Application of Olive Stone Based Activated Carbon in the ...5) Application of Olive... · activated...

Arab Journal of Nuclear Science and Applications, 47(3), (67-79) 2014

67

Application of Olive Stone Based Activated Carbon in the Sorption of Lanthanum (III) Ions from Aqueous Solution

H.M.H. Gad1*, M. M. S. Ali1, W.F Zaher1, E.A. El-Sofany1, S. A. Abo-El-Enein2

1 Hot Laboratory Center, Atomic Energy Authority,13759, Cairo, 2 Chemistry Department, Faculty of Science, Ain-shams University, Egypt.

E-mail: [email protected].

Received: 26/12/2013 Accepted: 16/1/2014 ABSTRACT

A biomass agricultural waste material, olive stone (OS) was used for preparation of activated carbon (AC) by chemical activation using 50% phosphoric acid (PA5) carbonized at 800ºC and holding time 90 min (OSPA58).The prepared AC was used for sorption of La(III) ions from nitrate solution.The effect of various factors such as shaking time, pH, carbon dose, particle size and different temperature on the adsorption capacity of Lanthanum onto activated carbon were quantitatively determined.The two equilibrium models; Langmuir and Freundlich, were discussed and the data were fit with Langmuir modelwith a monolayer capacity of 201.6 mg/g. The kinetics of sorption was described by a pseudo second-order rate model. Thermodynamic calculations pointed towards the feasibility of an adsorption process with spontaneous and endothermic nature with a value of ∆Gº= -19.3 KJ/mol, ∆H=10.98KJ/mol and ∆S=12.89x10-2KJ/mol.

Keywords: Activated Carbon, Olivestone, Lanthanum (III), Biosorption, Nitrate

Solution.

INTRODUCTION

Lanthanum is found in rare earth minerals such as cerite, monazite, allanite, and bastnasite. Monazite and bastnasite minerals are principal ores in which lanthanum occurs in percentages up to 25% and 38 % (1), respectively. Mischmetals are used in making lighter flints, contains about 25% lanthanum . Because lanthanum compounds bring about special optical qualities in glass, it is also used for the manufacture of specialized lenses. In addition, compounds of lanthanum with fluorine or oxygen are used in making carbonarc lamps for the motion picture industry(1). Lanthanum salts are included in the zeolite catalysts used in petroleum refining due to its stabilizing action on the zeolite at high temperatures(1). Due to increasing population and growth of technology the environmental pollution is the most serious problem that should be taken into consideration. Therefore, a number of investigations have been performed to prevent environmental pollution. In order to concentrate aqueous nuclear waste solutions containing metal ions into smaller volume, many processes are being used, such as precipitation, ion-exchange, solvent extraction and adsorption. The adsorption process has been used in the water and waste water industry for removal of color, odor and taste pollution (2–4). Adsorption onto various solids is important from purification,environmental and radioactive waste disposal point of view(5-7).The pre-concentration and separation procedures on adsorption phenomena are important in nuclear and radiation chemistry, industry, medicine and daily life(7). Lanthanide elements are the important fission product isotopes produced from irradiated nuclear fuel(1). Their removal is of major importance in treatment and disposal of radioactive wastes and its adsorption on solids is important for their pre-concentration and recovery and nuclear industry. Interest in the adsorption of metal ions for recovery purposeshas increased manifold in recent years, because of its simplicity, selectivity and efficiency(8). The adsorption process is suitable to adsorb and separate low molecular weight compounds and free metals. Useful adsorbents include carbon-based adsorbents such as activated carbon, zeolite-based, silica-based alumina-based and adsorptive resins such as styrene-vinyl benzene copolymers and acrylic polymers.


68

Activated carbons are the most popular adsorbents used for the removal of substances from water. This could be related to their extended surface area, high adsorption capacity, microporous structure and special surface reactivity(9). However, the adsorptive capacity of activated carbons depends mainly on the precursor nature (1), the operating conditions of adsorption (such as temperature and pH) and the nature of the adsorbate. About 50% of industrially available activated carbons are derived from precursors of botanical origin (10). These precursors are usually low-cost agricultural residues with no notable applications except as fuels for energy generation. Numerous agro-residue biomaterials have been used for the production of activated carbons, including olive stone, apricot stones, rice husk ash, nutshells and date pites (11-13). Olive stone used in this study is one of them, due to its high surface area, high adsorption capacity, microporous structure and special surface reactivity (8). Olive stone as the commodity waste, can be made into activated carbons which are used as adsorbents in water purification or the treatment of industrial wastewater (14, 15). It would add value to these agricultural commodities, help reduce the cost of waste disposal, and provide a potentially cheap alternative to the existing commercial carbons (16–19). Many researchers have prepared activated carbon from coals, resins and lignin–cellulose materials. However, the preparation of activated carbon from olive stone using a base leaching or acid-washing process has not been well studied. This study concerned with the preparation of activated carbon from olive stone using chemical activation by phosphoric acid and studying the factors affecting the sorption processes of La (III) ions from nitrate solution.

