CC BY-NC-ND
0Journal of Saudi Chemical Society (2012) xxx, xxx-xxx
King Saud University Journal of Saudi Chemical Society
www.ksu.edu.sa www.sciencedirect.com
ORIGINAL ARTICLE
Equilibrium, kinetic and thermodynamic studies for sorption of Ni (II) from aqueous solution using formaldehyde treated waste tea leaves
Jasmin Shah *, M. Rasul Jan, Atta ul Haq, M. Zeeshan
Institute of Chemical Sciences, University of Peshawar, Pakistan Received 14 December 2011; accepted 3 April 2012
KEYWORDS
Waste tea leaves;
Sorption;
Isotherms;
Kinetics;
Thermodynamics
Abstract The sorption characteristic of Ni (II) from aqueous solution using formaldehyde treated waste tea leaves as a low cost sorbent has been studied. The effect of pH, contact time, sorbent dose, initial metal ion concentration and temperature were investigated in batch experiments. The equilibrium data were fitted into four most common isotherm models; Freundlich, Langmuir, Tempkin and Dubinin-Radushkevich (D-R). The Langmuir model described the sorption isotherm best with maximum monolayer sorption capacity of 120.50 mgg-1. Four kinetic models, pseudo-first-order, pseudo-second-order, intraparticle diffusion and Elovich were employed to explain the sorption mechanism. The kinetics of sorption data showed that the pseudo-second-order model is the best with correlation coefficient of 0.9946. The spontaneous and exothermic nature of the sorption process was revealed from thermodynamic investigations. The effect of some common alkali and alkaline earth metal ions were also studied which showed that the presence of these ions have no effect on the sorption of Ni (II). The results showed that waste tea leaves have the potential to be used as a low cost sorbent for the removal of Ni (II) from aqueous solutions.
© 2012 King Saud University. Production and hosting by Elsevier B.V. All rights reserved.
* Corresponding author. Tel./fax: +92 91 9216652. E-mail address: jasminshah2001@yahoo.com (J. Shah).
1319-6103 © 2012 King Saud University. Production and hosting by Elsevier B.V. All rights reserved.
Peer review under responsibility of King Saud University. http://dx.doi.org/10.1016/jjscs.2012.04.004
1. Introduction
The natural environment received a high volume of wastewater containing heavy metals as a result of increase in industrial activities. Due to toxicity, accumulation in food chain and persistence in nature, heavy metals pose a significant threat to public health and environment. The most immediate concern of heavy metals include lead, cadmium, zinc, nickel, cobalt, chromium, copper and mercury according to the World Health Organization (WHO). The effluents of various industries like electroplating, ceramic, metallurgy, mining, stainless steel, pigments, enameling, porcelain and accumulator manufacturing of nickel contain undesirable amount of nickel ions
Production and hosting by Elsevier
(Patmavathy et al., 2003; Hasar, 2003; Villaescusa et al., 2004; Aksu, 2002). The trace amount of nickel is beneficial due to the activation of some enzymatic systems but higher intake than the permissible level causes various diseases like lung cancer, pulmonary fibrosis, skin dermatitis, renal edema, diarrhea, nausea and vomiting (Meena et al., 2005). According to the Water Sanitation and Hygiene (WSH) under the World Health Organization (WHO), the permissible concentration of Ni (II) as insoluble compounds of Ni (II), soluble compound of Ni (II), nickel carbonyl, nickel sulphide are 1.0, 0.1, 0.05-0.12 and 1.0 mg L_1 respectively (Xuan et al., 2006; Zafar et al., 2007; Aksu, 2002; Padmavathy, 2008; Dahiya et al., 2008; Sud et al., 2008; Lothongkum et al., 2009). Removal of heavy metals from wastewater is very important for the protection of environment and public health before going to natural water because of its toxicity.
