Selective Removal of Cu(II) Ions by Using Cation-exchange Resin

Preliminary kinetic experiments indicated that 10 h was sufficient to reach adsorption .... As for D001-PEI, increasing Mg2+, Ca2+, and Sr2+ from 0 to...
0 downloads 0 Views 4MB Size
Download PDF
Environ. Sci. Technol. 2010, 44, 3508–3513

Selective Removal of Cu(II) Ions by Using Cation-exchange Resin-Supported Polyethyleneimine (PEI) Nanoclusters Y I L I A N G C H E N , †,§ B I N G C A I P A N , * ,†,‡ H A I Y A N L I , § W E I M I N G Z H A N G , †,‡ L U L V , * ,†,‡ A N D J U N W U † State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing 210093, P.R. China, National Engineering Research Center for Organic Pollution Control and Resources Reuse, Nanjing 210046, P.R. China, and College of Chemical Engineering, Nanjing Forestry University, Nanjing 210037, P.R. China

Received January 30, 2010. Revised manuscript received March 15, 2010. Accepted March 29, 2010.

A novel hybrid adsorbent D001-PEI was fabricated for selective Cu(II) removal by immobilizing soluble polyethyleneimine (PEI) nanoclusters within a macroporous cation exchange resin D001. Negligible release of PEI nanoclusters unexpectedly observed during operation may result from the porous crosslinking nature of D-001 as well as the electrostatic attraction between PEI and D001. Increasing solution pH from 1 to 6 results in more favorable Cu(II) retention by D001-PEI, and Cu(II) adsorption onto D001-PEI follows the Langmuir model and the pseudosecond-order kinetic model well. Compared to the host cation exchanger D001, D001-PEI displays more preferable adsorption toward Cu(II) in the presence of competing Mg2+, Ca2+, Sr2+ at greater levels in solution. Fixed-bed adsorption runs showed that Cu(II) sequestration on D001-PEI could result in its conspicuous decrease from 5 mg/L to below 0.01 mg/L. Also, the spent hybrid adsorbent can be readily regenerated by 6-8 BV HCl (0.2 mol/L)-NaCl (0.5 mol/L) binary solution for repeated use with negligible capacity loss. The results reported herein validate that D001-PEI is a promising adsorbent for enhanced removal of Cu(II) and other heavy metals from waste effluents.

Introduction Increasingly strict regulations on heavy metals discharge has been implemented with the increased awareness of their toxicity and other adverse effects on human beings and environment (1). Till now various technologies have been developed to sequestrate heavy metals from waters (2), such as chemical precipitation (3), ion exchange (4, 5), adsorption (6, 7), solvent extraction (8), membrane separation (9), and electrochemical methods (10). Among them ion exchange and adsorption are the attractive options due to their simple operation, low investment, and potential recovery and reuse * Address correspondence to either author. Phone:+86-25-83685736. Fax: +86-25-8370-7304. E-mail: [email protected] (B.P.); [email protected] (L.L.). † State Key Laboratory of Pollution Control and Resource Reuse. § College of Chemical Engineering. ‡ National Engineering Research Center for Organic Pollution Control and Resources Reuse. 3508

