.33 40.39 47.14

30 5.4772 34.67 41.67 44.23 49.29

40 6.3246 37.33 43.33 46.15 51.43

50 7.0711 38.67 45.00 50.00 55.71

60 7.7460 40.00 48.33 53.85 60.00

90 9.4868 42.67 51.67 57.69 62.14

120 10.9545 44.00 56.67 63.46 64.29

150 12.2474 45.33 58.33 67.31 68.57

180 13.4164 46.67 60.00 69.23 72.86

Intercept 27.43 28.32 27.06 35.59

Slope (Kp) x 10-3 1.4976 2.547 2.786 3.434


97

Table 38

Intraparticle Diffusion Rate Equation for the Adsorption of Acid VioletDye from Aqueous Solution onto BGA

Conditions :

Adsorbent Dosage: 500mg

pH : 7.0 ± 0.2


Timein minutes √t

Initial concentration of Acid Violet Dyein mg/l


60mg 80mg 100mg 120mg

10 3.1623 17.7 27.4 35.72 45.3

20 4.4721 19.4 31.6 38.10 50.7

30 5.4772 21.2 33.7 40.48 56.0

40 6.3246 24.7 35.8 42.86 64.0

50 7.0711 26.5 37.9 47.62 69.3

60 7.7460 28.2 40.0 52.38 72.0

90 9.4868 30.0 42.1 57.14 80.0

120 10.9545 31.8 44.2 61.91 85.3

150 12.2474 33.5 46.3 66.67 88.0

180 13.4164 37.1 50.5 69.05 90.7

Intercept 12.24 22.56 22.83 33.02

Slope (Kp) x 10-3 1.84 2.07 3.53 4.62

Correlation Coefficient(r2) 0.9863 0.9864 0.9929 0.9824

98

Figure 37

Figure 38

20

40

60

80

100

2 4 6 8 10 12 14

Amou

nt o

f dye

ads

orbe

d (q

) in

mg

√ t

Intraparticle Diffusion Rate Equation for the Adsorption ofMethylene Blue Dye from Aqueous Solution onto BGA

60mg 80mg 100mg 120 mg

10

30

50

70

90

2 4 6 8 10 12 14Amou

nt o

f dye

ads

orbe

d (q

) in

mg

√ t

Intraparticle Diffusion Rate Equation for the Adsorption ofMethyl Violet Dye from Aqueous Solution onto BGA

60mg 80mg 100mg 120 mg

99

Figure 39

Figure 40

10

30

50

70

90

2 4 6 8 10 12 14Amou

nt o

f dye

ads

orbe

d (q

) in

mg

√ t

Intraparticle Diffusion Rate Equation for the Adsorption ofAcid Blue Dye from Aqueous Solution onto BGA

60mg 80mg 100mg 120 mg

10

30

50

70

90

3 5 7 9 11 13 15

Amou

nt o

f dye

ads

orbe

d (q

) in

mg

√ t

Intraparticle Diffusion Rate Equation for the Adsorption ofAcid Violet Dye from Aqueous Solution onto BGA

60mg 80mg 100mg 120 mg

100

ble 39

Intraparticle Diffusion Rate Equation for the Adsorption of Methylene BlueDye from Dyeing Industrial Effluent onto BGA

Conditions:


pH : 7.0 ± 0.2


Timein minutes √t

Initial Concentration of Methylene Blue Dye inmg/l


60mg 80mg 100mg

10 3.1623 26.11 31.36 35.21

20 4.4721 27.78 32.00 35.91

30 5.4772 28.33 32.64 36.62

40 6.3246 29.44 33.28 38.03

50 7.0711 30.00 33.92 38.73

60 7.7460 31.11 36.48 40.14

90 9.4868 32.22 37.76 41.55

120 10.9545 32.78 41.60 42.25

150 12.2474 33.89 42.24 43.66

180 13.4164 34.44 43.54 45.07

Intercept 23.94 25.84 31.83

Slope Kp x 10-3 0.7999 0.9798 1.3254

Correlation Coefficient (r2) 0.9892 0.9745 0.9905

101

Table 40

Intraparticle Diffusion Rate Equation for the Adsorption of Methyl Violet Dyefrom Dyeing Industrial Effluent onto BGA

Conditions :


pH : 7.0 ± 0.2


Timein minutes √t

Initial Concentration of Methyl Violet Dye in mg/lAmount of dye adsorbed (q) in mg

60mg 80mg 100mg

10 3.1623 26.51 34.78 42.86

20 4.4721 27.91 36.52 46.93

30 5.4772 29.30 38.26 48.98

40 6.3246 30.70 40.00 51.02

50 7.0711 36.28 48.70 53.06

60 7.7460 37.67 50.44 57.14

90 9.4868 39.07 52.17 63.26

120 10.9545 43.26 55.65 65.31

150 12.2474 44.65 57.39 67.35

180 13.4164 46.05 60.87 69.39

Intercept 19.4377 25.9155 34.7236

Slope Kp x 10-3 2.0785 2.6833 2.7136


102

Table 41

Intraparticle Diffusion Rate Equation for the Adsorption of Acid Blue Dyefrom Dyeing Industrial Effluent onto BGA

Conditions :


pH : 7.0 ± 0.2


Timein minutes √t

Initial Concentration of Acid Blue Dye in mg/lAmount of dye adsorbed (q) in mg

60mg 80mg 100mg

10 3.1623 28.6 35.3 38.5

20 4.4721 30.8 37.2 41.0

30 5.4772 34.2 38.8 43.2

40 6.3246 36.6 40.7 45.2

50 7.0711 40.0 42.9 47.4

60 7.7460 43.5 45.5 49.6

90 9.4868 4 5.9 47.9 53.1

120 10.9545 47.4 51.0 55.8

150 12.2474 49.1 53.2 58.9

180 13.4164 52.2 56.0 61.7

Intercept 22.168 28.230 31.078

Slope Kp x 10-3 2.0681 2.2850 2.3224


103

Table 42

Intraparticle Diffusion Rate Equation for the Adsorption of Acid Violet Dyefrom Dyeing Industrial Effluent onto BGA

Conditions :


pH : 7.0 ± 0.2


Timein minutes √t

Initial Concentration of Acid Violet Dye in mg/l


60mg 80mg 100mg

10 3.1623 23.75 32.31 39.62

20 4.4721 26.25 32.94 41.51

30 5.4772 27.50 36.08 43.40

40 6.3246 30.00 39.22 45.28

50 7.0711 31.25 42.35 47.17

60 7.7460 35.00 43.92 47.17

90 9.4868 36.25 45.49 50.94

120 10.9545 37.50 47.06 52.83

150 12.2474 38.75 48.63 56.60

180 13.4164 41.25 50.20 60.38

Intercept 19.1911 27.1441 32.8714

Slope Kp x 10-3 1.6873 1.8263 1.9436


104

Figure 41

Figure 42

20

25

30

35

40

45

50

3 5 7 9 11 13Amou

nt o

f dye

ads

orbe

d(q)

in m

g

√ t

Intraparticle Diffusion Rate Equation for the adsorption ofMethylene Blue Dye from Dyeing Industrial Effluent onto BGA

60mg 80mg 100mg

25

35

45

55

65

3 5 7 9 11 13Amou

nt o

f dye

ads

orbe

d(q)

in m

g

√ t

Intraparticle Diffusion Rate Equation for the Adsorption ofMethyl Violet Dye from Dyeing Industrial Effluent onto BGA

60mg 80mg 100mg

105

Figure 43

Figure 44

20

30

40

50

60

70

3 5 7 9 11 13Amou

nt o

f dye

ads

orbe

d(q)

in m

g

√ t

Intraparticle Diffusion Rate Equation for the Adsorption ofAcid Blue Dye from Dyeing Industrial Effluent onto BGA

60mg 80mg 100mg

20

30

40

50

60

70

3 5 7 9 11 13Amou

nt o

f dye

ads

orbe

d(q)

in m

g

√ t

Intraparticle Diffusion Rate Equation for the Adsorption ofAcid Violet Dye from Dyeing Industrial Effluent onto BGA

60mg 80mg 100mg

106

4.8.3 Elovich Rate Equation

The Elovich equation was developed to describe the kinetics of chemisorption of

gases onto solids and it is generally expressed as:

dqt/dt = α exp (-βqt)where,

‘qt’ is the amount of dye adsorbed (mg/g) by the adsorbent at time ‘t’

‘α’ is the initial adsorption rate (mg g-1 min-1) and

‘β’ is the desorption constant (g mg-1 ) during any experiment.

