Succinate-bonded cellulose: A regenerable and powerful sorbent for cadmium-removal from spiked high-hardness groundwater

Journal of Hazardous Materials 169 (2009) 831–837

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Succinate-bonded cellulose: A regenerable and powerful sorbent for cadmium-removal from spiked high-hardness groundwater Belkacem Belhalfaoui a , Abdellah Aziz a , El Hadj Elandaloussi a , Mohand Said Ouali a,∗ , Louis Charles De Ménorval b a b

Laboratoire de Valorisation des Matériaux, Université Abdelhamid Ibn Badis, B.P. 227, 27000 Mostaganem, Algeria ICG-AIME-UMR 5253, Université Montpellier 2, Place Eugène Bataillon CC 1502, 34095 Montpellier Cedex 05, France

a r t i c l e

i n f o

Article history: Received 23 December 2008 Received in revised form 10 March 2009 Accepted 6 April 2009 Available online 14 April 2009 This paper is dedicated to Professor Robert Louis Carrié on the occasion of his 80th birthday. Keywords: Cellulose Sorption Cadmium Isotherms Regeneration

a b s t r a c t The primary objective of this work was to evaluate a chemically modified cellulose for the sorption efficiency and selectivity to remove cadmium from spiked high-hardness groundwater. Heterogeneous esterification of cellulose with succinic anhydride in toluene under basic conditions has proceeded very efficiently to yield the succinylated cellulose (SC) with fairly high DS value, as confirmed by FTIR and solid-state MAS 13 C NMR spectroscopies. Deprotonation of the free carboxylic acid group was achieved by alkaline treatment of SC with saturated NaHCO3 aqueous solution. Batch experiments were carried out on the resulting sodic material (NaSC) to examine its cadmium-removing capability in both distilled water (DW) and spiked groundwater (GW). The results obtained from the sorption characteristics (kinetics, isotherms and pH effect) have revealed that NaSC material is particularly effective in removing cadmium from both DW and GW solutions, with a maximum uptake of 185.2 and 178.6 mg g−1 , respectively. These comparable sorption capacities strongly suggest that NaSC sorbent is highly selective to heavy metal over alkaline earth cations (Ca2+ and Mg2+ ) and therefore less susceptible to interference from background ions, naturally present in groundwater. On the other hand, cadmium sorption is shown to decrease with a decrease in pH which is indubitably inherent to the competing proton during the ion-exchange process. Furthermore, the material has proven to be efficiently regenerable by using a NaCl brine solution. Thus, the use of the sorbent sequentially to the first regeneration led to nearly no attenuation in the material’s capacity for cadmium-removal. Finally, the sorption effectiveness of NaSC is compared to those of other low-cost sorbents so far reported in the literature. © 2009 Elsevier B.V. All rights reserved.

1. Introduction Cadmium is a highly toxic environmental pollutant which is particularly present in household wastes containing used Ni–Cd batteries and plastics (pigments). The ground and water could be contaminated far from the emission source as cadmium particles can be transported in air to long distances. Nonetheless, water pollution with heavy metals, including cadmium occurs essentially as a result of industrial activities. Conventional techniques for heavy metals removal from water involve adsorption processes on activated carbon [1–2], ionexchange mechanism [3–5], complexation by natural and synthetic reagents [6–8] and so on. Although activated carbon remains the most widely used adsorbent for the removal of heavy metals from water, the process faces however some limitations, in particular the high operational cost.

∗ Corresponding author. E-mail address: [email protected] (M.S. Ouali). 0304-3894/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.jhazmat.2009.04.021

