basic dye adsorption on a low cost carbonaceous sorbent-kinetic...

Indi an Journal of Chemica! Technology Vol. 9, May 2002, pp. 201 -208

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Basic dye adsorption on a low cost carbonaceous sorbent- Kinetic and equilibrium studies

8 Stephen Tnbaraj & N Sulochana*

Department of Chemi stry , Regional Engineering College, Tiruchirappalli 620 015 , Indi a

Received 5 March 2001 : revised received 17 March 2002; accepted 20 March 2002

A carbonaceous sorbent prepared from an indigenous agricultural waste, jack fruit peel, by acid treatment was tested for its efficiency in removing basic dyes. Malachite green, a common basic dyestuff of triphenyl methane series used for dyeing silk and wool directly and cotton mordanted with tannin to deep green, was chosen for investigation. The process parameters studied include agitation time, initial dye concentration, carbon dose, pH and temperature. The adsorption followed first order reaction equation and the rate is mainly controlled by intraparticle diffusion. Freundlich, Langmuir and Redlich-Peterson isotherm models were applied to the equilibrium data. The adsorption capacity (Q0 ) obtained from the Langmuir isotherm plot was 166.37 mg g-

1 at an initial pH of 6.0 and at 32 ± 0.5°C. The influence of pH on dye removal was not significant and the adsorption capacity increased with increase in temperature. A portion of the dye was recovered from the spent carbon using 50% acetic acid (vlv).

The discharge of highly coloured effluents into natural water bodies is not only aesthetically displeasing, but it also impedes light penetration, thus upsetting biological processes within a stream. In addition, many dyes are toxic to some organisms causing direct destruction of aquatic communities 1• Some dyes can cause allergic dermatitis, skin irritation, cancer and mutation in man2• Recent estimates indicate that, approximately, 12 % of synthetic textile dyes used each year are lost during manufacture and processing operation and 20 % of these dyes enter the environment through effluents that result from the treatment of residual industrial waters3. Among the various classes of dyes, basic dyes were found to be the brightest class of soluble dyes used by the textile industry as their tinctorial value is very high4 .

Wastewaters from dyeing industries are released into nearby land or rivers without any treatment because the conventional treatment methods are not cost effective in the Indian context. On the other hand, low cost technologies don ' t allow a wishful colour removal or have certain disadvantages5. Adsorption is one of the most effective methods and activated carbon is the preferred adsorbent widely employed to treat wastewater containing different classes of dyes4 . However, recognising the economic drawback of commercial activated carbon, many investigators have

*For correspondence (E-mail: sulochan @rect.emet.in ; Fax: 091-0431-500133)

studied the feasibility of using inexpensive alternative materials like pearl millet husk6, date pits7, saw dust8, buffing dust of leather industrl, coir pith 10, crude oil residue' 1, tropical grass 12, olive stone and almond shells 13 , pine bark 14, wool waste 15, coconut shell 16 etc ., as carbonaceous precursors for the removal of dyes from water and wastewater.

The present study is undertaken to evaluate the efficiency of a carbonaceous sorbent prepared from jack fruit peel, an agricultural waste, for the removal of basic dyes from aqueous solution . Malachite green, a common basic dyestuff of triphenyl methane series used for dyeing silk and wool directly and cotton mordanted with tannin to deep green, was chosen for investigation. Batch-mode adsorption studies were carried out systematically involving process parameters such as agitation time, initial concentration, adsorbent dose, pH and temperature. Jack fruit (Artocarpus heterophyllus) is one of the most popular fruits in South India, where per hectare production is higher than any other fruit. A jack tree produces about 200-500 fruits annually, with each fruit weighing about ~3-40 kg. The outer peel (rind), which is mostly fibrous, constitutes about 59 % of the ripe fruit 17 . Apart from its use as a table fruit, jack is popular for making vegetable, pickles, for dehydration into thin round papad and many culinary preparations. Hence, significant amount of peel is expected to be discarded as waste. Earlier work on its efficiency in removing Cu(II) 18 and Hg(II) 19 from aqueous solution has shown an adsorption efficiency

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of 92.59 mg g- 1 and 125 mg g- 1, respectively at pH

5.0 and at 32 ± 0.5°C.