A variety of traditional methods have been employed for the removal of heavy metals from aqueous solutions such as ion exchange, reverse osmosis, filtration, solvent extraction, evaporation, electrochemical treatment, chemical oxidation or reduction, chemical precipitation, and membrane technologies (Rio et al., 2002; Gupta et al., 2003; Remoudaki et al., 2003; Zhao et al., 2005; Sharma et al., 1991; Yan and Viraraghavan, 2001). These technologies may not be applicable to small industries due to their high capital investment and running costs especially in developing and under developed countries. Another major disadvantage associated with these methods is the production of toxic chemical sludge and its disposal/treatment becomes an expensive matter and is not environment friendly. Therefore, it is necessary to remove heavy metals from aqueous solution and bring their concentrations to permissible level using cost effective and eco-friendly methods (Aksu, 2002; Ahluwalia and Goyal, 2007; Ergtugay and Bayhan, 2008; Shah et al., 2012). One of the most promising methods used for the removal of heavy metals is the biosorption which based on the binding and concentration of metals on the surface of inactive/dead biomass from even very dilute aqueous solutions. Biosorption has many advantages over other traditional methods; it effectively reduces the concentration of heavy metals to very low levels and the use of cost effective biosorbents. Recently, a variety of biological materials have been investigated for the removal of Ni (II) such as spent animal bones (Al-Asheh et al., 1999), crab shell (Vijayaraghavan et al., 2004), activated carbon prepared from almond husk (Hasar, 2003), dried aerobic activated sludge (Aksu and Akpinar, 2000) loofa sponge-immobilized biomass of Chlorella sorokiniana (Akhtar et al., 2004) and seaweeds (Vijayaraghavan et al., 2005).
Tea is the dried and processed leaves of plant species Camellia sinensis (Mokgalaka et al., 2004). Many people of the world consumed and considered it the second most popular beverage in the world after water. On industrial scale, canned or bottled tea drinks and instant tea drinks are produced by hot water extraction of tea leaves. The producers faced serious problems of disposal of these used tea leaves after extraction. There is a need to utilize such waste product for the treatment of wastewater containing heavy metals. The waste tea leaves was used for removal of heavy metals like Zn, Ni, Fe, Pb, Cu (Ahluwalia and Goyal, 2005); Amarasinghe and Willims, 2007; Modal, 2009). But main problem with the use of biosorbent is leaching of organic compounds. The method to prevent leaching and increase effectiveness of biosorbent is
treatment with formaldehyde solution. Formaldehyde is used for preservation of animal and plant tissues, which increase stability of the material. As well as formaldehyde react with the hydroxyl group of biomass material to form acetyl groups and increase the structural stability of the biomass. Formaldehyde treatment of Sargassum biosorbent increased the metal ion capacity of Ni (II) at pH 5-71.6 mg g_1 (Chen and Yang, 2005). The effect of formaldehyde pretreatment on Ni (II) sorption using waste tea leaves has not been studied. Therefore, the aim of the present work is to evaluate the sorption capacity of formaldehyde treated waste tea leaves for Ni (II) from aqueous solutions.
2. Materials and methods
2.1. Instruments
Atomic absorption spectrophotometer (Perkin Elmer model AA200), Orbital Shaker (Model OS-340C, Digisystem laboratory instrument Inc. Made in Taiwan ROC), Analog pH meter (Model-7020 Kent Industrial Measurement Limited Electronic Instrument LTD, Chertsey Survey England), Fourier Transform Infrared Spectrophotometer (NICOLET 380-FTIR, Thermoscientific, UK) and thermostatic water bath (Yu Jia, China) were used during this work.
2.2. Chemicals and reagents
All chemicals and reagents used were of analytical reagent grade purity. 1000 igmL-1 nickel standard solution (Merck Darmstadt, Germany) was used. Working standards were prepared from suitable serial dilution of stock solution. Britton Robinson buffer was used for the adjustment of pH of solutions.
2.3. Preparation of sorbent
Waste tea leaves were collected in bulk from local tea shops, washed with distilled water to remove any dirt, dried, crushed and powdered. The powdered leaves were sieved to obtain a particle size <355 im. A weighed amount of uniform sized waste tea leaves (10 g) was transferred in a beaker (250 mL) and added 100 mL of 0.4% formaldehyde solution, thoroughly mixed and kept for 24 h at room temperature. The tea leaves were filtered and washed several times with distilled water until the water was colorless. After filtration, waste tea leaves were dried in an oven at 60 0C till constant weight and stored in an air tight bottle for further use. The BET surface area (636.023 m2 g-1) was determined by surface area analyzer (Quantachrome model, QS-7).
2.4. Sorption study
Batch sorption experiments were conducted for Ni (II) by mixing known weights (0.1 g) of formaldehyde treated waste tea leaves and 50 mL of Ni (II) solution in the concentration range of 1-150 igmL-1. The pH of the solution was adjusted with Britton Robinson buffer of pH 7.0. The mixture was shaken on an orbital shaker for 30 min at 100 rpm for complete equilibration of metal ions. After equilibration time, waste tea leaves were separated by filtration and the residual concentra-
tions of Ni (II) in the filtrates were determined by atomic absorption spectrophotometer (Perkin Elmer model AA200) with air-acetylene flame.
