Kinetics and Equilibrium Studies of Adsorption of Anionic Dyes Using

Jul 23, 2010 - E-mail: [email protected]., † ... of different system variables like adsorbent dosage, pH, contact time, and temperature were s...
0 downloads 0 Views 342KB Size
Download PDF
8106

Ind. Eng. Chem. Res. 2010, 49, 8106–8113

Kinetics and Equilibrium Studies of Adsorption of Anionic Dyes Using Acid-Treated Palm Shell G. Sreelatha,† S. Kushwaha,‡ V. J. Rao,§ and P. Padmaja*,‡ Department of Applied Chemistry, Faculty of Technology and Engineering, The Maharaja Sayajirao UniVersity of Baroda, Vadodara, India, Department of Chemistry, Faculty of Science, The Maharaja Sayajirao UniVersity of Baroda, Vadodara, India, and Department of Metallurgy and Material Science, Faculty of Technology and Engineering, The Maharaja Sayajirao UniVersity of Baroda, Vadodara, India

This study investigates the potential uses of palm shell, pretreated with sulfuric acid (APSP) for the adsorption of AOII, DSB, and AV7. The effects of different system variables like adsorbent dosage, pH, contact time, and temperature were studied. Optimum pH values for all the three dyes were determined as 1.0. Equilibrium was achieved within 30 min. Langmuir I, II, III, IV and Freundlich isotherm models were applied to describe the equilibrium isotherms at different temperatures, and the langmuir model was found to agree very well with the experimental data. The maximum adsorption capacity was found to be 2180.05 mg/g, 1199.99 mg/g, and 243.9 mg/g for AOII, DSB, and AV7, respectively. Thermodynamic parameters such as change in free energy (∆G0), enthalpy (∆H0), and entropy (∆S0) were also determined. Pseudo-first-order, pseudo-secondorder, and intraparticle diffusion models were used to fit the experimental data. The pseudo-second-order equation was able to fit well and provide a realistic description of the adsorption kinetics. Introduction Waste waters from textile industries, dye manufacturing industries, paper and pulp mills, tanneries, electroplating industries, distilleries, food industries, etc. contain dyes, thus polluting water resources. The conventional methods for treating dye containing waste waters are activated sludge, chemical evaporation, activated carbon adsorption, electrochemical treatment, reverse osmosis, hydrogen peroxide catalysis, etc. Most of the above methods have some disadvantage or other and are not economically effective. Low-cost treatment methods have therefore been used as an alternative for dye removal. These include peat, chitin, wood, china clay, apple pomace, biogas waste slurry, wheat straw, organo-montmorillinite, coir pith, slag from manufacture of steel, fly ash, and activated slag from fertilizer plants.1-14 Recently, Esther Forgacs et al.,15 V. K. Gupta et al.16 and Gregorio Crini17 have reviewed the use of low cost adsorbents for the removal of dyes. Palm shell or Borassus Flabellifer is abundant in coastal areas throughout India. Preliminary investigations done to study the removal of anionic dyes, acid orange II, acid violet-7, and disulphine blue, using untreated palm shell powder revealed that removal was only 41.961, 29.351, and 22.866%, respectively (results not shown). In this work, we have investigated further the ability of acid treated palm shell powder (APSP) to remove acidic anionic dyes like acid orange II, acid violet-7, and disulphine blue. The kinetic and equilibrium data of adsorption studies were processed to understand the adsorption mechanism of the dye molecules onto the APSP.

°C, and the cleaned powder was mixed with conc. H2SO4 (sp. gr. 164) in 1:1.5 weight ratio and allowed to stand in an oven maintained at 140-160 °C for 24 h. The resulting char was thoroughly washed with water followed by 2% solution of NaHCO3 until effervescence ceased and then left to soak in a 2% solution of NaHCO3 overnight. The APSP was then separated, washed with water until free of bicarbonate, and dried at 105 °C. Preparation of Dye Solutions. Stock solutions of dyes (1 g/L) were prepared by dissolving an accurately weighed amount of AOII, DSB, and AV7 in double distilled water and subsequently diluting to the required concentration. Adsorption Experiments. A series of dye sorption experiments were conducted to study the effect of pH, dose, and temperature. In the adsorption experiment, 25 mL of dye solution of known initial concentration was kept in contact with a required dose of PSP at room temperature. Adsorption studies were carried out with 100 mL Durasil Stoppered flasks in a thermo-regulated water bath shaker at 180 rpm. The pH of solutions was adjusted using 0.1 N HCl or 0.1 N NaOH solution. After a specific time period the reaction mixture was filtered. The dye concentration in the filtrate was determined by measuring absorbance at the wavelength of maximum absorption (490, 640, and 530 nm for AOII, DSB, and AV7, respectively) using a SYSTRONICS digital 166 model visible spectrophotometer. The percentage removal of the dye and the amount adsorbed (mg/g) were calculated by the following relationship: qe ) (Ci - Ce)/m

