A. RASHEED KHAN, HAJIRA TAHIR, FAHIM UDDIN*; UZMA HAMEED

Transcription

1 JASEM ISSN A rights reserved Fu-text Avaiabe Onine at J. App. Sci. Environ. Mgt Vo. 9 (2) Adsorption of Methyene Bue from aqueous Soution on the Surface of Woo Fiber and Cotton Fiber A. RASHEED HAN, HAJIRA TAHIR, FAHIM UDDIN*; UZMA HAMEED Department of Chemistry, University of arachi-pakistan. E-mai: Fahim_uddin01@Yahoo. Com ABSTRACT: Adsorption of dye methyene bue from aqueous soution on the surface of sheep woo and cotton fibers was accompished under the optimize conditions of temperature, concentration, ph, stay time duration and quantity of adsorbent. Spectrometric technique was used for the measurements of concentration of dye before and after adsorption. The percentage remova and distribution constant ( D ) vaues for the remova of of methyene bue were aso cacuated. The vaues of % adsorption data for methyene bue sheep woo system show better adsorption capacity as compared to methyene bue cotton fiber system. The appicabiity of Langmuir and Freundich adsorption isotherm equations for the present system was aso tested. The experimenta data are fitted to the Langmuir and Freundich isotherm equations. The vaues of their corresponding constants were determined from the sope and intercepts of their respective pots. Thermodynamic parameters ike ΔG o, ΔH o and ΔS o were cacuated on the basis of Langmuir constant. The methyene bue sheep woo system show non spontaneous and exothermic behavior, whie methyene bue cotton fiber system show spontaneous and endothermic behavior. The resuts of these investigations suggested that natura adsorbents can be utiized as adsorbent materias, because of their seectivities for the remova of Goba viage is facing many issues regarding industria poution. Textie, eather, food, agro industries have brought enormous atmospheric changes. The aarming question is the disposa of effuent discharged by these industries. The basis of ISO is mainy for the disposa of residua contents of these industries. But unfortunatey the industries are acking some where in foowing the procedure recommended for this purpose. The effuent from textie industries is a big question mark, which has created environmenta probems around urban areas. The dyes present in the effuent discharged by textie industries are first to be treated for the separation of dyestuff and then send to disposing end. An attempt has been made in this connection. Earier adsorption of methyene bue and maachite green from aqueous effuent on the surface of woo carbonizing waste is reported [han et a 2004]. This method is found usefu for this purpose but it is more efficient for the effuent containing methyene bue. In this paper resuts obtained spectrophotometericay were discussed in the form of Langmuir and Freundich isotherms. This present work deas with the adsorption of methyene bue from aqueous soution on the surface of natura adsorbent. The concentration of dye was determined spectrophotometricay on the basis of reation between absorbance and concentrations. Percent adsorption before and after treatment gives the amount of dyestuff separated from effuent. The resuts are treated using the Langmuir and Freundich isotherms. The vaues of activation energy, enthapy change and entropy change were aso evauated. EXPERIMENTAL Preparations of adsorbents: The sheep woo fiber and cotton fiber were used as the natura adsorbent, which are coected from the natura resources. Cotton is very sensitive crop used as a fiber, which is easiy avaiabe. Sheep woo fiber was obtained from sheep. Both fibers were washed thoroughy with hot water to remove impurities associated with them and then dried in air under shade. MATERIAL Potassium choride, sodium acetate, citric acid, sodium citrate, acetic acid and hydrochoric acid of anaar grade were used and methyene bue of BDH were used. Preparations of buffers: Buffers of ph 1, 2 (HC- C), ph 3 (citric acid trisodium citrate), ph 4.5 (sodium acetate- acetic acid) and ph 6 (citric acidtrisodium citrate) were prepared in doube distied water. Stock soution of methyene bue (M.W. 374 ) of strength 1x 10-2 was prepared in doube distied water. For the determination of λ max of methyene bue, the soution of mo. dm -3 strength was prepared. The absorbance was measured on spectrophotometer (ERMA AE- 200). The vaue of λ max due to methyene bue was observed as 665 nm. Effect of Amount of Adsorbent: In order to find out optimum amount of adsorbent at which maximum adsorption takes pace, 30m of mo. dm -3 of dye soution for sheep woo fiber, mo. dm -3 of dye soution for cotton fiber system was taken. The dye soution of ph 5 for (sheep woo fiber), 3.5 *Corresponding author E-mai: Fahim_uddin01@yahoo. Com

2 Adsorption of mehtyene bue 30 for (cotton fiber) was added in the coumn packed with different quantity of adsorbent e.g. 0.3, 0.4, 0.5, 0.6, 0.8, g. The soution of dye was kept stand for 20 minutes for (sheep woo fiber) and 10 minutes for (cotton fiber). The resuts are shown in Tabe 1. Tabe 1: Optimization for the amount of adsorbent in the adsorption of aqueous soution of methyene bue (MB) on the surface of sheep woo fiber and cotton fiber.) Sheep woo fiber Amount of Ce %adsorption D Ce %adsorption D adsorbent (g) mo/l mo/l Concentration of adsorbate = mo. dm -3 (Sheep woo fiber), mo. dm -3 (), Voume of adsorbate =30m, Time= 20 minutes (Sheep woo fiber), 10 minutes () ph = 5.0(Sheep woo fiber), 3.5 minutes () Tabe 2: Optimization for the concentration of methyene bue in the adsorption of methyene bue from aqueous soution on the surface of sheep woo fiber and cotton fiber for 3 hours Sheep woo fiber Conc. of Ce %adsorption D Ce %adsorption D dye(mo/l) mo/l mo/l Amount of adsorbent = 0.5g, Voume of adsorbate =30m, ph = 5.0 (Sheep woo fiber), 3.5 () Effect of Concentration of Adsorbate: For this study eight coumns with 0.5g of adsorbent were prepared. The ph of methyene bue was maintained as 5.0 (sheep woo), 3.5 (cotton fiber) and time 3h. The resuts are summarized in Tabe 2. Effect of Stay Time:For the determination of the effect of time on the adsorption of dye, 0.5g of adsorbent was packed in each coumn and 30 m of mo. dm -3 dye for (sheep woo fiber), mo. dm -3 dye for (cotton fiber) at ph 5.0 and 3.5 for cotton and sheep woo fiber respectivey were added in the coumn for different intervas of time. When the soution of dye comes in contact with heterogenous surface of adsorbent, as usua unsaturated part of the dye strikes the surface of the adsorbent for adsorption. It was observed that the adsorption of dye increases with increasing in time to 30 minutes and reaches to maximum vaue and then attains a constant vaue when adsorption equiibrium is reached. In methyene bue on sheep woo fiber maximum adsorption occurs in 30 minutes as 82.50% whereas in cotton fiber the maximum adsorption occurs in 10 minutes as 72.0%. The resuts are tabuated in Tabe 3. Effect of ph: The infuence of ph for the adsorption of dye was observed. For this purpose six experiments at different ph for each dye were accompished. 30 m of mo. dm -3 soution of methyene bue carrying variabe ph (1.0 to 6.0) was added in different coumns packed with 0.5g adsorbent. Time period for both adsorbent was 3 hours. The resuts are depicted in Tabe 4. Effect of : For the determination of the effect of temperature on the adsorption of dye under optimize adsorption conditions, the adsorption process was proceeded at temperatures at the step of 10 ± 0.2 o C

3 Adsorption of mehtyene bue 31 Tabe 3: Optimization for the stay time in the adsorption of methyene bue from aqueous soution on the surface of sheep woo fiber and cotton fiber Sheep woo fiber Time Ce %adsorption D Ce %adsorption D (min) mo/l mo/l Amount of adsorbent = 0.5g, Voume of adsorbate =30m, Concentration of adsorbate = mo. dm -3 (Sheep woo fiber), mo. dm -3 (), Time= 20 minutes (Sheep woo fiber), 10 minutes () ph = 5.0(Sheep woo fiber) and 3.5 () Tabe 4: Optimization for the ph in the adsorption of methyene bue from aqueous soution on the surface of sheep woo fiber and cotton fiber for 3 hours Sheep woo fiber Buffer ph Ce mo/l %adsorption D Ce mo/l %adsorption Amount of adsorbent = 0.5g, Voume of adsorbate =30m, Concentration of adsorbate = mo. dm -3 Time= 3h METHOD 6 to 13 wide mouth coumn packed with optimize weight of adsorbent (0.2g, 1.5g sheep woo and cotton fiber respectivey) were arranged. nown quantity of dye soution of specific strength ( mo. dm -3, mo. dm -3 for sheep woo and cotton fiber) were added in the coumn and eft stand for (20 and 10 minutes for sheep woo and cotton fiber ) duration. After required time the fitrate was obtained and % absorbance of a portion of fitrate was determined spectrophotometricay at 665 nm. The % absorbance of dye before and after adsorption on the surface of adsorbent gives this quantity of dye separated from aqueous soution. During the process of adsorption after a shorter or onger period equiibrium was estabished between moecues in the buk and adsorbed phases. This is the adsorption equiibrium. It is dynamic equiibrium because the number of moecues eaving the surface per unit time is equa to the number of newy adsorbed D moecues; the tota number of moecues in the adsorbed state remains constant. RESULTS AND DISCUSSIONS Adsorption of dye methyene bue, cationic in nature was studied on sheep woo and cotton fiber under the optimize conditions of amount of adsorbents, adsorbate, stay time, temperature and ph. The resuts are summarized in Tabes 1, 2, 3 and 4. Concentration of dye before and after adsorption is determined by spectrophotometericay using caibration curves methods. For determining the effect of adsorbent on the adsorption of methyene bue from aqueous soution on sheep woo fiber and cotton fiber nine experiments for each fiber system were accompished. Concentration of adsorbate, time and ph for sheep woo fiber respectivey were mo. dm -3, 20 minutes and 5 respectivey whereas the parameters for cotton fiber were mo. dm -3, 10 minutes and 3.5 respectivey. The resuts (Tabe 1) indicate that maximum adsorption takes pace as 94.3% at 1.0g of sheep woo fiber and 97% at 1.50 g of cotton fiber. The distribution constant ( D ) vaues at this amount of adsorbent are The minimum adsorption occurs at 0.2g adsorbent as 50.6%. The equiibrium concentration is mo/l. On the other hand the maximum adsorption of dye was observed as 97% at 1.5g cotton fiber and Ce as mo/l. The vaue of D at this amount of adsorbent is where as minimum adsorption takes pace at Ce and adsorbent respectivey as mo/l and 17.2%. The vaue of D is These resuts show optimization for the amount of adsorbent occurring at 1.0g sheep woo fiber and 1.5 g cotton fiber. Over a adsorption for both fibers are random. Somewhere adsorption increases and thus abrupty drops. It shows that methyene bue show better affinity towards sheep woo fiber. But in the adsorption of methyene bue and maachite green on the surface of woo carbonizing waste, the maximum adsorption takes pace at 0.6g woo carbonizing waste as 98.7% and for maachite green this vaue is 99.1% at 2.0g adsorbent. At 1.0g adsorbent (woo carbonizing waste) the percent of adsorption of methyene bue was obtained as 83.3% whereas for maachite green the %adsorption was determined as The difference in % adsorption of these dyes on the surface of woo carbonizing waste, woo fiber and cotton fiber may be due to the presence of more or ess irreguar and defective edges. These edges pay significant roe on the adsorption phenomenon. These edges strike the unsaturated part of the dye and acceerate the remova of dye moecues (han et a, 2002, Tahir eta, 2003). These types of observations were aso observed in the adsorption of organic acids on the surface of finey divided charcoa (han eta 1991, 1994).