Sorption capacity of Ni (II) (qe) and percent sorption was calculated according to the following general equation:
C - CA
% Sorption =
'Ci- Cf
where qe is the amount of Ni (II) sorbed on the sorbent (mg g-1), Ci and Cf represent the initial and equilibrium concentrations of Ni (II), respectively; V is the volume of Ni (II) solution (mL) and m is the amount of sorbent (g).
3. Results and discussion
3.1. Characterization of waste tea leaves
In order to identify the functional groups of waste tea leaves washed with distilled water and treated with 0.4% formaldehyde, FTIR spectra was recorded in the frequency range from 600 to 4000 cm-1 and are shown in Fig. 1a and b respectively. The spectrum shows a number of peaks due to absorption of different functional groups present on tea leaves. The FTIR spectra of both samples indicated broad spectra in the range of 3340-3380 cm-1 due to -OH groups. The bands at about 2920-2850 cm-1 could be assigned to aliphatic C-H groups. A peak at 1610 cm-1 could be due to the carbonyl group of carboxyl and the peak observed at 1558-1520 cm-1 assigned to the secondary amine groups. At 1456 cm-1, symmetric bending of CH3 is observed. The peaks at 1242 cm-1 and 1157 cm-1 could be due to -SO3 stretching and C-O stretching of ether groups, respectively. Comparing the IR spectra of both sorbent materials, functional group intensity remains the same in water washed and formaldehyde (0.4%) treated
waste tea leaves. For further analysis formaldehyde treated waste tea leaves were used.
3.2. Effect ofpH
The pH of solution affects the surface charge of waste tea leaves. Therefore, it is important to study the effect of solution pH on the sorption process. The pH of Ni (II) solution for sorption process was varied from 3.0 to 8.0 and the results are shown in Fig. 2. At pH 3-4 range the sorption is very low and rapidly increases from pH 4 to 7 with increase in uptake from 11.2% to 70.2%. At lower pH, the % uptake is lower due to H+ ion present in the solutions, which compete with Ni (II) for active sites on the sorbent causing a decrease in the % uptake of Ni (II) but as pH increased from 4.0 to 7.0 the surface of tea leaves becomes negatively charged which leads to higher uptake of Ni (II) through electrostatic attraction. Decrease in sorption was observed due to formation of metal hydroxide precipitate at pH > 7. Therefore pH 7 was selected as optimum pH for sorption of Ni (II) on waste tea leaves.
3.3. Effect of contact time
Effect of contact time on the sorption of Ni (II) on waste tea leaves with shaking and without shaking was investigated. The contact time was varied from 30 to 100 min (Fig. 3). A steady increase in % uptake was observed with increase in contact time. In the beginning of sorption process, the sorption sites are open and Ni (II) interacts easily with the sites and therefore greater sorption is observed. Further it was also observed that with shaking greater uptake was occurred for the same equilibration time in contrast to the samples without shaking. At 90 min contact time 82% uptake of Ni (II) was observed with shaking as compared to 72% uptake without shaking.
Figure 1a IR spectrum of water washed waste tea leaves.
2400 1800 1400
Wavenumber (cm1)
Figure 1b IR spectrum of formaldehyde (0.4%) treated waste tea leaves.
D 40 J4 IS
Figure 2 Effect of pH on sorption of Ni (II) using waste tea leaves (initial concentration of Ni (II) 5 igmL^1, pH 3.0-8.0, sorbent dose 0.1 g, contact time 30 min at room temperature).
■ Without shaking " With shaking
Time (min)
3.4. Effect of sorbent dose
Sorbent dose is an important factor which affects the sorption process. Generally, as the sorbent dose increases the sorption also increases due to availability of the sorption sites for metal ions binding. Therefore the effect of sorbent dose on sorption of Ni (II) was studied and the amount of sorbent was varied from 0.03 to 0.15 g (Fig. 4). Initially, the sorption sites are occupied by available metal ions and no further sorption occur due to non-availability of sorption sites. As the sorbent dose increases from 0.03 to 0.15 g, the sites for sorption also increase and 100% uptake was achieved at 0.13 g of sorbent. Because at higher sorbent dose Ni(II) concentration decrease to a very lower value and the sorption process reaches equilibrium indicating the sorption sites still unsaturated. Therefore further studies were carried out with 0.13 g of sorbent dose.
0.10 Weight (g)
Figure 3 Effect of contact time on sorption of Ni (II) using waste tea leaves (initial concentration of Ni (II) 5 igmL"1, pH 7.0, sorbent dose 0.1 g, contact time 30-100 min at room temperature).