9

ENVIRONMENTAL SCIENCE & TECHNOLOGY / VOL. 44, NO. 9, 2010

of metals. However, the widely used adsorbents or ion exchangers, for example, activated carbon and polystyrenesulfonate cation exchangers, usually could not provide specific interactions with the targeted toxic metals (4, 6). Given that other environmental friendly ions such as Na+, Ca2+, and Mg2+ are present with targeted toxic metals in contaminated waters and greatly compete for active sites of the adsorbents, deep removal of toxic metals from contaminated waters is still a challenging task. To overcome the technical bottleneck, one of the effective approaches is to develop adsorbents of high selectivity toward toxic metals by incorporating the principle of metal complexation into traditional ion exchange technology, and various functional groups, including carboxylate, hydroxyl, phosphate, amide, and amino groups, have been chemically grafted to host adsorbents to improve their selectivity toward toxic metals (11–13). Polyethylenimine (PEI), which is composed of a large number of primary and secondary amine groups (14), exhibits outstanding adsorption ability for heavy metals (15, 16). However, due to the water-soluble nature of PEI, it has to be chemically grafted to the host adsorbents like insoluble polymers (15–18), biomass (19, 20), silica (21–23), and cellulose (24) to prevent its leaching during operation. As a result, the preparation steps of PEI-modified adsorbents are generally long, and other chemicals like crosslinking agents are required for PEI grafting (15–24). The main objectives of the current study were to propose a simple technique to fabricate a PEI-loaded hybrid adsorbent (denoted D001-PEI) for selective sequestration and deep removal of heavy metals from contaminated waters. A macroporous cation exchange resin D001 was employed as the host material mainly because of its satisfactory mechanical strength as well as the potential Donnan membrane effect (25), that is, the immobilized sulfonic groups bound to the polymeric matrix would result in preconcentration and enhanced permeation of target metal ions prior to its sequestration (26–28). Copper ion was selected as a representative pollutant of heavy metals because it is usually present in industrial effluents or even natural water bodies (29), and excessive uptake of copper can cause serious health problems such as damage to heart, kidney, liver, pancreas and brain, intestinal distress, and anemia (30).

Experimental Section Materials. D001, a strongly acidic cation exchange resin containing sulfonic groups covalently fixed to a macroporous polystyrene skeleton, was kindly provided by Suqing Water Treatment Engineering Group Co., Ltd., China. It was obtained as spherical beads with sizes ranging from 0.3 to 0.85 mm, and its basic structure information is available in Table 1. Polyethyleneimine (PEI) has a linear or branched structure, and the branched PEI generally contains primary, secondary, and ternary amine groups in a ratio of approximately 1:2:1 (14). Given that the stability constant of PEI-Cu(II) using the branched form was about 10 times higher than that of the linear form (31), we used the branched PEI (Mw ) 1.7 × 104-2 × 104, 35% aqueous solution available) in the current study, which was purchased from Qianglong Chemical Company (Wuhan, China). Other chemicals like Cu(NO3)2 · 3H2O, NaNO3, Mg(NO3)2 · 6H2O, Ca(NO3)2 · 4H2O, Sr(NO3)2 are of analytical grade, and were purchased from Chinese companies. Stock metal solutions were prepared by dissolving proper amount of their corresponding nitrate salts into double-distilled (D.I.) water. 10.1021/es100341x

 2010 American Chemical Society

Published on Web 04/07/2010

TABLE 1. Salient Properties of a Macroporous Strong-Acid Cation Exchanger D001 and its PEI-Loaded Derivative D001-PEIa

a

designation

D001

D001-PEI

matrix structure functional group BET surface area (m2/g) pore volume (cm3/g) average pore diameter (nm) apparent density (g/mL) ion-exchange capacity (meq/g)b nitrogen content (%)

polystyrene sulfonic group 20.05((1.25) 0.058((0.005) 23.1((0.75) 0.71((0.05) 4.1((0.4) 0

polystyrene sulfonic and amine group 17.08((0.90) 0.040((0.003) 22.2((0.08) 0.76((0.06) 2.4((0.2) 5.13((0.57)

95% confidence intervals are in parentheses when available.