Materials and Methods Preparation of Adsorbent. Palm shells obtained from the coastal areas of Andhra Pradesh were washed, sundried for 24 h, and ground using a jaw crusher. They were then dried at 110 * To whom correspondence should be addressed. E-mail: [email protected]. † Department of Applied Chemistry. ‡ Department of Chemistry. § Department of Metallurgy and Material Science.

where Ci is the initial concentration of dye in mg/L, Ce is the equilibrium concentration of dye in mg/L, m is the mass of adsorbent in g/L, and qe is the amount of dye adsorbed per gram of adsorbent. The experiments done without adsorbent were treated as blanks, and they showed that no precipitation of dye occurred under the conditions selected. Adsorption Isotherms. The results of the adsorption experiments were analyzed using Freundlich and Langmuir I, II, III,

10.1021/ie101004q  2010 American Chemical Society Published on Web 07/23/2010

Ind. Eng. Chem. Res., Vol. 49, No. 17, 2010

8107

and IV models to determine the mechanisitic parameters associated with adsorption. The linearized Freundlich isotherm is shown: log qe ) log KF +

1 log Ce n

(1)

where qe ) amount of solute adsorbed per unit weight of adsorbent(mg/g), Ce ) concentration of solute remaining in solution at equilibrium (mg/L), and KF and n are Freundlich constants. The Langmuir isotherm model used is given as qe ) (qmKaCe)/(1 + KaCe)

(2)

Four different linearized forms of Langmuir equation were used; qm ) amount of solute adsorbed per unit weight of adsorbent in forming a complete monolayer on the surface (mg/L) and Ka ) a constant related to the energy or net enthalpy. Adsorption Dynamics. The kinetics of sorption of anionic dyes was investigated using pseudo-first-order, pseudo-secondorder and intraparticle diffusion reaction models. The pseudofirst-order is given by (Lagergren, 1989): log (qe - qt) ) log qe - K1t/2.303

Figure 1. SEM of APSP.

(3)

where qe and qt are the adsorption capacity at equilibrium and at time t, respectively (mg/g); K1 is the rate constant of pseudofirst-order adsorption (L/min). K1 and qe can be determined from the slope and intercept of the plot, respectively. The pseudo-second-order reaction kinetic is expressed as t/qt ) 1/(K2qe2) + t/qe

(4)

where K2 is the rate constant of pseudo-second-order adsorption (g/mg-min), which is the integrated rate law for a pseudosecond-order reaction. Intraparticle Diffusion Study. The equation for the Weber Morris intraparticle diffusion model is qt ) kit0.5 where ki is the intraparticle diffusion rate constant (mg/g min0.5). Desorption Study. Desorption studies as a function of pH were conducted to analyze the possibility of reusability of the adsorbent. Desorption of all the three dyes was carried out using used 0.2 g APSP loaded with 160 ppm of dye. The adsorptiondesorption studies were repeated for three cycles. Fourier Transform Infrared Spectroscopy. Spectra for biosorbent and the metal-loaded biosorbents were obtained using a Perkin-Elmer RX1 model within the wavenumber range of 400-4000 cm-1. Specimens of samples were first mixed with KBr and then ground in a mortar at an appropriate ratio of 1/100 for the preparation of the pellets. The resulting mixture was pressed at 10 tons for 5 min; 16 scans and 8 cm-1 resolution were applied in recording spectra. The background obtained from the scan of pure KBr was automatically subtracted from the sample spectra. Results and Discussion Physical Characteristics. The BET surface area of APSP prepared was measured by nitrogen adsorption isotherms using a BET surface area analyzer (Micrometrics ASAP 2020 V3.03 H). The BET surface area was found to be 0.2979 m2/g. The X-ray diffraction pattern of APSP (Figure 2) shows a peak centered around 21° corresponding to a 002 reflection of

Figure 2. X-ray diffraction pattern of APSP.