Figure 4 Effect of sorbent dose on sorption of Ni (II) using waste tea leaves (initial concentration of Ni (II) 5 igmL"1, pH 7.0, sorbent dose 0.03-0.15 g, contact time 30 min at room temperature).
2.0 ■
1.0 ■
-0.8 -0.4 0.0 0.4 0.8 1.2
Figure 5 Freundlich isotherm for sorption of Ni (II) using waste tea leaves (initial concentration of Ni (II) 1-150 ig mL-1, pH 7.0, sorbent dose 0.13 g, contact time 90 min at room temperature).
-20 J In Ce
Figure 7 Tempkin isotherm for sorption of Ni (II) using waste tea leaves (initial concentration of Ni (II) 1-150 ig mL-1, pH 7.0, sorbent dose 0.13 g, contact time 90 min at room temperature).
Equilibrium concentration (|g mL'1)
Figure 6 Langmuir isotherm for sorption of Ni (II) using waste tea leaves (initial concentration of Ni (II) 1-150 ig mL-1, pH 7.0, sorbent dose 0.13 g, contact time 90 min at room temperature).
W 3 -s
100000
Figure 8 Dubinin-Radushkevich (D-R) isotherm for sorption of Ni (II) using waste tea leaves (initial concentration of Ni (II) 1150 ig mL-1, pH 7.0, sorbent dose 0.13 g, contact time 90 min at room temperature).
3.5. Sorption isotherms
The sorption systems were designed by using sorption isotherm models. These models provide a relationship between the amount of Ni (II) sorbed on the sorbent and the concentration of Ni (II) in solution at equilibrium. The sorption isotherms of Ni (II) on sorbent were studied by four most commonly used isotherms models, Freundlich, Langmuir, Tempkin and Dubi-nin-Radushkevich (D-R) isotherms. The Freundlich isotherm is used for non-ideal sorption on heterogeneous surfaces and is expressed by the following equation:
qe = KFce (3)
The linear form of Freundlich equation is given below:
log qe = logKF +1 log Ce (4)
where KF is the Freundlich sorption isotherm constant (mgg-1), 1/n (gL-1) is a measure of the sorption intensity
and qe is the amount sorbed (mg g-1) and Ce is the equilibrium concentration (igmL-1).
The Langmuir isotherm is used for monolayer sorption on a homogeneous surface and is expressed by the following equation:
1 + aLCe
In a linear form, it is expressed as follows:
___aLCe
q ~ kL
where Ce is the equilibrium concentration (ig mL-1), qe is the amount of solute sorbed per gram of sorbent; KL and aL are the Langmuir sorption isotherm constants and are related to the maximum capacity (Lg-1) and bonding strength (Lmg-1) respectively. The theoretical monolayer capacity is Qo and is numerically equal to KLaL-1.
Tempkin isotherm model contains a factor that obviously takes into account sorbing species-sorbate interactions. This model assumes that: (i) heat of sorption of all molecules in the layer decreases linearly with coverage due to sorbate-sorbate interactions and (ii) sorption is characterized by a uniform distribution of binding energies, up to some maximum binding energy. The derivation of the Tempkin isotherm assumes that the fall in the heat of sorption is linear rather than logarithmic, as implied in the Freundlich equation. The Temp-kin isotherm has commonly been applied in the following form:
qe — —ln(ATCe) Dt
The linear form of this isotherm is as
qe — BTlnAT + BTlnCe
where BT = (RT)/bT, T is the absolute temperature in Kelvin and R is the universal gas constant, 8.314 J/molK. The constant bT is related to the heat of sorption. The sorption data were analyzed using the linear form of Tempkin isotherm.
The Dubinin-Radushkevich (D-R) isotherm model was applied for estimation of porosity, apparent free energy and characteristic of sorption. The D-R isotherm does not assume a homogeneous surface or constant sorption potential and it has commonly been applied in the following form:
qe — Qmexp(-Ke})
The linear form of D-R isotherm is as: lnqe — lnQm - Ke2
where K is a constant related to the sorption energy, Qm the theoretical saturation capacity, e is the Polanyi potential can be calculated from the following equation:
e — RTln I 1 + C
The values of K (mol2 (kJ2)-1) and Qm (mg g-1) were calculated from the slope and intercept of the plot of ln qe against e2 respectively. The mean free energy of sorption (E), defined as the free energy change when one mole of ion is transferred from infinity in solution to the surface of the sorbent, was calculated from the K value using the following equation:
E = -ffi (12)
Various constant values calculated from the D-R isotherm model. The results of these isotherms are shown in Figs. 5-8 respectively. The constant parameters of these isotherms were calculated from slope and intercept of the linear form of their respective equations and are given in Table 1. The n value of the Freundlich model shows that Ni (II) is not sorbed favorably on waste tea leaves because it is less than unity. Maximum sorption capacity was calculated from the linear form of Lang-muir isotherm and was found to be 120.5 mgg-1. It may be concluded from these results that the sorption data of Ni (II) on waste tea leaves shows best fit into Langmuir isotherm model due to high correlation coefficient (R2 = 0.9405). It can be seen from the table that the data not followed the Tempkin isotherm model due to low correlation coefficient. The value of correlation coefficient for D-R model is very small as compared to the other models, suggesting that the
Table 1 Comparison of various isotherm constants for the sorption of Ni (II) on waste tea leaves.