Preparation of D001-PEI. Schematic illustration of PEI loading onto D001 to fabricate D001-PEI is depicted in Supporting Information (SI) Figure S1, and detailed processes can be represented as the following steps: (1) The Na+-type D001 was first transformed to H+-type by immersing the resin beads into 1 mol/L HCl for 24 h. After being filtered, the resin beads were flushing by D.I. water until neutral pH (6.8-7.2), and then vacuum-dried at 80 °C until reaching constant weight. (2) Five gram of D001 beads was introduced into a conical flask, followed by introducing 100 mL PEI solution (3.5% in mass). Then the flask was shaken continuously at 25 °C for 2 days. (3) After being filtered, the resin beads were rinsed with D.I. water and then immersed into 200 mL 0.1 mol/L NaHCO3 solution at room temperature for 3 h. (4) The resulting beads were washed with D.I. water until the effluent pH approached to 7.1-7.3. After that they were vacuum-dried at 60 °C until reaching constant weight, and we obtained the PEI-immobilized hybrid adsorbent D001-PEI. Batch Adsorption Experiments. Batch adsorption experiments were carried out in 250 mL polyethylene bottles. To start the experiment, 0.100 g of a given adsorbent was introduced into a 100 mL solution containing known Cu(II) concentration. Other competing ions including Na+, Mg2+, Ca2+ and Sr2+ were added when necessary. A 1.0 M HNO3 solution was used to adjust the solution pH. Detailed experimental conditions are presented in the related figure captions for clear identification. The flasks were then transferred to an incubator shaker and vibrated at 160 rpm for 24 h to ensure the equilibrium adsorption. Preliminary kinetic experiments indicated that 10 h was sufficient to reach adsorption equilibrium onto D001 and D001-PEI. The amount of Cu(II) trapped by the adsorbent particles was calculated based on mass balance before and after the test. For the kinetics experiments, 1000 mL Cu(II) solution with initial concentration of 100 mg/L was transferred into a 2000 mL flask, into which 1.00 g of a given adsorbent particle was added subsequently. A 0.5 mL solution at various time intervals was sampled from the flasks to determine Cu(II) concentration in solution. Fixed-Bed Column Runs. Colum adsorption test were carried out with a polyethylene column (12.6 mm internal diameter and 200 mm length) equipped with a water bath to maintain constant temperature. A 5.0 mL of D001 or D001-PEI particles were packed within two separate columns. The feeding solution containing Cu(II) and other competing cations were prepared and pumped down-flow through the column. A Lange-580 pump (Baoding, China) was used to control the flow rate, and an automated fraction collector was chosen to collect the effluent samples. The hydrodynamic conditions, that is, the superficial liquid velocity (SLV) and empty bed contact time (EBCT), were identical for both column adsorption, and presented in the related figures. After adsorption, a binary solution of HCl (0.2 mol/L)-NaCl (0.5 mol/L) was used as the eluting agent for column desorption.

b

Determined by pH titration.

Characterization and Analyses. Copper content in solution were determined by atomic absorption spectrophotometer (AAS-990, China). The nitrogen content of D001PEI was determined by the elemental-analysis device (Elementar Vario MICRO, Germany). To observe the surface topography of the adsorbents before and after PEI loading, scanning electron micrographs of the gold-coated samples were taken with a scanning electron microscope (LEO 1530VP, Germany) as well as the transmission electron microscope (JEM-200CX, Japan). FT-IR spectra of the adsorbent beads were obtained by using a FT-IR spectrophotometer (NEXUS 870, U.S.). N2 adsorption-desorption test onto both adsorbents were carried out at 77K to determine their surface area and pore size distribution based on BJH model by using Micromeritics ASAP 2020 (U.S.).