Experimental Procedure Carbon was prepared by treating air-dried jack fruit

peel (after removing the carpel fibers) with concentrated sulphuric acid in a weight rat io of 1:1 .8 (peel:acid). The resulting black product was kept in an air-oven maintained at 160 ± 5°C for 6 h followed by washing with water until free of excess acid and dried at I 05 ± 5°C. The carbon product obtained from jack fruit peel (JPC) was ground and the portion retained between 44 and 89 )..lm s ieves was used in all the experiments. The characteristics of the carbon such as pH, moisture content, bulk density, ash content, water soluble matter, acid soluble matter, decolourising power, ion exchange capacit/0 and iron content were determined according to lSI methods21 . Surface area was measured using direct reading Carlo Erba Sorptomatic-1800 by assuming that the adsorbed nitrogen forms a monolayer and possess a molecular cross sectional area of 16 A 2. Ash analysis was carried

20.22 Th out as per the standard procedures . e characteristics of JPC are summarized in Table 1. Scanning electron micrograph (SEM) was recorded at two different magnifications (Fig.1a&b) using a software controlled digital scanning electron microscope-LEO 420. The SEM clearly reveals the surface texture and porosity of JPC with holes and small openings found on the surface indicating that it would increase the contact area and facilitate pore diffusion during adsorption.

Malachite green dye was supplied by Bayer Ltd. All adsorption experiments were carried out by agitating the carbon with 100 mL dye solution of desired concentration at pH 6.0 and at room temperature (32 ± 0.5°C) in a mechanical shaker (200 rpm). After the defined time intervals, samples were withdrawn from the shaker, centrifuged and the supernatant solution was analysed for residual dye concentration using a Jasco Double Beam Spectrophotometer (UVIDEC-4308) at 620 nm. Kinetic study was can·ied out by taking three dye concentrations viz., 20, 40 and 60 mg L - I and agitating with 25 mg of carbon dose at predetermined intervals of time. Effect of adsorbent dosage was studied by varying the carbon dose from 5 to 60 mg, taking 60 mg L - I as initial dye concentration. For studies on the effect of pH, the initial pH of 20 mg L - I dye solution was adjusted to a desired value using small amounts of dilute hydrochloric acid or sodium

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Indi an J. Chern. Techno!. , May 2002

Table I - Charac teristics of jack fru it peel carbon

Parameter

pH

Moi sture content, %

Bulk density. g mL- 1

Ash. %

Solubility in water, %

Solubility in 0.25 mol m- .1 HCI ,%

Decolouri sing power, mg g- 1

Ion exchange capacity, mequi g- 1

Surface area, n/ g- 1

Iron , %

Ash analysis, %

Si02

Na20

K20

MgO

CaO

7.24

18.70

0.76

5. 10

1.40

10.20

127.50

101

13 1.73

0.07

16.0

4.03

0.72

33.8

16.6

hydroxide and agitated with 25 mg of the carbon . For temperature variation study, 25 mg of the carbon was agitated with 60 mg L - I dye solution using a temperature-controlled water bath-cum-shaker. Freundlich isotherm was derived from the studies on the effect of carbon dosage on the percent dye removal. Langmuir and Redlich-Peterson isotherm study was carried out with dye solutions of different initial concentrations ranging from 20 to 100 mg L - I and agitating with a fixed carbon dose (25 mg), until equilibrium was reached. Control experiments were carried out to examine possible adsorption of dye in the absence of adsorbent by container walls . It was found that there was no dye adsorption by the container walls. Experiments were repeated at least three times and mean values are reported. Standard deviations and analytical errors were calculated and the maximum error was± 5 %.

After adsorption of 60 mg L- 1 of malachite green by 60 mg 100 mL - I of the carbon, the carbon loaded with dye was separated and gently washed with distilled water to remove any unadsorbed dyes. The dye-laden carbons were agitated wi (h 100 mL of neutral pH water, 1 M sulphuric acid, 1 M sodium hydroxide, 10 % acetic acid (vlv) and 50 % acetic acid (vlv) separately for 60 min .