Extensive investigations were therefore conducted for the development of alternate solid adsorbents deriving from less expensive natural materials. Owing to their abundance and renewable nature, research on agricultural byproducts has dramatically expanded during the past decade. Thus, effective approaches to the removal of heavy metal from contaminated water have been well-founded by means of low-cost sorbents, whether in their raw form, carbonized form or chemically modified. With respect to the chemical modification of lignocellulosics, it is well-known that most agricultural byproducts contain large proportions of lignin in their composition. Nevertheless, lignin is a polyfunctional polymer with a three-dimensional structure which consequently renders agricultural waste less inclined towards functionalization to some extent. Cellulose on the other hand, is a linear monofunctional polymer bearing abundant reactive hydroxyl groups that make it an attractive support for straightforward functionalization. Recently, the attention of many research groups has been attracted to the synthesis and characterization of cellulose derivatives. Thus, functional groups such as xanthogenate [9], calix [4] arene [10], polyglycidyl [11], polyethyleneimine [12], succinate

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Fig. 1. Synthesis of succinylated cellulose (SC) and its sodium salt (NaSC).

[13–16] and even functional polymers [17] were successfully incorporated into the cellulose matrix by performing adequate functionalization. Some of these cellulose-based materials were applied to heavy metals removal from aqueous solutions. As to the synthesis, except that of succinate derivative, all the other reported materials were however attained through either timeconsuming or high-cost procedures. Indeed, Gurgel et al. [13] have recently reported a simplest way to prepare succinylated cellulose (SC), although the cellulose used for the esterification was of chromatographic grade, which is relatively expensive. Besides, the application of the sorbent material to heavy metal removal was performed only on distilled water (DW) solutions. Crucial to the design of low-cost sorbents is of course the price of starting materials, which is a factor that needs to be taken into consideration. Similarly, the adsorption capacity is a particularly important consideration when evaluating candidates for use in low-cost sorbents. Ultimately however, the regeneration capacity of these materials often poses a serious drawback, which considerably limits their practical application. Hence, when any given sorbent is efficiently regenerated without any essential loss in sorption capacity in the repeated sorption–desorption cycles, the material could then offer a cost-effective solution to the removal process, yet a better approach to waste disposal problem. The purpose of this work was set to (i) synthesize an appropriate low-cost sorbent material by a cost-effective chemical modification, (ii) evaluate and compare its cadmium-removal capacity from distilled water and high-hardness groundwater, (iii) check the performance of the sorbent material after regeneration to ascertain its stability and reusability. To meet these objectives, we synthesized our sorbent material by esterifying bulk cellulose, a filter aid grade, with succinic anhydride in heterogeneous conditions. The functionalized cellulose (SC) was converted into its sodic form (NaSC) and the latter material was then used to sorb cadmium from both distilled water and spiked high-hardness groundwater (GW) solutions. 2. Experimental 2.1. Materials and reagents The cellulose used in the present study was provided by Sorasucre, a local sugar factory (Mostaganem). The material is used

in sugar refining process as filter aid. Groundwater was collected from a well located in the city outskirts and it was selected on account of its high hardness and high ionic strength. Chemical characteristics of the groundwater (pH 7.2, Cl− = 323 mg L−1 , total hardness = 504 mg CaCO3 L−1 ) were determined using known analytical techniques. All reagents used were analytical grade. 2.2. Synthesis of SC and NaSC SC containing free carboxylic groups was prepared by reaction of cellulose with succinic anhydride in toluene (Fig. 1). To a suspension of cellulose (16.2 g, 100 mmol of AGU or 300 mmol of hydroxyl groups in cellulose) and pyridine (50 mL, excess) in toluene (350 mL) heated at 60 ◦ C succinic anhydride (60 g, 600 mmol) was added at once. The resulting mixture was left to stir overnight at 90 ◦ C. After cooling to 60 ◦ C, the solid was filtered off, washed thoroughly with acetone to remove the unreacted succinic anhydride and then dried to yield SC (26.95 g) as an off-white solid which was sieved to a particle size of 0.5 mm. NaSC was prepared by alkaline treatment of SC with saturated sodium bicarbonate solution. The suspension was stirred at room temperature for 2 h and then filtered. The solid was repeatedly washed with distilled water until neutral pH, then with acetone and finally dried and passed through 0.5 mm sieve. 2.3. Characterization of materials 2.3.1. Determination of the zero point charge pH (pHZPC ) The pH corresponding to the point of zero charge, ZPC for the succinylated cellulose was determined by the pH drift method reported by Khan and Wahab [18]. The pH drift was measured on 0.01 M NaCl solutions (20 mL) placed in jacketed titration vessels and thermostated at 298 K. Nitrogen was bubbled through the solutions to stabilize the pH. The pH was then adjusted to successive initial values between 2 and 10 by adding HCl or NaOH and SC (0.1 g) was then added to each solution. The final pH was reached after 48 h. The material’s surface is neutral when pH = pHpzc .. The surface is negatively charged at pH values greater than pHZPC , and positively charged at pH values lower than pHpzc [19].