disordered packing of micrographites. The peak is broad and suggests an amorphous structure. The peak at 21° corresponds to an interlayer distance of 0.423 nm which suggested a disordered carbonaceous interlayer. The morphology of APSP was studied using a scanning electron microscope (SEM) (Figure 1). The surface is magnified 1000 times which shows that the adsorbent has an irregular rough and porous surface with identifiable micropores and mesopores. Uptake Studies. Effect of Temperature. The effect of temperature on the adsorption of AOII, DSB, and AV7 was studied by carrying out a series of experiments at 30-70 °C for equilibrium time of the respective dyes. Figure 3 shows that the adsorption of AOII and DSB increases with increasing temperature while adsorption of AV7 decreases with increasing temperature suggesting exothermic adsorption of AOII, DSB, and endothermic adsorption of AV7. An increase in adsorption capacities of the dyes AOII and DSB with increasing temperature could be attributed to the increased mobility of the dye molecules with temperature and is an indication of a chemisorption mechanism. Similar observations have been reported for adsorption of basic and reactive dyes.18 The increase in dye adsorption with increasing temperature might also be due to the enhanced rate of intraparticle diffusion of the sorbate as diffusion is an endothermic process.14

8108

Ind. Eng. Chem. Res., Vol. 49, No. 17, 2010

Figure 3. Uptake studies with respect to temperature, pH, dose, and time.

Figure 4. Kinetics for DSB, AOII, and AV7.

Effect of pH. pH plays a very important role in effective decolourization of dye color of any adsorbate-adsorbent system. The pH of the system effects the nature of the surface charge of the adsorbent, effect of ionization of dye, and the extent and rate of adsorption. The hydrogen ion concentration (pH) primarily affects the degree of ionization of AOII and the surface properties of APSP. These, in turn, lead to alterations in the amount of sorbate removed. In this study, the effect of solution pH on the sorption of dyes (80-160 ppm) was investigated in the range of 1-10 at ambient temperature (30 °C). The results in Figure 3 indicate that adsorption of all the three dyes

decreases with an increase in solution pH up to pH ≈ 4 and then the amount adsorbed remained the same up to a pH 10. At low pH, the positive charge on the adsorbents surface increases, which increases the electrostatic attraction between the negatively charged sulfonate anion of the dyes and the positively charged surface. But at alkaline pH, significant adsorption of anionic dye occurred suggesting that chemisorption might be operating. Effect of Dose. Figure 3 shows the removal of AOII, DSB, and AV7 by APSP at different adsorbent doses (0.1-0.6 g/25 mL) for dye concentrations 80-160 mg/L. As the dose of the

Ind. Eng. Chem. Res., Vol. 49, No. 17, 2010

8109

Table 1. Kinetics Parameters for DSB, AOII, and AV7

experimental pseudo-first-order pseudo-second-order

type I type 2 type 3

type 4

type 4

intraparticle

qe (mg/g) qe (mg/g) K (min-1) r2 qe (mg/g) K (g/mgmin) r2 qe (mg/g) K (min-1) r2 qe (mg/g) K (g/mgmin) r2 qe (mg/g) K (g/mgmin) r2 Ki (mg/gmin0.5) r2

adsorbent increased from 0.1 to 0.6 g the amount adsorbed increased which can be attributed to the increase in adsorbent surface area and availability of more adsorption sites. Effect of Agitation Time. The effect of agitation time on the amount adsrobed of the three dyes is shown in Figure 3. It was observed that as the agitation time increases from 5 to 60 min the adsorbed amount also increased. But the equilibrium was achieved within 30 min in the case of all the three dyes. The curves were smooth and continuous. Similar results were reported for various dye sorption by other sorbents.19-22 Equilibrium time is reported to be one of the important considerations for a water treatment system and hence economics of the treatment system.23 Adsorption Dynamics. To study the adsorption kinetics, pseudo-first-order, pseudo-second-order and intraparticle diffusion models were checked (Figure 4), and calculated rate constants and r2 values are given in Table 1. It is seen that the correlation coefficient was found to be 0.97 in the pseudo-firstorder model, and qe experimental values are comparatively closer with qe theoretical values than that of the pseudo-secondorder model but with minor deviations, suggesting that pseudofirst-order is not a good fit. As seen from Figure 5, though the pseudo-second-order equation better describes the biosorption with a correlation coefficient of 0.99, the qe experimental values are not at all comparable with qe theoretical. The study of the intraparticle diffusion model gave r2 values of ∼0.91 and the plot between sorbate concentration and square root of time was linear (figure not shown) suggesting that the

Figure 5. Isotherms for DSB, AOII, and AV7.