Results and Discussion Characterization of D001-PEI. Figure 1 depicts the micrographs of the resulting hybrid adsorbent D001-PEI as compared to the host resin D001. After PEI loading, the as obtained D001-PEI still remains spherical with the particle size ranging from 0.3 to 0.9 mm. TEM of both adsorbents indicates that PEI was encapsulated within the polymeric phase as nanoclusters. Pore size distribution of both adsorbents was characterized, and the results in Figure 2 and Table 1 suggest that PEI loading onto D-001 would result in an understandable drop in pore volume. Elemental N content variation before and after PEI loading as well as FT-IR spectra (SI Figure S2) further demonstrate that PEI has been successfully immobilized within the inner pore phase of D-001. It is of noteworthy finding that negligible leaching of the encapsulated PEI was observed from the polymeric phase to solution during adsorption runs in the pHs from 0.5 to 10 (Figure 3). Such interesting properties are very attractive because it is crucial to repeated use of D001-PEI. The results of the repeated column adsorption runs were presented later. As for the mechanism responsible for PEI immobilization, we assume that it might result from the cross-linking nature of the host resins, which would prevent the loaded PEI nanoclusters from leaching into the surrounding solution (32, 33). In our earlier study we prepared several new polymerbased hybrid nanocomposites by encapsulating inorganic nanoparticles, namely hydrous ferric oxide (34), hydrous manganese oxide (28), Zr(HPO4)2 (27), and Zr(HPO3S) (26), within porous polymeric resins, and found that the loaded nanoparticles are steadily immobilized within the polymeric phase during continuous operation. In addition, the electrostatic interaction between the positively charged amino groups of PEI and sulfonate groups bound to D001 (as illustrated in SI Figure S1) may play a favorite role in PEI immobilization. However, further study is still required to clearly reveal the underlying mechanism. Effect of pH on Cu(II) Retention. Effect of solution pH on Cu(II) uptake by D001-PEI was examined, and the results are illustrated in Figure 4. It can be observed that Cu(II) VOL. 44, NO. 9, 2010 / ENVIRONMENTAL SCIENCE & TECHNOLOGY

9

3509

FIGURE 2. Pore size distribution of D001-PEI as compared to the host resin D001.

FIGURE 3. Effect of solution pH on PEI leaching from D001-PEI to solution (All the test adsorbent particles were shaken in the given solution for 3 days)

FIGURE 1. Microphotographs of D001 and D001-PEI. (a) SEM of D001-PEI; (b) TEM of D001-PEI; and (c) TEM of D001. adsorption increases as the solution pH increases from 1.0 to 5.8. Such pH-dependent copper sequestration could be reasonably explained from the structure of D001-PEI. D001PEI consists of two different functional groups responsible for copper adsorption, the sulfonate groups binding Cu(II) through a nonspecific electrostatic interaction (4, 5), and PEI of amino groups capturing Cu(II) through a specific metal coordination (15, 35). 2R-SO3Na + Cu 3510

9

2+

h (R-SO3)2Cu + 2Na

+

(1)

ENVIRONMENTAL SCIENCE & TECHNOLOGY / VOL. 44, NO. 9, 2010

FIGURE 4. Effect of solution pH on Cu(II) uptake by D001-PEI at 298 K (Initial Cu(II) 100 mg/L; S/L ratio 1.00 g/L). R1R2R3N:+Cu2+ f R1R2R3N - Cu2+

(2)

R1R2R3N:+H+ f R1R2R3N+H

(3)

Where R represents the polymeric matrix of D001, R1, R2, and R3 are the alkyl groups or hydrogen atom binding with nitrogen. Obviously, increasing acidity is unfavorable for

FIGURE 5. Effect of competing cations on Cu(II) retention by D001 and D001-PEI at 298 K (Initial Cu(II) 100 mg/L; S/L ratio 1.00 g/L). Cu(II) retention through ion exchange (eq 1). On the other side, lower solution pH could result in more positively charged amino groups (eq 3), which is also unfavorable for Cu(II) coordination by PEI (eq 2). Effect of Competing Cations on Cu(II) Retention. Alkali metals and alkaline earth metals are usually present in natural waters and industrial effluents. Though they are usually environmentally friendly, these metal ions, especially divalent metal ions, strongly compete with the toxic metals for active sites of a given adsorbent. Thus, it is crucial to determine adsorption preference of PEI-001 toward Cu(II) ions in the presence of other metal ions. Here we tested the effects of Na+, Mg2+, Ca2+ and Sr2+ on Cu2+ uptake by the hybrid adsorbent, and the host cation exchanger D001 was also involved for reference. The results are illustrated in Figure 5. It can be seen that Na+ does not pose any significant effect on Cu(II) retention in the test concentration ranges, whereas the divalent competing ions Mg2+, Ca2, and Sr2+ result in a dramatic decrease in Cu(II) adsorption onto both adsorbents. For D001, the capacity even approaches to near zero with the increasing concentrations of these divalent cations. As for D001-PEI, increasing Mg2+, Ca2+, and Sr2+ from 0 to 5 times of the Cu(II) concentration leads to an obvious drop of its adsorption from 65 to 20-30 mg/g, and further increase in all these competing ions even to 30 times of Cu(II) concentration does not result in further capacity decrease. The initial adsorption drop is possibly caused by the nonspecific adsorption interaction between D001 and