Isotherm
Freundlich Kf (mg g-1) n
1/n R2
Langmuir
aL (Lmg-1)
Kl (L g-1)
Qo (mgg-1) R2
Tempkin
Dubinin-Radushkevich
Qm (mg g-1)
E (kJ mol-1) R2
19.22 0.946
I.056 0.9263
0.354 42.73 120.5 0.9405
II.49 17.36 11.97 0.9030
81.57 2 x 100.158 0.7725
data is not fitted into D-R isotherm model. Moreover, the value of Qm, calculated from the D-R model is not close to the value of maximum sorption capacity calculated from the Langmuir isotherm model.
3.6. Sorption kinetics
Four common kinetic models that are pseudo-first-order, pseudo-second-order, intraparticle diffusion and Elovich equations were used for sorption kinetics of Ni (II) on waste tea leaves. The model for pseudo-first-order is expressed as follow:
log(qe- q() —log qe
where qe is the amount of metal ion sorbed (mg g-1) at equilibrium, qt is the amount of metal ions sorbed (mg g-1) at any given time (min) and K1 is the pseudo-first-order reaction rate constant for sorption (min-1). The model for pseudo-second-order is as:
qe Kiq\
where qe is the amount of metal ion sorbed (mg g-1) at equilibrium, qt is the amount of metal ions sorbed (mg g-1) at any given time (min) and K2 is the pseudo-second-order reaction rate constant for sorption (g mg-1 min-1).
A linear plot of time against log(qe - qt) was plotted for the determination of rate constant and sorption capacity for pseudo-first-order. The results are shown in Fig. 9. The pseudo-second-order model is given in Eq. (14) and was obtained by plotting time (t) versus t/qt. The results are shown in Fig. 10. Similarly, the constant values of first order kinetics K1, qe, R2 and the second order kinetics K2, qe and R2 were calculated from the slope and intercept of each model respectively and are given in Table 2. It was observed that the correlation
Time (min)
Figure 9 Pseudo-first-order kinetics of Ni (II) uptake using waste tea leaves (sorbent dose 0.13 g, initial concentration of Ni (II) 5 ig mL-1, volume of Ni (II) solution 10 mL, pH 7.0).
20 40 60 80 100
Time (min)
Figure 10 Pseudo-second-order kinetics of Ni (II) uptake using waste tea leaves (sorbent dose 0.13 g, initial concentration of Ni (II) 5 ig mL-1, volume of Ni (II) solution 10 mL, pH 7.0).
Table 2 Kinetic parameters of Ni (II) sorption on waste tea
leaves.
Model Parameters Values
Pseudo-first order kinetics
qe (mg g-1) (exp) 8.213
k (min-1) 0.026
qe (mg g-1) 4.880
R2 0.9856
Pseudo-second order kinetics
k2 (gmg-1 min-1) 0.005
qe (mg g-1) 9.800
R2 0.9946
Intraparticle diffusion model
Kint (mg g-1 s/2) 1.537
C -3.499
R2 0.9997
Elovich model
a (mg g-1 min-1) 4.390 x 10-35
b (gmg-1) 0.178
R2 0.9924
ел j=
t1/2 (min)
Figure 11 Intraparticle diffusion model of Ni (II) uptake using waste tea leaves (sorbent dose 0.13 g initial concentration of Ni (II) 5 ig mL-1, volume of Ni (II) solution 10 mL, pH 7.0).
coefficient values of the pseudo-second-order model are higher than the first order model. This suggests that the sorption might be controlled by second-order-model.
During sorption process, different steps occurs like in the first step sorbate (Ni) ions are transferred from aqueous media to the surface of sorbent (waste tea leaves) while in second step the diffusion of sorbate ions into pores of sorbent taken place. There is a possibility that the controlling step is the transferring of sorbate from solution into pore of sorbent if the experiments are carried out in batch system with shaking of the reaction mixture. For checking of this possibility a graph of sorption capacity at time t (qt) against square root of time (t1/2) is plotted. The results are shown in Fig. 11.
Intraparticle diffusion is a kinetic model which is related to the transfer of Ni (II) from its aqueous media to the pores of sorbent. This model is generally expressed by the following equation:
qt = Kmtt1'2 + C (15)
where C is the intercept and related to the thickness of the boundary layer and Kint (mol L-1 min-1/2) is the intraparticle diffusion rate constant. The values of these constants were calculated directly from the intercept and slope of the graph and are given in Table 2. Form Fig. 12 it can be seen that the plot
4.0 lnt (min)
Figure 12 Elovich model of Ni (II) uptake using waste tea leaves (sorbent dose 0.13 g, initial concentration of Ni (II) 5 igmL-1, volume of Ni (II) solution 10 mL, pH 7.0).
of qt versus t1/2 is not passing through the origin which indicates that intraparticle diffusion is not the controlling step during sorption of Ni (II) on waste tea leaves and some other mechanisms are involved.
The Elovich kinetic equation is used to describe the kinetics of chemisorption on heterogeneous surfaces and is given as follows:
qt = b ln(ap) ln{t)
where qt is the amount of Ni (II) sorbed (mol L-1) at time (t), a and b are known as the Elovich coefficients, a represents the initial sorption rate (mol L-1 min-1) and b is related to the extent of surface coverage and activation energy for chemisorp-tion (g min-1) respectively. The Elovich coefficients were calculated from the linear plot of qt versus ln t (Fig. 12). The results from kinetic models shows that experimental data fitted well to the pseudo-second-order kinetic model with a high R2 value (R2 = 0.9946).
3.7. Thermodynamics of sorption
The study of thermodynamic assumes that the energy in an isolated system cannot be lost or gained when the entropy change is the driving force. Thermodynamic parameters were calculated for determination of sorption process that either occurs spontaneously or not. The change in free energy (AGO), enthalpy (DH0) and entropy (ASO) of sorption process was calculated by using the following equations:
Kd = C (17)
AG" = -RTInKD
InKD =
AG" RT
AH AS"
~RTT + ~R~
where KD is the distribution constant, qe is the amount of metal ion sorbed (mgg-1) at equilibrium and Ce is the equilibrium concentration (ig mL-1).
The values of ln KD were plotted against 1/T. The results are shown in Fig. 13. The values of KD, AG0, AH0 and AS0 for sorption of Ni (II) on waste tea leaves were calculated using
Table 3 Thermodynamic parameters for the sorption of Ni (II) on waste tea leaves.
Temperature -AG° AH° AS°
(K) (kJ mol-1) (kJ mol-1) (kJK-1 mol-1)
313 30.440 -23.680 0.022
323 31.090 - -
333 31.830 - -
343 31.480 - -
353 31.870 - -
363 31.560 - -
Eqs. (17)-(19) and are given in Table 3. The negative value obtained for enthalpy change (AH0) indicated an exothermic sorption process. The positive value of entropy (ASO) showed the affinity of waste tea leaves for Ni (II) whereas the negative value of AG0 showed that the sorption process is spontaneous at the studied temperature range.
3.8. Effect of interfering ions
The effect of some interfering ions relevant to wastewater e.g. alkali and alkaline earth metals, Na + , K + , Mg2 + and Ca2 + on the sorption of Ni (II) at optimum conditions was investigated. The sorption studies were conducted by adding 5 ig mL-1 of Na + , K + , Mg2+ and Ca2+ and mixture of these ions separately, in 5 igmL-1 of Ni (II) solution containing 0.13 g of waste tea leaves (Fig. 14). The results indicate that the presence of these interfering ions in solution have no pronounced effect on the sorption of Ni (II) using waste tea leaves.
The effect of concentrations of these interfering ions on sorption of Ni (II) at optimum conditions were also conducted by adding the concentrations of these ions in the range of 1070 ig mL-1 to a fixed concentration of Ni (II) (5 ig mL-1) and biomass (0.13 g). From the result in Fig. 15, it was observed that upto 70 ig mL-1 concentrations of these ions have no effect on the sorption of Ni (II) using waste tea leaves.
3.9. Analytical applications
The analytical applicability of waste tea leaves were tested for tap water and different river water samples collected from
0.0028
0.0029 0.003 0.0031 1/T (K-1)
0.0032 0.0033
Figure 13 Plot of lnKD versus 1/T for estimation of thermodynamic parameters for Ni (II) sorption on waste tea leaves (Initial concentration of Ni (II) 5 igmL-1, pH 7.0, sorbent dose 0.13 g, volume of Ni (II) solution 10 mL).
Control Na K Mg Ca Mixed Type of interfering ion in solution
Figure 14 Effect of interfering ions on sorption of Ni (II) using waste tea leaves (initial concentration of Ni (II) 5 igmL-1, concentration of interfering ions 5 igmL-1, pH 7.0 at room temperature, sorbent dose 0.13 g).
10 20 30 40 50 60 70 Concentration (|g mL-1) of interfering ions
Figure 15 Effect of interfering ions concentration on sorption of Ni (II) using waste tea leaves (initial concentration of Ni (II) 5 igmL-1, concentration of interfering ions 10-70 igmL-1, pH 7.0 at room temperature, sorbent dose 0.13 g).
Table 4 Determination of Ni (II) in various water samples.
Ni (II) added (ig) Ni (II) adsorbed (ig) % Removal
Tap water
0.00 0.00 -
100 100.00 100
300 300.00 100
500 500.00 100
River Badabaira, Peshawar
0.00 0.00 -
100 100.00 100
300 300.00 100
500 500.00 100
River Swat, Charsadda
0.00 0.00 -
100 100.00 100
300 300.00 100
500 500.00 100
Khyber Pakhtunkhwa, Pakistan. Each sample was filtered before conduction of analysis with ordinary filter paper. An aliquot of 20 mL water sample was spiked with known concentration of Ni (II) at pH 7.0. The spiked sample was shaken with 0.50 g waste tea leaves on an orbital shaker for 60 min at 100 rpm. Each experiment was conducted in triplicates. The mixture was filtered and the residual concentrations of Ni (II) were determined by flame atomic absorption spectro-photometer. The results are given in Table 4 and show that 100% removal of Ni (II) from water samples achieved with waste tea leaves as a sorbent.
4. Conclusion
Surface modification of sorbent has been used to enhance the sorption capacity of sorbents. In the present study formaldehyde treated waste tea leaves were found good sorbent for the removal of Ni (II) from aqueous solution with no leaching of organic into solution. The removal of Ni (II) was higher at
pH 7. The sorption rate was rapid in the beginning and then remains constant. The sorption data fitted to pseudo second order kinetic model. The Lanhmuir isotherm fit the experimental data with monolayer sorption capacity of 120.50 mgg-1. The effect of some common alkali and alkaline earth metal ions were also studied which showed that the presence of these ions have no effect on the sorption of Ni (II). The results showed that waste tea leaves have the potential to be used as a low cost sorbent for the removal of Ni (II) from aqueous solutions as alternative to conventional sorbents.
References
Ahluwalia, S.S., Goyal, D., 2005. Removal of heavy metals by waste tea leaves from aqueous solution. Engineering Life Science 5, 158162.
Ahluwalia, S.S., Goyal, D., 2007. Microbial and plant derived biomass for removal of heavy metals from waste water. Bioresource Technology 98, 2243-2257. Akhtar, N., Iqbal, J., Iqbal, M., 2004. Removal and recovery of nickel (II) from aqueous solution by loofa sponge-immobilized biomass of Chlorella sorokiniana: characterization studies. Journal of Hazardous Materials B 108, 85-94. Aksu, Z., 2002. Determination of equilibrium, kinetic and thermody-namic parameters of the batch biosorption of nickel ions on to Chlorella vulgaris. Process Biochemistry 38, 89-99. Aksu, Z., Akpinar, D., 2000. Modelling of simultaneous biosorption of phenol and nickel (II) onto dried aerobic activated sludge. Separation and Purification Technology 21, 87-99. Al-Asheh, S., Banat, F., Mobai, F., 1999. Sorption of copper and
nickel by spent animal bones. Chemosphere 39, 2087-2096. Amarasinghe, B.M.W.P.K., Willims, R.A., 2007. Tea waste as a low cost adsorbent for the removal of Cu and Pb from wastewater. Chemical Engineering Journal 132, 299-309. Chen, J.P., Yang, L., 2005. Chemical modification of Sargassum sp. For prevention of organic leaching and enhancement of uptake during metal biosorption. Industrial Engineering and Chemical Research 44, 9931-9942. Dahiya, S., Tripathi, R.M., Hegde, A.G., 2008. Biosorption of heavy metals and radionuclide from aqueous solutions by pre-treated Arca shell biomass. Journal of Hazardous Materials 150, 376-386. Ergtugay, N., Bayhan, Y.K., 2008. Biosorption of Cr from aqueous solutions by biomass of Agaricus bisporus. Journal of Hazardous Materials 154, 432-439. Gupta, V.K., Jain, C.K., Ali, I., Sharma, M., Saini, V.K., 2003. Removal of cadmium and nickel from wastewater using bagasse fly ash - a sugar industry waste. Journal of Colloid Interface Science 271, 21-328.