AV7

AOII

DSB

655.12 709.41 0.02542 0.942 125.6281407 0.000690514 0.993 598.8023952 0.001297163 0.995 1047.13533 1.99171 × 10-5 0.982 1068.006958 1.88388 × 10-5 0.982 47.74 0.994

48.408 33.267 0.96669 0.987 19.89258 0.015128 0.999 19.42125 0.018157 0.992 19.5105 0.017645 0.988 19.59156 0.017154 0.988 0.36763 0.90281

35.350 37.43 0.90141 0.943 20.30869 0.009513 0.99856 18.88574 0.014393 0.924 19.13669 0.013736 0.898 20.08326 0.010561 0.898 1.4226 0.93514

adsorption process could be controlled by intraparticle diffusion. The adsorption at higher temperatures becomes more dependent on intraparticle diffusion, which would be the rate determining step. Adsorption Isotherms. Linear plots of log(x/m) versus log Ce shows that adsorption follows the Freundlich isotherm model. The values of 1/n, less than unity are an indication that significant adsorption takes place at low concentration but the increase in the amount adsorbed with concentration becomes less significant at higher concentration and vice versa.21,24,25The magnitude of KF and n shows easy removal of dye and high adsorption capacity. Table 2 and Figure 5 show the values of the parameters of the two isotherms and the related correlation coefficients. As seen from Table 2, the Langmuir model yields a somewhat better fit [R2 ) 0.9435] than the Freundlich model [R2 ) 0.9265]. As also illustrated in Table 2, the value of 1/n is -1.7576 (AOII) calculated from the slope of the plot of Freundlich isotherm which indicates favorable adsorption.26 Conformation of experimental data to the Langmuir isotherm model indicates the homogeneous nature of APSP surface and monolayer coverage of dye molecules at the outer surface of the adsorbent. A similar observation was reported by the adsorption of acid orange onto activated carbon prepared from agricultural waste bagasse,27 adsorption of direct dyes onto activated carbon prepared from sawdust,28 and adsorption of congo red dye on activated carbon from coir pith.21 Table 3 shows the comparison of maximum monolayer adsorption capacity of some dyes on various adsorbents reported in

8110

Ind. Eng. Chem. Res., Vol. 49, No. 17, 2010

Table 2. Isotherm Parameters for DSB, AOII, and AV7

Freundlich experimental Langmuir-I Langmuir-II Langmuir-III Langmuir-IV

Kf (mg/g)(dm3/mg)1/n n r2 qe (mg/g) qm (mg/g) Ka (L/mg) r2 qm (mg/g) Ka (L/mg) r2 qm (mg/g) Ka (L/mg) r2 qm (mg/g) Ka (L/mg) r2

AV7

AOII

DSB

13898.6 -1.238 0.999 415.9 243.9 -0.03134 0.999 243.902 -0.03144 0.999 244.2743 -0.03143 0.999 244.16 -0.03245 0.999

16.66482 4.425758 0.993 2039.59 2180.05 0.075694 0.997 1766.731 0.162649 0.995 1782.092 0.15794 0.992 1789.078 0.15567 0.992

16.75355 7.566586 0.998 1193.991 1199.988 0.700287 0.998 1272.274 0.170129 0.963 1278.63 0.164548 0.948 1296.26 0.14779 0.948

Table 3. Comparison of Maximum Adsorption Capacities of Dyes material

dye

maize cob bagasse pith wood shavings sunflower stalks coir pith carbon sludge based activated carbon Chemviron GW activated carbon banana pith kapok fruit shell cashew nut shell carbon (CC) APSP APSP APSP

mg/g

references

acid blue 25 acid blue 25 congo red congo red congo red acid brown 283

41.4 20-25 0.8 31.5-37 6.7 20.5

36 39 38 37 21 31

acid brown 283

18.7

31

acid brilliant blue acid violet acid violet

4.4 1.780 1.975

34 35 35

AOII AV7 DSB

2180.05 243.9 1199.98

present study present study present study

literature with acid treated PSP used in this work. Table 3 shows that the adsorbent used in this work has higher adsorption capacity as compared to those cited in the literature. The