EXPERIMENTAL Preparation of Lanthanum solution:

The stock solution of lanthanum nitrate (1000 mgL−1) was prepared by dissolving a certain amount of lanthanum oxide (La2O3) in nitric acid. The resultant nitrate solution was carefully evaporated to dryness, washed by distilled water, and then dissolved in 0.1M sodium nitrate solution. Initial pH of Lanthanum solution was adjusted by the addition of HNO3 or NaOH. The concentration of La (III) ions were determined spectrophotometrically by Arsenazo (III) method. The samples were analyzed at wave length 650 using UV-visible spectrophotometer (Shimadzu model UV-1601). Preparation of activated carbon:

Olive stone, as an agro-residue byproduct, was chosen as a precursor for the production of activated carbons by one-step chemical activation using 50% H3PO4. In each experiment 30gm of olive stone was soaked in 50% phosphoric acid starting with 85 wt. % H3PO4 (BDH). The olive stone mass was soaked in 50 mL of H3PO4 solution, slightly agitated to ensure penetration of the acid throughout, then the mixture was heated to 80ºC for 1 hr and left overnight at room temperature to help appropriate wetting and impregnation of the precursor. The impregnated mass was dried in an air oven at 80ºC overnight then, admitted into the reactor (ignition tube), which was then placed in a tubular electric furnace open from both ends. The temperature was raised at the rate of 50ºC/10 min. to the required end temperature. The carbonization process was carried out at temperature of 800ºC for 1.5 hr. The product was thoroughly washed with hot distilled water, and finally dried at 110ºC.

Characterization of activated carbon: Particle size of prepared activated carbon was determined using sieves of different mesh size.

Packed and apparent densities were determined by using a 10mL graduated glass cylinder. Thetexture characteristics were determined by the standard N2adsorption isotherms, followed by their analysis to evaluate the porous parameters. Nitrogen adsorption isotherm was conducted at liquid nitrogen temperature using NOVA 1000e Quanta chrome.Surface area (SBET), mean pore diameter (d) and total pore volume (VP) were determined. The elemental analysis was measured by CHNS-O elemental analysis. Thermo gravimetric and differential thermal analyses of the prepared sample were determined. Fourier Transform-Infrared spectroscopy (FTIR):

IR spectra were analyzed using a Mattson 5000 FTIR spectrometer. These spectra were recorded on KBr discs of the dried sorbent. Before each measurement, the instrument was run to establish the background, which was then automatically subtracted from the sample spectrum.


69

Modification of Activated carbon:

The OSPA58 was modified by different modifier to study the effect of these modifications on the uptake of La(III) ions from nitrate solution: (1) Modification of OSPA58 by crystal violet (C.V); 0.05gm of OSPA58 was impregnated in 10ml of 100 mg/L of C.V. The result impregnated material was stirred for 2 hr, and then the impregnated material was dried at 70◦C overnight. (2) Modified of OSPA58 by carbon disulfide (CS2)/n-hexane; 0.25gm of OSPA58 was impregnated in 50 mL of 60% CS2/ n-hexane. The resulted impregnated material was stirred for 2 hr and n-hexane was then removed by evaporation at room temperature (25◦C), and then the impregnated material was dried at 70◦C overnight.

Batch kinetic studies:

To investigate the factors affecting on the sorption of La (III) ions from nitrate solution (effect of carbon types, agitation time, pH, particle size, temperature, concentration of adsorbent and adsorbate), adsorption experiments were carried out. This is achieved by agitating 20 mg of adsorbent with 10 mL of La (III) ions solution having concentration of 100 mgL−1 in a series of bottles of 30 mL at a temperature of 25±1ºC and shaking at 200 rpm.The residual concentration of La (III) ions was measured using UV visible spectrophotometer. The uptake of La (III) ions was calculated by the difference between the equilibrium concentration and the initial concentration. The amount of La (III) ions retained on the solid phase qe (mg/g) was calculated using the relation:

/ 1e o eVq C C x mg gm

Where Co and Ce are the initial and equilibrium concentrations (mg/L) of metal ions in the solution, respectively, V is the volume of solution (L) and m is the weight (g) of the adsorbent.The percent removal of La (III) ions from the aqueous phase was calculated from the relation:

% 100 2o e

o

C CR xC

RESULTS AND DISCUSSION

The present study is directed to investigate the feasibility of using prepared carbon derived from olive stone (OSPA58) for sorption of lanthanum (III) ions from aqueous solution.

1. Characterization of OSPA58:

Elemental analysis (CHNS&O) of OSPA58 was performed in the Hot Lab, Center. The infrared spectra of adsorbents were obtained from a Fourier Transform Infrared Spectrophotometer (FTIR) using the KBr disc. The surface area and the porous structure of adsorbent were measured by N2 adsorption isotherm at 77 K using surface area and pore size analyzer. The Physico chemical characterization of OSPA58 carbon was summarized in the Table (1).

Table (1): Physico chemical characterization of OSPA58-carbon.

Parameters Values Parameters Values SBET 388.67m2/gm S% 0.00 VP 2.061x10-1 O% 25.9% radius 10.60A◦ Ash 6.66% C% 63.20% Ap. D 0.58% H% 1.90% B. d 1.23% N% 0.40% pH 3.2

Notes: SBET: surface area, VP: total pore volume,C:carbon ,H:hydrogen, N: nitrogen, S:sulfur,O:oxygen,

Ash: ash content, Ap.d: apparent density and B.d: bulk density.


70

1.1 FTIR spectroscopy:

In order to gain better insight on the surface functional groups available on the carbon surface, FTIR spectra for the tested carbon are recorded as shown in Figure (1). The carbon showed the broad bands at 3420 and 1160 cm-1 which may be due to hydrogen bonded -OH and P-O. Thus, the surface OH groups probably interact with water molecules adsorbed by the carbon samples from the environment(20). Carbons OS,OSPA58and OSPA58 loaded La(III) ions show an absorption band at 1560 cm-1 which may be due to -NH bending . The shoulders at 2920 and 2845 cm-1 denote the presence of asymmetric and symmetric stretching C-H vibrations of CH3 group. The bands at 1039 and 507 cm-1 in OSPA58 and OSPA58 La (III), may be due to the stretching P-OH or S-O stretching vibrations and P-S stretching [21] respectively. Comparison of the spectra shows that the intense bands at 1611 cm-1, which could indicate a greater concentration of COO- or to skeletal C-C aromatic vibrations [22, 23] and the band at 1115 cm-1, may be due to phenolic OH groups in the sorbent (OSPA58) as a result of greater oxidation of the carbon surface by air at 800◦C. Some of bands disappear due to the chemical reaction which happened between adsorbate and adsorbent.

0 500 1000 1500 2000 2500 3000 3500 400065

70

75

80

85

90

95

100

raw material OSPA58 OSPA58-La

% T

rans

mitt

ance

Wave number (cm-1). Time (min.)

Fig. (1): (a) FTIR spectra of raw material, OSPA58 and OSPA58-La(III), (b) thermo gravimetric and

differential ther(mal analysis of OSPA58. 1.2 Thermo gravimetric analysis (TGA):

The thermal decomposition of OSPA58 sequentially revealed the following behavior as the temperature increased as shown in figure (1-b): in the temperature range 30–120 °C, a small amount of weight loss in DTA curve accompanied by a small peak in DTG curve corresponded to the release of moisture. A significant weight loss with the temperature changed from 200 °C to 500 °C accompanied by a large peak at the temperature of 360 °C in DTG curve, assigned to the degradation of OSPA58 and distillation of tar; and weight loss in a broad manner measured between 560 °C and 800 °C indicating that the basic structure of carbon was readily formed at the temperature of lower than 560 °C [24]. 2. Factors affecting on the sorption of La(III) using prepared activated carbon:

Different factors affecting the sorption of La(III) using prepared activated carbon were investigated. These factors are discussed and illustrated as the following.

2.1. Effect of carbon type:

The olive stone precursor was treated by different methods producing different types of activated carbon. The types of prepared activated carbons have a significant effect on the capacity of the sorption of La (III) ions as shown in Table (2). The results obtained indicated that there is a high variation in the efficiency of some type of prepared activated carbon toward La III) ions. From the data obtained, it was found that olive stone impregnated with 50%H3PO4 and heated to 800 oC is the best one for sorption of

a b


71

0 1 2 3 4 5 60

1 0

2 0

3 0

4 0

5 0

6 0

7 0

F i g ( 2 ) : E f f e c t o f p H o n t h e s o r p t i o n o f L a ( I I I ) i o n u s i n g O S P A 5 8 C a r b o n C 0 = 1 0 0 m g /L

0

q e (mg/

g)

p H 0 2 0 0 4 0 0 6 0 0 8 0 0 1 0 0 0 1 2 0 0 1 4 0 0 1 6 0 00

5

1 0

1 5

2 0

2 5

3 0

3 5

4 0

4 5

5 0

F ig ( 3 ) : E f f e c t o f c o n ta c t t im e o n t h e r e m o v a l o f L a (I I I ) io n u s in g O S P A 5 8 c a r b o n C 0 = 1 0 0 m g /L

0

q emg/

g

t im e ,m in

the La(III) ions and the sample treated with KOH did not used to avoid the precipitation of La(III) ions at high pH values, where this sample has a high pH value in solution (pH> 7.5) .

