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Journal of Environmental Science and Health, Part A: Toxic/Hazardous Substances and Environmental Engineering Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/lesa20
Feasibility studies on arsenic removal from aqueous solutions by electrodialysis Rose Marie O. Mendoza d
a f
b
c
, Chi-Chuan Kan , Shih-Shing Chuang , Sheila Mae B. Pingul-Ong e
, Maria Lourdes P. Dalida & Meng-Wei Wan
f
a
General Education Department , Far Eastern University-Nicanor Reyes Medical Foundation , Quezon City , Philippines b
Institute of Hot Spring Industry, Chia Nan University of Pharmacy and Science , Tainan , Taiwan (R. O. C.) c
Shell Kwong Sir Enterprise Co., Ltd. , Tainan , Taiwan (R. O. C.)
d
Environmental Engineering Program, National Graduate School of Engineering , University of Philippines Diliman , Quezon City , Philippines e
Department of Chemical Engineering , University of Philippines Diliman , Quezon City , Philippines f
Department of Environmental Engineering and Science , Chia Nan University of Pharmacy and Science , Tainan , Taiwan (R. O. C.) Published online: 10 Jan 2014.
To cite this article: Rose Marie O. Mendoza , Chi-Chuan Kan , Shih-Shing Chuang , Sheila Mae B. Pingul-Ong , Maria Lourdes P. Dalida & Meng-Wei Wan (2014) Feasibility studies on arsenic removal from aqueous solutions by electrodialysis, Journal of Environmental Science and Health, Part A: Toxic/Hazardous Substances and Environmental Engineering, 49:5, 545-554, DOI: 10.1080/10934529.2014.859035 To link to this article: http://dx.doi.org/10.1080/10934529.2014.859035
PLEASE SCROLL DOWN FOR ARTICLE Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) contained in the publications on our platform. However, Taylor & Francis, our agents, and our licensors make no representations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of the Content. Any opinions and views expressed in this publication are the opinions and views of the authors, and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be relied upon and should be independently verified with primary sources of information. Taylor and Francis shall not be liable for any losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use of the Content. This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden. Terms & Conditions of access and use can be found at http:// www.tandfonline.com/page/terms-and-conditions
Journal of Environmental Science and Health, Part A (2014) 49, 545–554 C Taylor & Francis Group, LLC Copyright ISSN: 1093-4529 (Print); 1532-4117 (Online) DOI: 10.1080/10934529.2014.859035
Feasibility studies on arsenic removal from aqueous solutions by electrodialysis ROSE MARIE O. MENDOZA1,6, CHI-CHUAN KAN2, SHIH-SHING CHUANG3, SHEILA MAE B. PINGUL-ONG4, MARIA LOURDES P. DALIDA5 and MENG-WEI WAN6 1
General Education Department, Far Eastern University-Nicanor Reyes Medical Foundation, Quezon City, Philippines Institute of Hot Spring Industry, Chia Nan University of Pharmacy and Science, Tainan, Taiwan (R. O. C.) 3 Shell Kwong Sir Enterprise Co., Ltd.,Tainan, Taiwan (R. O. C.) 4 Environmental Engineering Program, National Graduate School of Engineering, University of Philippines Diliman, Quezon City, Philippines 5 Department of Chemical Engineering, University of Philippines Diliman, Quezon City, Philippines 6 Department of Environmental Engineering and Science, Chia Nan University of Pharmacy and Science, Tainan, Taiwan (R. O. C.)
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2
The effectiveness of electrodialysis (ED) in removing inorganic arsenic (As) from aqueous solution was investigated. A tailor-made ED stack was used to perform current-voltage and optimization experiments in a recirculating batch mode. Samples were pre-oxidized with NaClO using 1:2 sample to oxidant weight ratio (RS :O) to transform 100% of As(III) to As(V) in 180 seconds. A high feed water conductivity of 1500 µS/cm and a low feed water conductivity of 800µS/cm had limiting currents of 595 mA and 525 mA, respectively. Optimum experimental conditions that provided maximum As separation were applied potential (E) of 12 V, feed flow rate (Q) of 0.033 L/s, feed concentration (C) of 662.0 µg L−1, and operating time (t) of 45 min, the most significant ones were applied potential, feed concentration and operating time. Model confirmation experiments showed a good agreement with experimental results with only 0.031% error. The total As in the diluate stream was 4.0 µg L−1, consisting of an average of 3.0 µg L−1 As(V) and 1.0 µg L−1 As(III). Keywords: Electrodialysis, arsenic removal, limiting current density.