copper ions, and other coexisting ions greatly compete for sulfonic functional groups of D001. The following preferable adsorption of D001-PEI toward Cu(II) in the presence of other competing ions is believed to result from the PEI nanoclusters immobilized within the polymeric phase, which selectively sequestrate Cu(II) through complex formation (15). Note that in the absence of competing ions, D-001 exhibits a little higher Cu(II) capacity than D001-PEI. This is possibly because some of the sulfonic groups are occupied by PEI for D001-PEI (SI Figure S1). From Table 1, we know that the accessible sulfonic groups decrease from 4.1 to 2.4 mmol/g as a result of PEI loading. Isotherm and Kinetic Study. Cu(II) adsorption isotherms onto PEI-001 were determined in the absence or presence of calcium ions, and the experimental data were further correlated by the Langmuir model. 1 1 1 1 ) · + Qe BLQm Ce Qm

(4)

Where Qm is the maximum amount of copper adsorbed; Ce is the Cu(II) concentration in equilibrium; Qe is the amount of copper adsorbed in equilibrium; BL is the binding constant to be determined. Results in Figure 6 show that copper adsorption on D001-PEI can be represented by Langmuir model well regardless of the presence of Ca2+, and the maximum capacity of D001-PEI is 99 mg/g (in the absence of Ca2+) and 24.1 mg/g (in the presence 4000 mg/L Ca2+), respectively. VOL. 44, NO. 9, 2010 / ENVIRONMENTAL SCIENCE & TECHNOLOGY

9

3511

FIGURE 6. Cu(II) adsorption isotherms onto D001 and D001-PEI at pH 5.0 ( 0.1 (298 K).

FIGURE 7. Cu(II) adsorption kinetics onto D001 and D001-PEI at 298 K (Initial Cu(II) 100 mg/L; S/L ratio 1.00 g/L). Figure 7 presents the plots of copper uptake versus contact time for D001-PEI and D001. It can be seen that Cu(II) adsorption approaches to equilibrium within 2 h for D001PEI. Kinetic data for both adsorbents were then represented by the pseudosecond-order model (36): t 1 1 + ) t 2 Qt Q k2Qe e

(5)

where Qt are the amount adsorbed at time t, k2 is the pseudosecond-order adsorption kinetic constant. High correlation coefficients larger than 0.99 indicate that copper uptake onto both adsorbents can be approximated favorably by the pseudosecond-order model. As suggested by the K2 values presented in Figure 7 and the equilibrium time required for both adsorbents, PEI loadings do not pose any negative role in adsorption kinetics (21), though it occupied some of the pore space and rendered part of the sulfonic functional groups inaccessible for copper uptake. Fixed-Bed Column Adsorption and Regeneration. Figure 8 illustrates an effluent history of a separate fixed-bed column packed with D001-PEI for a feeding solution containing Cu(II) and competing cations (Na+, K+, Mg2+, Ca2+), and the cation exchanger D001 was also employed here for comparison. As seen in Figure 8, copper breaks through quickly onto D001, and the effective treatment volume is about 80 bed volumes (BV), whereas that for D001-PEI approaches to around 420 BV under otherwise identical conditions. Specifically, Cu(II) 3512

9

ENVIRONMENTAL SCIENCE & TECHNOLOGY / VOL. 44, NO. 9, 2010

FIGURE 8. Comparison of breakthrough curves of Cu(II) retention by D001-PEI and D001 during two separate fixed-bed column runs.