4 Adsorption of mehtyene bue 32 The effect of dye concentration on adsorption was carried out under the optimized conditions of ph (5 for sheep woo and 3.5 for cotton fiber), amount of adsorbent (0.5g), voume of adsorbate (30m) and stay time (3h). The resuts are summarized in Tabe 2. For sheep woo fiber, the adsorption in genera increases with increase in concentration of dye but it drops (%35.6) when concentration reaches to mo.dm -3. But abrupty gets increased (71.6%) at mo.dm -3 and then drops. The maximum and minimum adsorption occurs respectivey at concentrations mo.dm -3 and mo.dm -3. The vaues of D are random through out the system. In the case of cotton fiber, the maximum adsorption (84.4%) occurs at concentration mo.dm -3 whereas minimum adsorption (57.7%) takes pace at the concentration mo.dm -3. Aso, in this system the vaues of D are random. There is no reguarity found in the %adsorption and as we as in vaues of D. But in the case of adsorption of methyene bue on carbonising waste, the maximum adsorption occurs at mo.dm -3 concentrations as 98.7%. On the other hand the % adsorption 69.9 was obtained at mo.dm -3 concentrations. It shows that woo fiber works better than carbonizing waste (han et a 2004). Tabe 3 iustrates the adsorption of dye at different duration. Maximum and minimum adsorption of dye from aqueous soution on sheep woo fiber takes pace respectivey in 20 minutes (Ce mo/l, % adsorption 84.9) and 50 minutes (Ce mo/l, % adsorption 75.1). On the other hand for cotton fiber, the maximum and minimum adsorption occurs in 10 minutes (Ce mo/l, % adsorption 72.0) and 60 minutes (Ce mo/l, % adsorption 19.4). The vaues of D for both adsorbent are random. There is no reguarity found in both cases. But maximum adsorption of methyene bue on woo carbonizing waste takes pace in 40 minutes as 97.8 whereas maachite green adsorbs in 30 minutes as 94.7 % [han eta 2004]. On comparison woo fiber is better adsorbent than cotton fiber. Tabe 4 incudes the resut obtained from the adsorption of dye at different ph. The maximum and minimum adsorption respectivey, occurs at ph 5 (%81.9) and ph 3 (%21.4) for sheep woo fiber where as maximum and minimum adsorption is due to cotton fiber respectivey takes pace at ph 3.5 (%59.60) and ph 3 (%14.70). Maximum and minimum adsorption occurs in the units of ph 3 and 3.5. Therefore for a subsequent studies initia ph was adjusted by using buffer soution of ph 5 and 3.5. The vaues of D were aso found random in both systems. It was aready reported in the earier paper (han eta 2004) that the maximum adsorption of methyene bue on woo carbonizing waste occurs as 97.2 % at ph 5 whereas the maximum adsorption of maachite green is observed as %82.2 at ph 5. When dye soution comes in the vicinity of adsorbent the action of partia forces at the boundary of surface of adsorbent acceerate at ph 3.5 (cotton fiber) and ph 5 (sheep woo fiber) hence maximum adsorption takes pace. These resuts aso support that sheep woo fiber is better adsorbent than cotton fiber. In brief when a pure iquid is paced in contact with soid, the state of affairs at the interface between soid and the iquid wi be different from that in the interior part of the iquid because of moecue or ions of the soid now repace the moecue of iquid, the force acting on the iquid moecue transferred ater and this aternation resuts in an increase in the concentrations of the iquid at the interface as compared with intentions of iquid. The iquid may be adsorbed at the surface of the soid but adsorption is obvious much ess than in soid gaseous system. The number of moecue, which wi be adsorbed at a surface of soid or iquid from soutions, wi be directy proportiona to the concentration. During the period of adsorption after a shorter or onger duration, equiibrium estabished between moecues in the buk pace and adsorbed phase. For better understanding, the phenomena of the adsorption, when aqueous soution of methyene bue comes in contact with cotton or wooen fiber, the unsaturated part of methyene bue strikes the irreguar or defective edges of adsorbent, the separation of methyene bue moecues starts rapidy in the initia stages. It is because by striking the moecues of methyene bue with irreguar edges of adsorbent, radicas are formed and methyene bue moecues get started to join adsorbent surface hence thick ayer of dye is formed on the surface of adsorbent. Wherever the open surface of adsorbent is found avaiabe, striking of ionic dye moecues woud take pace and heps in the separation of dye moecues. Amount of adsorbent, concentration of adsorbate, ph and stay time wi together infuence on the rate of adsorption. It is very cear to observe that there wi be no reguar increase or decrease of rate of adsorption. Maximum adsorption wi depend upon the conditions stated above. The reason is not cear why it happens. Our aboratory experiences note that there wi be random rate of adsorption. Some time at the eary stages the maximum adsorption takes pace rapidy and some time it does not happen. There are many references found in the iterature for this phenomenon (han, 1987, han eta 1985, Coover, 1964). It shoud be necessary to note that the poar ends of the dye moecue have a tendency to attach themseves to the active sites of cotton or wooen fiber surface. Dye moecues speedy join the heterogeneous surfaces of fibers and hence dye separates out from aqueous soution.