Assuming the initial boundary condition, q = 0 at t=0, the above equation on

integration become,

1/qt = 1/β ln (1+ αβt)

To simplify the Elovich’s equation, Chien and Clayton (1980) assumed αβ >> 1 and

applying the boundary conditions qt = 0 at t= 0 and qt = qt at t = t, equation becomes

(Zeldowitsch, 1934; Satish Patil et al., 2011)

qt = 1/β ln (αβ) +1/β ln t

This equation is commonly used for the chemisorptions and this model can be

applied with success in liquid solution (Gulmardes Gusmao et al., 2012). Elovich plots of

ln t vs q (amount of dye adsorbed (mg/g) by the adsorbent at time‘t’) gives a linear

relationship with a slope of 1/β and an intercept of 1/β ln (αβ). The Elovich rate equation

data obtained in this study for the adsorption of MB, MV, AB and AV from aqueous solution

onto BGA are summarised in Tables 43 - 46 and graphically shown in Figure 45 - 48. The

high correlation coefficient (r2) shows the successfulness of the Elovich model.

Attempts are made for the adsorption of the dyes used in this study from dyeing

industrial effluent onto BGA. The Elovich rate equation data obtained in this study are

summarised in the Tables 47 – 50 and the graphical representations are shown in Figures

49 - 52.

The higher value of initial adsorption rate (α) may be due to the greater surface area

of the adsorbent BGA, for the immediate adsorption of dyes from aqueous solution and

also from dyeing industrial effluent (Satish Patil et al., 2011). The value of desorption

constant (β) decreases with the increase of the initial concentration of the dye solutions.

107

The results obtained in this study are similar with the results reported for the

adsorption of methylene blue using teak tree bark powder by Satish Patil et al., (2011) and

the adsorption of methylene blue and genetian violet onto succinylated sugar cane bagasse

by Gulmardes Gusmao et al., (2012).

Table 43

Elovich Rate Equation for the Adsorption of Methylene Blue Dyefrom Aqueous Solution onto BGA

Conditions :


pH : 7.0 ± 0.2

Temperature : 32 ± 2˚ C

Timein minutes ln t

Initial Concentration of the Dye in mg/lAmount of dye adsorbed (q) in mg

60mg 80mg 100mg 120mg10 2.3030 50.3 62.6 75.7 79.6

20 2.9960 52.8 63.3 77.7 78.3

30 3.4012 53.3 67.6 82.4 83.8

40 3.6889 53.9 69.5 86.5 87.1

50 3.9120 54.4 70.7 87.2 89.2

60 4.0943 54.9 71.3 87.8 90.3

90 4.4998 55.4 71.9 88.5 92.1

120 4.7875 55.9 72.6 90.5 93.4

150 5.0106 56.4 73.8 91.2 94.8

180 5.1930 56.9 74.4 92.6 96.3

Intercept (1/β) x ln αβ 45.99 44.91 61.76 29.47

Slope (1/β) 2.140 6.019 6.123 12.522

Desorption Constant (β) 0.4673 0.1661 0.1633 0.0799Initial adsorption rateconstant (α) x102 2.715 1.549 1.471 0.348


108

Table 44

Elovich Rate Equation for the Adsorption of Methyl Violet Dyefrom Aqueous Solution onto BGA

Conditions :


pH : 7.0 ± 0.2


Timein minutes ln t


60mg 80mg 100mg 120mg10 2.3030 35.63 36.57 43.90 45.36

20 2.996 37.60 38.86 48.78 50.23

30 3.4012 39.68 45.71 53.66 55.81

40 3.6889 41.25 48.00 58.54 58.60

50 3.9120 43.13 52.57 63.41 66.98

60 4.0943 44.68 54.86 65.87 72.56

90 4.4998 45.23 57.14 70.73 75.35

120 4.7875 46.88 59.43 73.17 80.93

150 5.0106 47.08 61.71 75.61 86.51

180 5.1930 48.75 64.00 78.05 89.30

Intercept (1/β) x ln αβ 24.57 25.72 12.81 9.66

Slope (1/β) 0.46 0.434 1.263 1.486

Desorption Constant(β) 0.2090 0.0995 0.0792 0.0657

Initial adsorption rateconstant (α) x102 6.074 3.2477 3.4834 2.5646


109

Table 45

Elovich Rate Equation for the Adsorption of Acid Blue Dyefrom Aqueous Solution onto BGA

Conditions :


pH : 7.0 ± 0.2


Timein minutes ln t


60mg 80mg 100mg 120mg

10 2.3030 32.00 36.67 38.46 45.00

20 2.996 33.33 38.33 40.39 47.14

30 3.4012 34.67 41.67 44.23 49.29

40 3.6889 37.33 43.33 46.15 51.43

50 3.9120 38.67 45.00 50.00 55.71

60 4.0943 40.00 48.33 53.85 60.00

90 4.4998 42.67 51.67 57.69 62.14

120 4.7875 44.00 56.67 63.46 64.29

150 5.0106 45.33 58.33 67.31 68.57

180 5.1930 46.67 60.00 69.23 72.86

Intercept (1/β)x ln αβ 17.54 12.70 11.66 18.13

Slope (1/β) 5.497 8.848 8.126 9.906

Desorption Constant (β) 0.1819 0.1169 0.1231 0.1010



110

Table 46

Elovich Rate Equation for the Adsorption of Acid Violet Dyefrom Aqueous Solution onto BGA

Conditions :


pH : 7.0 ± 0.2


Timein minutes ln t


60mg 80mg 100mg 120mg

10 2.3030 17.7 27.4 35.72 45.3

20 2.996 19.4 31.6 38.10 48.7

30 3.4012 21.2 33.7 40.48 51.0

40 3.6889 24.7 35.8 42.86 56.0

50 3.9120 26.5 37.9 47.62 59.3

60 4.0943 28.2 40.0 52.38 62.0

90 4.4998 30.0 42.1 57.14 68.0

120 4.7875 31.8 44.2 61.91 75.3

150 5.0106 33.5 46.3 66.67 78.0

180 5.1930 37.1 50.5 69.05 80.7

Intercept (1/β)x ln αβ 1.5664 8.6046 0.6691 1.6694

Slope (1/β) 6.7375 7.6077 12.6668 17.1647

Desorption Constant (β) 0.1484 0.1315 0.0789 0.0583


Correlation Coefficient(r2) 0.9841 0.9884 0.9591 0.9904

111

Figure 45

Figure 46

40

60

80

100

2 2.5 3Amou

nt o

f dye

ads

orbe

d (q

) in

mg

Elovich Rate Equation for the Adsorption of Methylene BlueDye from Aqueous Solution onto BGA

60mg

30

50

70

90

2 2.5 3Amou

nt o

f dye

ads

orbe

d (q

) in

mg

Elovich Rate Equation for the Adsorption of Methyl VioletDye from Aqueous Solution onto BGA

60mg

111

Figure 45

Figure 46

3 3.5 4 4.5 5 5.5ln t


80mg 100mg 120 mg

3 3.5 4 4.5 5 5.5ln t

Elovich Rate Equation for the Adsorption of Methyl VioletDye from Aqueous Solution onto BGA

80mg 100mg 120 mg

111

Figure 45

Figure 46

5.5


5.5

112

Figure 47

Figure 48

30

40

50

60

70

80

2 2.5 3 3.5 4 4.5 5 5.5Amou

nt o

f dye

ads

orbe

d (q

) in

mg

ln t

Elovich Rate Equation for the Adsorption of Acid Blue Dyefrom Aqueous Solution onto BGA

60mg 80mg 100mg 120 mg

30

40

50

60

70

80

2 2.5 3 3.5 4 4.5 5 5.5Amou

nt o

f dye

ads

orbe

d (q

) in

mg

ln t

Elovich Rate Equation for the Adsorption of Acid Violet Dyefrom Aqueous Solution onto BGA

60mg 80mg 100mg 120 mg

113

Table 47

Elovich Rate Equation for the Adsorption of Methylene Blue Dyefrom Dyeing Industrial Effluent onto BGA