FIGURE 9. A column desorption history of copper preloaded onto D001-PEI (the column used for desorption test was identical to that of Figure 8). retention by D001-PEI would result in its conspicuous decrease even to below 0.01 mg/L, which further demonstrates the preferable removal of the heavy metal by the hybrid adsorbent. The exhausted D001-PEI was subjected to in situ regeneration by using the binary HCl (0.2 mol/L)-NaCl (0.5 mol/L) solution as the eluting agent. The results in Figure 9 indicate that the preloaded copper is completely extracted by 6-8 BV of the eluting agent, with the corresponding desorption efficiency higher than 99%. After regeneration, the D001-PEI column was rinsed with 3 BV of 0.10 mol/L NaHCO3 solution to transfer the positively charged amino groups into the free amine type, which is important for the reusability of D001PEI. Continuous 3-cycle adsorption-regeneration runs of the identical D001-PEI column were performed to validate its feasibility for application. The superposition of copper breakthrough curves achieved from the identical column in the 1st and 3rd cycle (Figure 8) indicated that D001-PEI can be entirely regenerated for repeated use without any significant capacity loss. Additionally, the N content of the D001PEI beads was determined to be 5.10% after three column cycles, further evidencing negligible loss of PEI during the adsorption-desorption cycles, that is, PEI can be steadily immobilized within the polymeric phase through a simple dipping technique instead of chemical grafting. Given that PEI can selectively remove many toxic metals including Cd(II),

Ni(II), Pb(II), Zn(II), Cr(IV) (15, 19, 20) through complex formation, the resulting D001-PEI is believed to act as a promising adsorbent for deep removal of other heavy metals from contaminated waters.

(16)

Acknowledgments

(17)

We greatly acknowledge the support from Program for New Century Excellent Talents in University of China (NCET07-0421), the Ministry of Education of China (200802840034), 863 Programm of China (2009AA06A418), State Key Scientific Program on Water Pollution Control and Treatment (2008ZX07010-005-03), and Jiangsu Department of Science and Technology (BE2009669).

Note Added after ASAP Publication An error was discovered in the version published ASAP April 7, 2010. A small text change was made to the Abstract and the corrected version was published ASAP on April 12, 2010.

(18)

(19) (20)

(21)

Supporting Information Available Figure S1 depicts the schematic illustration of PEI loading onto D001. Figure S2 illustrates FT-IR spectra of D-001, PEI, and their hybrid composite D001-PEI. Table S1 presents Kd values for Cu(II) adsorption onto D-001 and D001-PEI at different competing cation levels. This material is available free of charge via the Internet at http://pubs.acs.org.

(22) (23)

(24)

