13 Chapter 5

CHAPTER 5

Mahogany Fruit Shell: A new low-cost adsorbent for removal of basic dye from

aqueous solutions

Swietenia mahogani (Mahogany)

Mahogany Fruit

Mahogany Shells

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REMOVAL OF DYES AND HEAVY TOXIC METALS WITH ADSORPTION TECHNIQUE USING LOW COST

ADSORBENTS

5.1 INTRODUCTION

The first synthetic dye, Mauveine, was discovered by Perkin long time

back in 1856 and hence the dyestuff industry can rightly be described as mature.

However, it remains a vibrant, challenging industry, requiring a continuous stream

of new products because of the quickly changing world in which we live. Apart

from one or two notable exceptions, all the dye types used today were discovered

in the 1800s. The most important basic dye is Methylene Blue (MB), discovered

by Caro in 1878. Methylene Blue is a dark green powder or crystalline solid [1].

Highly colored substances, widely known as colorants, can be used to

impart color to an infinite variety of materials described technically as (1) dyes

and (2) pigments. Colorants can be subdivided into dyes, which are soluble in the

medium in which they are applied and pigments, which are insoluble in the

application medium. Dyes are defined as coloured substances that when applied to

fibers impart them a permanent color which are resistant to action of light, water,

and soap. Practically every dyestuff is made from one or more of the compounds

obtained by the distillation of coal tar [2]. Among all industrial sectors, textile

industries are rated as high polluters, taking into consideration the volume of

discharge and effluent composition. Colour is a visible pollutant. Textiles, dye

manufacturing industries, paper and pulp mills, tanneries, electroplating industries,

distilleries, food industries and a host of other industries discharge coloured waste

water. It is resented by the public on the ground that colour is an indicator of

pollution [3].

Dye wastewater arises as a direct result of the production of the dye and

also as a consequence of its use in the textile and other industries. There are more

than 1,00,000 commercially available dyes and nearly 7x105 tones of dyes

produced annually. It is estimated that 2% of dyes produced annually are

discharged in effluent from manufacturing operations while 10% is discharged

from textile and associated industries [4]. The release of colored waste water from

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these industries may present an eco-toxic hazard and introduce the potential

danger of bioaccumulation, which may eventually affect man through the food

chain [5]. Methylene Blue can cause eye burns which may be responsible for

permanent injury to the eyes of human and animals. On inhalation, it can give rise

to short periods of rapid or difficult breathing while ingestion through mouth

produces a burning sensation and may cause nausea, vomiting, profuse sweating,

mental confusion and methemoglobinemia [6]. Methylene Blue exhibits several

synergistic modes of actions which enable the dose-limiting neurotoxicity of

alkylating chemotherapy with ifosfamide in cancer patients to be overcome [7].

The dyes absorb and reflect sunlight entering water and so can interfere with

growth of bacteria and hinder photosynthesis in aquatic plants [4].Therefore, the

treatment of effluent containing such dye is of interest due to its harmful impacts

on receiving waters.

In general, several difficulties are encountered in removal of dyes from

waste waters. By design, dyes are highly stable molecules, made to resist

degradation by light, chemical, biological and other exposures. Commercial dyes

are usually a mixture of large number complexes and have often unreported

molecular structure and properties. Dyes also vary widely in chemical

composition. Furthermore, dyeing waste water compositions are not simple

solutions of dye in water, but include many other materials such as particulates,

processing assistants, salts, surfactants, acids and alkalis. Basic dyes are

considered as one of the more problematic classes of dye which are consider as

toxic colorants. As a result, improved or cost effective technologies are required to

remove them from textile effluents [8].

During the past three decades, several physical, chemical and biological

decolorization methods have been reported. Amongst the numerous techniques of

dye removal, adsorption is the procedure of choice and gives the best results as it

can be used to remove different types of coloring materials. Recently, numerous

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approaches have been studied for the development of cheaper and effective

adsorbents. Many non-conventional low cost adsorbents, including natural

materials, biosorbents, and waste materials from agriculture and industry, have

been proposed by several workers. These materials could be used as adsorbents for

the removal of dyes from aqueous solution [6]. Many treatment processes have

been applied for the removal of dyes from waste water such as: photocatalytic

degradation [9], sonochemical degradation [10], ultrafiltration [11], membrane

technology [12], and adsorption [13]. The synthetic dyes in waste water cannot be

efficiently decolorized by traditional methods, such as coagulation, flocculation,

oxidation, precipitation, filtration, electrochemical processes, etc. Chemical

methods of dye removal accumulate sludge that can create disposal problems.

These methods require chemicals and large amount of electrical energy which

further poses problems for environment as well as economically they are not

feasible. Amongst the techniques, adsorption seems to be one of the most effective

methods because of simple operation and easy handling [13]. The adsorption of

synthetic dyes on inexpensive and efficient solid supports was considered as a

simple and economical method for their removal from water and waste water.

In present study, we are introducing the novel adsorbent Mahogany

fruit shell. As the medicinal uses of Mahogany concerned, the bark extracts are

used as an astringent for wounds. It is used to cure malaria, anemia, diarrhea,

fever, dysentery and depurative. Its wood is used in making furniture, fixtures,

musical instruments, inlay, boat, caskets and many more. Its wood is a very

popular material for drum making. Meanwhile, saponins have efficacy as a pest

deterrent, could also be used to reduce the fat in the body, to boost the immune

system, to prevent blood clotting, to strengthen heart function and to lower the

blood clotting process. Mahogany could also heal, high blood pressure

(hypertension), lack of appetite, fever; diabetes (Diabetes Mellitus), cold, ekzema,

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rheumatism [14]. The fruit shell is unemployed, so we have decided to apply it as

adsorbent.

The adsorption study of MG has been carried out with inexpensive

Mahogany fruit shell adsorbent, to determine the parameters like, pH, agitation

period, speed, initial concentration of MB etc. as well as the isotherm models were

applied. The kinetic study was done with pseudo-first and pseudo-second order

model. The result of this study reveals that, the present adsorbent is effective and

economical for removal of MB dye from aqueous solution.

5.2 LITERATURE SURVEY OF ADSORPTION OF METHYLENE BLUE

Adsorption techniques for waste water treatment have become more

popular in recent years owing to their efficiency in the removal of pollutants.

Adsorption can produce high quality water, while also being a process that is

economically feasible [4]. The vital role in this process is selection of adsorbent.

There are number of adsorbents developed as the advantages of this technique

come in front of the world in both sense to control the pollution as well as

economical. The adsorbents such as sand, fly ash, clay, zeolite, polymer, carbon

nanotubes, activated carbon, biomass etc. are now in very much focus.

Removal of MB dye from aqueous solution on sand surface, carried out at

room temperature was reported by S B. Bukallah (2007). The conditions of

maximum adsorption of the dye were optimized. It was observed that under

optimized conditions, up to 92% dye can be removed from solution on the sand

surface [15]. Fly ash is a waste material originating in great amounts in

combustion processes. At present, a number of thermal power plants fuelled with

coal are in operation in many countries. When the fly ash was used as adsorbent,

maximum removal of 58.24% of MB was observed at adsorbent dosage of 900

mg/dm3 at pH 6.75 for an initial MB concentration 65 mg/dm3 [16]. The zeolites

synthesized from coal fly ash were investigated as adsorbent to remove MB, from

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aqueous solution. The maximum adsorption capacity of MB by fly ash, calculated

using the Langmuir equation, ranged from 23.70 to 50.51 mg/g [17].

The naturally available things were used for removal of MB; natural

zeolite is one of them. Natural zeolite, which exists and is easily obtained in many

places, is vast and cheap and could be used effectively for removal of MB from

aqueous solution [18]. R. Han et al. (2009) were studied adsorption equilibrium

and kinetic of MB on natural zeolite in a batch system. Langmuir isotherm

nonlinear method and linear method has shown 19.94 and 16.37 mg/g adsorption

capacity respectively both at 298 K for same adsorbent [19]. Adsorption isotherms

and kinetics of MB onto mesoporous carbons prepared by using acid and alkaline

treated zeolite X as the template and furfuryl alcohol as carbon source through

vapor deposition polymerization method were determined. The maximum

adsorption capacities of MB at 293 K on the carbons prepared using acid and

alkaline treated zeolite X as the template were found to be 262.87 and 436.55

mg/g respectively [20].

The ability of clay to remove MB from aqueous solution has already been

shown with high adsorption capacity, which is exceeding that of activated carbon

under the same conditions of temperature and pH in various reports. One of the

case with higher adsorption capacity, montmorillonite clay has been utilized as the

adsorbent with 348.87 mg/g capacity [21]. The enhancement of adsorption

capacity had been reported with various treatments; in case of the Moroccan clay

capacity has increased up to 500 mg/g by thermal activation [22], while purified

Moroccan clay mineral known as a ghassoulite or rhassoulite has been reported

135 mg/g as the adsorption capacity [23]. As kaolin itself was a relatively good

adsorbent, the adsorption capacity was improved by purification and by treatment

with NaOH solution. The adsorption capacities where reported for raw kaolin

27.49 mg/g, pure kaolin 91.87 mg/g, calcined raw kaolin 13.44 mg/g, calcined

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pure kaolin 56.31 mg/g, NaOH treated raw kaolin 204.00 mg/g, and NaOH treated

pure kaolin 122.01 mg/g [24].

Removal of MB from aqueous solution by adsorbing it on gypsum was

investigated by batch method and the maximum monolayer adsorption capacity

was reported to be 36 mg/g [25]. The removal of MB from aqueous solution by

peat was analyzed. An adsorption time of around 4.5 h was sufficient to reach the

equilibrium for all temperatures, in the concentration range studied. Peat was

found to be highly effective in the removal of MB from aqueous solution with

removals exceeding 90 % [26]. In a slightly basic medium synthetic magnesium

silicate (Florisil), Amberlite XAD-2 and activated carbon showed 149.3 mg/g,

16.8 mg/g and 212.8 mg/g adsorption capacity respectively [27]. In case of

industrial waste like Fe(III)/Cr(III) hydroxide, adsorption capacity was reported to

be 22.8 mg/g [28].

Carbon nanotubes (CNTs), with nano-sized diameter and tubular

microstructure, have been the world wide hotspots of study since their discovery

because of their unique morphologies and various potential applications. Because

of their relatively large specific surface areas and easily modified surfaces, much

attention has been paid to the adsorption of various contaminants as well as dyes

by CNTs. The batch adsorption experiments were carried out for the removal of

MB as a basic dye from aqueous solutions using CNTs which has shown 64.7

mg/g adsorption capacity [29] and in another report it was 132.6 mg/g [30]. The

adsorption of MB from an aqueous solution by polyacrylic acid-bound iron oxide

magnetic nanoparticles was prepared which had maximum adsorption amount of

0.199 mg/g [31]. A series of porous carbon xerogels were synthesized from

resorcinol-formaldehyde resin and one of the series had maximum adsorption

capacity of 222 mg/g, which is comparable to good adsorbing activated carbons

[32]. Calcined titanate nanotubes were synthesized with hydrothermal treatment of

the commercial TiO2 (Degussa P25) followed by calcination. The samples

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exhibited a tubular structure and a high surface area of 157.9 m2/g with maximum

adsorption capacity of 133.33 mg/g [33]. The halloysite nanotubes (HNTs) were

used as nano-adsorbents for the removal of the MB, from aqueous solutions and a

maximum adsorption capacity of 84.32 mg/g of MB was achieved. It was noted

that the dye adsorbed halloysite nanotubes had poor stability in aqueous

suspension and deposited completely within 30 minutes while the original aqueous

suspension of halloysite nanotubes remained stable for months [34].

Depending on the layers involved the carbon nanotubes have been referred

to single walled or multiwalled carbon nanotubes. The kinetics, isotherms and

thermodynamic of atrazine adsorption on multiwalled carbon nanotubes

(MWCNTs) containing 0.85%, 2.16%, and 7.07% oxygen was studied. The

adsorption capacities of three MWCNTs followed a descending order: MWCNTs-

O (0.85%) > MWCNTs-O (2.16%) > MWCNTs-O (7.07%) and having 61.10,

36.62 and 25.62 mg/g adsorption capacities respectively. This suggests that the

adsorption capacity decreased when the surface oxygen contents of the MWCNTs

increased [35]. The adsorption kinetics of MB, on the silica nano-sheets derived

from vermiculite via acid leaching was investigated in aqueous solution in a batch

system and maximum adsorption capacity was found to be 11.77 mg/g for MB

[36]. A novel nano adsorbent was fabricated by the surface modification of Fe3O4

nanoparticles (MNP) with carboxymethyl-β-cyclodextrin (CM- β-CD) and the

feasibility of employing these nano-adsorbents for removal of MB from aqueous

solutions was investigated. The adsorption capacities of MB on CMCD–MNP (P)

and CMCD–MNP (C) are found to be 277.8 and 140.8 mg/g respectively [37]. The

introduced montmorillonite could generate a loose and porous surface that is of

benefit to adsorption ability of the nanocomposite. Batch adsorption experiments

were carried out for the removal of MB cationic dye from its aqueous solution

using chitosan-g-poly(acrylic acid)/montmorillonite nanocomposites as adsorbent

having maximum adsorption capacity 1859 mg/g [38].

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The activated carbon has proved the ability to remove the coluring matter

effectively at application level. The commercial sample of activated carbon has

great adsorption capacity as compared to the other adsorbents. Activated carbon

F-400 was reported to remove the MB, with increasing the adsorption capacity

from 469.6 to 708.8 mg/g with increasing temperature from 303 to 338 K [39].

Various activated carbons have been used for MB removal from aqueous solution.

It has been found that the adsorption capacity is influenced by the physical and

surface chemical properties of carbon and the pH of the solution. S. Wang et al.

(2005) used three types activated carbons, the order of the adsorption capacity of

them was as, BPL = BDH > F100 [40]. In another case, three commercial granular

activated carbons, 12x40 mesh size, namely Filtrasorb 400, Norit and Picacarb

have been used as adsorbents. The adsorptive capacities of these were 319 ± 14,

280 ± 7 and 260 ± 6 mg/g for Filtrasorb 400, Norit and Picacarb, respectively [41].

The powdered activated carbon (Norit SA3) and granular activated carbon

(Nuchar WWH) showed the adsorption capacity 91 mg/g and 21.5 mg/g

respectively [42].

As it is well known that, the adsorption with commercial activated carbon

has great efficiency to remove the contaminant, but it is not economical, so there is

need to develop the alternative to it. Many researchers have tried to develop the

low cost activated carbon; some reports have shown the great adsorption capacity

which is comparable to commercial samples. The removal of basic dye MB from

aqueous solution using bituminous coal-based activated carbon has been

investigated and maximum adsorption capacity of 580 mg/g at equilibrium was

achieved [43]. Activated carbons were prepared from walnut shells by vacuum

chemical activation with zinc chloride as the activation agent have surface area of

1800 m2/g and 315 mg/g maximum adsorption capacity [44].

Adsorption of MB from aqueous solutions on activated carbon prepared

from Egyptian rice hulls has studied experimentally and results indicate the

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removal efficiency of MB at 298 K exceeds 99% and the adsorption process is

highly pH-dependent which has 60.1 mg/g adsorption capacity [45]. The activated

carbon prepared from cotton stalk with ZnCl2 activation was investigated under

microwave radiation with optimum conditions such as microwave power of 560

W, microwave radiation time of 9 min and the impregnation ratio of ZnCl2 was of

1.6 g/g which had the maximum 315.04 mg/g adsorption capacity [46]. Activated

carbons were prepared from the biomass of oil palm wood via two stages,

pyrolysis and physical activation. By using an environmentally friendly pyrolysis

pilot plant and an activation pilot plant were studied. The latter uses the outlet flue

gases from limestone calcination process as activating agents and the maximum

adsorption capacity 90.9 mg/g was reported [47]. Preparation of the activated

carbon from sunflower oil cake by sulphuric acid activation with different

impregnation ratios was carried out. The developed activated carbons were

denoted as AC1 without impregnation, AC2 with the impregnation ratio of 0.85,

and AC3 with the impregnation ratio of 1.90. The maximum adsorption capacity

for MB was found to be 10.21, 16.43 and 15.798 mg/g for AC1, AC2 and AC3

respectively [48].

Commercial activated carbon (CAC) and indigenously prepared activated

carbons (IPACs) such as bamboo dust carbon (BDC), coconut shell carbon (CSC),

groundnut shell carbon (GNSC), rice husk carbon (RHC) and straw carbon (SC)

were studied to find out the possibility of using these carbonaceous materials as

low cost adsorbents for the removal of MB. Relative adsorption capacity values of

these carbons for adsorption of MB are, CAC=100 mg/g, BDC=7.20 mg/g,

GNSC=7.50 mg/g, CSC=8.16 mg/g, RHC=37.57 mg/g, and SC=42.60 mg/g. Cost

wise the IPACs are nearly five times cheaper than the CAC. Hence, the IPACs are

cost effective adsorbent materials for the removal of dyes/colour [49]. Microwave

radiation has been proved to be an efficient and rapid method for the modification

of activated carbons. Modification of bamboo based activated carbon was carried

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out in a microwave oven under N2 atmosphere which has 286.1 mg/g maximum

adsorption capacity [50]. Activated carbon prepared from non-wood forest product

waste (rattan sawdust) has been utilized as the adsorbent for the removal of MB

dye from an aqueous solution with maximum monolayer adsorption capacity of

294.14 mg/g [51].

Activated carbons were obtained by activation with H3PO4 at 773 K, under

increasing acid concentrations of 30-70%. Products were characterized by N2 at 77

K and proved to be highly microporous with high surface area and pore volume

that increased with impregnation ratio. Two modified carbons were prepared by

concurrently passing N2 during pyrolysis of impregnated precursor with 50% and

70% H3PO4 at 773 K and post-heat treatment at 1073 K. The adsorption capacity

was from 198 to 412 mg/g as per treatment which is associated with the texture

properties [52]. For the dehydrated wheat bran carbon, the optimum adsorption

conditions were found to be pH 2.5 and temperature 318 K and it shows 222.20

mg/g adsorption capacity [53]. Thermally activated coir pith carbon prepared from

coconut husk was used for removal of MB and the adsorption capacity was found

to be 5.87 mg/g [54]. The vetiver roots have been utilized for the preparation of

activated carbon by chemical activation with different impregnation ratios of

phosphoric acid, (g H3PO4/g precursor): 0.5:1; 1:1 and 1.5:1. Textural

characterization, determined by nitrogen adsorption at 77 K shows that mixed

microporous and mesoporous activated carbons with high surface area

(>1000m2/g) and high pore volume (up to 1.19 cm3/g) can be obtained and having

375 to 423 mg/g adsorption capacity [55]. High surface area activated carbons

were prepared by simple thermo-chemical activation of Jatrophacurcas fruit shell

with NaOH as a chemical activating agent. The results present that the activated

carbon possesses a large apparent surface area (SBET = 1873 m2/g) and high total

pore volume (1.312 cm3/g) with average pore size diameter of 28.0Å [56]. Jute

fiber obtained from the stem of a plant was used to prepare activated carbon using

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phosphoric acid. Feasibility of employing this jute fiber activated carbon for the

removal of MB from aqueous solution was investigated whose adsorption capacity

was found to be 225.64 mg/g [57].

From the list of adsorbent, one of the very important is biosorbent which

may be used as it is or by activation and having good capacity. The Brazilian pine-

fruit shell (Araucaria angustifolia) is a food residue, which was used in natural

and carbonized forms, as low cost adsorbent for the removal of MB from aqueous

solutions. Chemical treatment of Brazilian pine-fruit shell (PW), with sulfuric acid

produced a non-activated carbonaceous material (C-PW). Both PW and C-PW

were tested as low-cost adsorbents for the removal of MB from aqueous effluents

and showed 185 and 413 mg/g adsorption capacity respectively [58]. Batch and

column kinetics of MB adsorption on calcium chloride, zinc chloride, magnesium

chloride and sodium chloride treated beech sawdust were simulated, using

untreated beech sawdust as control, in order to explore its potential use as a low-

cost adsorbent for dye removal. The results showed that salt treated beech

sawdust enhances its adsorption properties considerably. The maximum

adsorption capacity for MB by beech sawdust treated with calcium chloride, zinc

chloride, magnesium chloride and sodium chloride found to be 12.2 ± 1.8, 13.2 ±

2.0, 15.6 ± 2 and 9.7 ± 0.6 mg/g respectively [59]. It was seen that cotton stalk

(CS), cotton dust (CD) and cotton waste (CW) could be used successfully as

adsorbent for the removal of MB from aqueous solution by sorption technique.

The maximum dye removals for CS, CW and CD were between 26.0% and 48.36

%, between 50.0% and 85.41%, between 62.0% and 97.50% as well as 4.52, 8.33,

9.75 mg/g adsorption capacity respectively [60].

Recently the use of low cost materials to remove colour has been reported

by several workers. The ability of coconut husk to remove MB from solution was

investigated with 99 mg/g as Langmuir isotherm maximum adsorption capacity

[61]. Batch experiments were carried out for the adsorption of MB on mango seed

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kernel particles, which had reported 142.857 mg/g adsorption capacity at 303 K

[62]. A natural wheat straw was used adsorbent for removal of copper and MB

from aqueous solution. A batch system was applied to study the behavior of Cu(II)

and MB adsorption in single and binary systems on wheat straw. The adsorption

capacities of Cu(II) and MB at 273 K and pH 5 were 7.05 and 60.66 mg/g

respectively [63]. Rice straw was esterified thermochemically with citric acid to

produce potentially biodegradable cationic adsorbent. The modified rice straw

(MRS) and crude rice straw (CRS) were evaluated for their MB removal capacity

from aqueous solution. Langmuir model was used to determine adsorption

capacities which were found to be 80.0 and 270.3 mg MB per gram of CRS and

MRS, respectively [64]. The study indicates the potential use of pretreated rice

husk (RH) and rice husk ash (RHA) for the removal of MB from waste water.

Maximum monolayer adsorption capacity has a value of 1347.7 mg/g for

adsorption on RH and 1455.6 mg/g for adsorption on RHA at a temperature of 323

K [65]. In another report maximum percentage removal of MB was 99.939 %,

with 18.149 mg/g adsorption capacity for same adsorbent [66].

Tea waste has been used as adsorbent for the removal of MB from its

aqueous solution. It is a household waste available in huge amount which is an

oxygen demanding pollutant and also it takes a long time for biodegradation. The

tea waste was incinerated and used as a cost effective adsorbent having 85.16

mg/g adsorption capacity [67]. Langmuir isotherm model with maximum

monolayer adsorption capacities of rejected tea were found to be 147, 154 and 156

mg/g at 303, 313 and 323 K respectively [68]. The removal of a MB from aqueous

solution using NaOH-modified rejected tea was investigated, the adsorption

isotherm data fitted well to Langmuir isotherm with monolayer adsorption

capacity of 242.11 mg/g [69]. Spent tea leaves were used as a new non

conventional and low cost adsorbent for the MB adsorption in a batch process, at

303 K and the Langmuir isotherm monolayer adsorption capacity was found to be

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300.052 mg/g [70]. Spent coffee powdered residue from the soluble coffee

industry was evaluated as an adsorbent for the removal of MB from aqueous

solution with 18.7 mg/g adsorption capacity [71].

An algal industrial waste from agar extraction process, algae Gelidium and

a composite material obtained by immobilization of the algal waste with

polyacrylonitrile were used as biosorbents for dyes removal using MB as model.

Equilibrium isotherms are described by the Langmuir equation, giving maximum

uptake capacities of 171, 104 and 74 mg/g, respectively for algae, algal waste and

composite material [72]. The biomass of baker’s yeast was modified with poly

(methacrylic acid) through a graft copolymerization reaction which was prepared

to improve the adsorption capacities for three dyes: MB, Rhodamine B (RB) and

basic magenta (BM). The maximum uptake capacities for MB, RB and BM were

869.6, 267.4 and 719.4 mg/g respectively [73]. Adsorbents prepared from

Parthenium hysterophorus, weed, was successfully used to remove MB from an

aqueous solution in a batch reactor. The adsorbents included sulphuric acid treated

parthenium and phosphoric acid treated parthenium have 39.68 and 88.49 mg/g

adsorption capacities respectively [74].

Cost effective cedar sawdust and crushed brick were selected as adsorbents

for the investigation of adsorption of MB from aqueous solution with maximum

adsorption capacities of 142.36 and 96.61 mg/g respectively [75]. Meranti

(Philippine mahogany) sawdust, an inexpensive material, showed strong

scavenging behaviour through adsorption for the removal of MB from aqueous

solution. The monolayer adsorption capacity of meranti sawdust for MB was

found to be 120.48, 117.64, 149.25 and 158.73 mg/g at 303, 313, 323 and 333 K

respectively [76]. The potential use of Indian Rosewood (Dalbergia sissoo)

sawdust, pretreated with formaldehyde (SD) and sulphuric acid (SDC), for the

removal of MB dye from simulated waste water was reported. Maximum dye was

removed within 30 min from start of every experiment. The adsorption for SDC

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was increased from 12.49 mg/g to 51.4 mg/g as the MB concentration in the test

solution was increased from 50 mg/dm3 to 250 mg/dm3. Similarly, unit adsorption

for SD was increased from 11.8 mg/g to 46.1 mg/g as the dye concentration in the

test solution was increased from 50 mg/dm3 to 250 mg/dm3 [77]. The ability of

coconut bunch waste, an agricultural waste available in large quantity to remove

MB from aqueous solution by adsorption was studied and capacity was found to

be 70.92 mg/g at 303 K [78]. The feasibility of using papaya seeds, abundantly

available waste, for the MB adsorption has been investigated; a maximum

adsorption capacity of 555.56 mg/g was found [79]. E. I. Unuabonah et al. (2009)

were defatted Carica papaya seeds and used for the adsorption of MB dye. The

specific surface area of the defatted undefatted Carica papaya seeds was found to

be 143.27 m2/g respectively as well as defatting Carica papaya seed adsorbent

increased its adsorption capacity for MB dye from 769.23 to 1250 mg/g [80].

Modified wheat straw with citric acid was employed to enhance the

adsorption capacity of the by-product for selected copper ions and MB. Langmuir

model capacity for Cu(II) and MB was found to be 39.17 and 396.9 mg/g at 293

K, respectively [81]. Broad bean peels, an agricultural waste, was evaluated for its

ability to remove MB from aqueous solutions and adsorption capacity was found

to be 192.7 mg/g [82]. The potential of garlic peel, agricultural waste, to remove

MB from aqueous solution was evaluated in a batch process. The maximum

monolayer adsorption capacities were found to be 82.64, 123.45, and 142.86 mg/g

at 303, 313, and 323 K temperatures, respectively [83]. To obtain the potential

feasibility of removing colour by peanut hull, it was dehydrated with sulphuric

acid and used for adsorption of MB from aqueous solution and adsorption capacity

was found to be 161.3 mg/g [84]. Ethylenediaminetetraacetic dianhydride

(EDTAD) modified sugarcane bagasse (SB) was prepared. The adsorption

capacity of the EDTAD-modified SB 115.3 mg/g for MB showed a significant

increase compared with SB [85]. The adsorption kinetics of MB on the hazelnut

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shell was tested and activation energy was reported to be 45.6 kJ/mol. The pseudo-

second order equilibrium adsorption capacity of hazenut shell was reported as 20.6

mg/g [86].

Caulerpa racemosa var. cylindracea is one of the well known invasive

species in the Mediterranean Sea. Dried biomass of C. racemosa var. cylindracea

was shown 5.23 mg/g adsorption capacity for MB at 291 K [87]. Kinetics

adsorption experiments were conducted to evaluate the adsorption characteristics

of a MB on nitric acid treated water-hyacinth. This study showed 333 mg/g

adsorption capacity [88]. Yellow passion fruit peel (Passiflora edullis, F.

flavicarpa) and mandarin peel (Citrus reticulata) as biosorbents were used and

they got the equilibrium in 48 h [89] and in another case it was 56 h with yellow

passion fruit (Passiflora edulis Sims. f. flavicarpa Degener) peel a powdered solid

waste, which has the maximum adsorption capacity of 2.06 mg/g after 50 h of

contact time at pH 9.0 and temperature 298 K [90]. The study described

adsorption of MB by peanut husk in batch and fixed-bed column modes at 293 K

and observed the 72.13±3.03 mg/g adsorption capacity [91].

Many solid wastes, that are available in large quantities, have the potential

to adsorb pollutants from aqueous effluents. The gulmohar plant leaf powder was

investigated for its potential adsorption capacity of 186.22 mg/g [92]. Batch

sorption experiments were carried out using guava leaf powder, for the removal of

MB from aqueous solutions, maximum dye uptake was observed to be 295 mg/g

[93]. Kinetics of MB adsorption on three low cost adsorbents namely guava leaf

powder teak leaf powder and gulmohar leaf powder was predicted using film pore

diffusion model. Based on the values of Biot number it was concluded that MB

adsorption on guava, teak and gulmohar leaf powders were controlled by internal

pore resistance. It was also noticed that external-film coefficient increased with

increase in temperature [94]. Continuous fixed-bed studies were undertaken to

evaluate the efficiency of jackfruit leaf powder as an adsorbent for the removal of

Chapter 5 244


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MB from aqueous solution and under the effect of various parameters, it showed

252.83 mg/g as adsorption capacity [95]. The MB dye was adsorbed on an

adsorbent prepared from mature leaves of the neem tree (Azadirachta indica). The

Langmuir monolayer capacity had a mean value of 8.76 mg/g [96]. The ability of

an unconventional bio-adsorbent, pineapple leaf powder for the adsorption of MB

from aqueous solution was studied. The adsorption was favorable at higher pH and

lower temperature, and the equilibrium data were well fitted by the Langmuir

isotherm. The maximum adsorption capacity varied from 141.81 to 281.18 mg/g

when pH increases from 3.5 to 9.5 [97]. The adsorption of two basic dyes, MB and

crystal violet on wood apple shell was investigated using a batch adsorption

technique. It was observed that the wood apple shell adsorbent showed higher

adsorption capacity for crystal violet (130 mg/g) than MB (95.2 mg/g) and

followed the pseudo-second order kinetics [98].

The literature survey shows that the various adsorbents were used for

removal of MB from aqueous solution, the fruit shell also used for the same but

they are very few in number. As per all remarks about adsorption capacity there is

still need of inexpensive adsorbent. We are introducing the fruit shell of Swietenia

mahagoni, known as West Indian or Indian mahogany as adsorbent, the names are

as per the region. After complete development the fruit gets burst self. The seed

for next germination is medicinally useful and shells are unemployed, so we have

tried to use this shell as adsorbent.

The adsorbent characterization has been done with FTIR, SEM, C, H, N, S

analyzer as well as the properties were determined. In the study various

parameters were investigated as well as the isotherm study has been done with

Langmuir and Fruedlich isotherm models. The pseudo-first and pseudo-second

order models were used for the kinetic study. The results indicated that, the

Swietenia mahagoni fruit shell is good adsorbent to remove the MB from aqueous

solution effectively and economically.

Chapter 5 245


ADSORBENTS

5.3 EXPERIMENTAL

5.3.1 Preparation of materials and dye solution

The Swietenia mahagoni, fruit shell is used as adsorbent for the adsorption

of MB. The general botanical classification of mahogony as; Kingdom-plantae,

Division- Magnoliophyta, Class- Magnoliopsida Order – Sapindales, Family-

Meliaceae, Genus- Swietenia, Species- S. mahagoni, Scientific Name- Swietenia

mahagoni [99].

The Mahogany Fruit Shell (MSF) has been employed successfully as

adsorbent in this study without any chemical or physical treatment. The MSF

material was collected from the Shivaji University, Campus. Fruit has the bursting

characteristic to spread the seeds, and the shells remains as worthless. These shells

were collected and developed as adsorbent. The shells were dried naturally and

then washed thoroughly under tap water to remove dirt and again dried in oven at

383 K and then cut into small pieces and again washed. The dried sample was

crushed and at this stage the material was washed till all colouring contents are

removed out which may interfere into further process. The material was dried at

383 K for 24 h and sieved through BSS 25.

The Methylene Blue dye structure is shown in Fig. 5.1. It has molecular

formula C16H18N3SCl, (λmax=670 nm). Stock solution of 1g/dm3 was prepared

with deionized water. All working solutions used in tests were prepared by

appropriate dilutions of the stock solution to a pre-determined concentration. All

chemicals used in this study were of analytical reagent grade and purchased from

S. D. Fine Chem. Ltd. India.

5.3.2 Characterization of adsorbent

The characterization of adsorbent has been done with Fourier Transform

Infra Red Spectroscopy (FTIR) to analyze the functional groups present, Scanning

Electron Microscopy (SEM) has employed to know the surface morphology of the

Chapter 5 246


ADSORBENTS

adsorbent and C, H, N, S analyzer was used for quantitative elemental analysis.

The elemental analysis and various properties such as ash content, moisture

content and bulk density are given in Table 5.1.

The FTIR (Perkin Elmer Spectrum 100) spectrum of MFS is given in Fig.

5.2 for before adsorption and Fig. 5.3 for after adsorption. From the Fig. 5.2, the

value at 3400 cm-1 has denoted the presence of OH group, while 2923 cm-1

corresponds to C-H stretching. The values at 1733, 1626, 1434, 1372, 1250 and

1049, 896 cm-1 gives the information about the presence of C=O, N-H bending, -

CH2 from cellulose, N=O symmetric stretching, C-O stretch and C-H bending and

=C-H bending respectively. The SEM (JEOL, JSM-6360) images are shown in

Fig. 5.4(a) before adsorption and Fig. 5.4(b) after adsorption, which indicates the

difference in the external appearance of the MFS. Before adsorption the surface

was very rough and after adsorption it appears getting just like formation of a layer

on surface. The C, H, N, S elemental analyzer (Quanta 3D FEI) confirms the

presence of carbon is maximum percentage amongst all.

5.3.3 Batch adsorption experiment

The experiments were carried out by batch adsorption method. The

isotherm study has been done by varying the initial concentration of the MB from

100 to 700 mg/dm3 at constant MFS of 450 mg/dm3 as adsorbent. The batch was

agitated for 420 min on orbital shaker at constant temperature 299 ± 2 K and at pH

of 9 in the Erlenmeyer flasks with 180 rpm as agitation speed. For the

thermodynamic study, temperature was varied from 303 K to 323 K. The

equilibrium adsorption capacity of MSF was evaluated.

Adsorption of Methylene blue dye on Mahogany fruit shell

Chapter 5 247


ADSORBENTS

5.4 RESULT AND DISCUSSION

5.4.1 Analysis of adsorbent

The adsorption of MB on MFS was clearly identified from Fig. 5.3, FTIR

spectrum of MFS (Fig.5.3 (A)), MB (Fig.5.3 (B)) and MB adsorbed on MFS

(Fig.5.3(C)). The major peaks are present from 2000 to 400 cm-1. The several

peaks from MFS and MB are merged or they are slightly shifted. The peak at 1736

cm-1 in Fig.5.3(C) is due to C=O which is only present in MFS (Fig. 5.3(A)) at

1733 cm-1. The peak at 1626 cm-1 is due to presence of N-H bending present in

MFS (Fig. 5.3(A)) and 1601 cm-1 peak from (Fig. 5.3(B)) MB is due to C=C

group. Both these are merged and show weak peak at the 1620 and 1602 cm-1 and

form broad peak together. The peak at 1508 cm-1 is due to C=N stretching from

MB in Fig.5.3(C) as it shows peak originally at 1488 cm-1 in MB (Fig. 5.3(A)).

Peak at 1383 cm-1 in Fig.5.3(C) is due to merging of peak from both MSF and MB

peak at 1372 and 1396 cm-1 respectively but peak at 1330 cm-1 (Fig. 5.3(C)) is

shifted from 1356 cm-1 which indicates C-H bending in MB (Fig.5.3(B)). In case

of MSF, peak at 1250 cm-1 (Fig. 5.3(A)) is due to C-O stretching which is shifted

to 1248 cm-1 in Fig. 5.3(C) MB adsorbed on MFS. The peaks from MB (Fig.

5.3(B)) at 1142 and 1182 cm-1 are due to merging of C=S stretching with strong

peak at 1048 cm-1 from MFS (Fig. 5.3(A)) and show broad peak at 1051 cm-1 in

MB adsorbed on MFS (Fig. 5.3(C)). Peak at 886 cm-1 in MB (Fig. 5.3(B)) is due

to C=C aromatic bending, it slightly shifted at 889 cm-1 in Fig.5.3(C). The FTIR

results reveal the adsorption of MB on MFS. The merging and shifting was

already observed in some reports [72, 74, 81].

In case of SEM study, the change in surface morphology was observed. In

Fig. 5.4 (A) before adsorption and Fig. 5.4(B) after adsorption it is clearly

observed that, the layer was formed on initial rough surface. Similar observations

in case of SEM are also reported [69, 70, 76, 78, 82, 83].

Chapter 5 248


ADSORBENTS

5.4.2 Effect of pH

The pH study is important for development of every successful method,

because pH can alter the results. In present study pH was varied from 1 to 11

(Table 5.2) with concentration of MB of 100 mg/dm3, 450 mg amount of MFS,

299± 2 K temperature and agitation at 180 rpm for 420 min. The result in Fig. 5.5

shows that, the maximum adsorption was observed at pH above 6. At pH 6 the

MB removal percentage was 98.24% and amount adsorbed was 10.91 mg/g which

was risen up to 99.05 % and 11.01 mg/g when pH rises up to 9.0. We have chosen

pH 9.0 as constant pH throughout the study.

The Methylene Blue adsorption usually increases as the pH is increased.

Lower adsorption of MB at acidic pH is probably due to the presence of excess H+

ions competing with the cation groups on the dye for adsorption sites. At higher

pH, the surface of MFS particles may get negatively charged, which enhances the

adsorption of positively charged dye cations through electrostatic forces of

attraction [78]. Such observations were also reported by B.H. Hameed [82] and S.

Cengiz [87].

5.4.3 Effect of time

The effect of agitation period on the removal of MB by MFS at initial

concentrations of MB 100 mg/dm3, pH 9, 450 mg adsorbent and agitation speed at

180 rpm is shown in Fig. 5.6. The agitation period was varied from 0 to 600 min

(Table 5.3) at constant temperature. The time plot shows that, the removal of

adsorbate is rapid in early stages but it gradually slows down until it reaches the

equilibrium. This is due to the fact that a large number of vacant surface sites are

available for adsorption during the initial stage, and after a lapse of time the

remaining vacant surface sites are difficult to be occupied due to repulsive forces

between the solute molecules on the solid surface and in bulk phase [76]. The

equilibrium was attained after shaking for 420 min. Once equilibrium was

Chapter 5 249


ADSORBENTS

attained, the percentage sorption of MB did not change with further increases of

time. So, it was assumed that longer treatment might not have further effect to

change the properties of the adsorbent therefore time 420 min was fixed for further

study. A similar trend was also observed for MB adsorption on hazelnut shells

[86].

5.4.4 Effect of initial concentration of MB

The amount of MB adsorbed per unit mass of adsorbent increased with the

increase in initial concentration and percentage removal of MB from aqueous

solution decreased with the increase in initial concentration (Fig.5.7). The amount

of MB adsorbed at equilibrium (qe) increased from 11.01 to 50.73 mg/g as the

initial concentration was increased from 100 to 700 mg/dm3 (Table 5.4). The

initial concentration provides an important driving force to overcome all mass

transfer resistances of the MB between the aqueous and solid phases. Hence, a

higher initial concentration of dye will enhance the adsorption process [70].

However, the MB percentage removal decreased from 99.05% to 65.23% as the

MB concentration was increased from 100 to 700 mg/dm3. For this study the pH,

temperature, agitation speed, time etc. were kept constant. The same observation

was also reported for other adsorbents like meranti sawdust [76].

5.4.5 Effect of adsorbent dosage

The effect of adsorbent dosage on the removal of MB was studied for an

initial dye concentration of 100 mg/dm3, by varying the adsorbent from 50 to 450

mg/dm3 at temperature 299 ± 2 K and by keeping all other parameters constant

(Fig. 5.8, Table 5.5). The Percentage dye removal increased with increase in

adsorbent dosage. Only 4.33% removal of MB was observed when 50 mg

adsorbent was used, but it increases up to 99.05% removal when 450 mg

adsorbent was employed. This may be due to the fact that the active sites could be

Chapter 5 250


ADSORBENTS

effectively utilized when the dosage was low (i.e. low ratio of adsorbent /

adsorbate). When the adsorbent dosage is higher (high ratio of adsorbent /

adsorbate) it is more likely that a significant portion of the available active sites

remains uncovered, leading to lower specific uptake [92]. The amount of dye

adsorbed per unit mass of adsorbent decreased with increasing adsorbent mass,

due to the reduction in effective surface area [71]. The present observations are in

good agreement with the previous findings by Bhattacharrya and Sharma [96], D.

Ozer [84] and S.Cengiz [87].

5.4.6 Effect of agitation speed

In the batch adsorption systems, agitation speed plays a significant role in

affecting the external boundary film and the distribution of the solute in the bulk

solution. The experiments were carried out by varying agitation speed from 50

rpm to 240 rpm by keeping all other conditions constant. When the speed was

increased from 50 to 240 rpm (Fig. 5.9, Table 5.6) the amount adsorbed and

percentage removal of MB, both were increased simultaneously. At the 50 rpm,

50.75 % removal of MB was observed, which was increased up to 99.05% with

increasing speed of agitation up to 180 rpm. The influence of agitation speed was

negligible after 180 rpm; both amount and percentage remains steady. Thus we

selected 180 rpm agitation speed for further study. The simialr observations were

also reported in the literature [59, 97].

5.4.7 Adsorption isotherm

Equilibrium studies that give the capacity of the adsorbent and adsorbate

are described by adsorption isotherms, which is usually the ratio between the

quantity adsorbed and remained in solution at equilibrium at constant temperature

[45]. The amount of MB dye adsorbed (qe) has been plotted against the

equilibrium concentration (Ce) and plot is shown in Fig. 5.10 (Table 5.7). The

Chapter 5 251


ADSORBENTS

equilibrium adsorption density, qe increased with the increase in dye

concentration. Several models have been reported in the literature to describe the

experimental data of adsorption isotherms. The Langmuir and Freundlich are the

most frequently employed models. In this work, both models were used to

describe the relationship between the amount of dye adsorbed and its equilibrium

concentration.

5.4.8 Langmuir isotherm

The Langmuir adsorption isotherm has been successfully applied to many

adsorption processes and has been the most widely used.

The Langmuir adsorption isotherm study has been done by varying the

initial concentration of MB from 100 to 700 mg/dm3, keeping all other conditions

constant. A plot of Ce/qe versus Ce (Fig. 5.11, Table 5.8) indicates a straight line of

slope 1/qm and an intercept of 1/KLqm, where, Ce is the equilibrium concentration

(mg/dm3), qe is the amount of metal ion adsorbed (mg/g), qm is qe for a complete

monolayer (mg/g); KL is sorption equilibrium constant (dm3/mg).

The essential characteristic of a Langmuir isotherm, related to the isotherm

shape, can be expressed in terms of a dimensionless constant separation factor,

also called the equilibrium parameter RL. The adsorption of MB on MFS follows

the Langmuir isotherm model for metal adsorption. The value of qm and KL were

evaluated and given in Table 5.9. The dimensionless parameter RL between 0.039

to 0.913 is consistent with favorable adsorption. The high value of correlation

coefficient R2 indicates a good agreement between the parameters and confirms

the monolayer adsorption of MB on the adsorbent surface.

5.4.9 Freundlich isotherm

The Freundlich isotherm assumes that the adsorption occurs on

heterogeneous surface at sites with different energy of adsorption and with non-

Chapter 5 252


ADSORBENTS

identical adsorption sites that are not always available. The KF value is related to

the adsorption capacity; while 1/n value is related to the adsorption intensity.

A plot of log qe versus log Ce (Fig. 5.12) from the values in Table 5.10

gives a straight line. KF and 1/n were determined from the intercept and the slope,

respectively and the results are given in table 5.11. The value of the correlation

coefficient, R2, obtained in this case indicates that the Langmuir isotherm model

fits better than the Freundlich isotherm model.

5.4.10 Adsorption kinetics

The experiments were carried out at constant temperature as well as speed

and pH. Amount of adsorption of MB on MSF was studied at various time

intervals from 0 to 420 min. In order to investigate the mechanism of adsorption

on MSF, kinetic model has been used to identify the possible mechanisms of such

adsorption process. In this study, pseudo-first and pseudo-second order kinetic

models have been proposed to elucidate the mechanism of adsorption depending

on the characteristics of the adsorbent.

Plot of log (qe−qt) vs. t (Fig. 5.13, Table 5.12) gives a straight line for first

order adsorption kinetics, which allow computation of the adsorption rate constant,

k1. The k1 and qe value for the initial concentration of 100 mg/dm3 are given in

Table 5.14 which are not correlated much accurately. The value R2 was 0.932 for

pseudo-first order which is not so promising.

The pseudo-second-order rate equation is used to study the adsorption of

MB on MSF. The rate parameters k2 and qe can be directly obtained from the

intercept and slope of the plot of t/qt vs. t (Fig. 5.14, Table 5.13). The values

obtained graphically for pseudo-first and pseudo-second order models are listed in

Table 5.14. The results show that the pseudo-second order model provided a better

approximation to the experimental kinetic data than the pseudo-first order model.

Chapter 5 253


ADSORBENTS

5.4.11 Intraparticle diffusion study

The adsorbate species are most probably transported from the bulk of the

solution in to the solid phase through intraparticle diffusion process, which is often

the rate limiting step in many adsorption processes. The possibility of intraparticle

diffusion was explored by using the intraparticle diffusion model [100]. The

intraparticle diffusion rate constant (kid) was determined from the slope of the

linear gradients of the plot qt versus t1/2 as shown in Fig. 5.15 (Table 5.15). The

rate constant of intraparticle diffusion at different temperatures is shown in Table

5.16.

The adsorption of MB on MSF adsorbent was a multi-step process,

involving adsorption on the external surface and diffusion into the interior. All the

steps slow down as the system approaches equilibrium. If the steps are

independent of one another, the plot of qt vs. t1/2 usually shows two or more

intersecting lines depending on the exact mechanism, the first one of these lines

representing surface adsorption and the second line shows intraparticle diffusion.

The absence of such features in the plots of the present work indicated that the

steps were indistinguishable from one another and that the intraparticle diffusion

was a prominent process right from the beginning of dye-solid interaction. If the

uptake of the adsorbate varies with the square root of time, intraparticle diffusion

can be taken as the rate limiting step. If the qt vs. t1/2 plots pass through the origin

then intraparticle diffusion is the sole rate limiting step [96]. Since this was also

not the case in the present work it may be concluded that, surface adsorption and

intraparticle diffusion were concurrently operating during the MB-MSF

interactions.

5.4.12 Adsorption thermodynamics

The temperature plays a vital role in the adsorption capacity of adsorbent

and it is clear from Fig. 5.16 (Table 5.17), that increase in temperature increases

Chapter 5 254


ADSORBENTS

the amount of adsorption. The temperature was increased from 303 to 323 K with

5 K interval and the results were showing very much difference in the adsorption;

it was increased from 53.05 to 61.85 mg/g. This indicates that the adsorption

reaction was endothermic in nature. The enhancement in the adsorption capacity

may be due to the chemical interaction between adsorbate and adsorbent, creation

of some new adsorption sites and the increased rate of intraparticle diffusion of

MB into the pores of the adsorbent at higher temperatures.

The thermodynamic parameters such as standard Gibb’s energy (∆G○),

standard enthalpy (∆H°) and standard entropy (∆S°) were determined at MB

concentration of 700 mg/dm3 by keeping all other parameters constant.

The plot of lnKc vs 1/T gives straight line as shown in Fig. 5.17 (Table

5.18). ∆H° and ∆S° values were obtained from the slope and intercept of this plot.

The standard free energy change (∆G°), standard enthalpy change (∆H°) and

standard entropy change (∆S°) were obtained from the Gibb’s free energy

equation. Thermodynamic parameters for the adsorption of MB on MSF are listed

in Table 5.19. Negative values of ∆G° indicate the feasibility of the process and

spontaneous nature of the adsorption with a high performance of MB for MSF.

Positive value of ∆H° indicates the endothermic nature of the process, while

positive value of ∆S° reflects the affinity of the adsorbents for the MB and

suggests some structural changes in adsorbate and adsorbent.

5.5 Comparison of adsorption capacity of MFS with other adsorbents

In Table 5.20, the adsorption capacity of MFS is compared with other

reported adsorbents. From the economical and adsorption capacity point of view,

MFS is good adsorbent.

Chapter 5 255


ADSORBENTS

5.6 CONCLUSION

1) The results of the adsorption of MB on MFS are very satisfactory and the

preparation cost of adsorbent is nearly zero.

2) The removal of MB was possible by MFS up to 99.05 % when concentration

of the dye was 100 mg/dm3.

3) The study was evaluated with isotherm models amongst them, Langmuir

adsorption was fitted better than Freundlich isotherm. The maximum

adsorption capacity was 51.81 mg/dm3 as well as regression factor was 0.997.

4) The kinetic study has shown that, the pseudo-second order is more suitable

than pseudo-first order.

5) The process is endothermic and spontaneous, and evaluated thermodynamic

parameters such as standard free energy change (∆G°), standard enthalpy

change (∆H°), and standard entropy change (∆S°) which supports the favorable

adsorption.

6) The MSF is effective, inexpensive adsorbent to remove MB from aqueous

solution as well as it may be useful for waste water treatment.

Chapter 5 256


ADSORBENTS

Table 5.1

Elemental Analysis and properties of MSF

Property Result

Ash content 2.53%

Bulk density 0.237gm/cm3

Moisture content 9.92%

Carbon 60.77

Hydrogen 1.76

Nitrogen 0.57

Chapter 5 257


ADSORBENTS

Table 5.2

Effect of pH on removal, % and amount adsorbed, mg/g of MB

MB =100 mg/dm3, Time = 420 min, T= 299 ± 2 K, MFS=405 mg, agitation

speed= 180 rpm

pH Amount adsorbed, q mg/g Removal of MB, %

1 3.42 30.77

2 5.38 48.43

3 7.86 70.70

4 9.76 87.80

5 10.53 94.73

6 10.91 98.24

7 10.97 98.69

8 10.99 98.95

9 11.01 99.05

10 10.99 98.90

11 10.94 98.44

Chapter 5 258


ADSORBENTS

Table 5.3

Effect of shaking period on removal, % and amount adsorbed, mg/g of MB

MB=100 mg/dm3, pH=9, T= 299 ± 2 K, MFS=450 mg, agitation speed= 180 rpm

Time, min Amount adsorbed, qt mg/g Removal of MB, %

30 3.41 30.73

60 5.66 50.02

120 7.53 67.73

180 9.18 82.58

240 10.1 90.88

300 10.74 96.65

360 10.97 98.75

420 11.01 99.05

480 11.01 99.05

540 11.01 99.05

600 11.01 99.05

Chapter 5 259


ADSORBENTS

Table 5.4

Effect of initial concentration of MB on amount adsorbed, mg/g, and removal, %

of MB

Time=420min, pH=9, T= 299 ± 2 K, MFS= 450 mg, agitation speed= 180 rpm

Initial Conc MB

mg/dm3

Amount adsorbed, q

mg/g

Removal of MB, %

100 11.01 99.05

150 16.33 98.02

200 21.59 97.19

250 26.98 96.04

300 31.62 94.85

350 34.87 90.04

400 38.98 87.70

500 45.76 81.50

600 48.03 72.05

700 50.73 65.23

Chapter 5 260


ADSORBENTS

Table 5.5

Effect of adsorbent dosage on removal, % and amount adsorbed, mg/g, of MB

pH=9, MB = 100mg/dm3, Time= 420min, T= 299 ± 2 K, mg/dm3, agitation

speed= 180 rpm

MSF, mg Amount adsorbed, q mg/g Removal of MB, %

50 4.33 4.33

100 5.48 10.95

150 6.72 20.17

200 8.54 34.14

250 9.66 48.30

300 10.12 60.75

350 10.79 75.58

400 11.00 88.05

450 11.01 99.05

Chapter 5 261


ADSORBENTS

Table 5.6

Effect on agitating speed on removal, % and amount adsorbed, mg/g of MB

MB=100 mg/dm3, Time= 420 min, T= 299 ± 2 K, MFS=450 mg, pH=9

Agitation speed, rpm Amount adsorbed, q mg/g Removal of MB, %

50 5.64 50.75

70 6.68 61.75

100 7.86 70.75

120 9.53 85.72

140 10.20 91.76

160 10.75 96.75

180 11.01 99.05

200 11.01 99.05

220 11.01 99.05

240 11.01 99.05

Chapter 5 262


ADSORBENTS

Table 5.7

Adsorption isotherm for the adsorption of MB on MSF


Ce q

0.95 11.01

2.97 16.33

5.62 21.59

9.91 26.98

15.44 31.62

36.17 34.87

49.20 38.98

72.52 45.76

167.70 48.03

243.41 50.73

Chapter 5 263


ADSORBENTS

Table 5.8

Langmuir isotherm for adsorption of MB on MSF


Ce Ce/q

0.95 0.086

2.97 0.182

5.62 0.260

9.91 0.373

15.44 0.488

36.17 1.037

49.20 1.262

72.52 1.585

167.70 3.492

243.41 4.798

Table 5.9

Langmuir constant for the adsorption of MB on MSF

qm (mg/g)

KL(1/mg)

R2

51.81

0.101

0.997

Chapter 5 264


ADSORBENTS

Table 5.10

Freundlich adsorption isotherm for the adsorption of MB on MSF


log Ce log qe

-0.022 1.042

0.473 1.213

0.750 1.334

0.996 1.431

1.189 1.500

1.558 1.543

1.692 1.591

1.861 1.661

2.225 1.682

2.286 1.705

Table 5.11

Freundlich constant for the adsorption of MB on MSF

Kf

n

R2

12.72

3.556

0.964

Chapter 5 265


ADSORBENTS

Table 5.12

Pseudo first order model for the adsorption of MB on MSF


t min log (qe-qt)

0 1.0418

30 0.881

60 0.736

120 0.542

180 0.263

240 -0.041

300 -0.569

360 -1.398

Chapter 5 266


ADSORBENTS

Table 5.13

Pseudo second order model for the adsorption of MB on MSF MB=100 mg/dm3, pH=9, T= 299 ± 2 K, MFS=450 mg, agitation speed= 180 rpm

t t/qt

0 0

30 8.798

60 10.791

120 15.936

180 19.608

240 23.762

300 27.933

360 32.817

420 38.147

Table 5.14

Kinetic parameters for the adsorption of MB on MSF

Pseudo first order Pseudo second order

qe exp.

(mg/g)

k1x10–3

(min–1)

qe calc.

(mg/g)

R2 k2 x10–3 qe calc.

(mg/g)

R2

11.01

6.40

17.02

0.932

6.26

12.64

0.991

Chapter 5 267


ADSORBENTS

Table 5.15

Intraparticle diffusion for the adsorption of MB on MSF


t 1/2 qt

5.477 3.410

7.746 5.560

10.955 7.530

13.417 9.180

15.492 10.100

17.321 10.740

18.974 10.970

20.494 11.010

Table 5.16

Study of intraparticle diffusion of adsorption of MB on MSF

kid

(mg g−1 min−1)

R2

0.512

0.942

Chapter 5 268


ADSORBENTS

Table 5.17

Effect of temperature on amount of MB adsorbed on MSF

MB=700 mg/dm3, Time=420 min, MFS= 450 mg, pH=9, agitation speed= 180

rpm

T K Amount adsorbed, q mg/g

303 53.05

308 56.03

313 59.03

318 60.57

323 61.85

Chapter 5 269


ADSORBENTS

Table 5.18

Van't Hoff plots for the adsorption of MB on MSF


rpm

1/T lnKc

0.00330 1.563

0.00324 1.618

0.00319 1.671

0.00314 1.696

0.00309 1.717

Table 5.19

Thermodynamic parameters of adsorption of MB on MSF

T K ΔG° kJ/mol ∆H° kJ/mol ∆S° J/mol k

303 -3.938

0.746

4.034

308 -4.143

313 -4.348

318 -4.484

323 -4.611

Chapter 5 270


ADSORBENTS

Table 5.20

Comparison of adsorption capacity of MSF with other adsorbents

Adsorbent qm (mg/g) Reference

Natural zeolite 16.37 [19]

Raw kaolin

Calcined raw kaolin

27.49

13.44

[24]

[24]

Gypsum 36 [25]

Amberlite XAD-2 16.8 [27]

Fe(III)/Cr(III) hydroxide 22.8 [28]

Polyacrylic acid-bound iron oxide

magnetic nanoparticles

0.199

[31]

Halloysite nanotubes 84.32 [34]

Multiwalled carbon nanotubes

containing oxygen 0.85%

2.16%,

7.07%

61.10

36.62

25.62

[35]

[35]

[35]

Silica nano-sheets 11.77 [36]

Oil palm wood activated carbon 90.9 [47]

Sunflower oil cake activated carbon

Impregnation with 0.85 H2SO4

Impregnation with 1.90 H2SO4

10.21

16.43

15.798

[48]

[48]

[48]

Straw carbon

Rice husk carbon

Groundnut shell carbon

Coconut shell carbon

Bamboo dust carbon

42.60

37.57

7.50

8.16

7.20

[49]

[49]

[49]

[49]

[49]

Dehydrated wheat bran carbon 82.00 [53]

Chapter 5 271


ADSORBENTS

Activated coir pith carbon 5.87 [54]

Cotton stalk

Cotton dust

Cotton waste

4.52

8.33

9.75

[60]

[60]

[60]

Natural wheat straw 60.66 [63]

Rice husk ash 18.15 [66]

Spent coffee grounds residue 18.70 [71]

Parthenium hysterophorus 39.68 [74]

Coconut bunch waste 70.92 [78]

C. racemosa var. cylindracea 5.23 [87]

Neem tree 8.76 [96]

Mahogany Fruit Shell 51.81 Present work

Chapter 5 272


ADSORBENTS

N

N

S N

CH3

CH3

CH3

CH3

Cl

Fig. 5.1

Structure of methylene blue dye

Chapter 5 273


ADSORBENTS

Fig. 5.2

FTIR spectrum of MSF

4000 3500 3000 2500 2000 1500 1000 500

24

28

32

36

40

14

34

13

72

1733

2923

89

6

60

8

1250

1048

1626

3400

609

Tra

ns

mit

an

ce

(%

)

Wavenumber (cm-1)

Chapter 5 274


ADSORBENTS

1800 1500 1200 900 600

15

08

6091

37

2

14

88

11

82

11

42

13

56

13

96

88

6

16

01

89

6

12

50

10

48

14

34

16

26

17

33

13

30

13

83

10511620

1736

1602 14

23

12

48

609

88

9

609

Tra

nsm

itan

ce (

%)

Wavenumber (cm-1)

A

B

C

Fig. 5.3

FTIR spectrum of (A) MSF, (B) MB, (C) MB adsorbed on MSF

Chapter 5 275


ADSORBENTS

Fig.5.4

(A) SEM image before adsorption of MB

Fig.5.4

(B) SEM image after adsorption of MB

Chapter 5 276


ADSORBENTS

0

20

40

60

80

100

0 2 4 6 8 10 12

pH

Rm

ov

al o

f M

B, %

0

2

4

6

8

10

12

Am

ou

nt

ad

so

rbe

d o

f M

B, m

g/g

Fig. 5.5

Effect of pH on removal, % and amount of MB adsorbed, mg/g

MB=100 mg/dm3, Time = 420 min, T= 299 ± 2 K, MSF=450 mg, agitation speed=

180 rpm

Chapter 5 277


ADSORBENTS

0

20

40

60

80

100

120

0 200 400 600 800

time, min

Re

mo

va

l of

MB

, %0

2

4

6

8

10

12

Am

ou

nt

ad

so

rbe

d o

f M

G, m

g/g

Fig. 5.6

Effect of shaking period on removal, % and amount adsorbed, mg/g of MB

MB=100 mg/dm3, pH=9, T= 299 ± 2K, MFS=450 mg, agitation speed= 180 rpm

Chapter 5 278


ADSORBENTS

0

20

40

60

80

100

0 200 400 600 800

Initial conc. MB, mg/dm3

Re

mo

va

l of

MB

, %

0

10

20

30

40

50

60

Am

ou

nt

ad

so

rbe

d o

f M

B, m

g/g

Fig. 5.7

Effect of initial concentration of MB on amount adsorbed, mg/g and removal, %

of MB

Time= 420 min, pH=9, T= 299 ± 2 K, MFS= 450 mg, agitation speed= 180 rpm

Chapter 5 279


ADSORBENTS

0

20

40

60

80

100

0 100 200 300 400 500

Adsorbent dose, mg

Re

mo

va

l of

MB

, %

0

2

4

6

8

10

12

Am

ou

nt

ad

so

rbe

d o

f M

B, m

g/g

Fig. 5.8

Effect of adsorbent dosage on removal, % and amount adsorbed, mg/g on MB

MB = 100mg/dm3, Time= 420 min, pH=9, T= 299 ± 2 K, agitation speed= 180

rpm

Chapter 5 280


ADSORBENTS

0

20

40

60

80

100

50 100 150 200 250

rpm

Rem

oval o

f M

B, %

0

2

4

6

8

10

12A

mo

un

t ad

so

rbed

of M

B, m

g/g

Fig. 5.9

Effect on agitating speed on removal, % and amount adsorbed, mg/g of MB

MB=100 mg/dm3, Time=420 min, T= 299 ± 2 K, MFS= 450 mg, pH=9

Chapter 5 281


ADSORBENTS

0

10

20

30

40

50

60

0 50 100 150 200 250 300

Ce mg/dm3

qe

mg

/g

Fig. 5.10

Adsorption isotherm for adsorption of MB on MSF

Time=420 min, T= 299 ± 2 K, MFS= 450 mg, pH=9, agitation speed= 180 rpm

Chapter 5 282


ADSORBENTS

0

1

2

3

4

5

6

0 50 100 150 200 250 300

Ce

Ce/q

e

Fig. 5.11

Langmuir isotherm for adsorption of MB on MSF

Ttime=420 min, T= 299 ± 2 K, MFS= 450 mg, pH=9, agitation speed= 180 rpm

Chapter 5 283


ADSORBENTS

0

0.4

0.8

1.2

1.6

2

-0.5 0 0.5 1 1.5 2 2.5

log Ce

log

qe

Fig. 5.12

Freundlich adsorption isotherm for adsorption of MB on MSF

Time=420 min, T= 299 ± 2 K, MFS= 450 mg, pH=9, agitation speed= 180 rpm

Chapter 5 284


ADSORBENTS

-2

-1.5

-1

-0.5

0

0.5

1

1.5

0 100 200 300 400

t minlog

(q

e-q

t)

Fig 5.13

Pseudo-first order plot for adsorption of MB on MSF

MB=100 mg/dm3, T= 299 ± 2 K, MFS= 450 mg, pH=9, agitation speed= 180 rpm

Chapter 5 285


ADSORBENTS

0

10

20

30

40

50

0 100 200 300 400 500

t min

t/qt

Fig. 5.14

Pseudo-second order plot for adsorption of MB on MSF


Chapter 5 286


ADSORBENTS

0

2

4

6

8

10

12

14

0 5 10 15 20 25

t1/2

qt

Fig. 5.15

Intraparticle diffusion plot for adsorption of MB on MSF


Chapter 5 287


ADSORBENTS

40

45

50

55

60

65

300 305 310 315 320 325

T K

Am

ou

nt

ad

so

rbe

d o

f M

B, m

g/g

Fig. 5.16

Effect of temperature on amount adsorbed of MB on MSF


rpm

Chapter 5 288


ADSORBENTS

1.52

1.56

1.6

1.64

1.68

1.72

1.76

0.00305 0.0031 0.00315 0.0032 0.00325 0.0033 0.00335

1/T

ln K

c

Fig. 5.17

Van't Hoff plots for adsorption of MB on MSF


rpm

Chapter 5 289


ADSORBENTS

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Chapter 5 297


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