Results and Discussion Effect of agitation time and initial dye concentration

The kinetics of adsorption of malachite green by JPC is shown in Fig. 2, with smooth and single plots indicating monolayer adsorption of dye on the

Stephen lnbaraj & Suloc hana: Bas ic Dye Adsorption on Low Cost Carbonaceous Sorbent Articles

(a)

(b)

Fig. !- Scanning elec tron micrograph o f jack fruit pee l carbo n. (a) and (b) represent lx 200 and lx 2000 magni fications. respcc ti vel y.

carbon23 . The removal of dye increases with the lapse time and attains eq uilibri um in 45 min for 20 mg L- 1

and 180 mi n for 40 and 60 mg L- 1• With increase in dye concentration from 20 to 60 mg L- 1, the amount of dye adsorbed increased from 77.6 to 167.6 mg g- 1

while the per cent removal decreased from 97 to 69.8, indicating that the dye removal by adsorption on JPC is concentration dependent.

Adsorption rate constant The rate constant of adsorption of malachite green

on JPC was determined using the following rate . . b L 24 expresston gtven y agergren :

200.-------------------------,

~ l BO

'"' "' 16 0 E -;. 140

·g 120 a. 8 tOO c

80 0 a. ~ 6 0 0 .. '0 40

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.,. I .. .,. "' ~

2·5

2

1.5

0.5

0 20 40 60 80 100 120 140

Ti me (m in)

Fig. 3- Lagergren first order kineti c plots. Dye concentrations: (• ) 20 mg L· ' , (• ) 40 mg L-1• ( .&. ) 60 mg L-1•

0 .14 .----- -----------,

0 -1 2

0.1 7

r::

E 0 -08

c c

"' 0 -0 6

r:: c

" .!! Q.Q4 c

cr:

0 -02

0 20 40 60 eo Initi a l dye conce nt ra ti on( mg L

1 l

Fig. 4-Effect of dye concentrati on on the observed rate of adsorpti on.

The rate constant for intraparticle diffusion IS obtained using the equation

... (2)

where Kp (mg g- 1 min-~'') is the intrapartic le diffusion rate constant. The nature of the plots in Fig. 5 suggests that the initial curved portion is attributed to the film or boundary layer diffusion effect and the subsequent linear portion to the intrapartic le diffusion effect23·28. Fig. 5 also depicts that the intrapartic le diffusion is the slow and the rate-determining step. Kr val ues were obtained from the slope of the linear portions o f the curves at each dye concentration (Table 2). The Kr values increased with increase in the dye concentration, which revea ls that the rate of

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Indian J. Chem. Techno!. , May 2002

180

160

140

..,. 120 "' 100 E .,.

80

r 60 40 -20

0 2 4 6 8 10 12 14 16

T ime t ( min)T

Fig . 5- lntrapartie le diffusion plots. Dye conce ntrat ions: ( • ) 20 mg L-1, ( • ) 40 mg L-1, ( .&. ) 60 mg L-1•

Table 2- Kinetic parameters for the adsorption o f malachite green dye by JPC

Dye concentrati on K,"' KP Dr .(mg L- 1) (min- 1) (mg g- 1 min-'' ') (c m1 s- 1)

20 0.1195 1.3765 0.953x l0- 11

40 0.0223 3.400 I 0.178x 10- 11

60 0 .0159 5.0824 0.127x l0- 11

adsorption is governed by the diffusion of adsorbed dye within the pores of the adsorbent.

Assuming spherical geometry for the adsorbent29 , the adsorption rate constant for the process can be correlated to the pore diffusion coefficient in accordance with the expression, Dp = 0.03(r} /t y, ), where, ty, = time for ha lf change (s), Dr = pore diffusion coefficient (cm2 s- 1) and r0 = radius of the adsorbent (em). According to Miche:son et a!. 30, for the pore diffusion to be the rate-li miting step in an adsorption process, the pore diffu sion coefficient

values obtained should fall in the range of I 0- 11 to

10- 13 cm2 s- 1. The average value of pore diffusion coeffic ients (Table 2) calculated for different dye concentrations is 0.415x l0- 11 cm2 s-· 1. Thi s agai n confirms that intrapartic le or pore d iffusion is the rate-contro ll ing step.

Effect of carbon mass The amount of dye adsorption increased with the

increase in carbon close and reac hed a max imum va lue after a particu lar close (Fig. 6). T aken an initia l

dye concentration of 60 mg L- 1, complete dye re moval was obtained at a maximum carbon close of

60 mg 100 mL - I. The increase in the adsorption o f

Stephen Inbaraj & Sul ochana: Basic Dye Adsorption on Low Cost Carbonaceous Sorbent Articles

0 > 0 E ., a:: ~ .

tOO

80

60

40

20

0 10 20 30 40 50 60 70

Corban dose ( mg 100 ml1)

Fi g. 6-Effec t of carbon dose on the per cent removal of dye.

dye with carbon dose was due to the introduction of more binding sites for adsorption.