maximum adsorption capacity (41.4 mg/g) was observed in the case of activated carbon prepared from maize cob.36 The adsorption capacity of APSP used in present studies was 2180.05 mg/g, 1199.99 mg/g, and 243.9 mg/g for AOII, DSB, and AV7, respectively. Thermodynamic Parameters. The thermodynamic parameters such as change in free energy (∆G°), enthalpy (∆H°), and entropy (∆S°) obtained for the adsorption of dyes under investigation are given in Table 4. The negative values of enthalpy for AOII and DSB are due to the exothermic nature of adsorption. Also negative values for the entropy for AOII and DSB show a high affinity of PSC for AOII and DSB; furthermore the negative values of free energy indicate the feasibility and spontaneous values of the process. The adsorption of AV7 is exothermic while the adsorption of DSB and AOII are endothermic. The structures of the dye molecules may be an important factor for their adsorption (Figure 6). The negative values of apparent enthalpy change show an endothermic physical adsorption favored by decreased temperature. The negative values of ∆G° confirm that the dye adsorption on APSP is a spontaneous process. It has been reported that ∆G° up to -20 kJg/mol are due to electrostatic interaction between sorption sites and the metal ion (physical adsorption), while ∆G° values more negative than -40 kJg/ mol involve charge sharing or charge transfer from the biomass surface to the metal ion to form a coordinate bond.29 The ∆G° values obtained in this study for the two dyes are less than -10 KJg/mol, which indicates that physical adsorption was the predominant mechanism in the sorption process. Ozer et al. stated that whatever the sign of ∆G°, the reaction will always occur, but its rate may be very slow. The positive values of free energy indicate that at equilibrium the amount of dye adsorbed on the sorbent is lower than the amount of dye in solution.30 Desorption studies. Desorption studies help to elucidate the mechanism of adsorption and recovery of the adsorbate and

Table 4. Thermodynamic Parameters for DSB and AOII at Different Time and Temperature Intervals -∆G° (KJ/mol)

ln K

∆S° (KJ/mol)

-∆H° (KJ/mol)

time

temp (K)

DSB

AOII

DSB

AOII

DSB

AOII

DSB

AOII

60 min

303 313 323 333 343

1.3303 1.8005 2.291 2.3777 2.4238

1.4573 1.5685 1.692 1.7595 1.8564

3.3513 4.6854 6.1524 6.5827 6.912

3.6712 4.0817 4.5438 4.8712 5.2938

-0.0669 -0.00209 0.00012 0.0066

-0.0163 -0.01432 -0.00937 -0.013

23.6207 5.3389 6.11396 4.3822

8.6204 8.5653 7.5689 9.2033

30 min

303 313 323 333 343

0.3509 1.0975 1.5794 1.6766 1.9404

0.6582 1.0023 1.055 1.1728 1.2436

0.88397 2.856 4.5414 4.6418 5.5334

1.6581 2.6083 2.8331 3.24697 3.5464

-0.1104 -0.071 -0.03834 -0.0613

-0.03627 -0.01461 -0.01812 -0.01046

34.3355 25.0775 16.6267 25.0561

12.6465 7.1798 8.6856 6.7304

20 min

303 313 323 333 343

0.2231 0.5295 1.0515 1.3891 1.4835

0.3991 0.6432 0.7167 0.7326 0.7847

0.5621 1.3778 2.8238 3.8459 4.2306

1.0053 1.6739 1.9247 2.0282 2.2378

-0.0878 -0.08629 -0.05285 -0.01536

-0.02418 -0.0081 -0.0037 -0.0088

27.226 28.3859 19.8953 8.9617

8.3313 4.2101 3.1298 4.9489

10 min

303 313 323 333 343

-0.9669 -0.34033 0.3827 0.6708 0.8485

-0.3863 -0.1386 -0.0849 0.1135 0.3504

-2.4358 -0.8856 1.0277 1.8572 2.4197

-0.9731 -0.3607 -0.22799 0.3142 0.9992

-0.1375 0.3149 0.0632 0.05625

-0.05574 -0.04764 -0.06277 -0.05625

39.2167 97.6928 21.4532 16.8738

15.9155 14.55096 20.0483 22.4951

5 min

303 313 323 333 343

-1.1044 -0.8541 -0.5193 -0.0745 -0.04719

-0.8663 -0.6451 -0.4325 0.01227 0.02774

-2.7821 -2.2226 -1.3945 -0.2063 -0.1346

-2.1823 -1.6787 -1.1614 0.03397 0.07911

-0.08455 -0.08379 -0.07164 -0.00841

-0.07094 -0.06932 -0.06922 -0.00431

22.83796 24.0052 21.7456 2.5935

19.313 20.01947 21.1953 1.4688

Ind. Eng. Chem. Res., Vol. 49, No. 17, 2010

8111

Figure 6. Structure of dyes.