Introduction The problem of high arsenic concentrations in groundwater systems is evident in many countries all over the world. Smedley and Kinniburgh [1] noted that major As-related incidents have been reported in Argentina, Bangladesh, Chile, Hungary, India, Mexico, the United States, Romania, Vietnam, China and Taiwan. By far, the largest effect was evident in the Ganges Delta between Bangladesh and India, where about 40 million people were at risk to As exposure.[2] Studies have discovered that As exposure causes many negative effects to human health, such as blackfoot disease (BFD), ischemic heart disease, hyperpigmentation, hyperkeratosis, diabetes, meningioma, and cancers of liver, kidney, bladder, prostate, lymphoid tissue, skin, lung, colon, and nasal cavity.[3–5] In fact, As is classified as a Group Address correspondence to Meng-Wei Wan, Department of Environmental Engineering & Science, Chia-Nan University of Pharmacy & Science, 60, Erh-Jen Rd., Sec.1, Jen-Te, Tainan 71710 Taiwan; E-mail: [email protected] Received July 9, 2013.
1 Human Carcinogen by the International Agency for Research on Cancer (IARC).[3,6] To control the damage caused by As contamination, World Health Organization has set a guideline value of 10 µg L−1 for arsenic in drinking water, which is the same value set by the European Union, the United States of America, Japan, and Taiwan. Common methods used for As removal from contaminated water are adsorption,[7–13] chemical oxidation,[14–15] phytoremediation,[16] photochemical,[17] and photocatalytic oxidation.[18] Membrane separation technologies such as reverse osmosis (RO), nanofiltration (NF), and ultrafiltration (UF) are also used to separate and transport ions such as As and yield a high-quality filtrate that is suitable for discharge or reuse.[19] However, UF is limited to physical sieving, which makes it less suitable for As removal, and NF allows changes in As speciation upon prolonged stay of treated water inside the filter.[20] Electrodialysis (ED) is an electrically driven membrane process that uses an applied electrical potential difference to transport ions through alternating cationic and anionic membranes arranged in parallel between an anode and a cathode,[21,22] resulting in two flow regimes—one
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stream concentrated with ions, and another more diluted stream.[23,24] ED has many advantages, such as it can tolerate feed waters with high chloride and sulfates, it does not need additional chemicals, and the recirculation promotes turbulent flow within the stack, requiring less applied potential for the system. In addition, ED utilizes highly cleanable, recoverable, and durable membranes.[25] With these many advantages, ED has the potential to remove ionic pollutants such as As from contaminated water. This study aimed to determine the capacity of a tailor-made ED stack in removing As from synthetic contaminated water down to the maximum contaminant level (MCL) of 10µg L−1, and optimize significant parameters for the most efficient As removal.
Materials and methods Arsenic solution Initial As concentrations of 700, 600, 500 and 50 µg L−1 were prepared from 1000 mg L−1 As stock solution formulated using 0.1320 g of (99.5% assay) arsenic trioxide (As2 O3 ) obtained from Acros Organics (Pittsburgh, PA, USA). Solid As2 O3 was dissolved in 10 mL of 4% (w/v) NaOH and 2 mL of 37% (w/w) HCl, and the solution was diluted to 100 mL using Ultrapure 18.2 m deionized water. The As solution was pre-treated with Merck sodium hypochlorite (NaClO) contaning 10% active Cl, 1.22 kg/L density and 1:2 sample to oxidant weight ratio (RS :O)[26] before it enters the ED stack, with a theoretical dose of 7.79 mL NaClO per mg As based on a stoichiometric reaction proposed by Ghurye and Clifford.[14] The pH of the solution was adjusted to 7.4–7.6 using NaOH and HCl. The chemical reaction for As (III) oxidation to As (V) follows:[26] H3 As O3 + NaCl O → H2 As O4− + Na + + Cl − + H+
Electrodialysis (ED) system The ED system, supplied by Shell Kwong Sir Enterprise Co., Ltd. (Tainan City, Taiwan), was composed of a single hydraulic and a single electrical stack with 20 cell pairs situated 0.9 mm apart. It was equipped with a control panel and a DC source of 500 W LD 66500 rectifier with a maximum input power of 300 V. The cationic (SKS-C) and anionic (SKS-A) membranes have a dimension of 40 cm × 20 cm and effective area of 11,200 cm2. The anode and cathode were made of titanium coated with ruthenium and iridium. A summary of the ED specifications is shown in Table 1. In addition, two 320 rpm IWAKI magnetic pumps (Saitama, Japan) were used to introduce the feed water and electrode rinse solution into the ED stack. The concentrated stream was used as electrode rinse and recirculated at a rate of
Mendoza et al. Table 1. The SKS electrodialysis (ED) stack specifications. Parameter
Values/Material
Number of hydraulic stages 1 Volume of stack 4,240 cm3 Anode Titanium coated with mixed oxides of ruthenium and iridium Cathode Titanium coated with mixed oxides of ruthenium and iridium Current 0–2 A Voltage 0–30 V Maximum Flow Rate 5 L/min Anion exchange membrane SKS-A (quarternary ammonium) Cation exchange membrane SKS-C (sulfonic acid group) Number of cell pairs 20 Membrane size 200 mm × 400 mm Spacer Polypropylene (PP) with 170 mmoˆ 360 mm flow pass length Spacer thickness 0.9 mm Effective membrane area 11,200 cm2 (sq.cm)
0.042 L s−1, as shown in Figure 1. The system was operated at 25 ± 1◦ C.
Experimental methods Conductivities of 1500 µS cm−1 and 800 µS cm−1 were used for the current-voltage experiments, while desalination tests used feed concentrations of 50, 500 and 1000 µg L−1. The following parameters were held constant: initial feed volume of 2 L, feed flow rate of 0.033 L s−1 or 2.0 liters per minute (LPM), and electrode flush volume of 4.5 L of tap water, the characteristics of which are indicated in Table 2. The electrode flush flow rate was kept at 0.042 L s−1 (2.5 LPM) to prevent formation of chlorine or hypochlorite in the electrode compartments.[23] The product/diluate stream and the concentrate stream were initially separated and recirculated into the ED stack until the conductivities of the two streams were constant. The rectifier was turned on, and current was initially set at 150 mA and increased stepwise, in increments of 50 mA, up to a maximum of 800 mA. After each increase, the system was allowed to reach steady state for 5 min, and the potential and conductivity of the diluate were recorded.[27] For optimization and model confirmation experiments, the controlled experimental parameters were the same as those used in the previous experiments. Applied voltage ranged from 5 to 20 V. The rectifier was turned off when a constant conductivity and current reading was observed continuously for 5 min. Total As in the feed, concentrate, and diluate streams, current and voltage values, and operating time were monitored throughout each experimental run.
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Arsenic removal from aqueous solutions by electrodialysis
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Fig. 1. Process flow diagram for the electrodialysis (ED) system.
Laboratory analysis The ORP and pH of the solution were monitored using Suntex pH-ORP meter SP-300 (Suntex Instruments Co., Ltd., Kaohsiung, Taiwan). Current and voltage measurements were performed using Hao Ling HL 833 digital ammeter and voltmeter. The conductivities of the diluate and concentrated streams were determined using Suntex EC410 digital conductivity meter. All the laboratory standards were freshly prepared to ensure proper standard calibration. Separation of As(III) and As(V) was done using a solid phase extraction membrane, Supelco LC-SAX strong anion resin (Shanghai, China), at an elution time of 1 min.[28] Table 2. Composition of tap water used as an electrode flush solution. Cations Na+ K+ Mg2+ Ca2+ Mn2+ Fetot Astot
Concentration mg/L 12.89 1.27 16.26 50.99 ND ND ND
Anions
Concentration Mg L−1
Cl− NO3 − SO4 2− HCO3 − PO4 3−
0.08 ND 74 131.75 2.17
Others: Eh = 463 mV; pH = 7.63; T = 24◦ C; EC = 490 µS cm−1. ND: none detected (700 µg L−1, SN and S were observed to vary inversely with C. This translates to high values of S when C is below 700 µg L−1, which was verified by optimization studies that showed maximum S was achieved at 662 µg L−1. According to ANOVA, Q does not significantly affect As separation percentage. This is due to the turbulence generated using a recirculated batch mode, where the thickness of the stagnant layer near the membrane-solution interface was reduced. High Q in the turbulent flow regime has no
97
S (%)
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SN S
93
Table 5. Signal-to-noise ratio of the controllable factors and their levels based on a LTB criteriaa. Level
Applied Potential
Feed Concentration
Feed Flow Rate
Operating Time
Low Middle High Deltaa Rank
38.903 39.672 39.858 0.955 1
39.211 39.527 39.579 0.394 4
39.249 39.644 39.540 0.483 3
39.132 39.548 39.753 0.621 2
a Delta is the amount of information in the design that is attributed to the factor or term. High delta means higher effects.
92
39.2
91 30
45
60
Operating Time (min.)
Fig. 6. Effects of (a) E, (b) Q, (c) C and (d) t on SN and S.
effect on E and t, as verified by Chandramowleeswaran and Palanivelu in their work.[23, 32] As shown in Figure 7, E has the greatest effect on S, followed by t and C. Therefore, based on the maximization of S and SN, numerical and
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Mendoza et al. Table 7. Characteristics of the feed, diluate and concentrate streams. Feed Water
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Parameters
Fig. 7. Contribution of each factor on As separation percentage.
graphical optimization yielded the same optimum conditions: E = 12 V, Q = 0.033 L s−1, C = 662 µg L−1 and t = 45 min.
pH EC, µS cm−1 Cations, mg L−1 Na+ K+ Mg2+ Ca2+ Mn2+ Fe (total) As (total) As (V) As (III) Anions, mg L−1 Cl− NO3 − PO4 3− SO4 2−
(Synthetic As solution)
Diluate Stream
Concentrated Stream
7.63 1489
4.8 35
5.3 1603
139.87 ND ND 2.858 ND ND 660 µg L−1 625 µg L−1 35 µgL−1
2.473 ND ND ND ND ND 4 µg L−1 3 µg L−1 1 µg L−1
686.20 349.30 33.90 12.65 ND ND 724 µgL−1 180 µg L−1 543 µg L−1
228 ND ND ND
0.11 ND ND ND
299.00 2.68 5.22 167.09
Synthetic As water solution concentration = 660 µg L−1. ND: None detected (< 5–10 ppb).
Model confirmation Based on the optimum conditions, namely E = 12 V, Q = 0.033 L s−1, C = 662 µg L−1 and t = 45 min, model confirmation runs were conducted using synthetic As water. In addition to the optimized conditions, electrode flush solution was maintained at 0.042 L s−1 and the stack was operated under the limiting current. The recirculation process and high electrode flush solution flow rate prevented significant deposition of Cl– ions and gases in the electrodes.[23, 34–36] Table 6 shows that an average of 99.471% As separation was obtained, with 4.0 µg L−1 total As in the diluate stream. The model prediction on S was 99.500%, where the total As was 3.0 µg L−1. A 0.031% error indicates a very good agreement between the model and experimental values for As separation percentage, implying that the Table 6. Results of the model confirmation experiments on As separation percentagea.
model can adequately predict the value of S. In terms of the inorganic As species, it was found that an average of 3.0 µg L−1 As(V) and 1.0 µg L−1 As(III) were detected in the diluate stream, values which are lower than the MCL of As in drinking water set by WHO and US EPA. Other characteristics of the feed, diluate and concentrate stream are listed in Table 7. Since a considerable amount of Na+ and Cl– were present in the feed stream during sample preparation and pre-oxidation stage, the amount of Na+ and Cl– in the feed and concentrate streams at the end of desalination were extremely important. Table 7 shows that Na+ and Cl– were depleted from the diluate stream and transported to the concentrate stream. Na+ was reduced from 139.875 to 2.473 mg L−1, while Cl– decreased from 228 to 0.110 mg L−1.
Conclusion
Experimental Results
Parameter
Run 1
Run 2
Average
Model Predicted S
Total As S (%)
3.992 99.399
3.036 99.543
3.514 99.471
3.301 99.500
Error % 6.453 0.031
Performed at optimum experimental conditions: E = 12 V; Q = 0.033 L s−1; C = 660 µg L−1; t = 45 min. Other ED settings: Electrode flush = 0.042 L s−1; Vfeed = 2 L; Vrecir. stream = 4.5 L. Recirculation ratio: Feed = 1.15; Concentrate = 0.85; Electrode flush solution = 1.0.
a
Inorganic As was efficiently removed from contaminated water using a tailor-made ED stack operated in recirculated batch mode. Limiting current was 595 mA for high conductivity As (1500 µS cm−1) and 525 mA for low conductivity As solution (800 µS cm−1), corresponding to an average LCD of 0.0455 mA cm−2 for the entire process. Taguchi L9 OA design with LTB criteria was used to obtain optimum experimental conditions, which were found to be as follows: 12 V applied potential (E), 0.033 L s−1 feed flow rate (Q), 662 µg L−1 feed concentration (C), and
Arsenic removal from aqueous solutions by electrodialysis 45-min operating time (t). ANOVA illustrated that the E, C and t were the significant factors that affect As separation (P = 0.0344). Predicted values were consistent with experimental values, with only 0.031% error for S when the operation was performed under optimum experimental settings. Total As in the diluate stream was 4.0 µg L−1, with an average of 3.0 µg L−1 As(V) and 1.0 µg L−1 As(III). Results indicate that ED operated under recirculated batch condition is an efficient process in removing As from contaminated water, achieving As concentrations below the 10 µg L−1 provisional guideline for treated water. The durability of the membranes makes an ED unit effective up to over 20 years, making the system an economical investment.
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Funding The authors would like to thank the Taiwan National Science Council for financially supporting this research under Contract No. NSC 101-2221-E-041-010-MY3, in collaboration with the Commission on Higher Education–Higher Education Development Program (CHED-HEDP) of the Republic of the Philippines.
References [1] Smedley, P.L.; Kinniburgh, D.G. A review of the source, behaviour and distribution of Arsenic in natural waters. Appl. Geochem. 2002, 17, 517–568. [2] Alam, M.G.; Allinson, G.; Stagnitti, F.; Tanaka, A.; Westbrooke, M. Arsenic contamination in Bangladesh groundwater: a major environmental and social disaster. Int. J. Environ. Health Res. 2002, 12(3), 235–253. [3] Chen, Y.-C.; Su, H.-J.J.; Guo, Y.-L.L.; Hsueh, Y.-M.; Smith, T.J.; Ryan, L.M.; Lee, M.S.; Christiani, D.C. Arsenic methylation and bladder cancer risk in Taiwan. Cancer Cause Contr. 2003, 14, 303–310. [4] Chan, P.C.; Huff, J. Arsenic carcinogenesis in animals and in humans: mechanistic, experimental, and epidemiological evidence. Environ. Carcin. Eco. Res. 1997, C15, 83–122. [5] Chiou, H.Y.; Hsueh, Y.M.; Liaw, K.F. Incidence of internal cancers and ingested inorganic arsenic: a seven-year follow-up study in Taiwan. Cancer Res. 1995, 55, 1296–1300. [6] International Agency for Research on Cancer (IARC). Arsenic and its compounds; In Monographs on the Evaluation of Carcinogenic Risk of Chemicals to Humans: Some Metals and Metallic Compounds; Author: Lyon, 1980; 23. [7] Mohan, D.; Pitmann, C.U. Jr. Arsenic removal from water/wastewater using adsorbents–A critical review. J. Hazard. Mater. 2007, 142, 1–53. [8] Lin, T.F.; Wu, J.K. Adsorption of arsenite and arsenate with phosphate and molybdate on oxide minerals. J. Soil Sci. Soc. Amer. 2001, 60 (1), 121–131. [9] Reed, B.E.; Vaughan, R.; Jiang, L. As(III), As(V), Hg and Pb removal by Fe-oxide impregnated activated carbon. J. Environ. Eng. 2000, 126 (9), 869–873. [10] Genc-Fuhrman, H.; Tjell, J.C.; McConchie, D. Increasing the Arsenate adsorption capacity of neutralized red mud (Bauxol). J. Coll. Interf. Sci. 2004, 27 (2), 313–320.
553
[11] Thirunavukkarasu, O.S.; Viraraghavan, T.; Subramanian, K.S.; Chaalal, O.; Islam, M.R. Arsenic removal in drinking water-impacts and novel removal technologies. Energ. Sour. 2005, 27 (1–2), 209–219. [12] Guibal, E. Interactions of metal ions with chitosan-based sorbents; A review. Sep. Purif. Technol. 2004, 38(1), 43–74. [13] Boddu, V.M.; Abburi, K.; Talbott, J.L.; Smith, E.D.; Haasch, R. Removal of Arsenic (III) and Arsenic (V) from aqueous medium using chitosan-coated-biosorbent. Water Res. 2008, 42 (3), 633–642. [14] Ghurye, G.; Clifford, D. As(III) oxidation using chemical and solidphase oxidants. J. Am. Water Works Ass. 2004, 96 (1), 84–96. [15] Ferguson, M.A.; Hoffmann, M.R.; Hering, J.G. TiO2 photocatalyzed As(III) oxidation in aqueous suspensions: reaction kinetics and effect of adsorption. Environ. Sci. Technol. 2005, 39, 1880–1886. [16] Dickinson, N.M.; Baker, A.J.M.; Doronila, A.; Laidlaw, S.; Reeves, K.D. Phytoremediation of inorganics: realism and synergies. Int. J. Phytorem. 2009, 11, 97–114. [17] Emett, M.T.; Khoe, G.H. Photochemical oxidation of arsenic by oxygen and iron in acidic solutions. Water Res. 2001, 35, 649–656. [18] Dutta, D.K.; Pehkonen, S.O.; Sharma, V.K.; Ray, A.K. Photocatalytic oxidation of Arsenic(III): evidence of hydroxyl radicals. Environ. Sci. Technol. 2005, 39, 1827–1834. [19] Harisha, R.S.; Hosamani, K.M.; Keri, R.S.; Aminabhavi, T.M. Arsenic removal from drinking water using thin film composite nanofiltration membrane. Desalination 2009, 300, 1–6. [20] US Environmental Protection Agency (US EPA). Drinking Water Regulation for Arsenic and Clarification to Compliance and New Source Monitoring; In National Primary Drinking Water Regulations; Implementation Guidance for Arsenic Rule; Author: Washington, DC, 2004; 6975–7066. [21] Smara, A.; Delimi, R.; Chainet, E.; Sandeaux, S. Removal of heavy metals from diluted mixtures by a hybrid ionexchange/electrodialysis process. Separ. Purif. Technol. 2007, 57(1), 103–110. [22] Sadrzadeh, M.; Rami, A.; Mohammadi, T. Separation of monovalent, divalent and trivalent ions from wastewater at various operating conditions using electrodialysis. Desalination 2007, 205, 53–61. [23] Chandramowleeswaran, M.; Palanivelu, K. Treatability studies on textile effluent for total dissolved solids reduction using electrodialysis. Desalination 2006, 210, 164–174. [24] Zhong, K.W.; Zhang, W.R.; Hu, Z.Y.; Li, H.C. Effect of characterization spacers in electrodialysis cells on mass transfer. Desalination 1983, 46, 243–252. [25] Valerdi-Perez, R.; Loez-Rodriquez, M.; Ibanez-Mengual, J.A. Characterizing an electrodialysis reversal plant. Desalination 2001, 137, 199–206. [26] Sorlini, S.; Gialdini, F. Conventional treatments for the removal of arsenic with chlorine dioxide, hypochlorite, potassium permanganate and monochloramine. Water Res. 2011, 31(2), 289–297. [27] Kocherginsky, N. Mass transport and membrane separations: Universal description in terms of physicochemical potential Einstein’s Mobility. Chem. Eng. Sci. 2010, 65, 1474–1489. [28] Lu, K.L.; Liu, G.W.; Wang, S.W.; Jang, C.S.; Lin, K.L.; Liao, V.H.C.; Chang, F.J. Assessing the characteristics of groundwater quality of aquifers in the black foot disease endemic area. J. Hazard. Mater. 2011, 185(2–3), 1458–1466. [29] Mohammadi, T.; Moheb, A.; Sadrzadeh, M.; Razmi, A. Modelling of metal ion removal for wastewater by electrodialysis. Separ. Purif. Technol. 2005, 41, 23–82. [30] Montgomery, D.C. Design and Analysis of Experiments, 3rd Ed.; John Wiley & Sons: New York, 1991. [31] Maghsoodloo, S.; Ozdemir, G.; Jordan, V.; Huang, C.H. Strengths and limitations of Taguchi contributions to quality, manufacturing, and process engineering. J. