Synthesis of the cotton cellulose based Fe(III)-loaded adsorbent for arsenic(V) removal from drinking water

Synthesis of the cotton cellulose based Fe(III)-loaded adsorbent for arsenic(V) removal from drinking water

Desalination 249 (2009) 1006–1011 Contents lists available at ScienceDirect Desalination j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o ...

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Desalination 249 (2009) 1006–1011

Contents lists available at ScienceDirect

Desalination j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / d e s a l

Synthesis of the cotton cellulose based Fe(III)-loaded adsorbent for arsenic(V) removal from drinking water Yaping Zhao a,⁎, Minsheng Huang a, Wei Wu a, Wei Jin b,⁎ a b

Department of Environmental Science, East China Normal University, 200062, Shanghai, China College of Environmental Science and Engineering, Tongji University, Shanghai, 200092, China

a r t i c l e

i n f o

Article history: Received 13 March 2008 Accepted 29 June 2009 Available online 7 October 2009 Keywords: Arsenic(V) removal Fe(III) loaded Cotton cellulose adsorbent Ligand exchange adsorption Drinking water

a b s t r a c t A novel macroporous bead adsorbent, Fe(III)-loaded ligand exchange cotton cellulose adsorbent [Fe(III) LECCA], is synthesized for selective adsorption of arsenate anions [As(V)] from drinking water in batch and column systems. As(V) adsorption on Fe(III)LECCA was independent of pH, especially in drinking water pH range. Film diffusive control mechanism will benefit As(V) exchange with Fe(III)LECCA whether in batch or in column experiments. When treating the tap water at 26.0 BV/h, the column still preserves 83% of the original saturation adsorption capacity of the As(V) aqueous solution. These results have indicated that Fe (III)LECCA has the potential to act as an adsorbent for the removal of As(V) from drinking water considering its availability, nontoxicity and cost-effectiveness. © 2009 Elsevier B.V. All rights reserved.

1. Introduction Arsenic is one of the most toxic elements in the world [1]. The arsenic concentrations were different in diverse regions, such as the arsenic concentration were up to 1 mg/L in Bangladesh and India, the water bodies of Southwest America, Germany, Xinjiang and Inner Mongolia of China all contained high arsenic water, especially, most of them in ground water [2]. Long-term ingestion of high arsenic drinking water causes ordinary poisoning. It is also a human carcinogen and affects many people around world. Take for instance, 70 million people in Bangladesh and the Indian sub-continent are suffering the biggest scourge of drinking water arsenic poisoning, 14.6 million in Northwest China, such as Xinjiang, Inner Mongolia and Guizhou province are living in the region where arsenic concentrations are 30 µg/L or even higher in groundwater [3]. In order to reduce arsenic threat to health and of cancer, strict arsenic regulations have drawn global attention. For example, the United State Environmental Protection Agency (USEPA) not only continuously changes its environmental standards but also considers lowering its maximum contaminant level from its present requirement of 50 parts per billion (ppb) to 10 ppb or less [4,5]. In response to this conclusion, the USEPA revised the public drinking-water standard from 0.050 to 0.010 mg/L. These actions challenged contemporary arsenic removal techniques. Currently, the main arsenic removal techniques include coagulation– filtration, membrane separation, ion exchange and adsorption. Because of the simplicity of the column adsorption process, it has become one of the most promising and applied method in arsenic removal. The crucial point ⁎ Corresponding authors. Tel.: +86 021 62238393. E-mail addresses: [email protected] (Y. Zhao), [email protected] (W. Jin). 0011-9164/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.desal.2009.09.015