5 Adsorption of mehtyene bue 33 Many theories of adsorption have been put forward to expain the phenomena of adsorption. Langmuir and Freundich isotherms are some of them. The we known Langmuir equation (Langmuir 1918) is given beow. (Cs / X/m) = (1/ kv m ) + (Cs / V m ) (1) Where X/m expains the amount of adsorbate per unit mass of adsorbent, C s is the equiibrium concentration of adsorbate in soution, V m is the monoayer capacity or surface area of the soid and indicates the binding constant which is reated to the heat of adsorption. A straight ine is obtained by potting Cs/(X/m) Vs. C s. The sope and intercept of this pot respectivey are 1/V m and 1/ (kv m ). Experiments were accompished at different temperatures. The pots are shown in Figs. 1 and 2 Ce(mo/)/X/M(mo/g) x 10(-3) FOR SHEEP WOOL EQUILIBRIUM CONC(mo/L) 293k k 323 k Ce/x/mCe(mo/)/X/M(mo/g ) FOR COTTON FIBER EQUILIBRIUM CONC(mo/L) Fig. 1 &2. Langmuir pots at different temperature for sheep woo and cotton fiber methyene bue system. whereas these resuts are summarized in Tabes 5 and 6. The decrease in k (Langmuir constant) vaues with the rise in temperature indicates weakening of adsorbate - adsorbent interactions at high temperature whist the increase in vaues predicts strong interaction. It reveas that the adsorption affinity of dye decreases with the rise in temperature. So adsorption is ess favorabe at high temperature (Saeem eta 1994, Ge-hui eta 1999). A the adsorption systems obey Langmuir adsorption isotherms equations except at 313 temperature [Hameed 2004].. The monoayer capacity (V m ) decreases with increase in temperature indicating high affinity of cationic dye at ow temperature (except at 293). So when dye moecues strike a part of this uncovered surface of the adsorbent at that moment the separation of dye from aqueous soutions and adsorption on adsorbent starts and ends when a thick ayer is formed. The vaues 1/Vm and 1/Vm are random. Considering the concentration of dye if 1/ increases with decrease in concentration of dye, it means that at the high concentration dye moecues (han eta 2002) wi utiize more surface area. On the other hand if the vaue of 1/Vm gets decreased with decrease in the concentration of dye then the strength of adsorption of of dye on the surface of fibers wi be increased with decrease in the concentration of dye. Tabe 5: Langmuir parameters of methyene bue -sheep woo fiber Intercept 1/ (V m ) Sope 1/V m V m (mo/g) Tabe 6: Langmuir parameters of methyene bue dye cotton fiber Intercept 1/ (V m ) Sope 1/ V m V m (mo/g) The inear form of Freundich isotherm (Adsmson 1960} may be written as Log X/m = og +1/n og C s (2) Where X/m is the amount adsorbed per gram of the adsorbent C s is the equiibrium concentration and og and 1/n are Freundich constants. A pot of og X/m against og C s gives a straight ine. The sope and intercept of which corresponds to 1/n and og respectivey. The vaues of these constants are summarized in Tabes 7 and 8 and pots are shown in Figs. 3 and 4. Fig. 3& 4. Freundich pots at different temperature for cotton fiber and sheep woo. The parameters and 1/n obtained from this isotherm give a measure of adsorbing capacity of the adsorbent and the intensity of adsorption respectivey. The decrease in the vaues of with rise of temperature reveas that adsorption affinity of methyene bue decreases with rise in temperature showing ess adsorption favorabe at high temperature. Both parameters ( and 1/n) are obtained random for both fibers.

6 Adsorption of mehtyene bue 34 Tabe 7: Freundich parameters of methyene bue dye- sheep woo fiber Intercept Sope n Log (1/n) Tabe 8: Freundich parameters of maachite green dye- cotton fiber Intercept Sope n (og ) (1/n) Tabes 9 and 10 incude the vaues of thermodynamic parameters such as free energy (ΔG o ), enthapy (ΔH o ) and entropy (ΔS o ) of adsorption which were cacuated from the Langmuir constant using the foowing reation: ΔG o = -RT n (3) n = -ΔH o / RT + Constant (4) Tabe 9: Thermodynamic parameters of methyene bue dyesheep woo fiber system ΔG o (J/mo) ΔH o (J/mo) ΔS o (J/mo) Tabe 10: Thermodynamic parameters of methyene bue dyecotton fiber system ΔG o (J/mo) ΔH o (J/mo) ΔS o (J/mo) The ΔH o and ΔS o were cacuated from the sope and intercept of the inear variation of n with reciproca of temperature (1/T). The vaues of ΔG o at different temperatures are negative except at 313. This indicates a positive behavior in the case of methyene bue- cotton fiber system whereas in the case of woo fiber these vaues are positive in a cases except at 303 temperature. The positive vaue of ΔG o predicts spontaneous behavior. The vaues of ΔH o and ΔS o in methyene bue- cotton fiber system were found positive whereas the vaues are negative for methyene bue- sheep woo system which indicates respectivey endothermic and exothermic behavior respectivey. A the resuts obtained for methyene bue - sheep woo system show best adsorption capacity as compared to methyene bue cotton fiber system at high temperatures. Tabes 11 and 12 show the vaues of % remova at different temperatures for both systems. Methyene bue sheep woo system shows best adsorption capacity as compared to the Methyene bue cotton fiber system at high temperatures. Tabe 11: % Remova of methyene bue dyesheep woo fiber system at different temperatures Concentratio %Remova %Remova %Remova %Remova n (mo/l) Tabe 12: % Remova of methyene bue dye- Coo fiber system at different temperatures Concentratio %Remova %Remova %Remova %Remova n (mo/l) REFERENCES Adamson, A W (1960) Physica Chemistry of surfaces Fifth edition, John Wiey and sons. p Coover, H W(1964) Jr in Macromoe Chem. C 4 M. Magat, Ed. Inter science New York, J. Poym. Sci Ge-hui, W; Zheo-qian, S (1999) Appication of natura fiber materias for the treatment of industria wastewater Research institute of chemica processing and utiization of fest products, CAF, Nanjing, Rep. China. 19 (3),

7 Adsorption of mehtyene bue 35 Hameed, U (2004) Thesis entited Remova of ionic dye methyene bue using natura adsorbents, submitted in for the partia fufiment of degree of M. Sc. University of arachi. han, AR; Tahir H; Uddin, F; Waqar, S (2004) Adsorption of methyene bue and maachite green on the surface of woo carbonizing waste. Saudi. J. Chem. Soc. (Submitted). han, AR; Uddin, F; han, GU (1991) Adsorption of gycoic and actic acids from aqueous soutions on charcoa, Pak. J. Sci. Ind. Res., 34, Pak. J. Sci. Ind. Res. 34(5), han, AR; Uddin, F. Ahmed, Z (2002). Adsorption behavior of citric acid from aqueous soution on activated charcoa. Pak. J. Sci. Ind. Res. 45(2), han, AR; Uddin, F; Ai, S (1994) Adsorption studies of tartaric acid from aqueous soution on charcoa. Pak. J. Sci. Ind. Res. 37(1-2), han, A R; Lodhi, S A (1985) Copoymerization of styrene and methy acryate in the presence of some inorganic sats. Pak. J. Sci. Ind. Res. 28, Langmuir, I (1918). The adsorption of gases on pane surfaces of gass mina and patinum. J. Am. Chem. Soc. 40, Saeem, M; Afza, M; Mahmood, F ; Hameed, A (1994) Thermodynamics of adsorption of rodamine B and nie bue suphate on aumina from aqueous soutions. J. Chem. Soc. Pak. 16(2), Tahir, H; Uddin, F (2003) Comparative statistica approach for the assessment of poution of heavy metas in rawa ake water and main streams entering raw ake. Saudi J. Chem. Soc. 7(2) han, A R (1987) Therma copoymerization of acrryonitrite and styrene in the presence of some compexing agents. Pak. J. Sci. Ind. Res. 30,