Figure 7. Desorption and reusability of APSP for AV-7, AOII, and DSB.

adsorbent. Percent desorption increases with increase in pH of the aqueous medium (Figure 7). This is just opposite to pH effect, indicating that ion exchange is probably the major adsorption process. The adsorption efficiency decreased by ∼4.6, ∼0.4, and ∼0.7% for AV-7, AO-II, and DSB, respectively, after first cycle, by ∼10, ∼7, ∼5.5% for AV-7, AO-II, and DSB, respectively, after second cycle and ∼14, ∼10.2, ∼7.7% for AV-7, AO-II, and DSB, respectively, after third cycle. The higher percentage of desorption at higher pH will be helpful for recycling the spent adsorbent. Fourier Transform Infrared Spectroscopy. Possible interactions of APSP and dye was studied by comparing the features of the spectra obtained from IR spectroscopy studies of dye, dye-loaded, and dye-unloaded APSP (Figure 8 and Table 5). APSP showed a broad frequency at ∼3419.42 cm-1, which can be assigned to N-H/-OH stretching. After the adsorption of the dye molecule the peak is shifted to 3424.65, 3383.76, and 3174.57 cm-1 for AO-II, DSB, and AV-7 dyes, respectively. The peak at ∼1625.29 cm-1 was assigned to the N-H bond of amine or characteristics of the elongation of the aromatic -CdC- bonds which also have been shifted to 1617.62, 1608.24, and 1609 cm-1 for AO-II, DSB, and AV-7 dyes, respectively. The peak at 1378.58 which corresponds to C-N stretching is missing after the adsorption of dye molecules. The

peak at 1200 cm-1 is associated with the C-O stretching of the aromatic ring which is also shifted to a lower frequency region. Adsorption Mechanism. pH studies and Langmuir isotherms are indicative of two mechanisms operating for adsorption of anionic dyes on APSP. They include electrostatic attraction between the protonated adsorbents and acidic dyes and the chemical reaction between adsorbate and adsorbent. Conformation to Langmuir isotherms also indicates the homogeneous nature of the APSP surface suggesting each dye molecule/acid treated PSP adsorption has equal adsorption activation energy and monolayer coverage of dyes.32 Conformation to the pseudosecond-order model suggests that the rate-determining step may be chemisorption involving valency forces through sharing or exchange of electrons between sorbent and sorbate. The endothermic nature of adsorption of AOII and DSB suggests that intraparticle diffusion also plays a significant role in the adsorption process of these dyes. Netrapadit et al. stated that a lower amount of sulfonic groups (SO3-) decreases the amount of negative charge and attractive force with positive charges.33 Though AOII has a lower number of SO3- (Figure 6), it has the greatest adsorption capacity followed by DSB and AV7 probably due to geometry and size of the molecule. AV7 could be more protonated at pH1 than

Table 5. Fourier Transform Infrared Spectra of Dye, Dye-Loaded, and Dye-Unloaded APSP APSP

AOII

APSP-AOII

DSB

APSP-DSB

AV7

APSP-AV7

assignment

3419.42 1625.29 1378.58

3433.40 1619.55

3424.65 1617.62

3383.76 1608.24

1200.01

3425.43 1582.66 1346.68 1175.70 1035.17

3174.57 1609.00

1209.64 1034.89

3411.48 1627.66 1348.56 1187.67 1049.66

N-H and OH stretching CdC N-H bending C-N stretching C-O stretching C-O stretching

1176.38 1008.12

1175.39

8112

Ind. Eng. Chem. Res., Vol. 49, No. 17, 2010

APSP, might be partly ion exchange, chemisorption, physisorption, and intraparticle diffusion. Conclusion In this study the adsorption of three anionic dyes by APSP was studied. The results indicate that acidic pH is favorable for adsorption of anionic dye. Increasing temperature favors the adsorption of AOII and DSB dyes while lower temperature favors the adsorption of AV7 dye. Removal capacity of AOII dye was highest. Thermodynamic results indicate that the adsorption of DSB is spontaneous and endothermic while adsorption of AOII dye is exothermic. Isotherm modeling indicates that the langmuir model has better correlation. The values of maximum adsorption capacity were found to be 2180.05, 1199.99, and 243.9 mg/g for AOII, DSB, and AV7, respectively, which is comparable with the values reported in literature. Acknowledgment This work has been funded by The M. S. University of Baroda, Vadodara. The authors thank Dr. P. K. Mehta, Department of Physics, The M. S. University of Baroda, for carrying the XRD analysis and also thank Head, Department of Applied Chemistry, The M. S. University of Baroda, for providing laboratory facilities. Literature Cited

Figure 8. FTIR spectra of dye, dye loaded, and unloaded APSP.

DSB, and hence adsorption of DSB is more comparable to that of AV7 because of the electrostatic repulsion of AV7 with the adsorbent surface. Moreover since chemisorption is also operating the trend cannot be explained on the basis of electrostatic attraction/repulsion alone. On the basis of the results obtained from the IR analysis and pH, kinetic, desorption, and isotherm studies, we conclude that the biosorption mechanism, underlying the sorption of dyes onto

(1) Khare, S. K.; Panday, K. K.; Srivastava, R. M.; Singh, V. N. Removal of Victoria blue from aqueous solution by fly ash. J. Chem. Technol. Biotechnol. 1987, 38, 99–104. (2) Kay, Mc. G.; Otherburn, O. S.; Jamal, A. A. Fuller’s earth and fired clay as adsorbents for dye stuffs: Equilibrium and rate studies. Water, Air Soil Pollut. 1985, 24, 307–322. (3) Kay, Mc. G.; Blair, H.; Gardiner, J. R. The adsorption of dyes onto chitin in fixed bed column and batch adsorbers. J. Appl. Polym. Sci. 1989, 28, 1499–1544. (4) Namasivayam, C.; Kardivelu, K. Coir pith, an agricultural waste byproduct, for the treatment of dyeing waste water. Biores. Technol. 1994, 48, 79–81. (5) Namasivayam, C.; Kanchana, N. Waste banana pith as adsorbent for colour removal from waste waters. Chemosphere 1992, 25, 1691–1705. (6) Namasivayam, C.; Yamuna, R. T. Removal of congo red from aqueous solutions by biogas waste slurry. J. Chem. Technol. Biotechnol. 1992, 53, 153–157. (7) Namasivayam, C.; Yamuna, R. T. Removal of rhodamine-B by biogas waste slurry from aqueous solutions. Water, Air Soil Pollut. 1992, 65, 101–109. (8) Namasivayam, C.; Yamuna, R. T. Color removal from aqueous solution by biogas residual slurry. Toxicol. EnViron. Chem. 1993, 38, 131– 143. (9) Namasivayam, C.; Yamuna, R. T. Utilizing biogas residual slurry for dye adsorption. Am. Dyestuff Rep. 1994, 83, 22–28. (10) Namasivayam, C.; Yamuna, R. T. Adsorption of direct red 12B by biogas residual slurry: Equilibrium and rate processes. EnViron. Pollut. 1995, 89, 1–7. (11) Namasivayam, C.; Jayakumar, R.; Yamuna, R. T. Dye removal from waste water by adsorption on waste Fr(III)/Cr(III) hydroxide. Waste Manage. 1994, 14, 643–648. (12) Namasivayam, C.; Muniasamy, N.; Gayathri, K.; Rani, M.; Ranganathan, K. Removal of dyes from aqueous solutions by cellulosic waste orange peel. Biores. Technol. 1996, 57, 37–43. (13) Namasivayam, C.; Sumithra, S. Adsorption of Anionic Dyes on the Waste Fe(III)/Cr(III). J. EnViron. Sci. Eng. 2006, 48 (1), 69–74. (14) Namasivayam, C.; Dinesh, M. K.; Selvi, B. K.; Ashruggunissa, R.; Vasanthi, T.; Yamuna, R. T. Waste coir pith, a potential biomass for the treatment of dyeing waste water. Biomass Bioenergy 2001, 21, 477–483. (15) Esther, F.; Tibor, C.; Gyula, O. Removal of synthetic dyes from waste waters: A review. EnViron. Int. 2004, 30 (7), 953–971. (16) Gupta, V. K.; Suhas. Application of low cost adsorbent for dye removalsA review. J. EnViron. Manage. 2009, 90 (8), 2313–2342.