Table(2):Effect of carbon type on the sorption (percent removal) of La(III) ions.

2.2 Effect of pH:

Since the surface charge of an adsorbent could be modified by changing the pH of the solution, pH plays an important role in the sorption of La (III) ions.The extent of sorption of La (III) ions by activated carbon was studied, for overnight shaking, at various pH values ranging from 1.0 to 6.0. The uptake of La (III) ions from aqueous solution was increased from 42.2 mg/g to 49.0 mg/g with increasing the pH values from 1 to 6 as shown in figure (2). The higher uptake of La(III) ions was obtained at pH = 4. Therefore, the remaining experiments were carried out at pH=4.

2.3 Effect of agitation time:

The adsorption experiments were carried out for contact times ranging from 15 minto 24 hr with fixed amounts of adsorbent (20mg) at 25◦C.The results were plotted in Figure (3) from which it is clear that the sorption capacity increased rapidly where over 98% of the La (III) ions is adsorbed during the first 120 minute and then becomes constant. So, the equilibrium time considered for furtherwork has been taken as 180 minute (25). 2.4 Effect of carbon dose and the batch ratio:

Figure (4), shows the relationship between the amounts of La (III) ions remaining in solution Ce (mg/L) and percent removal of La (III) ions versus carbon dose (mg) of OSPA58. The effect of adsorbent dose on the sorption of La (III) ions was studied by varying the dose of adsorbent from 2 to 50 mg at pH=4, temperature=25◦C and initial concentration=100mg/L. It has been observed from Figure (4), that the percentage removal of La (III) ions was increased with increasing the adsorbent dose and maximum adsorption was recorded at adsorbent dose 20mg beyond which no further increase was noticed. This could be due to increasing surface area and consequently availability of active adsorption sites of the adsorbent especially at higher adsorbent dose (26).

Sample %R Sample %R Carbonization 400◦C 54.55 H3PO4 800◦C 95.5 Carbonization 600◦C 77.28 HNO3 400◦C 68.2 Carbonization 800◦C 85.8 HNO3 600◦C 13.62 Steam 400◦C 73.19 HNO3 800◦C 10.23 Steam 600◦C 74.55 KOH 400◦C 41.14 Steam 800◦C 85.64 KOH 600◦C 32.2 H3PO4 400◦C 89.50 KOH 800◦C 99.89 H3PO4 600◦C 93.98


72

0 10 20 30 40 500

10

20

30

40

50

60

70

80

90

100

0

10

20

30

40

50

60

70

80

90

100

Fig(4): Effect of carbon dose on remaining concenterations and removal percent of La (III) ion by OSPA58-carbon V=10mL T=250C , t=3hr, pH=2, C0=100 mg/L

%R

Cemg/L % R

Ce m

g/L

Carbon dose (mg)

0.0 0.2 0.4 0.6 0.8 1.00

5

10

15

20

25

30

35

40

45

50

Fig.(5):Effect of particle size on removal of La(III)

q e (m

g/g)

particle size (mm)0 50 100 150 200 250 300 350 400 450

0

5

10

15

20

25

30

35

40

45

50

55

60

q emg/

g

Comg/L

2.5 Effect of particle size: Adsorption is a surface phenomenon, as such; the extent of adsorption is proportional to the

surface area i.e to that portion of the total surface area that is available for adsorption. Thus, the amount of adsorption accomplished per unit weight of a solid adsorbent is greater, due to the presence of more finely divided and more porous solid. This behavior can be attributed to the fact that specific surface area for adsorption increase with decrease particle size (27,28). As shown in Figure (5), the particle size has a considerable influence on the carbon ability to adsorb La (III) ions. It was observed that increase in capacity for the smaller particle sizes may be due to(29):(1) The smaller particles more closely approach a true equilibrium than do the large particles, (2) Particle size affects the transport rate of La(III) ions within the activated carbon particles (interparticle diffusion)(30),(3) A greater portion of the total pore volume is available to adsorb La(III) ions in smaller particles, (4) The way in which the small particles are prepared from larger particles. The small particles are produced by grinding larger particles of the same sample of carbon. The external surface is in direct contact with the liquid phase, the larger this surface, the greater are the amounts up taken by the sorbent. Therefore, from the tested particle size (0.19, 0.31, 0.42, 0.5 and 1.0 mm) the best particle size is 0.5mm.

Fig.(5): Effect of particle size on uptake of La(III) ions. Fig.(6): Effect of initial concentration on uptake of La(III) ions.