Literature Cited (1) Southichak, B.; Nakano, K.; Nomura, M.; Chiba, N.; Nishimura, O. Phragmites australis: A novel biosorbent for the removal of heavy metals from aqueous solution. Water Res. 2006, 40 (12), 2295–2302. (2) Kurniawan, T. A.; Chan, G. Y. S.; Lo, W. H.; Babel, S. Physicochemical treatment techniques for wastewater laden with heavy metals. Chem. Eng. J. 2006, 118 (1-2), 83–98. (3) Charerntanyarak, L. Heavy metals removal by chemical coagulation and precipitation. Water Sci. Technol. 1999, 39 (1011), 135–138. (4) Dabrowski, A.; Hubicki, Z.; Podkoscielny, P.; Robens, E. Selective removal of the heavy metal ions from waters and industrial wastewaters by ion-exchange method. Chemosphere 2004, 56 (2), 91–106. (5) Woodberry, P.; Stevens, G.; Snape, I. Removal of metal contaminants by ion-exchange resin columns, thala valley tip, casey station, antarctica. Solvent Extr. Ion Exch. 2006, 24 (4), 603–620. (6) Wilkins, E.; Yang, Q. Comparison of the heavy metal removal efficiency of biosorbents and granular activated carbons. J. Environ. Sci. Health, Part A: Toxic/Hazard. Subst. Environ. Eng. 1996, 31 (9), 2111–2118. (7) Demirbas, A. Heavy metal adsorption onto agro-based waste materials: aA review. J. Hazard. Mater. 2008, 157 (2-3), 220–229. (8) Lee, B. G.; Lee, H. J.; Shin, D. Y. Effect of solvent extraction on removal of heavy metal ions using lignocellulosic fiber. Mater. Sci. Forum 2005, 486-487, 574–577. (9) Pa´ez-Hernandez, M. E.; Aguilar-Arteaga, K.; Gala´n-Vidal, C. A.; Palomar-Pardave´, M.; Romero-Romo, M.; Ramı´rez-Silva, M. T. Mercury ions removal from aqueous solution using an activated composite membrane. Environ. Sci. Technol. 2005, 39 (19), 7667– 7670. (10) Meunier, N.; Drogui, P.; Gourvenec, C.; Mercier, G.; Hausler, R.; Blais, J. F. Removal of metals in leachate from sewage sludge using electrochemical technology. Environ. Technol. 2004, 25 (2), 235–245. (11) Crini, G. Recent developments in polysaccharide-based materials used as adsorbents in wastewater treatment. Prog. Polym. Sci. 2005, 30 (1), 38–70. (12) Bhattacharyya, K. G.; SenGupta, S. Adsorption of a few heavy metals on natural and modified kaolinite and montmorillonite: A review. Adv. Colloid Interface Sci. 2008, 140 (2), 114–131. (13) Miretzky, P.; Cirelli, A. F. Hg(II) removal from water by chitosan and chitosan derivatives: A review. J. Hazard. Mater. 2009, 167, 10–23. (14) Dick, C. R.; Ham, G. E. Characterization of polyethylenimine. J. Macromol. Sci., Part A: Pure Appl. Chem. 1970, 4 (6), 1301–1314. (15) Duru, P. E.; Bektas, S.; Genc, o¨.; Patir, S.; Denizli, A. Adsorption of heavy-metal ions on poly(ethyleneimine)-immobilized poly-

(25)

(26)

(27)

(28)

(29)

(30)

(31) (32)

(33) (34)

(35) (36)