Ind. Eng. Chem. Res., Vol. 49, No. 17, 2010 (17) Gregorio, C. Nonconventional low cost adsorbent for dye removal: A review. Biores. Technol. 2006, 97 (9), 1061–1085. (18) Dogan, K.; Akgul, E.; Sema, T.; Ferruh, E.; Mehmet, A. K.; Mustafa, T. Basic and reactive dye removal using natural and modified zeolites. J. Chem. Eng. Data 2007, 52, 2436–2441. (19) Low, K. S.; Lee, C. K. The removal of cationic dyes using coconut husk as an adsorbent. J. Sci. Technol. 1990, 13, 221–228. (20) Thangamani, K. S.; Sathishkumar, M.; Sameena, Y.; Vennilamani, N.; Kardivelu, K.; Pattabhi, S.; Yun, S. E. Utilization of modified silk cotton hull waste as an adsorbent for the removal of textile dye (reactive blue MR) from aqueous solution. Biores. Technol. 2007, 98, 1265–1269. (21) Namasivayam, C.; Kavitha, D. Removal of congo red from water by adsorption onto activated carbon prepared from coir pith, an agricultural solid waste. Dyes Pigm. 1989, 54, 47–58. (22) Sugunadevi, S. R.; Sathishkumar, M.; Shathi, K.; Kardivelu, K.; Pattabhi, S. Removal of direct T-blue R from aqueous solution onto carbonized sugarcane bagasse waste. Indian J. EnViron. Protect. 2002, 22, 500–505. (23) Deepa, K. K.; Sathishkumar, M.; Binupriya, A. R.; Murugesan, G. S.; Swaminathan, K.; Yun, S. E. Sorption of Cr(VI) from dilute solutions and waste water by live and pretreated biomass of Aspergillus Flavus. Chemosphere 2006, 62, 833–840. (24) Haghseresht, F.; Lu, G. Adsroption characteristics of phenolic compounds onto coal-reject-derived adsorbents. Energy Fuels 1998, 12, 1100–1107. (25) Fytianos, K.; Voudrias, E.; Kokkalis, E. Sorption-desorption behaviour of 2,4-dichlorophenol by marine sediments. Chemosphere 2000, 40, 3–6. (26) Adamson, A. W. Physical Chemistry of Surfaces, 5th ed.; Wiley: New York, 1990. (27) Tsai, W. T.; Chang, C. Y.; Lin, M. C.; Chien, S. F.; Sun, H. F.; Hseih, M. F. Adsorption of acid dye onto activated carbons prepared from agricultural waste bagasse by ZnCl2 activation. Chemosphere 2001, 45, 51– 58. (28) Mallik, P. K. Dye removal from waste water using activated carbon developed from sawdust; Adsorption equilibrium and kinetics. J. Hazard. Mater. 2004, B113, 81–88.

8113

(29) Tsai, W. T.; Chang, C. Y.; Lai, C. W.; Lo, C. C. Adsorption of ethyl violet dye in aqueous solution by regenerated spent bleaching earth. J. Colloid Interface Sci. 2005, 289, 333. (30) Ozer, A.; Akkaya, G.; Turabik, M. The biosorption of acid red 337 and acid blue 324 on enteromorpha prolifera: The application of nonlinear regression analysis to dye biosorption. Chem. Eng. J. 2005, 112, 181. (31) Martin, M. J.; Artola, A.; Balaguer, M. D.; Rigola, M. Activated carbons developed from surplus sewage sludge for the removal of dyes from dilute aqueous solution. Chem. Eng. J. 2003, 94, 231–239. (32) Gupta, V. K.; Imran, A.; Saini, V. K.; Tom, V. G.; Bart, V. D. B.; Carlo, V. Removal of dyes from waste water using bottom ash. Ind. Eng. Chem. Res. 2005, 44, 3655–3664. (33) Netpradit, S.; Thiravetyan, P.; Towprayoon, S. Application of waste metal hydroxide sludge for adsorption of azo reactive dyes. Water Res. 2003, 37, 763–772. (34) Namasivayam, C.; Prabha, D.; Kumutha, M. Removal of direct red and acid brilliant blue by adsorption on banana pith. Biores. Technol. 1998, 64, 77–79. (35) Kannan, N.; Murugavel, S. Comparative study on the removal of acid violet by adsorption on various low cost adsorbents. Global Nest J. 2008, 10 (3), 395–403. (36) El-Geundi, M. S. Color removal from textile effluents by adsorption techniques. Water Res. 1991, 25, 271. (37) Sun, G.; Xu, X. Sunflower stalks as adsorbents for color removal from textile waste water. Ind. Eng. Chem. Res. 1997, 36, 808–812. (38) Abo-Elila, S. I.; El-Dib, M. A. Color removal via adsorption on wood shaving. Sci. Total EnViron. 1987, 66, 269–273. (39) McKay, G.; Geundi, M. El.; Nassar, M. M. Equilibrium studies during the removal of dyestuffs from aqueous solutions using bagasse pith. Water Res. 1987, 21, 1513–1520.

ReceiVed for reView May 2, 2010 ReVised manuscript receiVed July 2, 2010 Accepted July 7, 2010 IE101004Q