I ndian Journal of Chemical Technology Vol. 1 0, M arch 20{)3, pp. 2 1 [ -2 [ 6

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Removal of basic dye from industrial wastewater by adsorption

Arvind K Singh & Prem N Tiwari *

Department of Chem ical Engi neering and Technology, I nsti tute of Technology, I3anaras Hindu Un iversity. Varanasi 22 1 (0). India

Received 4 February 200 I ; revised received 1 0 September 2002; accepted 17 Novelllber 2002

For proper understanding, the process of removal of solute dye by adsorption and to reveal the manner in which this adsorption process can be adopted for removal of the solute material from the solution, the study of isotherm, kinetics and thermodynamic parameters is of paramount importance, The growth of adsorption with time is function of the initial concentration, temperature and pH of the system. The kinetics of adsorption was found to be of first order with intra-particle diffusion at the rate-controlling step. The values of different thermodynamic properties

such as />"C", Mt' and />,.So indicate that the process is spontaneous, feasible and exothermic in nature. The adsorption pt'ocess satisfies Langmuir isotherm.

A safe potable drinking water for every human is necessary. I ndia i s highly populated country and safe drinking and domestic water demand i s h igh. Major cit ies of I ndia are dependent on the fresh water stream (ri vers, estuaries, lakes etc . ) for dai ly uses. Dye and dye intermediate i ndustries are the largest sector of chemical i ndustries in I ndia l . Mostly, the dyes are the raw material for the text i le, pain ts, pulp and paper, print ing inks and carpet i ndustries. Text i le i ndustry i s the largest consu mer of the dyestuff consuming more than 80 percent of the total production I . A huge amount of water is used by these industries for the washing and clean ing purposes and they discharge highly coloured effluent contain ing d ifferent dyes. The high concentration of dyes i n wastewater i s highly objectionable for domestic use due to their high COD and toxic i ty upsets the biological process. Some of the dyes found are carc inogenic als02. Unless properly col lected, treated and disposed of such type of wastewater create serious water pol lution problems. The present investigation i s concerned with the removal of dyes from the aqueous solution. The dye used for this purpose is methyl v iolet and adsorbents are bagasse and wood charcoal. Methyl violet ( B asic v iolet-3) is a c lass of triphenylmethane colour hav ing molecul ar formula C2sH30ClN3. Most bleach paper industries are used, as t inter, which causes the paper, appear v isual ly brighter. I t i s also used for colouring the cotton and s i l k fabrics .

* For correspondence (E-mai l : pntiwar i@ banaras.erneLi n ; Fax +9 1 -542-368428)

Adsorption of dyes onto sol id/water i nterface has been found to be an efficient and economically cheap process

3 and an effective method to control the extent

of water pol lution due to the metal l i c species4 . The most commonly used adsorbent for colour removal is activated carbons but it is relatively expensive. The objective of the present i nvestigation has to eval uate the efficiency of removal of methyl violet dye using bagasse and wood charcoal . Bagasse i s agricul tural! i ndustrial waste/by-product and produced in large amount by the sugarcane mi l l s and wood charcoal is produced by the t imber industries. These are eas i ly available, cheap and biodegradable and possess economic advantages.

Experimental Procedure The adsorbent bagasse was col l ected from the

Kashi Sahakari M i l l s i tuated at Orai , Bhadohi and wood charcoal from the local i ndustry s i tuated at Ramnagar, Varanasi, I ndia. The bagasse was crushed and boiled wi th d i l . HCI and washed with double disti l l ed water to remove water sol uble i mpuri t ies and dried at SO°C whi le the wood charcoal was washed wi th doubly dist i l l ed water to remove water soluble i mpurities and dried at 40°C in an electric oven for 8 h . The adsorbent was characterized for bulk density, moisture content, combustible matter, ash content as per standard methods . XRD indicates the existence of a luminium oxide, manganese oxide, ammoni um phosphate, Ca-P, calcite for bagasse and i ron oxide, alumin ium oxide, t i tanium oxide, calc i te, ammonium phosphate for wood charcoal . The surface area was

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analysed by B ET method us ing low temperature N2 .. gas adsorption techn ique. The characteristics of

adsorbents are presented i n the Table I . The dye­methyl v iolet used in present study was suppl ied by Qualigens Fi ne Chemicals Di v ision of Glaxo I nd ia Limi ted, Bombay, I ndia. Accurately weighed quant i ty of the dye was dissolved in double dist i l led water to prepare stock solut ion . Experi mental sol ut ions of the des ired concentration were obta ined by successi ve d i lu t ion. Batch adsorption studies were carried out by shaking 1 .0 g of adsorbents wi th 50 mL of aqueous so lution of methyl violet dye of des i red concentration in 250 mL borosi l conical tlask at different temperatures, pH and at a constant agitation speed of 200 rpm in shaki ng thermostat. The amount of adsorpt ion was determi ned at d ifferent t ime i ntervals t i l l the equ i l ibri um atta ins . The suspension solution was centri fuged and supernatant l iqu id was analysed using the U V -VIS spectrophotometer, type 1 1 8 ,

systronics make, at corresponding A",,,, to fi nd out res idual dye concentrat ion. The pH of system was adjusted using HCI and NaOH and experi ment was carried out at d ifferent i n i t i al concentrations of the dye ranging from 80 to 1 40 mgL' ! for bagasse and 20 to 50 mgL' ! for wood charcoal .

Resu lts and Discussion

Effect of initial dye cOllcelltratioll alld cOlltact time

The amount of dye adsorbed by adsorbent bagasse from 3.600 to 4.70 1 mgg' ! and percentage decreases from 90.00 to 67.50 on increas ing concentrat ion range from 80 to 1 40 mgL' ! , wi th t i me and attai ns equ i l ibrium in 60 min whi le WC adsorbed from 0.938 to 1 . 389 mgg' ! and percentage decreases from 93.80 to 55.48 on increas ing concentration from 20 to 50 mgL' ! and atta ins equ i l ibri u m in 1 30 min at the tem­

perature 30°C and p H 7.2 ( Figs 1 & 2 ) and Table 2. The result indicates that the amount adsorbed per un i t mass of adsorbent i s too h igh i n the case of bagasse than on the WC and thus the bagasse establ i shes the supremacy over the We. The amount of dye adsorbed i ncreases with the i ncreas ing i n i t i al dye concen­trat ion6.7 . Thi s is because at lower concentrat ion, the ratio of the in i t ial number of moles of dye to the avai lable surface area i s low and subsequently the fractional adsorption becomes i ndependent of i n i t ial dye concentration. However, at h igher concentration the avai lable s i tes for adsorption become fewer and hence percentage removal of dye is dependent upon the in i t ial concentration<J . The variation curves of adsorption versus t ime are smooth and cont i nuous,

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I nd ian J . Chern. Techl1o l . . March :.wm

Table I -Physical and prox i mate analy�is of" adsorbel1t� bagasse and wood charcoa I

Physical properties l3agasse W oocl charco:! I

Su rface arca ( m� g. 1 ) 23 .7 22.0

Bulk density (g cn'-') 0. 1 258 0.3858

Particle size (Jlm) 252.0 1 25.0

Proximate analysis ( % )

Moisture content 1 1 .3 20.92

Volatile matter 52. 1 0 43.28

A sh content 1 .88 2.73

Fixed carbon 32.0 26.9

6 · 0 ,--------------------,

'", '" � " . D � �

" 0

" 6 E "

, 0

2·0

-.-.... _--------"

Init icl concentration (mg 1 _') o BO

Temptroture : 300e .:) 100 Portlde sl ze : < 2 5 2 IJm a 110 pH : 7.2 · 1.1. 0

o · O L........_-'-__ -"--_--"-__ -'--_--' __ -'-_---' o 1 0 6 0 80 ' 00 ' 1 0

T i m t ( m i n.)

Fig. I-Effect of i n i t i a l concentrat ion of methy l violet dye on adsorption by bagasse

" b

� '" E '·1 " � -e � " o e 0

C , E 4 0 ·,

0 ·0

Ini t lol conctntra tfon (mg C1, 30 ·C 0 20

" < 1 1 S um A 30

• 50

'--_-"-__ -'--__ '--.L. ___ L __ _ 0 40 eo ' 1 0 ' 60 100 1 4 0 l eo l i m p ( mi n. )

Fig. 2-Effect of in i t ia l concentration of met hyl violet dye on adsorption by wood charcoal

i ndicating the formation of monolayer coverage on the surface of adsorbent" (' and equ i l ibrium t i me is i ndependent of i nit ial concentration of dye.

Effect of temperature The percentage removal of dye decreases from

74. 1 6 to 68 .00 and 66.60 to 62 .90 with rise i ll

Singh & Tiwari: Rcmoval of basic dye from industrial wastewater by adsorption A rticles

Table 2-A lIlount and percent of methyl violet adsorbed at the d i fferent concentrations a nd temperatures at pH 7 .2

13agasse WC l3agasse WC

Tcmp:30°C Temp:30°C Conc: 1 20 mgL" ' Cone: 40 IllgL" '

Con. Ads 0;", Con. Ads % Temp Ads (M-J Ads (�I mgL" ' 111gg " ' Ads mgL" ' Ingg Ads (0C) Ingg Ads Ingg Ads

80 3.600 90.00 20 0.938 93.80 20 4.450 74. 1 0 1 .332 oo.flO

1 00 4.056 8 1 . 1 2 30 1 . 1 85 79.00 30 4.3 1 0 7 1 .83 1 .297 64.85

1 20 4.3 1 0 7 1 .83 40 1 .297 64.85 40 4. 1 93 69.88 1 .276 63.80

1 40 4.70 1 67. 1 5 50 1 .387 55.48 50 4.080 68"00 1 .258 62 .90

Table }--Thermody namic parameters for the methyl violet

Bagasse. conc: 1 20mgL" ' . pH:7 .2

Temp. -t';.co -Mf' -t';.S' (OC) k cal mol" ' k cal mol" ' cal K" ' mol" '

20 0.7493 2.0893 4.5733

30 0.5636 1 .780 1 4.0 1 48

40 0.5235 1 .7730 3.9738

50 OA837

temperature from 20 to 500e at part icu lar pH 7 .2 for the bagasse and we respectively (Table 3) i nd icating the process to be exothermic6. This may be due to the relative escaping tendency of dye molecu les from the sol id phase to the bu lk phase wi th increase i n

t' h i ' s" 1 0 Th d .

temperature a t e so ut lOn , e ecrease In adsorption of dye on the adsorbents a t di fferent temperatures has been explained on the basis of thermodynamic parameters i .e . , change in standard

free energy I1Co, standard enthalpy Mt and standard

entropy I1SJ by the fol lowing equations,

( I ) (2)

. . . (3)

where, R is the gas constant, T is the temperature on the absolute scale and Kc, KC I and KC2 are the equ i l ibriu m constants at temperatures T, TI and T2 respectively. The values of Kc, KC I and KC2 were determined from the equation,

. . . (4)

where, Kc is the equi l ibri u m constant and CAe and CFc are the equ i l ibrium concentrations of adsorbate on the adsorbent and solution respectively. The calcu lated values of standard free energy change I1Co, standard

We. cone:40 mgL" ' , pH : 7 .2

-t';.C' -Mr' -t';.S' k cal mol" ' k cal mol" ' el i K" ' mol" '

OA009 1 . 3442 3.2 1 94

0.3687 0.8622 1 .6287

0.3524 0.7787 1 .36 1 9

0.3388

enthal py change I1F/J and standard entropy change

I1SJ are summarized in Table 2. The negative values

of I1Co i nd icates that the process is feasible and the higher negative value is i ndicative of h igh adsorpt ion. The posi t ive value of I1SJ shows the increase in translation entropy caused by randomness of displaced water molecu les from the s urface of the adsorbent. The negat ive values of standard enthalpy

change 11F/) indicate that the process i s exothermic in nature.

Adsorption dynamics The rate constant, kad were determined using the

fi rst order rate equation proposed by Lagergren " .

I ( ) I kilt! og qc - q = og qc - -- . t

2.303 . . . (5)

where qe and q are the amounts of the dye adsorbed at equ i l ibrium and at any t ime t respectively. The straight l ine plots of log (qe-q) versus t for adsorption of methyl violet on both the adsorbents suggest the first order ki netics (Figs 3 & 4). The val ues of rate constants for removal of dye for a part icular system were calculated at d ifferent temperatures ranging

from 20 to 500e from the slopes of these plots and shown in the Table 4.

Intraparticle rate constallt study

I n batch mode, the adsorption studies were performed by agi tating the adsorbate solution with the

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adsorbent in adsorption cel l . In the process of transport of adsorbate species from aqueous solution to the sol id surface of adsorbent there is a possib i l i ty of diffusion of adsorbate species into the pores of adsorbent due to the rapid st irring. This was determined by the respective plots of amount of dye adsorbed agai nst the square root of t ime I 2 . 1 3 ( Figs 5 & 6). The double nature of these plots may be due to vary ing extent of adsorption in in i tia l and fi nal stages. The in i t ial curved portion of the p lots is due to the boundary layer d iffusion effect, whi le the final l i near portion is due to the i ntrapart ic le d iffusion effects7. However, the prevai l i ng l i near portion of these plots

0.4

0

- 0 4

Co n c� n t ro t i on : 1 20 m g 1 -1 Po r t l c l � 51 .. ' < 2 5 2 I' m

p H : 7 . 2

T� mp�roture ( · C)

o 2 0 6 3 0 o 40

a: - 0 8 • SO OJ tr

en g _ , ·2

- 1 . 6 0 2 0 4 0 6 0 80 , 0

Time ( min )

Fig. 3-Lagergren rate constant p lot for the adsorption of methyl v i olet dye on bagasse

en g

O r--------------------------------,

08

1 . 2

1 .6

Conc e n t ra t i o n : 4 0 mg 1 - ' Par ti c le siu : < 1 2 5 pm p H : 7 . 1

Te m p � ra l u re ( o c) o 20 6 30 [] 40 • SO

20 L....O----4.,...O".-----80::--7.12::-;O�-'--'-;-,�---;:2�Ocr;O---"

Time( min }

Fig. 4--Lagergren rate constant plot for the adsorption of methyl violet dye on wood charcoal

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I ndian J . Chclll. Techno! . . March 20m

i nd icates the poss ibi l i ty of intrapart ic le di ffusion as the rate-contro l l i ng steps. The s lope of the I i near portion of these plots has been defi ned as a rate parameter kid. The values of kid were calcu lated from the respective s lopes of these plots at different temperatures and recorded in Table 4.

Adsorptioll isotherm The Langmuir adsorption i sotherm is based on

monolayer coverage at the surface of adsorbent. The saturation of monol ayer can be represented by the fol lowing equation. The plots of Cjqc versus Co show the l i near nature. (Figs 7 & 8) for methyl violet giving the val id i ty of the equation,

Cc 1 Cc - = -- + ­qc QOb QO . . . (6)

The values of Langmuir constants QO and b have been determined frolll the slopes and intercepts of the respective plots in each system at different temperatures and recorded in Table 4. From the resu lts it is c lear that the value of adsorption capac ity

E G O

Conc�,.,i ro t i on : 1 2 0 mg ( -1 Pa r t lel@ s i z e : < 2 5 2 }Jm p H : 7. 1 Te m p e rature (-C)

o 20 • JO o LO • 50

0 �0---�2-----�-�--""'8----'1�0--------�

Fig. 5--Weber-Morris intra-part icle di I'fusion plot for the adsorption of methyl v iolet dye on bagasse

2.0 .,. '"

O' 1 ·6· E

'0 .. .0 1 2 � '0 .. C " 08 0 E <t

O�

--------- --------_ . ' --" ---,

C o n c e ntra t i on : "'0 m g l - 1 P a r t i c l e s i z (' : < l l S fl m pit . J .2

L, 8 ./Tim. ( mi n) y,

1 0 12

Fig. 6--Weber-Morris intra-part icle d i ffusion plot for the adsorption of methy l violet dye on wood charcoal

Singh & Tiwari : Removal of basic dye from industrial wastewater by adsorption A rticles

Table 4--Rate constants kat" i ntrapart icle d iffusion rate kid, and Langmuir constants melhyl v iolet at d i fferent temperatures

Bagasse. conc: 1 20 mgL' I , pH:7 ,2 We. conc:40 mgL' I , pH: 7 .2

Temp. kad ( I O,1) kid. mgg,1 QO b kad ( I O'�) kid mgg'l QU " lll in' I/2 mgg' l I g' l min' l m in· ln (OC)

. , I m ill , I I " , I l11gg c

,

2: '" � '" u

20 3. 1 74

30 3.03 1

40 2 .836

50 2.73 1

1 3 .75

1 3. 50

1 3 .26

1 3 . 1 7

5 .3 1 53

5 . 1 282

5 .0847

5 .0()O

1 0 ·0 .----------�-----___, Padiclt s i z e : < 1S2 }J m p H : 7 . 5

1 2' 0

6·0 Ttmptrolurt ('C) o 70 6 3 0 o 40 • SO

0.3833

0.2437

0. 1 573

O. I I I 1

20 �o 60 100 120

Fig. 7-Langlllu ir i sothcrm plot for the adsorption of methyl v iolet dye on bagasse

2 1.·0 Partic.le siu : < 1 2 S j.J m p H : 1 . 1

.;:-- 16·0 '"

1 0 1 0 3 0 4 0 C e ( m g , -1 )

TemperakJn, c · e ) o 20 o 30 o �O • 5 0

5 0 6 0 10

Fig. R--Langmuir i sotherm plot for the adsorption of methyl v iolet dye on wood charcoal

QO of bagasse is h igher than the WC, which suggests the supremacy of the adsorbent and also it decreases on increas ing the temperature further, i t confirms the exothermic nature of the processes invol ved i il the system.

Effect of pH The percent dye adsorbed i ncreases from 65 .33 to

78 .60 and 54.00 to 77 .60 with the increase of pH from

3.0 to 1 0.0 at the temperature of 30°C and attains equ i l ibrium i n 60 and 1 30 min for the adsorbents bagasse and WC respectively. No further adsorption has been observed up to the I 1 .2 pH value. This

1 .280

1 .263

1 . 1 53

1 .093

4.85

4.44

4.3 1

4.09

1 ,5957 0.5222

1 ,5625 0.3560

1 .5200 0.2438

1 . 5 1 50 0. 1 796

i ndicates the adsorbents have high uptake capacity of methyl v iolet from the aqueous sol ution at higher pH values. The adsorbents contain various ox ides and these oxides are hydroxylated on the adsorbent surface in alkal i ne medium. At h igher

. pH the

assoc iation of dye cations with negatively charged oxide surfaces6 takes places as,

(SOHh +2 OH' +Dye+ + � S(OHh - Dye - S(OHh

Above mechanism clearly shows that the adsorption decreases with pH of so lution. The posit ive charge densi t ies on the surface i ncreases and adsorption decreases whi le at high pH adsorpt ion i ncreases.

Conclusions

From the above studies i t i s i nferred that, (i) Adsorbent bagasse has better adsorption

capaci ty than the We. ( i i ) Removal of methyl violet by both the adsorbents

happens to be attractive s ince the adsorbents are cheaper and eas i ly ava i lable.

( i i i ) The rate of adsorption has been found to fol low first order k inetics .

( iv ) Investigation of adsorption isotherm was found to be i n good agreement with Langmuir i sotherm, which indicates monolayer adsorption.

(v) Thermodynamic parameters i nd icate that the process i s spontaneous and exothermic in nature.

(v i ) Tntraparticle d iffusion i s the rate-contro l l ing step.

Acknowledgements

Author thanks Prof. Padmakar M i sh ra H ead, Department of Chemical Engineering & Technology, I nstitute of Technology providing lab fac i l i t ies and financial support by Banaras H i ndu Un iversity.

Nomenclature

Ads Adsorption mgg' l

b Energy of adsorpt ion I mg l

Co Equi l i brium concentrmioll mg L' I

2 1 S

A rticles

t,.GJ MIl t,.S'1 kad k;d

f/ f/c Q Il I

WC

Standard G ibbs free energy change k cal mole' I

Standard enthalpy change k cal mole- I

Standard entropy change cal K - ' mole- I

Rate constant min- I

I ntrapart icle d i ffusion rate constant mgg- I min' If!

Amount adsorbed at any t ime mgg- I

A mount adsorbed at equ i l i brium Illgg- 1

Adsorption capacity mgg- I

Temperature °C Wood charcoal

Rcfcl'CIlCCS KOlhllri !ndllslrial Direclorv of !ndill. edited by Arnkiaswamy S ( Kothari Enterprises Publication. Madras. I ndia) . 1 994

2 Mal l I D & Upadhyay S N. !PPTA. 7( 1 ) ( 1 995) 5 1 3 Desai M. Dogra A. Yora S. l1ahadur P & Ram R N. !ndilln J

Chelll. 36 II ( 1 997) 938

2 1 6

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4 A hmed M N, John J & Ram R N. J £n vir(J/l Sci Heallh. A 2R (7) ( 1 993) 1 5 8 1

5 Yeh R Yu·Li & Thomas A . J Chelll Tech /Jililecil/IOI. (ll ( 1 995) 55

6 K hattri S D & S ingh M K. !ndian J Chelll Techl/ol, 6 ( 1 999) 1 1 2

7 S ingh Y K & Tiwari P N, J Choll Tech I?iolechnol. 69 ( 1 997) 376

8 K hattri S D & S i ngh M K. !lIdian J Chelll TecllllOl. 6 ( 1 999) 1 1 2

9 Fraiji L K. Hayer D M & Werner T C. J Chelll £dllL'. fi9 ( 1 992) 20S

1 0 Panday K K. Prasad G & S ingh Y N. J Chelll Tecllllol

l?illleci/1/lll. 34A ( 1 984) 3fi 7 I I Lagergren S & l1 i l K. Svell.l'kll VatellSkllf1.Hlklld IIlInd, 24

( 1 898) 1 2 Weber W J & Morris J C . .I SlIlI £ng Oil' IISC£. 11 9 (SAZ)

( 1 963) 3 1 1 3 Mc Kay G. Ottcrburn M S & Sweeny A G. Waler Res. 1 4

( 1 980) I S