Conditions :


pH : 7.0 ± 0.2


Timein minutes ln t

Initial Concentration of the Dye in mg/l


60mg 80mg 100mg

10 2.3030 26.11 31.36 35.21

20 2.9960 27.78 32.00 35.91

30 3.4012 28.33 32.64 36.62

40 3.6889 29.44 33.28 38.03

50 3.9120 30.00 33.92 38.73

60 4.0943 31.11 36.48 40.14

90 4.4998 32.22 37.76 41.55

120 4.7875 32.78 41.60 42.25

150 5.0106 33.89 42.24 43.66

180 5.1930 34.44 43.54 45.07

Intercept (1/β)x ln αβ 19.00 19.05 26.34

Slope (1/β) 2.90 4.32 3.32

Desorption Constant (β) 0.3448 0.3016 0.2315

Initial adsorption constantrate (α) x102 4.988 2.931 1.044


114

Table 48

Elovich Rate Equation for the Adsorption of Methyl Violet Dyefrom Dyeing Industrial Effluent onto BGA

Conditions :

Adsorbent Dosage : 500mgpH : 7.0 ± 0.2


Timein minutes ln t



60mg 80mg 100mg

10 2.3030 26.51 34.78 42.86

20 2.996 27.91 36.52 46.93

30 3.4012 29.30 38.26 48.98

40 3.6889 30.70 40.00 51.02

50 3.9120 36.28 48.70 53.06

60 4.0943 37.67 50.44 57.14

90 4.4998 39.07 52.17 63.26

120 4.7875 43.26 55.65 65.31

150 5.0106 44.65 57.39 67.35

180 5.1930 46.05 60.87 69.39


Slope (1/β) 7.5615 9.8191 9.9034




115

Table 49

Elovich Rate Equation for the Adsorption of Acid Blue Dyefrom Dyeing Industrial Effluent onto BGA

Conditions :


pH : 7.0 ± 0.2


Timein minutes ln t


Amount of dye adsorbed (q) in mg60mg 80mg 100mg

10 2.3030 28.6 35.3 38.5

20 2.996 30.8 37.2 41.0

30 3.4012 34.2 38.8 43.2

40 3.6889 36.6 40.7 45.2

50 3.9120 40.0 42.9 47.4

60 4.0943 43.5 45.5 49.6

90 4.4998 45.9 47.9 53.1

120 4.7875 47.4 51.0 55.8

150 5.0106 49.1 53.2 58.9

180 5.1930 52.2 56.0 61.7


Slope (1/β) 8.6101 7.4471 8.2514


Initial adsorption constantrate (α) x102

0.7047 0.3631 0.3871


116

Table 50

Elovich Rate Equation for the Adsorption of Acid Violet Dyefrom Dyeing Industrial Effluent onto BGA

Conditions :


pH : 7.0 ± 0.2


Timein minutes

ln tInitial Concentration of the Dye in mg/l

Amount of dye adsorbed (q) in mg60mg 80mg 100mg

10 2.3030 23.75 32.31 39.62

20 2.996 26.25 32.94 41.51

30 3.4012 27.50 36.08 43.40

40 3.6889 30.00 39.22 45.28

50 3.9120 31.25 42.35 47.17

60 4.0943 35.00 43.92 47.17

90 4.4998 36.25 45.49 50.94

120 4.7875 37.50 47.06 52.83

150 5.0106 38.75 48.63 56.60

180 5.1930 41.25 50.20 60.38


Slope (1/β) 6.016 6.777 6.139

Desorption constant (β) 0.1662 0.1476 0.1329



117

Figure 49

Figure 50

25.0

30.0

35.0

40.0

45.0

50.0

2 2.5 3 3.5 4 4.5 5 5.5

Amou

nt o

f dye

ads

orbe

d (q

)in m

g

ln t

Elovich Rate Equation for the Adsorption of Methylene BlueDye from Dyeing Industrial Effluent onto BGA

60mg 80mg 100mg

20

30

40

50

60

70

2 2.5 3 3.5 4 4.5 5 5.5Am

ount

of d

ye a

dsor

bed

(q) i

n m

g

ln t

Elovich Rate Equation for the Adsorption of Methyl Violet Dyefrom Dyeing Industrial Effluent onto BGA

60mg 80mg 100mg

118

Figure 51

Figure 52

25

35

45

55

65

2 2.5 3 3.5 4 4.5 5 5.5Amou

nt o

f dye

ads

orbe

d (q

) in

mg

ln t

Elovich Rate Equation for the Adsorption of Acid Blue Dyefrom Dyeing Industrial Effluent onto BGA

60mg 80mg 100mg

2025303540455055606570

2 2.5 3 3.5 4 4.5 5 5.5Amou

nt o

f dye

ads

orbe

d (q

) in

mg

ln t

Elovich Rate Equation for the Adsorption of Acid Violet Dyefrom Dyeing Industrial Effluent onto BGA

60mg 80mg 100mgLinear (60mg) Linear (80mg) Linear (100mg)

119

4.9 Adsorption Isotherms

The application of adsorption isotherm is very useful to describe the interaction

between the adsorbate and the adsorbent of any system. The parameters obtained from

the adsorption isotherms provide important information on the adsorption mechanism, the

surface properties and affinities of the adsorbent (Vargas et al., 2011). The equilibrium

isotherm value is of fundamental importance for the design and optimisation of the

adsorption system for the removal of the dyes from aqueous solution. Therefore, it is

necessary to establish the most appropriate correlation for the equilibrium curves

(Saeed et al., 2010).

In the present study, the most commonly used isotherm models, namely, the

Langmuir and Freundlich adsorption isotherms, are used to describe the adsorption

equilibrium. Adsorption isotherms are studied by varying the initial concentration of the dye

solution (Methylene Blue, Methyl Violet, Acid Blue and Acid Violet) using the adsorbent

Blue-Green Algae (BGA).

4.9.1 Langmuir Adsorption Isotherm

Langmuir adsorption isotherm was developed by Irvin Langmuir, describe the

surface coverage of adsorbate on a solid surface. Langmuir adsorption isotherm is based

on the assumption that points of valency exist on the surface of the adsorbent and that

each of these sites is capable of adsorbing only one molecule. Thus, the adsorbed layer

will be one molecule thickness. Further, it is assumed that all the adsorption sites have

equal affinities for the adsorbate and the presence of adsorbed molecules at one site will

not affect the adsorption of molecules at an adjacent site (Renugadevi et al., 2009a). The

intermolecular forces decrease rapidly with distance, and consequently the existence of

monolayer coverage of the adsorbate at the outer surface can be predicted

(Saeed et al., 2010). The Langmuir adsorption isotherm is generally expressed as

(Langmuir, 1916; Renugadevi et al., 2009a)

k1 Cex/m =

1 + k11Ce

where,

x is the amount of the dye adsorbed (mg/l),

m is the amount of adsorbent (mg),

Ce is the equilibrium concentration of dye adsorbed on BGA and

120

k1 is a Langmuir constant corresponding to the measure of maximum energy of

adsorption capacity.

On rearranging, the above equation becomes,

m/x = 1/ (k1/ k11) + 1/ k1Ce

The linear plot of 1/Ce versus m/x (Figure 53 - 60) obtained in this study shows

the applicability of Langmuir adsorption isotherm indicating the formation of monolayer

coverage of adsorbate on the surface of the adsorbent Blue-Green Algae. The Langmuir

adsorption isotherm data obtained for the removal of dyes from aqueous solution and from

dyeing industrial effluents onto BGA are summarised in the Tables 51 - 58 and the

graphical representations are shown in Figures 53 - 60.

Separation Factor (RL): The effect of isotherm has been taken into consideration

with a view to predict whether the studied adsorption system is favourable or unfavourable.

The essential characteristics of Langmuir isotherm can be expressed in terms of a

dimensionless constant, separation factor or equilibrium parameter ‘RL’ which is defined as

RL = 1 / 1+ bC0where,

C0 is the initial concentration of the dye solution and

b is the Langmuir constant.

The value of RL and the feasibility of the adsorption process are as follows

(Unuabonah et al., 2009):

RL value Type of isotherm

RL > 1

RL = 1

RL < 1

RL = 0

Unfavourable

Linear

Favourable

Irreversible

In this study, RL values obtained are found to be less than one, confirming the

favourable uptake of the dyes onto BGA adsorbent. The Langmuir model shows the best fit

with the highest correlation coefficient (r2) values in the range of 0.9759 - 0.9971, indicates

the feasibility of the adsorption of the dyes from aqueous solution and from dyeing

industrial effluents using the adsorbent Blue-Green Algae, also suggest the monolayer

121

coverage of the dyes onto BGA (Yi Liu et al., 2010) and the homogeneous distribution of

active sites on the surface of the adsorbent BGA.