Hasar, H., 2003. Adsorption of nickel (II) from aqueous solution onto activated carbon prepared from almond husk. Journal of Hazardous Materials B 97, 49-57. Lothongkum, A., Khemglad, Y., Usomboon, N., Pancharoen, U., 2009. Selective recovery of nickel ions from wastewater of stainless steel industry via HFSLM. Journal of Alloys Compound 476, 940949.
Meena, A.K., Mishra, G.K., Rai, P.K., Rajagopal, C., Nagar, P.N., 2005. Removal of heavy metal ions from aqueous solutions using carbon aerogel as an adsorbent. Journal of Hazardous Materials 122, 161-170.
Modal, M.K., 2009. Removal of Pb (II) ions from aqueous solution using activated tea waste; adsorption on a fixed-bed column. Journal of Environmental Management 90, 3266-3271. Mokgalaka, N.S., McCrindle, R.I., Botha, B.M., 2004. Multi element analysis of tea leaves by inductively coupled plasma optical emission spectrometry using slurry nebulization. Journal of Analytical Atomic Spectroscopy 19, 1375-1378.
Padmavathy, V., 2008. Biosorption of nickel ions by baker's yeast: kinetic, thermodynamic and desorption studies. Bioresource Technology 99, 3100-3109.
Patmavathy, V., Vasudevan, P., Dhingra, S.C., 2003. Biosorption of nickel (II) ions on Baker's yeast. Process Biochemistry 38, 13891395.
Remoudaki, E., Hatzikioseyian, A., Tsezos, K., Tsezos, M., 2003. The mechanism of metals precipitation by biologically generated alkalinity in biofilm reactors. Water Research 37, 3843-3854.
Rio, M., Parwate, A.V., Bhole, A.G., 2002. Removal of Cr6+ and Ni2+ from aqueous solution using bagasse and fly ash. Waste Management 22, 821-830.
Shah, J., Jan, M.R., Haq, A., Sadia, M., 2012. Removal of Ni (II) from aqueous solutions using modified carbon derived from Mulberry wood sawdust. Journal of the Chemical Society of Pakistan 34, 5866.
Sharma, Y.C., Prasad, G., Rupainwar, D.C., 1991. Removal of Ni (II) from aqueous solutions by sorption. International Journal of Environmental Studies 37, 183-191.
Sud, D., Mahajan, G., Kaur, M.P., 2008. Agricultural waste material as potential adsorbent for sequestering heavy metal ions from aqueous solutions - a review. Bioresource Technology 99, 60176027.
Vijayaraghavan, K., Jegan, J., Palanivelu, K., Velan, M., 2004. Removal of nickel (II) ions from aqueous solution using crab shell particles in a packed bed up-flow column. Journal of Hazardous Materials B 113, 223-230.
Vijayaraghavan, K., Jegan, J., Palanivelu, K., Velan, M., 2005. Biosorption of cobalt (II) and nickel (II) by seaweeds: batch and column studies. Separation and Purification Technology 44, 53-59.
Villaescusa, I., Fiol, N., Martinez, M., Miralles, N., Poch, J., Serarols, J., 2004. Removal of copper and nickel ions from aqueous solutions by grape stalks wastes. Water Research 38, 992-1002.
Xuan, Z., Tang, Y., Li, X., Liu, Y., Luo, F., 2006. Study on equilibrium, kinetics and isotherm of biosorption of lead ions on to pretreated chemically modified orange peel. Biochemical Engineering Journal 31, 160-164.
Yan, G., Viraraghavan, T., 2001. Heavy metal removal in a biosorption column by immobilized M. Rouxii biomass. Bioresource Technology 78, 243-249.
Zafar, M.N., Nadeem, R., Hanif, M.A., 2007. Biosorptions of nickel from protonated rice bran. Journal of Hazardous Materials 143, 478-485.
Zhao, G., Li, M., Hu, Z., Hu, H., 2005. Dissociation and removal of complex chromium ions containing in dye wastewaters. Separation and Purification Technology 43, 227-232.