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2.3.2. Degree of substitution The degree of substitution of SC was determined by backtitration method [13–14]. 0.1 g of the sample was suspended in 100 ml of an aqueous 0.02 M NaHCO3 solution and the resulting mixture was stirred for 2 h at room temperature. After filtration, the excess of NaHCO3 was back-titrated with 0.02 M HCl using methyl orange as the indicator. The titration was repeated three times and the average value of the HCl volume was used for the calculations. The DS was calculated by using the following equation: DS =

162 × nCOOH m − 100 × nCOOH

(1)

where 162 g mol−1 is the molar mass of an AGU, 100 g mol−1 is the net increase in the mass of an AGU for each substituted succinyl group, m is the weight of the sample analyzed, and nCOOH is the amount of COOH calculated from the obtained value of the equivalent volume of known HCl molarity according to the following equation: nCOOH = VNaHCO3 × CNaHCO3 − VHCl × CHCl

(2)

Fig. 2. FTIR spectra of unmodified cellulose (dashed) and succinylated cellulose (solid).

2.3.3. FTIR characterization The IR spectra of the samples (in KBr) were recorded using a PerkinElmer FTIR spectrometer operating in the range 400–4000 cm−1 .

The recovered material was washed with distilled water, air dried and suspended in 100 mL of saturated sodium chloride solution. The obtained suspension was left to rest overnight, centrifuged and then washed with distilled water until negative silver nitrate test. The regenerated material was suspended in cadmium aqueous solution under the same conditions as above and the cadmium concentration was measured.

2.3.4. MAS NMR characterization Cross polarization magic angle spinning (CPMAS) 13 C NMR spectra of cellulose and succinylated cellulose were recorded on a Bruker 300 (Digital NMR Avance) spectrometer.

3. Results and discussion

2.4. Study of cadmium-removal on NaSC 2.4.1. Kinetic study The kinetic study was conducted on suspensions of NaSC (50 mg) in 100 mL of cadmium nitrate in distilled water and groundwater solutions (50 mg L−1 ). The mixtures were stirred during different time intervals, ranging from 5 to 150 min and then centrifuged. The cadmium concentration in supernatants was determined by flame atomic absorption spectrophotometer (Pye Unicam SP9 model), equipped with air–acetylene flame. The wavelength used for monitoring Cd was 228.8 nm. The sorbed amounts of cadmium were determined from the difference between the initial and final concentrations. 2.4.2. Effect of pH on cadmium-removal The pH effect was studied on suspensions of NaSC (25 mg) in 50 mL of cadmium solutions (25 mg L−1 ). The pH was adjusted in the range 2–10. The resulting mixtures were stirred for 30 min and then centrifuged. The cadmium concentrations in the supernatants were determined by FAAS. 2.4.3. Sorption isotherms The sorption isotherms were established using NaSC suspensions in DW and GW cadmium solutions at pH 6.2. The solid/solution ratio was 0.25 g/L. The cadmium concentrations in the aliquots were ranging from 5 to 150 mg L−1 . The suspensions were stirred for 1 h and subsequently centrifuged. The cadmium equilibrium concentrations were determined by FAAS. 2.4.4. Regeneration tests The regeneration study of NaSC was performed in saturated sodium chloride solutions. NaSC was firstly subjected to cadmiumremoval in DW solutions (50 mg L−1 ) with a solid/solution ratio of 1 g/L. After 30 min of contact time, the suspension was centrifuged and the cadmium concentration was determined by FAAS.