of column adsorption was the innate performance of the adsorbent. In POE/POU adsorption systems, for example, Activated alumina(AA) was one of most studied adsorbent for its selectivity and effectiveness towards arsenic [6,7]. While Activated alumina showed low adsorption capacity, short service life, slow adsorption rate, making it an inconvenient operation to adjust the pH of influent and effluent solution, the adsorption capacity obviously decreased by 5%–10% after the regeneration and dissolving of the aluminum as well as being regarded as human nerve toxin. These disadvantages may make this approach impractical for water systems serving a few thousand people. When it comes to ion exchange resin, the ion exchange process was feasible when the sulfate ions were lower and empty bed contact time was less than that of AA (3–5 min). But effluent pH and alkalinity of scores of bed volume in initial operation decreased sharply, which needed to readjust pH. At the same time, arsenic removal ability reduced greatly when high concentration of sulfate competed with arsenic. However, the traditional adsorbents and adsorption methods also have many limitations restricting these adsorbents' application and development in practice. Following studies have been conducted to characterize the adsorption of arsenic on other solid materials, such as goethite [8], basic Yttrium carbonate [9], red earth [10], activated carbon [11], zeolite [12], etc. The removal of toxic ions from water by means of adsorption onto solid materials is a well-known process. However, the selection of the most appropriate forms of these materials for present application depends mainly on their adsorption capacity and commercial availability. So researchers begin to find more feasible arsenic removal adsorbents, i.e. modified materials or resins. Detailed description of the adsorption of arsenic by inorganic ion exchangers, such as Lanthanum-impregnated silica gels [13], La(III)-and Y(III)-impregnated alumina [9], Fe (III)-doped alginate gels [14], Fe(III)-modified zeolite

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[15], Fe(III) or Zirconium oxide loaded porous resins [16], etc. have been reported recently. Many operational factors like pH, temperature, contact time, etc, affect sorption efficiency. These adsorbents show certain capacity to adsorb arsenic, but they still contain many inherent limitations. For example, first, the adsorbents have a limited adsorption capacity and leaking of metal-impregnated for adsorbing arsenic species. Second, these methods have to adjust pH and have some operation problems. Third, common anions interfere with the selectivity towards arsenic. Forth, there is a problem in terms of either in efficiency or in cost, and so on. All these factors make it less attractive as a chosen method for removing arsenic from aqueous medium. In order to meet the needs of people of arsenic-contaminated regions, alternative techniques are required that can effectively reduce arsenic concentration from drinking water to environmentally acceptable level at affordable costs. A novel adsorbent, Fe(III)LECCA, is synthesized for selective adsorption and removal of arsenic from drinking water. The availability of an inexpensive and biodegradable carrier – a macroporous cellulose material with a high surface area – further enhanced our interest in choosing this path for our research. The adsorbents are basically modified cotton cellulose through crosslinking, activation and function to improve the three-dimensional chelating ability of introduced ligands. The improvement in metal affinity is thought to be structurally mediated, which indicates a more flexible ligand arrangement to satisfy different coordination geometries in the adsorbents. For the metal of concern, Fe(III) is primarily considered due to its strong affinity toward arsenic anions, environment safe and low cost. It is estimated that the adsorption of As(V) on Fe(III)LECCA can have high selectivity and high adsorption capacity. The macroporous structure of adsorbent carrier can form hydrophilic environment, which benefit to improve As(V) adsorption rate, adsorption capacity and facilitate stripping and regeneration of adsorbent. This work aims at employing Fe(III)LECCA to perform a series experiments and evaluate the performance of As(V) removal under varying conditions. Good results are obtained, which show that the treatment water can meet USEPA 10 ppb or lower standards and the absorbent will be promising to apply for As(V) removal from drinking water. 2. Materials and methods 2.1. Reagent All the chemicals were of analytical grade. Sodium arsenate is prepared into 1000 mg As/L stock solution stored in polyethylene bottle at 0 °C. Sodium chloride and sodium sulfate are employed to study the influences of the common foreign anions. Deionized water is used throughout the experiments. All other reagents were of analytical reagent grade and purchased from local suppliers. 2.2. Preparation of absorbent Cotton cellulose beads were made into cotton beads through antiphase polymerization [17–20]. The cellulose xanthate viscose was prepared by reacting 45 g alkali-treated and aged degreasing cotton with 20 mL CS2 and then dissolving into 6% (w/w) NaOH solution. 100 g viscose was dispersed in a solution of 200 mL chlorobenzene in 400 mL pump oil in a 1 L flask with agitation at 350 rpm for 0.5 h at 25 °C. The suspension was heated up to 95 °C and kept for 1 h under continuous stirring, then cooled down and filtered. The resulting particles were washed successfully with benzene and methanol. After washing with water and sieving with standard test sieves in water. The cotton cellulose beads were activated by epoxy chloropropane and 2 mol/LNaOH at 25 °C for 24 h then ammonification through ammonia water at 65 °C for 12 h. The amino cotton cellulose beads reacted with phosphorous acid and chloride acid at 75 °C for 8 h to get the phosphonomethyl amino group adsorbent carrier, i.e. ligand exchange

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cotton cellulose adsorbent, LECCA. After being washed with alcohol, 5% NaOH solution, deionized water, 5% HCl solution and deionized water in series. LECCA was shaken with a excessive volume 0.6 mol/L FeCl3– 0.2 mol/L CH3COONa buffer solutions (pH = 5.26) for 8 h at room temperature, yielding Fe(III)-loaded LECCA, Fe(III)LECCA. It was washed with deionized water until residual ferric ions cannot be detected. Surface was measured by B.E.T. method — N2 gas adsorption using a QS-7 Quantasorb surface-area analyzer. The topology of adsorbent surface was examined by Hitachi S-4000 scanning electron microscope. IR spectrum was performed by FT-IR Nieolet 50X IR spectrometry. 2.3. Batch adsorption experiments The batch adsorption experiments were carried out using the completely mixed batch reactor techniques. The adsorbent Fe(III)LECCA 0.0691 g was put into conical flasks containing 10 ml 1 mg/L As(V) solution. The contents at the desired concentration and pH were agitated in a shaking thermostat in 105 rpm. Solution pH was adjusted by 1 mol/L HCl or NaOH solution. At the end of the desired period, the content was taken out and filtered with 0.45 μm membrane and filtrate was analyzed for leaking Fe(III) by colorimetric method and residual As(V) by Hydride generation-Cold trapping-Gas chromatograph-Atomic adsorption spectrometry [21]. 2.4. Column adsorption experiment The column adsorption experiments were carried out using fixedbed minicolumn techniques [22]. The adsorbent Fe(III)LECCA 0.4353 g was packed into a water-jacketed glass column (φ9.5 × 300 mm) and the column temperature was maintained by thermostat. The certain concentration As(V) solution was continuously fed to the top of the column at a constant rate and the effluent was collected at the bottom of the column by a electric peristaltic pump (LDB-M electric peristaltic pump with one channel made in China) at regular intervals and analyzed. The breakthrough point of column was chosen as the USEPA maximum environmental permission concentration 10 ppb and saturation point was chosen as effluent As(V) concentration equaling influent As(V) concentration. Desorption experiments were simply column adsorption experiments in reverse. The elution and regeneration of adsorption saturated Fe(III)LECCA for arsenic were carried out at the flow rate of 26.0 BV/husing 1 mol/L NaOH solution. 3. Results and discussion 3.1. Characterization of Fe(III)LECCA Functional phosphonomethy amino Cotton cellulose beads are the carriers of Fe(III)LECCA with the particle size of 0.4–0.8 mm. Fe(III) ions are chelating centers (with the content 0.6 wt.%) which gave adsorption ability to the As(V) ions for Fe(III) ions had a high affinity towards As(V) ions. Fe(III)LECCA (SEM shown in Fig. 1) with the surface area of 2.23 m2/g and moisture of 87% so it had a lot of large pores (5–30 μm) on the surface and among inner part which greatly improved its hydrophilic surface in water solutions. 3.2. Effect of pH pH is an important factor that influenced the arsenic removal under certain condition. The As(V) removal efficiencies were basically above 95% in the range of pH 3.0–8.5 (Figure not shown). When pH was out of the range, there is a little downward for the As(V) adsorption. Comparing with drinking water pH range (6.5–8.5), Fe(III)LECCA could be applied in wide pH range. Maeda et al. [23] reported that the adsorption of As(V) by Fe(OH)3 loaded-coral was also not dependent on initial pH. Our result differed from those absorbents whose adsorption of As(V) were markedly

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Y. Zhao et al. / Desalination 249 (2009) 1006–1011

Fig. 1. SEM micrograph of Fe(III)LECCA and its pore size nm.

influenced by pH in operating solutions. A large amount of similar adsorbents showed narrow arsenic removal pH range, for example, Activated Alumina whose arsenic(V) removal pH was in the range of 5.5– 6.0. Alumina will lost its adsorption ability in strong acid or strong alkaline solutions because of part dissolve thus made its optimum pH range narrow [24]. Meanwhile, Fe(III) loaded-Chelex100 would decompose beyond its optimum pH range of 2–3 and its adsorption ability would remarkably decrease about 20%–70%. Matsunagn et al. [25] also found, for example, that only between pH 2 and 4 As(V) could be strongly adsorbed on the Fe(III)-loaded chelating resin. This difference caused by different characters of the two kinds of polymer substrates, such as substrate affinity for water, ingredients and structure of substrates. In the pH range of 3.0–8.5, the leaking ratio of Fe(III) below drinking water 0.3 mgFe/L standard of China (GB5749-85). It showed that the functional group of adsorbent had a very stronger binding force with chelating center Fe(III) which guaranteed Fe(III)LECCA had a stable adsorption ability towards As(V) in a wide pH range.

manner of monotone increase and continuation. It possibly implied monolayer adsorption of As(V) on Fe(III)LECCA. Adsorption from solution involves the transfer of soluble As(V) species from the liquid phase to the surface of the adsorbent. The uptake of the solute involves four basic steps: 1) bulk transport of the solute to the hydrodynamic boundary layer surrounding the adsorbent particle; 2) diffusive film transport through the boundary layer (film diffusion); 3) intraparticle transport, which may be diffusive transport within the fluid inside the pores (pore diffusion); 4) attachment of the solute onto the adsorbent surface (adsorption). Fick's first law and second law combined with the equilibrium of mass transfer to describe the rate limitation step in dynamic processes. From Fick's first law and the equilibrium of mass transfer, film diffusion control [26] equation can be obtained: 0

ðct −c0 Þ = ðc0 −c∞ Þ = expð−R tÞ

ð1Þ

As c∞ to 0, Eq. (1)can be simplified as 3.3. Kinetic study The effect of reaction time on the As(V) adsorption by Fe(III)LECCA was shown in Fig. 2. The adsorption is rapid and the As(V) removal is nearly completed for about 15 min. The curve tended to be in the

0

ct = c0 = expð−R tÞ

From Fick's second law and the equilibrium of mass transfer, particle diffusion control [26] equation can be obtained: ct = c0 = 1−Kt

Fig. 2. Effect of time on the adsorption of As(V) by Fe(III)LECCA. Fe(III)LECCA: 0.0691 g; As(V) concentration: 1 mg/L (10 ml); pH:7.0; RT: 25 °C.

ð2Þ

1=2

ð3Þ

where co and ct are concentration of As(V) at initial and at any time (mg/L), respectively; R′ and K are rate constants of film diffusion and particle diffusion, separately. If the experimental data fit well with Eq. (2) and have a good linear relationship under certain circumstances, the adsorption can be described by film diffusion control. If the experimental data fit well with the Eq. (3) and have a good linear relationship under certain circumstances, the adsorption can be described by particle diffusion control. Using the relation between uptake of As(V) with time at 25 °C in Fig. 2, the rate constants of film diffusion R′, rate constants of particle diffusion K and correlation coefficient R2 can be calculated by Eqs. (2) and (3), respectively. R′ and K and R2 are 0.13 min− 1with R2 0.956 and 0.27 min− 1/2 with R2 0.5. The result of linear plot Ln(ct/co) versus t confirmed the validity of ct/co = exp(−R′t), illuminating that the film diffusive control was the rate limitation step of the adsorption. Usually, the sharp initial adsorption curves (in Fig. 1) indicated that the adsorption of As(V) might occur on the surface of the adsorbent. While the intraparticle diffusion of As(V) was less because the curves

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showed extremely gentle increment. Not only the curve model was consistent well with the film diffusion control equation but also the macrospores structure and hydrophilicity of Fe(III)LECCA greatly increased As(V) transfer among Fe(III)LECCA adsorbents. Haron [16] reported that the As(V) apparent adsorption constant of Fe(III)loaded hydroximic acid polymer was 0.08 min− 1, which was far less than that of Fe(III)LECCA. So Film diffusive control mechanism will benefit for Fe(III)LECCA exchanging rate with As(V) to increase agitation rate in batch or flow rate in column. This result will provide base for the effect of flow rate of As(V) solutions on Fe(III)LECCA adsorption in column experiments. 3.4. Effect of flow rate In engineering application the flow rate usually in the range of 10– 40 BV/h. In our experiment 65% As(V) can be adsorbed by Fe(III) LECCA within 2 min, then the adsorption rates are very slow (showed in Fig. 1). So we can choose following flow rate to study the influence of the flow rate on the performance of As(V) adsorption process, results presented in Fig. 3. It indicates that the increasing of the flow rate from 26.0 BV/h to 45.7 BV/h causes an apparent decrease of the performance of the adsorption system. Relevant parameters were obtained using formulates of adsorption zone theory. QB ¼ ðC0 × VB Þ = M

ð4Þ

QT ¼ qz = M þ QB

ð5Þ

f ¼ qZ = C0 × ðVT −VB Þ

ð6Þ

HZ ¼ HT × ðVT −VB Þ = VT −ð1−f Þ × ðVT −VB Þ

ð7Þ

where VB and VT are the effluent volume at breakthrough and saturation point separately, C0, C are concentration of fluoride solution in initial influent and at any time in effluent, respectively, m is the amount of the adsorbent, Q B̅ and Q T̅ are the mean adsorption capacity in column at breakthrough and saturation point for fluoride, separately, qZ is adsorption capacity of adsorption zone, f is fraction of the utilized adsorbent in adsorption zone formed, HZ and HT are the height of adsorption zone and the adsorbent bed respectively, and N is the number of series column. When the flow rate increased from 26.0 BVh/h to 45.7 BV/h, the breakthrough capacity decreased from 5.2837 to 1.4473 mg/g dry weight; the saturation capacity decreased from 23.7767 to 13.6917 mg/g dry weight, respectively, while the efficiency of column decreases by 11.6%. When flow rate was 26 BV/h, the As(V) saturated

Fig. 3. The effect of flow rate on column absorption of As(V) by Fe(III)LECCA. Fe(III) LECCA :0.4353 g; As(V) concentration: 1 mg/L; pH:7.10; RT: 25 °C.

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adsorption capacity of Fe(III)LECCA was decreased 9.5 fold compared with that of batch experiment. Chandan [27] reported that effluent profile of Fe(III)Chelex100 was very flat at flow rate of 2 BV/h. Compared with equilibrium adsorption capacity of 17 mg/g in batch experiment, the saturated adsorption capacity was 6.4 mg/g and decreased about 2 fold. Rajakovic [28] also reported that the As(V) saturated adsorption capacity (13.5 mg/g) of Cu-loaded Activated Carbon was only half of the batch equilibrium adsorption experiment. It was obvious that the As(V) combining ability or adsorption capacity with adsorbents were all decreased because of an imbalance in exchange caused by the irreversible adsorption process in column systems. These irreversible adsorption phenomena would enlarge with the increase of the flow rate in column processes thus causing the decrease in the adsorption capacity of adsorbents. When the drinking water containing As(V) was allowed to pass through anions exchange resin at the flow rate below 20 BV/h, the As(V) adsorption capacity of the resin was increased with the decreasing of flow rate. When flow rate was larger than 20 BV/h, the obvious As(V) leakage will occur. Usually, the lower space flow rate would be favorable to As(V) adsorption. Toshishige [29] has reported that As(V) was favorably retained on the porous resin loaded with crystalline hydrous zirconium oxide column at 5 BV/h to allow the passage of the feed solution for 5100 ml, approximately 35.0 mg of As(V) was retained on 1 g of the resin at the breakthrough point 50 ppb. While in our experiment, 12 mg of As(V) is maintained on 1 g Fe(III)LECCA at the same breakthrough point 50 ppb to allow the passage of the feed solution for 5100 ml at the same condition with that of Toshishige except flow rate being 26 BV/h. Though the adsorption capacity of Fe(III)LECCA was less than that of the porous resin loaded with crystalline hydrous zirconium oxide, the higher flow rate was fitted to the practical requirement and had a better application value. 3.5. As(V) removal from tap water spiked with As(V) Tap water containing 250 mg/L sulfate ions, 250 mg/L chloride ions and 1 mg/L As(V) was used at pH 7.10, 25 °C and 26BV/hto evaluate how the capacity of adsorption varied. The influent and effluent water indexes were list in Fig. 4, Table 1. Chloride concentration of effluent remain 250 mg/L, the Cl− ions also didn't affect the adsorption of As(V) on column experiment. Compared with the batch experiments, the 250 mg/L sulfate ions competed with As(V) in column experiment, affecting breakthrough and saturation adsorption capacity, causing selectivity dropping of the adsorbents by certain degree. But the column still kept 65% breakthrough point adsorption capacity and 83% saturation capacity of the original. The

Fig. 4. The effect of common anions on column absorption of As(V) by Fe(III)LECCA. Fe(III) LECCA:0.4353 g; pH:7.10; flow rate: 26.0 BV/h; As(V) concentration: 1 mg/L (arsenic in aqueous solution and tap water); RT: 25 °C.

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Table 1 Influent and effluent drinking water quality (mg/L).

As(V) Hardness pH F− Cl− SO2− 4 NO− 3 a

Influent water

Effluent water

Standardsa

1.0 202.39 7.90 0.45 24.83 65.05 4.73

<0.01 182.94 6.50 0.50 28.40 63.6 6.20

< 0.01 450 6.5–8.5 ≤1 250 250 20 Scheme 1. P: cotton cellulose adsorbent carriers.

Living drinking water quality of China (GB5749-85), hardness calculated as CaCO3.

number of series column was also 3. The adsorbent still had better adsorption capacity. The effluent tap water qualities are fitted well with living drinking water quality of China (GB5749-85). It was suggested that the adsorbent was highly selective for the adsorption of As(V) in drinking water. According to the results of selectivity in batch experiment, the decrease of the column adsorption may be noted that the interference was mainly caused by the high concentration sulfate in tap water. This selectivity dropping may be ascribed to the affinity between As(V) with Fe(III)LECCA being weaker than sulfate. Comparing with batch experiments, the higher the sulfate concentration, the lower the breakthrough volume of As(V). Korngold [30] reported that the As(V) saturated column could be regenerated by NaCl solution, then about 99% As(V) could be precipitated by adjusting pH. The regenerant NaCl can be reused by adjusting its concentration. In this experiment faster stripping of the Fe(III)LECCA column saturated by 1 mg/L As(V) can be obtained with 1 mol/L NaOH. Sharp elution curves showed that more than 96% As(V) fed into the column is contained in only 82 ml stripping solution at 26.0BV/h elution rate at 25 °C. This corresponded to enrichment being nearly 123 times the volume of the initial feed solution. The elutant can be further treated and recovered. The effective regeneration can guarantee the adsorbent to be used continuously. 3.6. Adsorption mechanism In order to remove anions selectively, metal-impregnated polymer substrate must serve as anion exchanger [27]. Fe(III) belongs to 3d5 metal ion and it is easy for it to accept electron pairs of LECCA (as methyl aminophosphorous ligands), water and other anions (Cl−) to form stable complexes. Far-IR spectrum of Fe(III)LECCA in Fig. 5 showed that the main characteristic absorbance peak of Fe–Cl were 555, 442, 377 and 314 cm− 1. After adsorbing As(V) by Fe(III)LECCA, the main characteristic absorbance peak of Fe–Cl disappears and main characteristic absorbance peak of Fe–As(V),1541, 621, 550 and 310 cm− 1, occurs. In

nature water, arsenic species distribution depends on pH and redox potential [30]: When pH < 3.5, arsenic was mainly H3AsO4; when 3.5 < pH< 7.0, arsenic was mainly H2AsO− 4 ; and when 7.0 < pH< 11.0, arsenic was mainly HAs2− 4 . All experiments were performed in pH range of 4.0 to 11.0 in our study. From batch experiments and physiochemical characteristics of adsorbent Fe(III)LECCA, the ligand exchange mechanism was suggested as following (shown in Scheme 1): The exchange of chloride of Fe(III)LECCA by arsenate anions showed that the reaction mechanism was ligand exchange mechanism. From Table 1, the changes of chloride and sulfate quality index, can also demonstrate this ligand exchange mechanism. In regeneration process, OH− exchange with As(V) to achieve the stripping aim. It can be concluded that the adsorption process was ligand exchange mechanism from chemical analysis and Far-IR spectrum results. 4. Conclusions Fe(III)LECCA exhibited good performances in arsenate removal under varying conditions in batch experiments. The carrier of the Fe(III) LECCA has wide sources and biodegradable characteristic. The chelating center Fe(III) is low price and nontoxic. Fe(III) also coordinates with strong electron donating groups of methyl aminophosphonic cotton carriers, showing high stability. These properties made the novel adsorbent more attractive and competitive in drinking water treatment. Lab-scale experiment showed that Fe(III)LECCA also has good adsorption capacity, selectivity and adsorption rate for arsenate removal from drinking water. So it can be concluded that Fe(III)LECCA would be an alternative novel adsorbent for arsenate removal from drinking water. Acknowledgements Financial support of the research is from the National Natural Science Foundation of China (Nos. 29977010 and 20707006) and SRF for ROCS, SEM (2008) are greatly acknowledged. References

Fig. 5. Far-IR of Fe(III)LECCA before (Fe–Cl) and after (Fe–As) adsorbing As(V).

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