Adsorption isotherms The distribution of dye between the liquid phase

and the adsorbent is a measure of the position of equilibrium in the adsorption process and can be generally expressed by three of the most popular isotherm theories viz., the Freundlich31, the Langmuir32 and the Redlich-Peterson isotherms33.

The equilibrium data obtained at varying carbon dosage and fi xed initi al dye concentration conform to the Freundlich equati on (Fig. 7), which has the foll owing forms:

X 1/ q =- = K C/" e F c

m

1 log qe =log K F + - log Cc

n

.. . (3)

. . . ( 4)

where x (mg L- 1) is the amount of solu te adsorbed, m (g L- 1) is the weight of the adsorbent used, Ce (mg L- 1) is the equilibrium solute concentration in solution and Kr- (mg g- 1) and n are constants incorporating factors affecting the adsorption process such as adsorption capacity and intensity of adsorption, respectively. The correlati on coefficient, r2, obtained for the linear plot (Fig. 7) is 0.968. The constants KF and n obtained from the intercept and slope of the plot are 116.49mg g- 1 and 6.69, respecti vely. According to Treybal34, it has been shown using mathematical calculation that n values between 1 and lO represent beneficial adsorption . The sorption equation arrived

2.4 .-------------~

2 .35 • 2 .3

., 0" 2 .25 • "' 0 •

2.2

2 .15 •

2 .1

2 . 01!>1----~---r---....--____J 0 0 .5 1.5 2

lo g Ce

Fig. ?-Freund li ch adsorpti on isotherm of malachite green dye on JPC.

(xlm = 116.49Ce 0 15) can be employed to determine the volume of wastewater that could be treated. Substituting the concentrati on of dye to be treated fo r C0 , the respecti ve sorption capacity can be calcul ated, which on di viding by the actual amount of dye to be removed gives the volume of wastewater that could be treated. About 16.5 L of wastewater, containing I 0 mg L- 1 of the dye under study, can be treated by using l g of JPC.

The adsorption isotherms f requentl y employed fo r single-solute systems are the 2-parameter Langmui r and 3-parameter Redlich-Peterson models that obey the correct thermodynami c boundary condition of Henry ' s law in the range of infinitely di lute concentrations35"36 . The Langmui r and the Redli ch-Peterson isotherms models fo r liquid-phase adsorpti on are written as fo ll ows.

. . . (5)

. .. (6)

In the Langmuir model, Q0 and b represent monolayer adsorption capacity and a constant related to energy of adsorption, respectively, while a, f3 and y are empirical constants for the Redlich-Peterson model.

The equilibrium adsorption results obtained at different initial dye concentrations were fitted with 2-parameter Langmuir and 3-parameter Redli ch-Peterson models. Fitted curves of both models are

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shown in Fig. 8 for compari son with the adsorption data. The isotherms obtained were of the type 137 , which were very close to irreversible adsorption . Such isotherms are characteristic of strong adsorbate-adsorbent interactions, probably due to nonpolar interactions. The adsorpt ion parameters of both models were obtained by a nonlinear opti mi zation method35·36 using GNUPLOT program (Version 3.7 for MS-Windows) that involves Marquardt-Levenberg algorithm. Adopt ing this method, Q0 and b values were found to be 166.37 mg g - I and 2.0902 L mg- 1, respect ively. Similarly empirical constants, a, f3 and y, involved in Red lich-Peterson model were found to be 298 .9 1 L g- 1, 1.6423 (L mg- 1)Y and 1.0267, respectively. As a measure of degree of fitness, the correlation coefficient, r1 was computed from the f II

. . 38 o owmg eq uation· .

.. . (7)

In the above equation, q; and Cfp denote the experimental adsorption data and the fitted results of each adsorption model for a sol ute, respectively . The

170

-- .... - -L ----ISO / -'"' I "' 150 ~ E - I 14 0 ·-~ ' ·;:; D 130 a. D u

" 120

2 a. 110 ~ ..,

100 0.99), although 3-parameter Red lich-Peterson model shows a little better fit to adsorption data than the 2-parameter Langmuir model.

The influence of isotherm shape has been considered with a view to predicting if an adsorption system is "favourab le" or "unfavourable". The essenti al charac teristics of a Langmui r isotherm can be expressed in terms of a dimensionless constant separation factor or equi librium parameter, RL·w, which is defined as RL=II(l+bC0 ), where b is the Langmuir constant and Co is the ini tial dye concentration. RL values obtained (0.0048-0.0234) were between 0 and I, which indicate favourable adsorption4 of dye on JPC for the concentration range stud ied .

Effect of temperature The adsorption capacity of JPC increased with

increase in the temperature of the system from 32 to 50°C (Table 3). Thermodynamic parameters such as change in free energy (L'lG0 ), enthalpy (L'lH 0 ) and entropy (L'lS0 ) were determined using the foll owing

. 40·4? equations -:

fiG o =- RT In K c

log K c = L'l.S o

2.303 R

.. . (8)

.. . (9)

2 .303 RT .. . ( I 0)

where Kc is the eq uilibrium constant , C Ae is the solid-phase concentration at equ ilibrium (mg L-1), Ti s the temperature in Kelvin and R is the gas constant. L'lH0

and L'lS0 were obtained fro m the slope and intercept of van't Hoff plot (Fig. 9) and are presented in Tab le 3. Positive value of L'lH0 (Table 3) shows the

Tab le 3- Thermodynamic parameters

Temperature qe Kc - f'..Go -f'..Ho

(K) (mg g- ') (kJ mol-1) (kJ mol- 1) (J mol - 1 K- 1)

305 164 2.1579 1.950

3 18 206.6 6. 1856 4.742 135.72 450.46

333 234.4 41.857 10.029

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Stephen lnbaraj & Sulochana: Bas ic Dye Adsorption on Low Cost Carbonaceous Sorbent Articles

1. 8

1·6 • 1-4

1.2

u :.::

~ O. B • 0 -6

0 .4

0 .2

3 -05 3.1 3. 15 3 .2 3 .25 3 -3

Fig. 9- va n · t Hoff plot

endothermic nature of adsorpti on. Thi s ru les o ut the poss ibi lity o f phys ical adsorpti on. Because in the case of phys ical adsorpti on, while inc reas ing the temperature of the system the extent of dye adsorpti on decreases, as desorptio n increases w ith temperature43. As chemi sorptio n is main ly an irreversib le process ,

the high pos iti ve !1H0 value ( 135.72 kJ mo r 1) depi cts that malachite green dye is che mi sorbed onto JPC43 . This is in ag reement w ith the type I isotherm (Fig . 8) obta ined which is c lose to irreversibl e adsorptio n.

The negati ve values of !1G0 (T able 3) ind icate th at the dye adsorption is spo ntaneous. The pos iti ve va lue

of !1S0 shows increased rando mness at the so lid-solution interface d uring the adsorpti on of dye on JPC. The adsorbed wate r mo lecules, whi ch are di splaced by the adso rbate species, gain mo re translational entropy than is los t by the adsorbate molecules, thus a ll ow ing the prevalence of randomness in the syste m44 . Enhancement of adsorption capac ity of JPC at higher te mperatures may be attributed to the enla rgement of pore size and/or acti vati on of the adsorbent surface45 .

Effect ofpH The experiments carried o ut at di ffe rent p H show

that there was no change in the pe r cent re moval of dye over the entire p H range, except that the re was 4% decrease when the p H was lowered from 3 to I . Thi s indicates the strong force of inte ractio n between the dye and JPC that e ither H+ or OH- ions could not influence the adsorptio n capacity. In other words, the adsorptio n of malachite g reen dye on JPC does not in volve ion exchange mechani sm. If the adsorpti o n

would have occurred through ion exchange mechani sm the re should have been an influence on the dye adsorption while varying the pH46 . Thi s observatio n is in line with the type I isotherm (Fig. 8)

and hi gh positive !1H0 value obta ined, which ind icates irreversible adsorpti on probably due to nonpo lar interactio ns.

Desorption studies Desorptio n studies he lp to e luc idate the nature of

adsorpti on and recyc ling of the spent adsorbent and the dye. If the adsorbed dye can be desorbed using neutral pH water, then the attachment of the dye on the adsorbent is by weak bonds. l f sulphuri c ac id or a lka line wate r can desorb the dye, then the adso rption is by ion exchange . If organic ac ids, like aceti c acid can desorb the dye, then the dye is he ld by the adsorbent through chemi sorption47. Neutra l pH water, l M sulphuri c ac id and I M sodium hydroxide did not show any desorption of the dye. However, I 0% acetic ac id (vlv) and 50 % aceti c ac id (v/v) solubili zed 9 and 56% of malachite green, respecti ve ly, fro m the dye-adso rbed carbon. T he no nrevers ibility o f adsorbed dye in minera l ac id or base is in agreement with the pH independent results obta ined . The desorptio n of dye in aceti c ac id (organic medium) indi cates that malachite green dye is adsorbed o nto JPC th ro ugh chemi sorpti on mechani sm.

Conclusion Carbon prepared from waste j ac k fruit peel was

fo und effecti ve in remov ing malachite green dye from aq ueous solution. The adsorptio n is fas ter and the rate is mainl y contro lled by intraparti c le d iffusion. Using the sorptio n equation obta ined fro m the Freundli ch isotherm, it was fo und th at about 16.5 L of wastewater, containing 10 mg L- 1 of malachi te green dye could be treated by I g of JPC. The equili bri um data conformed we ll with the Lang muir and Redl ic h-Pete rson isotherm models and the adsorption capac ity

of JPC is 166.37 mg g - I at an initi a l p H of 6.0 and at

32 ± 0 .5°C. The temperature vari ati on study showed that the dye adsorptio n is endothermi c and spo ntaneous with inc reased rando mness at the sol id-so luti on interface. No sig ni f icant effect o n adsorption was observed on vary ing the p H of the dye so lut ion.

The type I isotherm obtained , hi gh positi ve !1H0

value, pH independent results and desorpti on of dye in organic med iu m suggest that the adsorption o f malachite green dye on JPC in vo lves chemi sorpti on mechan ism.

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The encouraging results obtained prompted to work on the removal of other basic dyes that pose real challenge to the conventional methods of treatment.

Acknowledgement The authors thank Rajiv Gandhi National Drinking

Water Miss ion, Mini stry of Rural Development, Government of India for the financial assistance.

References I Mittal A K & Venkobachar C, Indian J Environ Hlth, 3 1

(1989) 327. 2 Ray P K, J Sci lnd Res, 45 ( 1986) 370. 3 Weber E J & Stickney V C, Water Res, 27 ( 1993) 63. 4 McKay G, J Chem Tech Biorechnol, 32 (1982) 759. 5 Yeh R Y L, Liu R L H, Chiu H M & Hung Y T, lnt J

Environ Stud, 44 ( 1993) 259. 6 Selvarani K, Studies on Low Cos! Adsorbents for the

Removal of Organics and lnorganics f rom Wa fer, Ph D Thesis, Regional Engi neering College, Tiruchirappalli , 2000.

7 Gaid A, Kaoua F, Mederres N, & Khodja M, Indian J Chem Tee/mol, 2 (I 995) 291.

8 Yeh R Y L & Thomas A, J Chem Tech Biotechnol, 63 ( 1995) 48.

9 Sekaran G, Shanmugasundaram K A, Mariappan M & Raghavan K V, Indian J Chem Techno/, 2 ( 1995) 3 11 .

10 Namasivayam C. Radhika R & Suba S, Waste Manageme/11, 2 1 (200 1) 38 1.

I I Ali L H & Saleem F, J Petrol Res, 7 ( 1988) 49. 12 Chughtai F A, Fakher-un-Nisa A, lllahi , Ejaz-ul-Haque &

Parveen N, J Pure Appl Sci, 6 ( 1987) 57. 13 Linares-Solano A, Rodriguez-Reinoso F, Molina-Sabio M &

Lopez-Gonalez J de D, Adv Sci Techno/ , I ( 1984) 223. 14 Gundes de Carvalho R A, Gonalez-Beca C G 0, Naves M N,

Sampaio M C, Sol Pereira & Macedo A, Agri Wastes , 9 ( 1984) 23 1.

15 Pcrineau F, Moinier J & Gaset A, Water Res, 17 ( 1983) 559. 16 Banerjee S K, Majumdar S, Dutta A C, Roy A K, Bane1jee S

C & Banerjee D K, Indian J Techno/, 14 ( 1976) 45. 17 Chadha Y R, The Wealth of India - Raw Materials

(Publication and Information Directorate, CS IR , New Delhi), 1985.

18 Stephen lnbaraj B & Sulochana N, in Proceedings of the International Symposium on Ceoenviromnental Reclamation , edi ted by Paithankar A G, Jha P K & Agarwal R K (Oxford & IBH Publishing Co Pvt Ltd, New Delhi), 2000, 285.

19 Stephen lnbaraj B & Sulochana N, in Proceedings of the International Conference on Solid Waste Technology and Management (Widener University, Philadelphia, PA), 200 I, 802.

20 Jeffery G H, Bassett J, Mendham J & Denny R C, Vogel's Text Book of Quantitative Inorganic Analysis (ELBS Publication, London), 1989.

208

Indian J. Chern. Techno!., May 2002

21 lSI, Methods of Sampling and Tests fo r AClivated Carbon used for Decolourizing Vegetable Oils and Sugar Solutions , lSI : 877 (Indian Standards Institution, New Delhi), 1977.

22 Greenberg A E, Rhodes T R & Clesceri L S, Standard Methods fo r the Examination of Water and Waslewater (American Public Health Assoc iati on, Ameri can Water Works Association and Water Pollution Control, Washington), 1980.

23 Khattri S D & Singh M K, Indian J Chem Tech no/, 6 ( 1999) 112.

24 Khare S K, Pandey K K, Srivastava R M & Singh V N. J Chon Tech Bioteclmol, 38 ( 1987) 99.

25 Weber W J, in Principal and Application of Water Chemistry, edited by Faust S D & Hunter J V (Wi ley, New York), 1967.

26 Knocke W R & Hemphill L H, Water Res, 15 ( 198 1) 275. 27 Weber W J & Morri s C J, in Proceedings of the 1"1

International Conference on Water Pollwion Research (Pergamon Press, New York). 1962, 23 1.

28 Lee C K, Low K S & Chung L C, J Chem Tech Bioteclmol, 69 ( 1997) 93.

29 Helfferich F, !on Exchange (McGraw Hill Pub li shers , New York), 1962.

30 Michelson L D, Gideon P G, Pace A G & Kutal L H. USD I, Off Water Res Techno/ Bull, 74 ( 1975) .

3 1 Freundlich H, Phys Chemie, 57 ( 1906) 384. 32 Langmuir I, J Amer Che111 Soc, 40 (1918) 136 1. 33 Jossens L, Prausnitz J M, Fritz W, Schlunder E U & Myers A

L, Chem Eng Sci, 33 ( 1978) I 097. 34 Treybal R E, Mass Tramfer Operations (McGraw Hill

Publi shers, New York), 1980. 35 Kim Y S, Song D I, Jean Y W & Choi S J, Sep Sci Techno/,

3 1 ( 1996) 28 15. 36 Bae J H, Song D I & Jean Y W, Sep Sci Techno/ , 35 (2000)

353. 37 Gregg S J & Sing K S W. 4dsorption Suiface Area and

Porosity (Academic Press, New York , NY), 1967 . 38 Kleibaum D G & Kupper L L, Applied Regression Analysis

and Other Multivariable Methods (Dux bury Press, North Sc ituate, MA), 1978.

39 Hall K R, Eagleton L C, Acrivos A & Vermeulen T, lnd Eng Chem Fundam, 5 ( 1966) 2 12.

40 Catena G C & Bright F V, Anal Clwn, 6 1 ( 1989) 905. 41 Fraiji L K, Hayes D M & WernerT C. J Chem Educ, 69

(1992) 424. 42 Si ngh A K, Singh D P, Pandey K K & Smgh V N, J Chem

Tech Biotechnol, 42 ( 1988) 39. 43 McKay G & Poots V J P, J Chem Tech Biotechnol, 30 ( 1980)

279 44 Namasivayam C & Yamuna R T, Environ Pollut, 89 (1995)

I. 45 Vishwakarma P P, Yadava K P & Singh V N, Pertanika , 12

( 1989) 357. 46 Sivaraj R, Namasivayam C & Kad irvelu K, Waste

Management, 2 1 (200 I ) 105. 47 Namasivayam C, Muniasamy N, Gayatri K, Rani M &

Ranganathan K, Biores Techno!. 57 ( 1996) 37.