73

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.505

1015202530354045505560657075

650C

450C

350C25 0C

q e mg/

g

Ce mg/L

2.6 Effect of initial concentration:

The uptake of La (III) ions from aqueous solution was increased with increasing the initial concentration of the solute up to 100 mg/L above which further increase of the initial concentration has no significant effect (Fig.6). This may be ascribed to the fact that an increase in the initial concentration of La (III) ions will increase the competition between the solute molecules to be adsorbed by the limited suitable sites on the surface of the adsorbent.

2.7 Effect of temperature:

The effect of temperature on the adsorption of La (III) ions was also investigated (pH=4, Cº=100mg/L, m=20 mg, V=10mL, time =3hr.). The temperature varied in the range 25ºC to 55 ºC. The amounts of La(III) ions adsorbed at equilibrium at various temperatures in this range are shown in Figure (7).The increase in the amount of adsorbed La(III) ionswith an increase in temperature may be due to:(1) acceleration of some originally slow adsorption steps,(2) the creation of some new active sites on the adsorbent surface,(3) transport of metal ions against the concentration gradient and,(4) diffusion controlled transport across the energy barrier [31].This thereby indicates that the adsorption process is an endothermic in nature. The concentration of adsorption sites may increase with raising temperature due to the breaking of some internal bonds near the edge of the particles [32].

Fig.(7): Effect of temperature on the uptake (qe) of La(III) ions.

Thermodynamic parameters such as standard Gibbs free energy (ΔG0), enthalpy (ΔH0), and entropy changes (ΔS0) for the sorption process can be determined using the following equations (33,34):

ΔG0 = – RT lnKd (3)

Log Kd = ∆ º.

- ∆ º.

(4)

Kd = º (V/m) ml/gm (5)

Where: Kd - distribution coefficient; Cº and C the initial and equilibrium concentration of La(III) ions respectively, V is the volume of La(III) ions in mL and m,weight of OSPA58 carbon in gm. From Van't Hoff equation, the values of ΔH0 and ΔS0 were obtained from the slope and intercept of the linear plot of log Kd vs 1/T as presented in Figure (8). From table (3) ΔG0 are negative, confirming that adsorption of La (III) ions onto OSPA58 carbon is spontaneous and thermodynamically favorable. The more negative values of ΔG0 imply a greater driving force to the adsorption process.The value of ΔH0 is positive indicating that the adsorption process is


74

2.95 3.00 3.05 3.10 3.15 3.20 3.25 3.30 3.354.2

4.4

4.6

4.8

5.0

5.2

5.4

5.6

5.8

Fig(8): Plot of LogKd versus 1/T for the adsorption of La(III) ion onto OSPA58

Log

Kd m

l/g

1/T x 10-3

endothermic in nature. The value of ΔH0 is in the range of 8-16 KJ. Mol-1, indicating that sorption is governed by ion – exchange (35, 36).The positive value of ΔS0 may be attributed to an increase in randomness and decrease of La (III) ions concentration in solution during adsorption of La (III) ions on the OSPA58-carbon surface.

Table (3): Thermodynamic parameters for the adsorption of La (III) ions onto OSPA58 carbon.

T (K) Kdx103 -∆ Gº KJ/mol ∆Hº KJ/mol ∆Sº KJ/mol. K

298 6.8 19.3

10.98

12.89x10-2

308 7.3 26.64

318 8.9 28.64

328 11.9 30.13

2.8 Sorption Isotherms:

The common sorption isotherm models; Freundlich and Langmuir; were considered for assessment of the obtained isotherm data.

2.8.1 Freundlich Isotherm Model:

Frundlich equation is derived to model the multilayer sorption and the sorption on heterogeneous surfaces. The logarithmic form of Freundlich equation is written as(37):

Log qe = Log Kf + Log Ce (6)

Where fK is the constant indicative of the relative adsorption capacity of the adsorbent (mg/g) and 1/n is the constant indicates the intensity of the adsorption process. The illustration of log qe versus log Ce is shown in figure (9) which suggests that the sorption of the La (III) ions is favorable over the entire range of sorption concentration studied. The numerical values of the constants 1/n and fK are computed from


75

0 5 10 15 20 250.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

0.45

0.50

0.55

0.60

Fig(10): Langmuir isotherm plots for removal of La (III) ion using OSPA58-carbon

Ce/q

eCe

0.6 0.7 0.8 0.9 1.0 1.11.45

1.50

1.55

1.60

1.65

1.70

1.75

Fig(9): Freundlich isotherm plots for removal of La (III)ion using OSPA58 - carbon

Log

q e

Log Ce

the slope and intercept by means of a linear least square fitting method and are given in Table (4). The Freundlich intensity constant (1/n) for this case is less than unity, indicating a concentration dependant sorption for ion onto the OSPA58 carbon.

2.8.2 Langmuir Isotherm Model:

Langmuir sorption isotherm model suggests the monolayer coverage of the sorption surfaces and assumes that it occurs on a structurally homogeneous adsorbent and all the sorption sites are energetically identical. The linearized form of the Langmuir equation(37)is given by:

=[1 푄º 푏⁄ ] + [1 ⁄ 푄º ] Ce (7)

Where qe is the amount of solute adsorbed per unit weight of adsorbent (mg/g), Ce is the equilibrium concentration of the solute in the bulk solution (mg/L), Qo is the monolayer adsorption capacity (mg/g) and b is a constant related to the free energy of adsorption.The graphic representation of (Ce/qe) versus Ce gives straight line for La (III) ions adsorbed onto the OSPA58 carbon as presented in figure (10). The numerical value of constants Qo and b were evaluated from the slope and intercept of plot and given in Table(4). The value of the monolayer adsorption capacity Qo corresponds to the monolayer coverage and defines the total capacity of the adsorbent for a specific metal ion.The essential characteristics of Langmuir isotherm can be expressed in terms of adimensionless separation factor RL given by(38):

RL=1/(1+bC0 ) (8)

Where C0 (mg/L) is the highest initial concentration of adsorbate, and b (L/mg) is Langmuir constant. The parameter RLindicates the nature and shape of the isotherm accordingly, RL>1, Unfavorable adsorption, 0<RL<1, Favorable adsorption, RL=0, Irreversible adsorption, Rl=1, Linear adsorption.

Table (4): Langmuir and Freundlich parameters for sorption of La (III) ions using OSPA58.

Adsorbent Langmuir constants Freundlish constants

b(mg/L)-1 Qo (mg/g) RL r Kf(mg/g) n r

OSPA58 0.6 201.6 0.86 0.998 89.2 1.26 0.918


76

0 50 100 150 200 2500.0

0.5

1.0

1.5

Fig(11): pseudo first order plot for removal of La(III) ion by OSPA58 activated carbon.

Log

(qe-q

t)

time,min0 200 400 600 800 1000 1200 1400

0

5

10

15

20

25

30

Fig(12): pseudo second order plot for removal of La(III) ion by OSPA58 activated carbon.

t/qt m

in.g

.mg-1

time (min)

2.9 Sorption Kinetics:

It is well recognized that the characteristic of the sorbent surface is a critical factor that affect the sorption rate parameters and that diffusion resistance plays an important role in the overall transport of ions. To describe the changes in sorption of metal ions with time, two simple kinetic models were tested. In this respect, the rate constant of La (III) ions adsorption from the nitrate solution by OSPA58-carbon was determined using pseudo first-order and pseudo second-order rate models. Lager green pseudo first-order expression (39) is written as:

Log (qe – qt ) = Log qe - . t (8)

Where qe is the concentration of the ions adsorbed at equilibrium (mg/g), qt is the concentration of the ions adsorbed at time t (mg/g) and K1 is the overall rate constant. Figure (11) shows that the straight line plots of Log (qe-qt) versus t for La(III) ions and the data observed that this model is not fit with the data obtained. The pseudo second-order rate model(40,41) is expressed as:

= 1 퐾 qe2 + 푡 (9)

Where K2 is the rate constant of pseudo second order equation (g/mg.min).

The kinetic plots of t/qt versus t for sorption of La (III) ions onto OSPA58activated carbon is shown in Figure (12). The kinetic parameters of this model are calculated from the slope and intercept of the linear plot and given in Table (5). The relation is linear and the values of the correlation coefficient (r2) suggest a strong relationship between the parameters and also explain that the process of sorption of La (III) ions follows the pseudo second-order kinetic model. The products K2qe

2 are the initial sorption rate represented as h = K2qe

2. The correlation coefficient (r2) has extremely high value and the calculated equilibrium sorption capacity (qe) is in consistent with the experimental data. So, it is possible to suggest that the sorption of La (III) ions onto OSPA58 carbon follow the pseudo-second order kinetic model and that the overall rate constant of sorption process appears to be controlled by the chemical sorption process.


77

Table (5): The calculated parameters of the pseudo first and pseudo second-order kinetic.

Carbon type

First -order

Kinetic parameters

Second -order

Kinetic parameters OSPA58 K1

(min-1)

qe(cal)

(mg/g)

r2 K2

(g/mg min)

h

(mg/g min)

qe(cal)

(mg/g)

r2 q exp

4.606x10-3 4.248 0.944 1.618x10-3 3.977 49.57 0.999 49.01

2.10 Effect of method of modification on the sorption of La (III) ions:

The OSPA58 was modified by Crystal Violet (CV) and 60 % Carbon disulfide (CS2) and the results of these modifications on the uptake of La (III) ions using the modified samples were given in Table (6) and Figure (13).

Table (6): Effect of modification on the uptake of La (III) ions.

Parameters Raw material OSPA58 OSPA58-CS2 OSPA58-C.V Uptake (mg/g) 32.75 47.75 49.45 30.25 %R 65.50 95.5 98.9 60.50

5560

6570

7580

8590

9510

0

OSPA58- CS2OSPA58Raw materialOSPA58-C.V

% R

emov

al

O r i g i n P r o 8 E v a l u a t i o n O r i g i n P r o 8 E v a l u a t i o n






Fig.(13): Effect of modification methods on the adsorption of La(III) ions using OSPA58.

2.11 Column Study and Break through Capacity:

This experiment was carried out to investigate the adsorption capacity of the modified activated carbon. 1.0 gm of OSPA58-CS2was packed into a glass column (bed height = 5 cm and column diameter = 1.0cm). La (III) ions solution with initial concentration of 100 mg L-1 was passed through the column (flow rate = 2 mL min-1). The outlet solution was analyzed for unabsorbed La (III) ions. The breakthrough curves obtained are shown in figure (14).The main theory which explains sorption and separation by column chromatography is plate theory. According to this theory, the column is considered to be divided into a number of equal units called theoretical plates. These units, although entirely hypothetical, give rise to a very useful way for the practical measurement of the column efficiency. Investigation was conducted to explore suitable condition for quantitative loading and


78

0 10 20 30 40 50 600.0

0.2

0.4

0.6

0.8

1.0

Fig. (14): Break-through curves of La(III) ion on OSPA58 carbon modified with 60% CS2 (carbon disulphide)

in pH=2, T= 25o C

C/C

o

volume,ml

sorption of La (III) ions (pH=4) by chromatographic column procedure at room temperature (25 ºC).The breakthrough capacity of the column is presented in figure(14) for La(III) ions for OSPA58-CS carbon impregnated with 60% carbon disulfide(CS2) column in the feed solution. The breakthrough curve depicts the percent concentration of the La (III) ions in the effluent to the feed solution (C/Cº %) Vs. effluent volume (Vml) as shown in figure (14).The corresponding uptake for the investigated La (III) ions per gram of solid is calculated using the following formula; Q0.5 (breakthrough capacity) = V(50%)x Cº/m ( 10 )

Where V(50%) is the effluent volume at 50% breakthrough (ml), Cº is the initial metal concentration in mg/L , m is the weight of dry activated carbon in gram. The breakthrough capacity of La (III) ions was calculated from figure (14) and it was found to be 4.16 mg/g.

CONCLUSIONS

The results obtained in this study revealed that the potential of olive stone, as agricultural by-product material, to be a low cost adsorbent for sorption of La(III) ions from aqueous nitrate medium. It was found that the optimum conditions for sorption of La (III) ions were ; pH=4, contact time=180min, particle size =0.5mm, adsorbent dose=20 mg. From the study of effect of temperature, it was found that the thermodynamic parameters has the following values ∆Gº= -19.3 KJ/mol, ∆S=12.89x10-2 KJ/mol K and ∆H=10.98KJ/mol. Equilibrium data agreed well with Langmuir isotherm model with monolayer adsorption capacity of 201.6 mg/g. The values of the separation factor, RL, indicated that the La–OSPA58 system was a favorable adsorption. The kinetic modeling study has shown that the experimental data were found to follow the pseudo-second-order model suggesting a chemisorption process. Therefore, the developed sorbent is considered as a better replacement material for removal of La(III) ions from aqueous solution due to its low-cost and good sorption efficiency.

REFERENCES

(1) N.S. Awwad, H.M.H. Gad, M.I. Ahmad, H.F. Aly,Colloids and Surfaces B: Biointerfaces ,(2010) (2) T.H. Liou, S.J. Wu, J. Hazard. Mater. 171 ,693,(2009). (3) T.G. Chuah, A. Jumasiah, I. Azni, S. Katayon, S.Y.ThomasChoong,Desalination175,305 (2005). (4) E.I. El-Shafey, J. Hazard. Mater. 175 , 319 (2010). (5) R. Qadeer, J. Hanif, Radiochim. Acta65 ,259 (1994).


79

(6) W.A. Abbasi, M. Streat, Sep. Sci. Technol. 29 (9) , 1217(1994). (7) M. Saleem, M. Afzal, R. Qadeer, J. Hanif, Sep. Sci. Technol. 27 (2) 239 (1992). (8) D. Nevskaia, A. Saantianes, V. Munoz, A. Guerrero-Ruiz, Carbon 37 , 1065(1999). (9) F. Banat, S. Al-Asheh, L. Al-Makhadmeh, Process Biochem. 39 (193) (2003). (10) A.A.M. Daifullah, N.S. Awwad, S.A. El-Reefy, J. Chem. Eng. Process. 43193–43201(2004). (11) H.M.H. Gad, N.S. Awwad, Sep. Sci. Technol. 42 3657–3680(2007). (12) R. Juang, F. Wu, R. Tseng, J. Colloid Interface Sci. 227 , 437(2000). (13) N.S. Awwad, A.A.M. Daifuallah, M.M.S. Ali, Solvent Extr. Ion Exc26 ,764(2008). (14) M. Akhtar, S. Iqbal, A. Kausar, M.I. Bhanger, M.A. Shaheen, Colloids Surf. B:Biointerfaces 75,

149(2010). (15) Y. Guo, J. Zhao, H. Zhang, S. Yang, J. Qi, Z. Wang, H. Xu, Dyes Pigments 66 ,123(2005). (16) D.H. Lataye, I.M. Mishra, I.D. Mall, J. Hazard. Mater. 154 858 (2008). (17) N.R. Bishnoi, M.B.N. Sharma, A. Gupta, Bioresour. Technol. 91, 305(2004). (18) D. Kalderis, D. Koutoulakis, P. Paraskeva, E. Diamadopoulos, E. Otal, J.O. Valle,C.F. Pereira, Chem.

Eng. J. 144 ,42(2008). (19) S.L. Ng, C.E. Seng, P.E. Lim, Chemosphere 78 , 510(2010). (20) J. Zawadzki, Carbon 18 (1980) 281. (21) D.H. Williams, I. Fleming, Spectroscopic Methods in Organic Chemistry, McGraw-Hill Book

Company, UK, 1973. (22) B. Stuart, D.J. Ando, Modern Infrared Spectroscopy, Wiley, 1996. (23) V. Gomez-Serrano, M. Acedo-Ramos, A.J. Lopez-Peinado, C. Valenzula- Calahorro, Fuel 73 (3)

(1994) 387. (24) F.,Caturla, M., Molin-Sabio, F., Rodriguez-Reinoso, Carbon 29, 999– 1007,(1991). (25) D.N.S. Hon, Polym. News 17 (1992) 102. (26) A.Ucer, A. Uyanik&Aygun S F, Sep PurifTechnol, 47(3), 113(2006). (27) G.Mckay, V.J.P. Poots, and .Healy, J.J., Removal of Acid Dye from Effluent Using.Natural

Adsorbents.Wat.Res.,10:1061(1976). (28) G.Mckay and V.J.P.Poots,Adsorption of Congo red from aqueous solution ontocalcium-rich fly ash.

Water poll. Control Red., 50:926(1978). (29) W.J.Weber, Voice, Jr.T.C. and Jodellah,A., JAWWA ,(1983). (30) N.J.D.Grahamt and J.Ma, G.Li,14, Amsterdam, 209(1994). (31) S.P. Mishra, D.Tiwari and R.S. Dubey., Appl.Radiat.Isol.48(7) 877 ,(1997). (32) K.Shaker,K.Benyamin, M.Aziz, J. Radioanal .andNucl.Chem.,Articles,173(1)141 ,(1993). (33) H. Ucun, Y.K. Bayhan, Y. Kaya, Kinetic and thermodynamic studies of the biosorption of Cr(VI) by

Pinussylvestris Linn, J.Hazard. Mater. 153 (2008) 52–59. (34) A. Sarı, M. Tuzen, O.D. Uluozlu, M. Soylak, Biosorption of Pb(II) and Ni(II) from aqueous

solution by lichen (Cladoniafurcata) biomass, Biochem. Eng. J. 37 (2007) 151–158. (35) S.Aksoyoglu,; J. Radional. Nucl.Chem., 140,301 (1990). (36) G. Atun,and N.Bodu; J. Radional.Nucl. Chem.; 253,275-279 (2002). (37) F. Slejko; "Adsorption Technology- A Step by Step Approach to Process Evaluation and Application",

Marcel Dekker, New York (1985). (38) H. R. Hall, L. C. Eagleton, A. Acrivos, and T. Vermeulen, I & EC Fundam. 5,212 (1966) (39) S. Langergren, KungligaSvenskaVetenskapsakademiesHandlingar 24 (4) ,1,(1898). (40) G., McKay and Ho, Y.S.,Water Res.; 33, 585 (1999). (41) McKay,G., and Ho, Y.S.,; Process Biochem. Pseudo-second ordermodel for sorption processes; 34, 451

(1999).

Application of Olive Stone Based Activated Carbon in the ...5) Application of Olive... · activated...

Documents

Transcript of Application of Olive Stone Based Activated Carbon in the ...5) Application of Olive... · activated...