3.1. Characterization of succinylated cellulose (SC) The grafting of succinic acid onto cellulose is evidenced by common features present in the FTIR spectra (Fig. 2) of SC and its precursor, the unmodified cellulose. As shown in Fig. 2, the spectrum of SC is featured by a strong overlapped absorption band at 1710 cm−1 due to the absorption of carbonyl bonds of both esters and carboxylic acid groups. The two absorption bands present in the IR spectrum of unmodified cellulose at 1153 and 1025 cm−1 appear significantly modified on formation of SC. The concomitant increase and decrease in the intensities of the absorption bands at 1153 and 1025 cm−1 , assigned for C–O antisymmetric stretching and C–O–C bond stretching, respectively, in the spectrum of SC gives an unequivocal evidence of efficient esterification. In addition, the band centred at 3287 cm−1 is characteristic of the OH stretching band of the terminal carboxylic acid group. As expected, the material is free of succinic anhydride as illustrated in the spectrum of SC by the absence of its characteristic band at 1787 cm−1 [20]. Similar values were reported by Gurgel et al. [13] and Liu et al. [15] for succinylated cellulose and succinylated sugarcane bagasse cellulose. The authentication of SC by MAS 13 C NMR spectroscopy (Fig. 3) confirms the occurrence of succinylation reaction as well. The spectrum of unmodified cellulose (Fig. 3a) shows signals attributable to six carbon atoms of the glucose unit whereas the spectrum of SC (Fig. 3b) shows two intense signals in addition to those of cellulose at ı: 175 and 29 ppm which are consistent with carbon atoms of carbonyl C O (ester and carboxylic acid) and CH2 (methylene), respectively, in succinate group. Moreover, the presence of carboxylic acid groups is equally suggested by the pHZPC value (4.4) obtained from Fig. 4, thus indicating the weak acid character of the material. Furthermore, the titration of carboxylic acid groups gave a CEC or a total concentration of carboxylic functions (CCOOH ) value of 5.60 meq. g−1 , which corresponds to a succinylation degree (DS) of 2.06. This DS value is in good agreement with the strong intensities of signals attributed to the succinate group observed in FTIR and MAS 13 C NMR spectra of

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Fig. 5. Plot of cadmium sorbed on NaSC as a function of contact time.

Fig. 3. MAS 13 C NMR spectra of unmodified cellulose (a), and succinylated cellulose (b).

SC and suggests that the esterification in heterogeneous conditions is a powerful tool for cellulose functionalization. 3.2. Kinetic study of cadmium-removal on NaSC 3.2.1. Effect of contact time The plots of sorbed cadmium from DW and GW on NaSC as a function of contact time (Fig. 5) show that the sorption process occurs rapidly for both solutions. While cadmium is entirely removed from DW in the first 5 min of contact time, the equilibrium is reached within 15 min with more than 90% of metal removed from GW solution. As shown in Fig. 5, cadmium-removal seems to occur in a single step process. This takes place so rapidly that the equilibrium plateau is almost established as soon as the sorbent is

wet. These observations suggest that the removal process follows an ion-exchange mechanism. Our assumptions can be argued by the availability of abundant reactive sodium succinate functionalities anchored onto cellulose, capable of making instantaneous metalinterchange with cadmium on the surface of the material. Another evidence that lends support to our hypothesis lies in the absence of a slope decrease between the fast initial step and the equilibrium plateau (Fig. 5, GW plot), a fact that exclude any intraparticle diffusion step. 3.2.2. Kinetic modeling Even though various kinetic models are available for describing the reaction order in sorption process, the first-order and pseudosecond-order models remain however the most appropriate, and are frequently used to determine the sorption rate law. The experimental data corresponding to the kinetic sorption were plotted according to the latter theoretical equations, and were found to fit the pseudo-second-order equation proposed by Ho and McKay [21]. The differential equation that describes the pseudo-second-order is the following: dqt = k(qe − qt )2 dt

where k is the rate constant (g mg−1 min−1 ), qe and qt (mg g−1 ) are the amounts of metal sorbed at equilibrium and at time t, respectively. Integration of Eq. (1) followed by its linearization give the expression: t 1 1 = + t qt qe kq2e

Fig. 4. pH drift plot of SC.