(methyl methacrylate) microspheres. J. Appl. Polym. Sci. 2001, 81 (1), 197–205. Denizli, A.; Senel, S.; Alsancak, G.; Tu ¨ zmen, N.; Say, R. Mercury removal from synthetic solutions using poly(2-hydroxyethylmethacrylate) gel beads modified with poly(ethyleneimine). React. Funct. Polym. 2003, 55, 121–130. Navarro, R. R.; Tatsumi, K.; Sumi, K.; Matsumura, M. Role of anions on heavy metal sorption of a cellulose modified with poly(glycidylmethacrylate) and polyethyleneimine. Water Res. 2001, 35, 2724–2730. Say, R.; Tuncel, A.; Denizli, A. Adsorption of Ni2+ from aqueous solutions by novel polyethyleneimine-attached poly(p-chloromethylstyrene) beads. J. Appl. Polym. Sci. 2002, 83 (11), 2467– 2473. Deng, S. B.; Ting, Y. P. Characterization of PEI-modified biomass and biosorption of Cu(II), Pb(II) and Ni(II). Water Res. 2005, 39 (10), 2167–2177. Deng, S. B.; Ting, Y. P. Polyethylenimine-modified fungal biomass as a high-capacity biosorbent for Cr(VI) anions: sorption capacity and uptake mechanisms. Environ. Sci. Technol. 2005, 39 (21), 8490–8496. Chanda, M.; Rempel, G. L. Polyethyleneimine gel-coat on silicahigh uranium capacity and fast kinetics of gel-coated resin. React. Polym. 1995, 25 (1), 25–36. An, F. Q.; Gao, B. J. Chelating adsorption properties of PEI/SiO2 for plumbum ion. J. Hazard. Mater. 2007, 145, 495–500. Arkas, M.; Tsiourvas, D. Organic/inorganic hybrid nanospheres based on hyperbranched poly(ethyleneimine) encapsulated into silica for the sorption of toxic metal ions and polycyclic aromatic hydrocarbons from water. J. Hazard. Mater. 2009, 170, 35–42. Ghoul, M.; Bacquet, M.; Morcellet, M. Uptake of heavy metals from synthetic aqueous solutions using modified PEI-silica gels. Water Res. 2003, 37, 729–734. Cumbal, L.; SenGupta, A. K. Arsenic removal using polymersupported hydrated iron(III) oxide nanoparticles: Role of donnan membrane effect. Environ. Sci. Technol. 2005, 39 (17), 6508– 6515. Zhang, Q. R.; Pan, B. C.; Zhang, W. M.; Pan, B. J.; Jia, K.; Zhang, Q. X. Selective sorption of lead, cadmium, and zinc ions by a polymeric cation exchanger containing nano-Zr(HPO3S)2. Environ. Sci. Technol. 2008, 42 (11), 4140–4145. Zhang, Q. R.; Jiang, P. J.; Pan, B. C.; Zhang, W. M.; Lv, L. Impregnating zirconium phosphate onto porous polymers for lead removal from waters: Effect of nanosized particles and polymer chemistry. Ind. Eng. Chem. Res. 2009, 48 (9), 4495– 4499. Su, Q.; Pan, B. C.; Pan, B. J.; Zhang, Q. R.; Zhang, W. M.; Lv, L.; Wang, X. S.; Wu, J.; Zhang, Q. X. Fabrication of polymersupported nanosized hydrous manganese dioxide (HMO) for enhanced lead removal from waters. Sci. Total Environ. 2009, 407, 5471–5477. ¨ zer, A.; O ¨ zer, D.; O ¨ zer, A. The adsorption of copper(II) ions on O to dehydrated wheat bran (DWB): determination of the equilibrium and thermodynamic parameters. Process Biochem. 2004, 39 (12), 2183–2191. Abu Al-Rub, F. A.; EI-Naas, M. H.; Ashour, I.; Al-Marzouqi, M. Biosorption of copper on chlorella vulgaris from single, binary and ternary metal aqueous solutions. Process Biochem. 2006, 41 (2), 457–464. Kobayashi, S.; Hiroshi, K.; Tokunoh, M.; Saegusa, T. Chelating properties of linear and branched poly(ethylenimine). Macromolecules 1987, 20 (7), 1496–1500. Sidorov, S. N.; Volkov, I. V.; Davankov, V. A.; Tsyurupa, M. P.; Valetsky, P. M.; Bronstein, L. M.; Karlinsey, R.; Zwanziger, J. W.; Matveeva, V. G.; Sulman, E. M.; Lakina, N. V.; Wilder, E. A.; Spontak, R. J. Platinum-containing hyper-cross-linked polystyrene as a modifier-free selective catalyst for L-sorbose oxidation. J. Am. Chem. Soc. 2001, 123, 10502–10510. Bao, X. H. Catalytic characters of the nano-confined systems. Sci. China, Ser. B: Chem. 2009, 39 (10), 1125–1133. Pan, B. J.; Wu, J.; Pan, B. C.; Lv, L.; Zhang, W. M.; Xiao, L. L.; Wang, X. S.; Tao, X. C.; Zheng, S. R. Development of polymerbased nanosized hydrated ferric oxides (HFOs) for enhanced phosphate removal from waste effluents. Water Res. 2009, 43, 4421–4429. Chang, D. R.; Harden, S.; Loverro, N. Protonation of polyethylenimine. J. Macromol. Sci., Part A: Pure Appl. Chem. 1986, 23 (6), 801–804. Ho, Y. S. Review of second-order models for adsorption systems. J. Hazard. Mater. 2006, 136 (3), 681–689.

ES100341X VOL. 44, NO. 9, 2010 / ENVIRONMENTAL SCIENCE & TECHNOLOGY

9

3513