Similar results have been reported in the adsorption of methylene blue on defatted

carica papaya seeds (Unuabonah et al., 2009), vermiculite hydrogel composites

(Yi Liu et al., 2010), and annona squmosa seed activated carbon (Santhi et al., 2010).

122

Table 51

Langmuir Isotherm for the Adsorption of Methylene Blue Dyefrom Aqueous Solution onto BGA

Timein

minutes

InitialConcentration

in mg/l1/Ce m/x Separation

Factor RL

Interceptk1

1 / k1

Slope1/ k1

1

CorrelationCoefficient

r2

10

6080

100120

0.10270.05760.04110.0172

9.9488.0767.9826.607

0.04810.03650.02940.0246

6.62 30.43 0.7379

20

6080

100120

0.13930.05970.04480.0189

9.4667.9047.4346.435

0.03820.02890.02330.0195

6.45 24.08 0.8528

30

6080

100120

0.14990.08070.05690.0195

9.3767.3976.0667.269

0.03820.02890.02330.0196

6.34 23.93 0.7909

40

6080

100120

0.16260.09490.07400.0218

9.2857.1985.7816.744

0.03880.02940.02360.0198

5.47 24.21 0.7949

50

6080

100120

0.17900.10750.07800.0234

9.1917.0725.7346.477

0.03290.02480.02000.0167

5.47 20.34 0.8869

60

6080

100120

0.21650.11520.08220.0252

9.1127.0116.2316.066

0.03360.02540.02040.0171

5.34 20.68 0.9381

90

6080

100120

0.21650.12410.08700.0279

9.0296.9505.9495.647

0.03230.02440.01960.0164

4.86 19.90 0.9227

120

6080

100120

0.24390.13440.10570.0327

8.9456.8915.5925.522

0.04310.03270.02630.0220

4.53 27.39 0.9339

150

6080

100120

0.27860.13440.11390.0397

8.8646.7755.4815.275

0.03450.02590.02080.0174

4.26 21.17 0.9601

180

6080

100120

0.32460.17920.12330.0422

8.7846.7195.4415.192

0.03160.02390.01920.0161

4.58 19.60 0.9759

123

Langmuir Isotherm for the Adsorption of Methylene Blue Dyefrom Aqueous Solution onto BGA

Figure 53

124

Table 52

Langmuir Isotherm for the Adsorption of Methyl Violet Dyefrom Aqueous Solution onto BGA

Timein

minutes


in mg/l1/Ce m/x

SeparationFactor

RL

Interceptk1/ k1

1Slope1/ k1

1CorrelationCoefficient

r2

10

6080100120

0.04100.02300.01780.0143

14.03313.67211.38909.954

0.09980.08480.06980.0545

9.05 13.37 0.8207

20

6080100120

0.04440.02430.01780.0143

13.30012.87010.25009.430

0.11000.09340.07670.0600

8.44 11.99 0.8444

30

6080100120

0.04840.02910.02150.0155

12.69010.93009.32008.960

0.11220.09520.07810.0611

7.11 11.74 0.9843

40

6080100120

0.05330.03130.02410.0163

12.12010.42008.54008.530

0.12530.10610.08690.0677

6.65 10.41 0.9609

50

6080100120

0.05920.03620.02780.0189

11.59009.51007.89007.470

0.12250.10370.08500.0663

5.33 10.66 0.9862

60

6080100120

0.06670.03980.02930.0211

11.11009.11007.59006.890

0.13870.11720.09580.0743

5.02 9.33 0.9906

90

6080100120

0.06670.04370.03420.0234

11.11008.75007.07006.340

0.11530.09770.08020.0627

3.53 11.40 0.9923

120

6080100120

0.07620.04860.03730.0256

10.67008.41006.83006.180

0.14100.11920.09730.0755

3.72 9.16 0.9931

150

6080100120

0.07620.05470.04100.0299

10.67008.10006.61005.780

0.12190.10320.08460.0659

2.38 10.73 0.9964

180

6080100120

0.08890.06250.04560.0325

10.26007.81006.41005.600

0.15350.12950.10560.0817

2.72 8.37 0.9971

125

Langmuir Isotherm for the Adsorption of Methyl Violet Dyefrom Aqueous Solution onto BGA

Figure 54

Table 53

126

Langmuir Isotherm for the Adsorption of Acid Blue Dyefrom Aqueous Solution onto BGA

Timein

minutes


in mg/l1/Ce m/x

SeparationFactor

RL

Interceptk1/ k1

1Slope1/ k1


r2

10

6080

100120

0.03570.02300.01620.0133

15.6313.6413.0011.11

0.24430.19520.16250.1392

9.16 0.00862 0.7789

20

6080

100120

0.03750.02390.01680.0137

15.0013.0512.3810.61

0.23320.18570.15430.1319

8.99 0.00610 0.9563

30

6080

100120

0.03950.02610.01790.0141

14.4211.9911.3110.14

0.22180.17610.14600.1247

8.09 0.00629 0.9875

40

6080

100120

0.04410.02730.01860.0146

13.3911.5410.839.72

0.20330.16040.13280.1132

8.34 0.00863 0.9875

50

6080

100120

0.04410.02730.01860.0146

12.9311.1110.008.98

0.17540.13760.11320.0961

7.42 0.00784 0.9888

60

6080

100120

0.05000.03160.02170.0166

12.510.359.298.33

0.16810.13160.10810.0918

6.48 0.00825 0.9966

90

6080

100120

0.05770.03530.02360.0172

11.729.688.678.05

0.13080.10140.08280.0699

6.51 0.0111 0.9999

120

6080

100120

0.06250.04290.02740.0179

11.368.827.887.78

0.14580.11350.09290.0787

5.87 0.0122 0.957

150

6080

100120

0.06820.04620.03060.0194

11.038.5727.4287.290

0.13330.10340.08450.0714

5.32 0.0126 0.9693

180

6080

100120

0.07510.05000.03250.0212

10.718.33

7.2226.86

0.10840.08350.06790.0573

5.02 0.137 0.9847

127

Langmuir Isotherm for the Adsorption of Acid Blue Dyefrom Aqueous Solution onto BGA

Figure 55

128

Table 54

Langmuir Isotherm for the Adsorption of Acid Violet Dyefrom Aqueous Solution onto BGA

Timein

minutes


in mg/l1/Ce m/x

SeparationFactor

RL

Interceptk1/ k1

1Slope1/ k1

1


r2

10

6080

100120

0.02360.01900.01560.0134

28.3318.2713.9911.03

0.20330.16070.13280.1132

8.4961 0.0065 0.8855

20

6080

100120

0.02460.02070.01620.0144

25.7615.8313.1209.87

0.23320.18570.15430.1311

8.3146 0.0055 0.9913

306080

100120

0.02580.02160.01680.0156

23.6114.8512.3508.93

0.22180.17610.14600.1247

7.6174 0.0059 0.9988

40

6080

100120

0.02830.02260.01750.0179

20.2413.9711.6707.8

0.20330.16070.13280.1132

7.8661 0.00650.9816

50

6080

100120

0.02980.02380.01910.0197

18.8913.2010.4907.21

0.17540.13760.11320.0961

7.4191 0.00780.9888

606080

100120

0.03150.02500.02090.0208

17.7112.5009.5506.94

0.16810.13160.10810.0917

6.4835 0.00830.9966

90

6080

100120

0.3330.02640.02330.0250

16.6711.8708.7506.25

0.13080.10140.08280.0691

6.5069 0.011 0.9999

1206080

100120

0.03540.02790.02620.0288

15.7411.3108.0805.86

0.14580.11350.09290.0785

5.0264 0.0098 0.9990

150

6080

100120

0.03780.02960.03030.0313

14.9110.8007.4905.68

0.13330.10340.08450.0714

4.5919 0.0108 0.9951

180

6080

100120

0.03780.02960.03030.0313

14.9110.8007.4905.68

0.10840.08350.06790.0573

5.0225 0.0137 0.9847

129

Langmuir Isotherm for the Adsorption of Acid Violet Dyefrom Aqueous Solution onto BGA

Figure 56

130

Table 55Langmuir Isotherm for the Adsorption of Methylene Blue Dye

from Dyeing Industrial Effluent onto BGA

Timein

minutes


in mg/l 1/Ce m/xSeparation

FactorRL

Interceptk1/ k1

1Slope1/ k1

1


r2

106080

100

0.02950.02060.0154

19.1515.9414.2

0.045140.033140.02761

-0.0248 0.002840.9998

206080

100

0.03010.02080.0156

17.9915.6313.92

0.056560.042900.03465

-0.0347 0.003590.9976

306080

100

0.03160.02110.0158

17.6515.3213.65

0.062270.047440.03832

-0.0369 0.00399 0.9957

406080

100

0.03270.02140.0161

17.6515.3213.65

0.065190.046550.04025

-0.0418 0.00419 0.9939

506080

100

0.03330.02170.0163

16.0713.7112.46

0.07320.05590.0425

-0.0429 0.00474 0.9995

606080

100

0.03460.02290.0167

16.0713.7112.46

0.076220.058280.04717

-0.0451 0.00496 0.9999

906080

100

0.03590.02370.0171

15.5213.2412.03

0.082240.062970.05102

-0.0477 0.005380.9999

1206080

100

0.03670.0260.0173

15.2512.0211.83

0.07140.0546

0.04425-0.0336 0.00463 0.9152

1506080

100

0.03830.02650.0177

14.7511.8411.45

0.082650.063290.05128

-0.0412 0.005420.9456

1806080

100

0.03910.02740.0182

14.5211.4911.09

0.08070.06170.0500

-0.0367 0.00525 0.9401

131

Langmuir Isotherm for the Adsorption of Methylene Blue Dyefrom Dyeing Industrial Effluent onto BGA

Figure 57

132

Table 56

Langmuir Isotherm for the Adsorption of Methyl Violet Dyefrom Dyeing Industrial Effluent onto BGA

Timein

minutes



FactorRL

Interceptk1/ k1

1Slope1/ k1

1


r2

106080

100

0.02990.02210.0175

18.8614.3811.67

0.28670.21490.1719

1.5082 0.0017 0.9999

206080

100

0.03110.02290.0188

17.9213.6910.65

0.28720.21540.1723

-0.0362 0.0017 0.9957

306080

100

0.03260.02390.0196

17.0713.0710.21

0.32130.24090.1928

0.2850 0.00190.9957

406080

100

0.03410.02500.0204

16.2912.509.8

0.35830.26870.2149

0.5305 0.0022 0.9957

506080

100

0.04220.03200.0213

13.7810.2709.42

0.80210.60160.4813

4.5459 0.0048 0.9395

606080

100

0.04480.03380.0233

13.279.928.75

0.78990.59250.4739

3.4804 0.0047 0.9669

906080

100

0.04780.03590.0272

12.799.587.9

0.69390.52050.4164

1.2119 0.0042 0.9958

1206080

100

0.05970.04110.0288

11.568.997.66

1.30920.98190.7855

3.4804 0.0079 0.9979

1506080

100

0.06520.04420.0306

11.28.717.42

1.45461.09100.8728

4.1085 0.0087 0.9716

1806080

100

0.07170.05230.0326

10.868.217.21

1.78301.33730.9916

3.8798 0.0107 0.9667

133

Langmuir Isotherm for the Adsorption of Methyl Violet Dyefrom Dyeing Industrial Effluent onto BGA

Figure 58

134

Table 57

Langmuir Isotherm for the Adsorption of Acid Blue Dyefrom Dyeing Industrial Effluent onto BGA

Time inminutes


in mg/l1/Ce m/x

SeparationFactor RL

Interceptk1/ k1

1Slope1/ k1


(r2)

106080

100

0.02760.02100.0167

21.115.512.6

0.21630.16230.1298

-0.3390.0013 0.9977

206080

100

0.02960.02130.0171

19.115.212.1

0.30520.22890.1831

3.0579 0.0018 0.9915

306080

100

0.03080.02280.0177

18.213.911.5

0.32590.24450.1956

2.3858 0.0019 0.999

406080

100

0.03330.02520.0183

16.712.811.0

0.44030.33020.2642

3.8827 0.0026 0.9922

506080

100

0.03480.02660.0189

16.011.810.6

0.48830.36620.2929

4.0045 0.0029 0.9966

606080

100

0.04000.02770.0189

14.311.410.6

0.95980.71980.5759

7.4112 0.0058 0.9972

906080

100

0.04200.02900.0204

13.810.99.8

0.89430.67070.5366

5.8561 0.0054 0.9933

1206080

100

0.04440.03040.0212

13.310.69.5

0.98640.73980.5919

5.7337 0.0059 0.9944

1506080

100

0.04710.0320.023

12.910.38.8

0.98410.73810.5905

4.9062 0.0059 0.9998

1806080

100

0.0530.03360.0252

12.129.968.28

1.00000.93670.7493

-0.0368 0.0075 0.9884

135

Langmuir Isotherm for the Adsorption of Acid Blue Dyefrom Dyeing Industrial Effluent onto BGA

Figure 59

136

Table 58

Langmuir Isotherm for the Adsorption of Acid Violet Dyefrom Dyeing Industrial Effluent onto BGA

Timein

minutes



FactorRL

Interceptk1/ k1

1Slope1/ k1

1


(r2)

106080

100

0.027590.020970.01656

21.0515.4812.62

0.21630.16220.1299

-0.3390 0.001298 0.9977

206080

100

0.02960.021250.0171

19.0515.1812.05

0.30520.22890.1831

3.0579 0.001831 0.9915

306080

100

0.030770.022770.01767

18.1813.8611.52

0.32590.24450.1956

2.3858 0.001956 0.9990

406080

100

0.033330.024520.01827

16.6712.7511.04

0.44030.33020.2642

3.8827 0.002642 0.9922

506080

100

0.034780.026560.01893

16.0011.8110.60

0.48830.36620.2929

4.0045 0.00293 0.9966

606080

100

0.04000.02770.0189

14.2911.3810.60

0.95970.71980.5759

7.4112 0.005759 0.9972

906080

100

0.04200.02900.0204

13.7910.999.82

0.89430.67070.5366

5.8561 0.005366 0.9933

1206080

100

0.04440.03040.0212

13.3310.639.46

0.98640.73980.5919

5.7337 0.005919 0.9944

1506080

100

0.04710.0320.023

12.9010.288.83

0.98410.73810.5905

4.9062 0.005905 0.9998

1806080

100

0.0530.03360.0252

12.129.968.28

1.24880.93670.7493

-0.0368 0.007494 0.9884

137

Langmuir Isotherm for the Adsorption of Acid Violet Dyefrom Dyeing Industrial Effluent onto BGA

Figure 60

138

4.9.2 Freundlich Adsorption Isotherm

The Freundlich isotherm is an empirical equation that can be used for heterogeneous

systems with the interaction between the adsorbate and the surface of the adsorbent

(Vargas et al., 2011). This model can be successfully adopted to almost all physical

adsorption process. The empirical equation proposed by Freundlich is,

x/m = Kf Ce1/n

Taking log on both side and rearranging, the linear form of the Freundlich isotherm

(Freundlich, 1906; Renugadevi et al., 2011) is given by the following equation:

log x/m = logKf + 1/n log Ce

where,

x = amount of dye adsorbed (mg/l)

m = amount of adsorbent (mg)

Ce = equilibrium concentration of dye adsorbed on BGA(mg/g)

Kf and 1/n are Freundlich constants, which are related to the adsorption capacity and

adsorption intensity respectively and x/m is the amount of adsorbate at equilibrium.

The Freundlich adsorption isotherm plots are obtained by plotting log x/m vs log Ce

for different concentration (60, 80, 100 and 120mg/l) of the dye solutions. The plots

obtained are linear shows the applicability of Freundlich adsorption isotherm for the

removal of the dyes from aqueous solution and from dyeing industrial effluent using BGA

as an adsorbent. The corresponding isotherms drawn are given in Figures 61 – 68. The

slope values indicate the adsorption intensity (1/n) and the intercept values give an idea

about the adsorption capacity (Kf). These values are tabulated in the Tables 59 - 66.

The ‘n’ is an empirical parameter that varies with the degree of heterogeneity and is

related to the distribution of dye species on the adsorbent surface. In general, n > 1

illustrates that adsorbate is favourably adsorbed on an adsorbent and higher the ‘n’ value,

stronger the adsorption intensity (Aksu and Balibek, 2010; Chakraborty et al., 2011). In

this study, the value of ‘n’ is greater than unity, indicating the favourable adsorption of the

dyes (MB, MV, AB and AV) onto BGA (Ahmad and Kumar, 2010) and a physical process

(Sen et al., 2011). The value of ‘n’ lies between 2 and 3 indicates an effective adsorption

(Satish Patil et al., 2011).

139

The value of the Freundlich constant, Kf represents the degree of adsorption

(Chakraborty et al., 2011) and higher values of Kf confirm the easy uptake of adsorbate

from the solution. The correlation coefficient (r2) confirms the validity of Freundlich

adsorption isotherm with the experimental data.

Similar results were obtained for the adsorption of methylene blue onto a biomass-

based activated carbon (Mittal et al., 2010) and acid violet onto various low cost

adsorbents (Kannan et al., 2008).

140

Table 59

Freundlich Isotherm for the Adsorption of Methylene Blue Dyefrom Aqueous Solution onto BGA

Timein

minutes


in mg/llog Ce log x/m

Interceptlog Kf Kf

Slope1/n n


r2

10

6080

100120

0.98861.23961.38601.7641

-0.9977-0.9072-0.9021-0.8200

1.057 0.3009 0.448 2.2 0.9769

206080

100120

0.85611.22381.34831.7221

-0.9762-0.8979-0.8086-0.8712

1.059 0.3467 0.285 3.5 0.6829

306080

100120

0.82411.09341.24481.7094

-0.9720-0.8690-0.8615-0.7829

1.116 0.3275 0.217 4.6 0.9622

406080

100120

0.78891.02281.13071.6614

-0.9967-0.8572-0.7620-0.9967

1.039 0.3539 0.465 2.2 0.5765

506080

100120

0.74800.96851.10701.6310

-0.9597-0.8495-0.7829-0.8114

1.002 0.3671 0.289 3.5 0.6894

606080

100120

0.71000.93851.08491.5993

-0.9600-0.8458-0.7829-0.8114

0.997 0.3691 0.269 3.7 0.7153

906080

100120

0.66460.90631.06031.5530

-0.9556-0.8420-0.7520-0.7380

-1.0635 0.3454 0.310 3.2 0.8619

1206080

100120

0.61280.87160.97561.4853

-0.9516-0.8383-0.7421-0.7476

1.032 0.3562 0.336 2.9 0.8023

150

6080

100120

0.55100.79240.94351.4018

-0.9476-0.8309-0.7389-0.7222

1.043 0.3523 0.329 3.0 0.8757

180

6080

100120

0.48860.74660.90901.3746

-0.9437-0.8273-0.7357-0.7153

1.024 0.3590 0.315 3.2 0.8897

141

Freundlich Isotherm for the Adsorption of Methylene Blue Dyefrom Aqueous Solution onto BGA

Figure 61

142

Table 60

Freundlich Isotherm for the Adsorption of Methyl Violet Dyefrom Aqueous Solution onto BGA

Time inminutes


in mg/llog Ce log x/m Intercept

log Kf

Kf Slope1/n

n CorrelationCoefficient

r2

10

6080

100120

1.38721.63831.74961.8447

-1.1472-1.1358-1.0565-0.9980

-1.6038 0.2041 0.3139 3.2 0.9501

20

6080

100120

1.35261.61441.74961.8447

-1.1239-1.1096-1.0107-0.9745

-1.5631 0.2129 0.3099 3.2 0.9678

30

6080

100120

1.31521.53611.66761.8097

-1.1034-1.0386-0.9694-0.9523

-1.5279 0.2116 0.3236 3.1 0.9922

40

6080

100120

1.27321.50451.61791.7878

-1.0835-1.0178-0.9314-0.9309

-1.4904 0.2315 0.3231 3.1 0.9998

50

6080

100120

1.22771.44191.55591.7235

-1.0641-0.9782-0.8971-0.8733

-1.5552 0.2159 0.4050 2.5 0.9996

60

6080

100120

1.17591.40011.53311.6757

-1.0457-0.9595-0.8802-0.8382

-1.5506 0.2153 0.4284 2.3 0.9992

90

6080

100120

1.17591.35951.46591.6308

-1.0457-0.9420-0.8494-0.8021

-1.6911 0.1862 0.5549 2.0 0.9956

120

6080

100120

1.11811.31331.42821.5917

-1.0281-0.9248-0.8344-0.7909

-1.6026 0.2034 0.5195 2.0 0.9965

150

6080

100120

1.1181.26201.38721.5243

-1.0281-0.9085-0.8202-0.7619

-1.7537 0.1732 0.6607 2.0 0.9897

180

6080

100120

1.05111.20411.34101.4881

-1.0112-0.8927-0.8069-0.7482

-1.6334 0.1952 0.6047 2.0 0.9898

143

Freundlich Isotherm for the Adsorption of Methyl Violet Dyefrom Aqueous Solution onto BGA

Figure 62

144

Table 61

Freundlich Isotherm for the Adsorption of Acid Blue Dyefrom Aqueous Solution onto BGA

Time inminutes



log Kf

Kf Slope1/n n


r2

106080

100120

1.4471.6371.7891.875

-1.1939-1.1348-1.1139-1.0457

-1.6491 0.1845 0.3124 3.2 0.9977

20

6080

100120

1.4261.6201.7751.863

-1.1761-1.1156-1.0927-1.0257

-1.6246 0.1893 0.3125 3.2 0.9984

306080

100120

1.4041.5841.7461.850

-1.1589-1.0788-1.0535-1.0060

-1.6050 0.1961 0.3224 3.1 0.9967

406080

100120

1.3561.5641.73121.8361

-1.1268-1.0622-1.0346-0.9877

-1.4974 0.2189 0.2741 3.7 0.9993

506080

100120

1.3291.5441.6991.808

-1.1116-1.0457-1.0000-0.9533

-1.5443 0.2135 0.3239 3.1 0.9973

60

6080

100120

1.3011.5011.6641.778

-1.0969-1.0149-0.9680-0.9206

-1.5646 0.2022 0.3616 2.8 0.9995

906080

100120

1.2391.4531.6261.762

-1.0689-0.9857-0.9380-0.9058

-1.4484 0.2349 0.3117 3.2 0.9534

1206080

100120

1.20411.36791.56281.7459

-1.0554-0.9455-0.8965-0.8909

-1.3799 0.2322 0.2944 3.4 0.9557

1506080

100120

1.16641.33591.51441.7112

-1.0426-0.9331-0.8709-0.8627

-1.3962 0.2476 0.3274 3.1 0.9234

180

6080

100120

1.12481.30101.48811.6734

-1.0298-0.9206-0.8585-0.8363

-1.3993 0.2468 0.3493 2.9 0.9537

145

Freundlich Isotherm for the Adsorption of Acid Blue Dyefrom Aqueous Solution onto BGA

Figure 63

146

Table 62

Freundlich Isotherm for the Adsorption of Acid Violet Dyefrom Aqueous Solution onto BGA

Time inminutes



log Kf

Kf Slope1/n

nCorrelationCoefficient

(r2)

106080

100120

1.6271.7211.8081.873

-1.4523-1.2617-1.1459-1.0426

-4.1018 0.01654 0.6059 1.7 0.9958

206080

100120

1.60841.68501.79181.8409

-1.4109-1.1995-1.1179-0.9943

-3.9889 0.01852 0.5801 1.6 0.9699

306080

100120

1.58911.66581.77471.8062

-1.3731-1.1717-1.0917-0.9509

-4.0441 0.01753 0.5456 1.7 0.9617

406080

100120

1.54771.64551.75691.7482

-1.3061-1.1452-1.0671-0.8921

-3.7160 0.02433 0.5122 1.6 0.8940

506080

100120

1.52541.62441.71921.7048

-1.2762-1.1206-1.0208-0.8579

-3.9721 0.01883 0.4546 1.8 0.8962

60

6080

100120

1.50201.60211.67781.6812

-1.2482-1.0969-0.9800-0.8414

-4.1715 0.015430.4595 1.9 0.9435

906080

100120

1.47711.57851.63211.6021

-1.2219-1.0745-0.9420-0.7959

-4.5114 0.01098 0.3037 2.2 0.8225

120

6080

100120

1.45091.55381.58091.5399

-1.1970-1.0535-0.8745-0.7679

-4.6545 0.00952 0.2107 2.4 0.7117

1506080

100120

1.42281.52741.52281.5052

-1.1735-1.0334-0.8745-0.7544

-4.6254 0.0098 0.1747 2.5 0.6537

180

6080

100120

1.36061.46941.49071.4673

-1.1300-0.9954-0.8597-0.7419

-4.1251 0.01616 0.2684 2.2 0.7697

147

Freundlich Isotherm for the Adsorption of Acid Violet Dyefrom Aqueous Solution onto BGA

Figure 64

148

Table 63

Freundlich Isotherm for the Adsorption of Methylene Blue Dyefrom Dyeing Industrial Effluent onto BGA

Time inminutes


in mg/l log Ce log x/m Interceptlog Kf

KfSlope

1/n nCorrelationCoefficient

(r2)

106080

100

1.53011.68691.8115

-1.2822-1.2025-1.1523

-1.9894 0.1368 0.4636 2.2 0.9979

206080

100

1.50811.68121.8068

-1.2550-1.1940-1.1436

-1.8166 0.1626 0.3717 2.7 0.9993

306080

100

1.50061.67541.8020

-1.2467-1.1853-1.1351

-1.8015 0.1651 0.3691 2.7 0.9994

406080

100

1.48521.66951.7922

-1.2299-1.1853-1.1351

-1.7619 0.1717 0.3558 2.8 0.9903

506080

100

1.47711.66351.7872

-1.2219-1.6849-1.1109

-1.5541 0.0115 0.1308 7.7 0.9750

606080

100

1.46071.63871.7771

-1.206-1.371

-1.0955-1.6949 0.0711 0.2897 3.5 0.9991

906080

100

1.44371.62571.7668

-1.1909-1.1219-1.0802

-1.6861 0.1852 0.3443 2.9 0.9977

1206080

100

1.43491.58431.7616

-1.1833-1.0799-1.0729

-1.6359 0.1948 0.3287 3.0 0.8697

1506080

100

1.41681.5771.7508

-1.1688-1.0734-1.0588

-1.6157 0.1988 0.3259 3.1 0.9112

1806080

100

1.40761.56211.7398

-1.1619-1.0603-1.0449

-1.6316 0.1956 0.3456 2.9 0.9037

149

Freundlich Isotherm for the Adsorption of Methylene Blue Dyefrom Dyeing Industrial Effluent onto BGA

Figure 65

150

Table 64

Freundlich Isotherm for the Adsorption of Methyl Violet Dyefrom Dyeing Industrial Effluent onto BGA

Time inminutes



logKf

Kf Slope1/n

n CorrelationCoefficient

(r2)

106080

100

1.52491.65541.7569

-1.2755-1.1578-1.0671

-2.64560.0710 0.8986 1.1 0.9999

206080

100

1.50641.63841.7246

-1.2533-1.1364-1.0274

-2.7992 0.0609 1.0228 1.0 0.9949

306080

100

1.48681.62051.7077

-1.2322-1.1163-1.0090

-2.7213 0.0658 0.9982 1.0 0.9952

406080

100

1.46691.60211.6899

-1.2119-1.0969-0.9912

-2.6508 0.0706 0.9776 1.0 0.9953

506080

100

1.37471.49551.6716

-1.1393-1.0116-0.9741

-1.8461 0.1579 0.5314 1.9 0.9162

606080

100

1.34871.47111.6326

-1.1229-0.9965-0.9420

-1.9427 0.1433 0.6214 1.6 0.9538

906080

100

1.32081.44451.5651

-1.1071-0.9814-0.8976

-2.2340 0.0658 0.8581 1.2 0.9942

1206080

100

1.22401.38621.5402

-1.0630-0.9538-0.8842

-1.7505 0.1071 0.5663 1.8 0.9937

1506080

100

1.18611.35431.5139

-1.0492-0.9400-0.8704

-1.6917 0.1737 0.5465 1.8 0.9937

1806080

100

1.14451.28151.4859

-1.0358-0.9143-0.8579

-1.5908 0.1842 0.5023 2.0 0.9487

151

Freundlich Isotherm for the Adsorption of Methyl Violet Dyefrom Dyeing Industrial Effluent onto BGA

Figure 66

152

Table 65

Freundlich Isotherm for the Adsorption of Acid Blue Dyefrom Dyeing Industrial Effluent onto BGA

Time inminutes


in mg/llogCe log x/m Intercept

logKf

Kf Slope1/n


(r2)

106080

100

1.53011.68691.8115

-1.2822-1.2025-1.1523

-1.9894 0.1368 0.4636 2.2 0.9979

206080

100

1.50811.68121.8068

-1.255-1.194-1.1436

-1.8165 0.1626 0.3717 2.7 0.9993

306080

100

1.50061.67541.8020

-1.2467-1.1853-1.1351

-1.8015 0.1651 0.3691 2.7 0.9994

406080

100

1.48521.66951.7922

-1.2299-1.1767-1.1189

-1.7618 0.1717 0.3558 2.8 0.9903

506080

100

1.47711.66351.7872

-1.6849-1.2219-1.1109

-4.4628 0.1153 1.9016 0.5 0.9750

606080

100

1.46071.63871.7771

-1.371-1.206-1.0955

-2.6438 0.0711 0.8734 1.2 0.9991

906080

100

1.44371.62571.7668

-1.1909-1.1219-1.0802

-1.6861 0.1852 0.3443 2.9 0.9977

1206080

100

1.43491.60001.7616

-1.1833-1.0799-1.0729

-1.6540 0.1913 0.3389 3.0 0.8957

1506080

100

1.41681.5771.7508

-1.1688-1.0734-1.0588

-1.6157 0.1988 0.3259 3.1 0.9112

1806080

100

1.40761.56211.7398

-1.1619-1.0603-1.0449

-1.6316 0.1956 0.3456 2.9 0.9037

153

Freundlich Isotherm for the Adsorption of Acid Blue Dyefrom Dyeing Industrial Effluent onto BGA

Figure 67

154

Table 66

Freundlich Isotherm for the Adsorption of Acid Violet Dyefrom Dyeing Industrial Effluent onto BGA

Time inminutes


in mg/llogCe log x/m Intercept

logKf

Kf Slope1/n


(r2)

106080

100

1.5591.6781.781

-1.323-1.1897-1.1011

-2.88170.0560

1.0026 1.0 0.9973

206080

100

1.5281.6731.767

-1.2799-1.1813-1.0809

-2.5381 0.0790 0.8197 1.2 0.9918

306080

100

1.5121.6431.753

-1.2596-1.1418-10615

-2.5031 0.0818 0.8240 1.2 0.9983

406080

100

1.4771.0001.610

41.738

2

-1.2219-1.1055-1.0430

-2.228 0.1078 0.6865 1.5 0.9872

506080

100

1.4591.5761.723

-1.2041-1.0722-1.0253

-2.15 0.1164 0.6622 1.5 0.9449

606080

100

1.3981.5571.723

-1.1550-1.0561-1.0253

-1.6987 0.1829 0.3975 2.5 0.9533

906080

100

1.3761.5381.691

-1.1396-1.0409-0.9921

-1.778 0.1689 0.4696 2.1 0.9845

1206080

100

1.3521.5181.674

-1.1248-1.0265-0.9759

-1.7449 0.1747 0.4638 2.2 0.9864

1506080

100

1.3271.4971.638

-1.1106-1.0119-1.9460

-1.8126 0.1632 0.5300 1.9 0.9982

1806080

100

1.2731.4741.598

-1.0835-0.9983-0.9180 -1.7256 0.1781 0.5011 2.0 0.9930

155

Freundlich Isotherm for the Adsorption of Acid Violet Dyefrom Dyeing Industrial Effluent onto BGA

Figure 68

156

4.10 Thermodynamic Studies

Thermodynamic parameters are the fundamental concept in which any chemical

system tends to attain a state of equilibrium, from the non-equilibrium state. The

thermodynamic parameter evaluates the nature of adsorbate and its magnitude during

adsorption process (Milind et al., 2010b). The Gibbs free energy change (∆G), the

enthalpy change (∆H) and the entropy change (∆S) for the adsorption of Methylene Blue,

Methyl Violet, Acid Blue and Acid Violet dyes from aqueous solution onto BGA are

determined using the following relations (Bahl et al., 2005).

Kc = qe / Ce

where,

Kc is the equilibrium constant

qe is the amount of dye adsorbed at equilibrium

Ce is the equilibrium concentration of dye adsorbed on BGA

By using the above relation, the value of Kc, the equilibrium constant is determined

and substituted in the following equation (Bahl et al., 2005),

∆G = - RT ln Kc ………………………Equation (A)

where,

R is the gas constant (8.314 J mole-1K-1) and

T is the Temperature in Kelvin

∆G values for the adsorption of the MB, MV, AB and AV dyes onto BGA adsorbent

are calculated by using the equation A. The Gibbs-Helmholtz equation (Bahl et al., 2005)is given below

∆G = ∆H - T∆S …………………………Equation (B)

From the equations A & B, the following relation is obtained,

ln Kc = - (∆H/ RT) + (∆S/ R)

157

Adsorption of Methylene Blue, Methyl Violet, Acid Blue and Acid Violet dyes using

500mg of the adsorbent BGA and 100ml of the dye solutions containing 100mg/l of the dye

at pH 7.0 ± 0.2 was carried out by varying the temperature (295K, 305K and 315K). The

Vant Hoff’s plots are obtained by plotting 1/T vs ln Kc (Figures 69 – 72). Enthalpy change

∆H and entropy change ∆S are obtained from the slope and intercept of the Vant Hoff’s

plots respectively. ∆G, ∆H and ∆S values obtained in this study are given in Table 67.

The negative values of the free energy change (∆G) indicate the feasibility and the

spontaneous nature of the adsorption, with respect to all the dyes used in this study.

The term ∆H indicates the heat change associated with the overall adsorption process. The

positive ∆H values imply that the adsorption of MB, MV, AB and AV dyes from aqueous

solution using adsorbent BGA is an endothermic process (Ma et al., 2012). The magnitude

of ∆H may give an idea about the type of adsorption. Basically, the heat evolved during

physical adsorption is in the range of 2.1-20.9kJ/mol and the heat of chemical adsorption

generally falls into a range of 80-200 kJ/mol (Chakraborty et al., 2011). The values of ∆H

for the adsorption of MB, MV, AB and AV dyes are given in Table 67, which indicate that

adsorption of these dyes would be attributed to physical adsorption.

The positive ∆S values obtained shows an increase in the randomness at

dye – BGA adsorbent interface which could possibly remove some of the adsorbed water

molecules from the adsorbent surface leading to higher dye removal (Rehman et al.,2012).

Similar results were obtained for the removal of methylene blue dye from aqueous

solution using the adsorbents rice husk (Safa and Bhatti, 2011), teak tree bark powder

(Satish Patil et al., 2011) and crystal violet dye from aqueous solution using the adsorbent

Opal (Ma et al., 2012).

158

Table 67

Thermodynamic Parameters for the Removal of Dyes from Aqueous Solution using Blue-Green Algae

Name of theDyes

Temperature(K) 1/T

qemg/g

cemg/g KC lnKC

∆GkJmol-1

∆HkJmol-1

∆SJmol-1K-1

MethyleneBlue

295 0.00339 87.84 12.16 7.2237 1.9774 -4.849821.1965 88.7443305 0.00328 91.89 8.11 11.3305 2.4275 -6.1556

315 0.00318 92.57 7.43 12.4589 2.5224 -6.6059

Methyl Violet

295 0.00339 73.17 26.83 2.7272 1.0033 -2.460729.2736 107.2323305 0.00328 78.05 21.95 3.5558 1.2686 -3.2169

315 0.00318 85.37 14.63 5.8353 1.7639 -4.6195

Acid Blue

295 0.00339 51.92 48.08 1.0799 0.0769 -1.886139.6414 135.5700305 0.00328 69.23 30.77 2.2499 0.8109 -2.0563

315 0.00318 75.00 25.00 3.0000 1.0986 -2.8771

Acid Violet

295 0.00339 54.76 45.24 1.2104 0.1910 -4.684532.7931 113.2202305 0.00328 69.05 30.95 2.2310 0.8025 -2.0349

315 0.00318 73.81 26.19 2.8183 1.0361 -2.7135

159

Figure 71 Figure 72

Figure 69 Figure 70

160

4.11 Scanning Electron Microscope and FTIR Spectral Analysis

Scanning Electron Microscope (SEM) Analysis has been a primary tool, for

characterising the fundamental surface morphology of an adsorbent. The surface

morphology of the adsorbent BGA before and after the dye adsorption are observed using

SEM analysis. Scanning Electron Micrograph of the adsorbent BGA and BGA with

adsorbed dye species used in this study are shown in Plate A and Plates B to Irespectively. This clearly indicates that the adsorbent BGA exhibits large number of pores

on the external surface and provides suitable binding sites for the dyes of MB, MV, AB and

AV from aqueous solution and from dyeing industrial effluents.

161

SEM Image of the Adsorbent BGA

Plate A

SEM Image of the Adsorbent with Adsorbed Methylene Blue Dye fromAqueous Solution (Plate B) and from Dyeing Industrial Effluent (Plate C)

Plate B Plate C

162


Plate A

SEM Image of the Adsorbent with Adsorbed Methyl Violet Dye from AqueousSolution (Plate D) and from Dyeing Industrial Effluent (Plate E)

Plate D Plate E

163


Plate A

SEM Image of the Adsorbent with Adsorbed Acid Blue Dye from AqueousSolution (Plate F) and from Dyeing Industrial Effluent (Plate G)

(Plate F) (Plate G)

164


(Plate A)

SEM Image of the Adsorbent with Adsorbed Acid Violet Dye from AqueousSolution (Plate H) and from Dyeing Industrial Effluent (Plate I)

(Plate H) (Plate I)

165

FTIR Spectral Analysis

Infrared Spectrum is an important record which gives sufficient information about the

structure of the organic compounds. The position of the peak or the band is used to identify

the presence of a particular functional group present in the compound. The infrared spectra

of the adsorbent BGA is shown in Figure 73.

The spectral data are assigned as below: (Sharma, 2012)

A broad and strong band stretch in the region between 3200cm-1 and 3600cm-1

indicates the presence of –NH2 groups and free or hydrogen bonded –OH groups.

Band at 1648.27cm-1 corresponds to the presence of -C=O group.

The band obtained at 1482.88cm-1 was due to the symmetric bending of CH3 group.

Band observed at 856.09cm-1 corresponds to ester group vibrations.

The band at 1082cm-1 might be due to P-OH stretching.

The IR spectrum of the adsorbent BGA supported the presence of –OH, -COOH,

–C=O, –NH2 and -P-OH functional groups present on the surface of Blue-Green Algae. The

functional groups present on the biomass Blue-Green Algae surface seems to play an

important role in dye adsorption. The adsorption of Methylene Blue, Methyl Violet, Acid Blue

and Acid Violet dyes onto BGA may be due to formation of hydrogen bonds formed

between the dye molecules and the adsorbent. Hydrogen bonds would occur between

hydroxyl, amine and carboxyl groups present on the adsorbent with the dye molecules

(Yonghui Lin et al., 2011).

166

FTIR Spectrum of the Adsorbent BGAFigure 73

166


166


167

Adsorption of Methylene Blue Dye onto BGA

BGA

NH2 C OH O H

O

S

N

NNC H 3

C H 3CH 3

C H 3+

Methylene Blue DyeOH H

OH C O N H

BGA

168

Adsorption of Methyl Violet Dye onto BGA

BGA

H N C O O H

H OH

Methyl Violet DyeOH H

OH C O N H

BGA

169

Adsorption of Acid Blue Dye onto BGA

BGA

OH C OH NH2

O

Acid Blue Dye

O H

OH C OH N H

BGA

169


BGA

OH C OH NH2

O

Acid Blue Dye

O H

OH C OH N H

BGA

169


BGA

OH C OH NH2

O

Acid Blue Dye

O H

OH C OH N H

BGA

170

Adsorption of Acid Violet Dye onto BGA

BGA

OH C OH N H

O H

Acid Violet Dye

OH

NH2 C O O H

BGA

170


BGA

OH C OH N H

O H

Acid Violet Dye

OH

NH2 C O O H

BGA

170


BGA

OH C OH N H

O H

Acid Violet Dye

OH

NH2 C O O H

BGA

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