(3)

(4)

Thus, straight lines were obtained when plotting t/qt versus t (Fig. 6). The equilibrium sorption capacity (qe ), the rate constant (k), and the linear regression determination coefficient (R2 ) values were calculated from the linear plots. Perfect correlation is observed between experimental data and the pseudo-second-order kinetic model, with values of determination coefficients equal to unity. Moreover, the results obtained show that the equilibrium removal capacity is slightly higher in DW (49.6 mg g−1 ) than in GW (46.1 mg g−1 ) with differences between the experimental and calculated values of qe that were lower than 0.2%. Under equivalent conditions for the same metal, the sorption rate constant value is greater in DW (2.04 g mg−1 min−1 ) than in GW (0.78 g mg−1 min−1 ). This result provides additional confirmation to the findings of contact time effect investigation where the metal sorption process was ascertained to occur much faster in DW than in GW.

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Fig. 6. Pseudo-second-order plot for cadmium-removal from GW () and DW () by NaSC.

3.3. Effect of pH on cadmium-removal The plots of the percentage of cadmium removed by NaSC from DW and GW solutions as a function of initial pH ranging from 2 to 10 are shown in Fig. 7. It is noteworthy to point out that for both solutions, the pH modification exerts a dramatic effect on the sorption extent as cadmium-removal increases with increasing solution initial pH. At low pHs, the sorption percentages are negligible. From pH 4 to 10, these percentages increase sharply, reaching maximum values at pH 6 for DW and pH 8 for GW. These results could be explained by the changes occurring in the chemical structure of NaSC sorbent which behaves distinctly when subjected to different pHs media. In fact, at low pHs the proton is preponderant, still cadmium as free cation is also present in solution; the protonation of NaSC will exclusively take place, however. The action of the competing proton over NaSC leads to its precursor SC which con-

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Fig. 8. Langmuir sorption isotherms of cadmium-removal by NaSC from GW () and DW ().

tains carboxylic acid functionalities and for which the pHZPC was determined to be 4.4. This means that for pH < 4.4, the surface of the material is positively charged. Beyond that pH the surface is negatively charged so the material could act as metal chelating sorbent only, thereby explaining the lower sorption capacity found at pH < 6. It is worth mentioning that the preliminary experiments carried out on SC to sorb cadmium were not encouraging since the material exhibited only little removal capacity (14%). These results bring further support to the assumption we previously formulated (see Section 3.2.1) and suggest that the most appropriate mechanism involved in cadmium-removal is an ion-exchange process. We have already encountered similar observations in a previous work on cadmium-removal by a chemically modified olive stone [22]. The natural pH of GW is 7.2 and the maximum sorption percentages of Cd2+ on NaSC were attained at pH 6 for DW and pH 8 for GW. In this context, pH 6.2 was selected to determine the adsorption isotherms. At this pH, and in the metal concentration used, Cd(OH)2 precipitation is avoided. 3.4. Sorption isotherms The experimental data corresponding to the isotherms were plotted according to the Langmuir model which provides the best fit for the sorption of cadmium on NaSC than the Freundlich equation. The Langmuir isotherms model is described by the following equation: qe =

Qmax KL Ce 1 + KL Ce

(5)

where qe (mg g−1 ) is the amount of metal removed per gram of sorbent, Qmax (mg g−1 ) is the maximum sorption capacity per gram of sorbent, Ce (mg L−1 ) is the equilibrium concentration of metal in solution, and KL␺ (L␺ mg−1 ) is the Langmuir constant related to the energy of sorption. For the convenience of plotting and determining the Langmuir constants, Eq. (5) can be rearranged to linear form as below: Ce Ce 1 = + qe Qmax Qmax KL

Fig. 7. Cadmium uptake from GW (+) and DW () by NaSC as a function of initial pH.

(6)

As shown in Fig. 8, the Langmuir plots for cadmium sorption in DW and GW on NaSC are straight lines for both solutions and are quite parallel. Langmuir parameters were calculated from the linear plots. The quite high determination coefficient R2 obtained (0.999

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Table 1 Comparison of activated carbons and other low-cost sorbents for cadmium-removal. Sorbents (treatment) ◦

Bagasse pith (200 and 400 C under steam with SO2 and H2 S) Jackfruit peel (H2 SO4 at 160 ◦ C) Corn stalk (H2 SO4 + ZnCl2 at 200 ◦ C) Apricot stone (H2 SO4 at 200 ◦ C) Olive stone (raw) Olive stone (H2 SO4 , room temperature + refluxing in 0.1N NaOH for 1 h) Mercerized cellulose chemically modified with succinic anhydride Sugarcane bagasse chemically modified with succinic anhydride Filter aid cellulose chemically modified with succinic anhydride

Sorption capacity (mg g−1 )

Reference

149.9 52 36.4 33.57 9.72 128.2 250 196 178.6 (from ground water)

[23] [24] [25] [26] [27] [22] [13] [14] This work

for DW and 0.985 for GW) confirms that the Langmuir model fits adequately the experimental data. Similar to the results obtained from sorption kinetics and as expected, the sorption of Cd2+ is greatly favored in groundwater. Consequently, NaSC maximum sorption capacities from DW (185.2 mg g−1 ) and GW (178.6 mg g−1 ) are nearly equivalent (∼3.5% less uptake in GW). The high performance of the sorbent in removing cadmium from both DW and GW strongly implies that NaSC is highly selective to heavy metal cations over alkaline earth cations (Ca2+ and Mg2+ ) and therefore less susceptible to interference from background ions, naturally present in groundwater. These results lead us to assume that cadmium would not only be capable to out-compete alkaline earth cations in the sorption process, but it could also displace them from sorption sites on the surface of succinate linkers. NaSC showed better sorption capacities for cadmium compared to those of other low-cost sorbents so far reported in the literature (Table 1), with the exception of the remarkably high sorption capacities reported by Gurgel et al. [13]. 3.5. Ion-exchange mechanism The existence of ion-exchange mechanism during cadmium sorption by NaSC is corroborated by major facts; at first, the preliminary tests have revealed that NaSC was incapable to remove anionic species from aqueous solutions, a fact that exclude any adsorption mechanism involvement. Then, under similar sorption conditions (pH 6.2), the precursor material SC showed low efficiency in removing cadmium (14%), this process is very likely driven by complexation mechanism, knowing that at this specific pH the surface of SC is negatively charged. The sorption process is very fast with an equilibrium reached in the first 5–15 min of contact time. Besides, no intraparticle diffusion was observed which suggests that the surface functional linkers (succinate groups) are accessible in first place for the metal sorption, thereby preventing the metal from diffusing throughout the cellulose matrix. The abundance of functional linkers (DS > 2) grafted onto cellulose is prominent since the alkaline treatment performed for the preparation of NaSC is straightforward and quantitative, therefore SC is totally converted into its sodic counterpart NaSC. Finally, the sorbed amounts of cadmium (1.65 and 1.59 mmol from DW and GW, respectively) onto NaSC were far below the succinate groups content (5.60 mmol), which denotes that cadmium occupied only 57–59% of the available sites for sorption. This loading defect could be attributed to the steric hindrance caused by the linker and accentuated by the free rotation of ethylene carbons in succinate groups, which eventually results in lowering the sorption capacity. 3.6. Regenerability The succinylated cellulose can be readily regenerated with saturated sodium chloride solution. In fact, regenerating the material in such mild conditions can offer a real possibility of repeated use that

Fig. 9. Percentages of cadmium-removal by NaSC after a first use and after regeneration.

neither an acid nor a base can do, since cellulose is sensitive to the former and the succinate linker to the latter. Moreover, NaCl brine solution has proven to be powerful in desorbing cadmium totally from succinylated cellulose. As shown in Fig. 9, the first repeated use resulted in only 1.8% decrease in the material’s capacity for cadmium sorption. This minor change in the performance of the sorbent indicates that its reusability is quite feasible. 4. Conclusion We have shown that by a cost-effective functionalization of low-price cellulose we synthesized a cellulose-based material bearing covalently attached succinate groups, that has extremely high removal capacities for cadmium in contaminated groundwater. Based on experimental data drawn from kinetics, pH effect, pHZPC value, sorption capacity and carboxylate groups’ content, we demonstrated that functional linkers play a major role in cadmium sorption. The removal process is governed by ion-exchange mechanism rather than adsorption–complexation seeing that sorption is merely relied on succinate content. Furthermore, the sorbent was found to be highly selective to the heavy metal over other cations, hence the sorption capacity was not affected by the ions naturally present in the studied groundwater. The succinylated material can be fully regenerated using brine solution and subsequent use of the regenerated material end up in practically no change in sorption effectiveness. The high recovery of the prepared sorbent material from the regeneration process allows us to consider this low-cost material as promising candidate for heavy metals removal with a possibility of repeated use.

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To summarize, we demonstrated the power of this concept with functionalized cellulose, but it should be relevant to agricultural byproducts as well. However, the latter materials possess multiple reactive functional groups that complicate the chemical reaction course, and thereby limiting substantially a proper functionalization. Therefore, further refinement of the linkers may overcome these limitations and may allow even further enhancement in sorption characteristics of low-cost sorbents. Work in this direction is now in progress in our laboratory, the results of which will be published in a subsequent paper. References [1] A. Macias-Garcia, V. Gomez-Serrano, M.F. Alexandre-Franco, C. ValenzuelaCalahorro, Adsorption of cadmium by sulphur dioxide treated activated carbon, J. Hazard. Mater. 103 (2003) 141–152. [2] P. Galiatsatou, M. Metaxas, V. Kasselouri-Rigopoulou, Adsorption of zinc by activated carbons prepared from solvent extracted olive pulp, J. Hazard. Mater. B91 (2002) 187–203. [3] J. Peric, M. Trgo, N. Vukojevic Medvidovic, Removal of zinc, copper and lead by natural zeolite: a comparison of adsorption isotherms, Water Res. 38 (2004) 1893–1899. [4] S. Rengaraj, K.H. Yeon, S.Y. Kang, J.U. Lee, K.W. Kim, S.H. Moon, Studies on adsorptive removal of Co(II), Cr(III) and Ni(II) by IRN77 cation-exchange resin, J. Hazard. Mater. 92 (2002) 185–198. [5] X. Zhao, W.H. Holl, G. Yun, Elimination of cadmium trace contaminations from drinking water, Water Res. 36 (2002) 851–858. [6] T. Saitoh, F. Satoh, M. Hiraide, Concentration of heavy metal ions in water using thermoresponsive chelating polymer, Talanta 61 (2003) 811–817. [7] A.W.P. Vermeer, J.K. McCulloch, W.H. Van Riemsdijk, L.K. Koopal, Metal ion adsorption to complexes of humic acid and metal oxides: deviations from the additivity rule, Environ. Sci. Technol. 33 (1999) 3892–3897. [8] J. Brown, L. Mercier, T.J. Pinnavaia, Selective adsorption of Hg2+ by thiolfunctionalized nanoporous silica, Chem. Commun. (1999) 69–70. [9] L. Tan, D. Zhu, W. Zhou, W. Mi, L. Ma, W. He, Preferring cellulose of Eichhornia crassipes to prepare xanthogenate to other plant materials and its adsorption properties on copper, Bioresour. Technol. 99 (2008) 4460–4466. [10] M. Tabakci, S. Erdemir, M. Yilmaz, Preparation, characterization of cellulosegrafted with calix[4]arene polymers for the adsorption of heavy metals and dichromate anions, J. Hazard. Mater. 148 (2007) 428–435. [11] R. Navarro, K. Tatsumi, K. Sumi, M. Matsumura, Role of anions on heavy metal sorption of a cellulose modified with poly(glycidyl methacrylate) and polyethyleneimine, Water Res. 35 (2001) 2724–2730.

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[12] R. Navarro, K. Sumi, N. Fujii, M. Matsumura, Mercury removal from wastewaters using porous cellulose carrier modified with polyethyleneimine, Water Res. 30 (1996) 2488–2494. [13] L.V.A. Gurgel, O. Karnitz Jr., R.P.F. Gil, L.F. Gil, Adsorption of Cu(II), Cd(II), and Pb(II) from aqueous single metal solutions by cellulose and mercerized cellulose chemically modified with succinic anhydride, Bioresour. Technol. 99 (2008) 3077–3083. [14] O. Karnitz Junior, L.V.A. Gurgel, J.C. Perin de Melo, V.R. Botaro, T.M.S. Melo, R.P.F. Gil, L.F. Gil, Adsorption of heavy metal ion from aqueous solution single metal solution by chemically modified sugarcane bagasse, Bioresour. Technol. 98 (2007) 1291–1297. [15] C.F. Liu, R.C. Sun, A.P. Zhang, J.L. Ren, X.A. Wang, M.H. Qin, Z.N. Chaod, W. Luod, Homogeneous modification of sugarcane bagasse cellulose with succinic anhydride using a ionic liquid as reaction medium, Carbohydr. Res. 342 (2007) 919–926. [16] C.F. Liu, R.C. Sun, A.P. Zhang, J.L. Ren, Z.C. Geng, Structural and thermal characterization of sugarcane bagasse cellulose succinates prepared in ionic liquid, Polym. Degrad. Stab. 91 (2006) 3040–3047. [17] D.W. O’Connell, C. Birkinshaw, T.F. O’Dwyer, Heavy metal adsorbents prepared from the modification of cellulose: a review, Bioresour. Technol. 99 (2008) 6709–6724. [18] M.N. Khan, M.F. Wahab, Characterization of chemically modified corncobs and its application in the removal of metal ions from aqueous solution, J. Hazard. Mater. 141 (2007) 237–244. [19] S. Nouri, F. Haghseresht, M. Lu, Adsorption of aromatic compounds by activated carbon: effects of functional groups and molecular size, Adsorpt. Sci. Technol. 20 (2002) 1–15. [20] Spectral database for organic compounds, SDBS, http://riodb01.ibase.aist.go. jp/sdbs/cgi-bin/cre index.cgi?lang=eng. [21] Y.S. Ho, G. McKay, Pseudo-second order model for sorption processes, Process Biochem. 34 (1999) 451–465. [22] A. Aziz, M.S. Ouali, E.H. Elandaloussi, L.C. De Ménorval, M. Lindheimer, Chemically modified olive stone: a low-cost sorbent for heavy metals and basic dyes removal from aqueous solutions, J. Hazard. Mater. 163 (2009) 441–447. [23] K. Anoop Krishnan, T.S. Anirudhan, Removal of cadmium (II) from aqueous solutions by steam-activated sulphurized carbon prepared from sugar-cane bagasse pith: kinetics and equilibrium studies, Water SA 29 (2003) 147–156. [24] B.S. Inbaraj, N. Sulochana, Carbonised jackfruit peel as and adsorbent for the removal of Cd (II) from aqueous solution, Bioresour. Technol. 94 (2004) 49–52. [25] A.M. Youssef, Th. El-Nabarawi, S.E. Samra, Sorption properties of chemicallyactivated carbons. 1. Sorption of cadmium (II) ions, Colloid Surf. A 235 (2004) 153–163. [26] M. Kobya, M. Demirbas, E. Senturk, M. Ince, Adsorption of heavy metal ions from aqueous solutions by activated carbon prepared from apricot stone, Bioresour. Technol. 96 (2005) 1518–1521. [27] M. Calero de Hoces, F.H. Bermudez de Castro, G. Blazquez Garcia, G. Tenorio Rivas, Equilibrium modeling of removal of cadmium ions by olive stones, Environ. Prog. 25 (2006) 261–266.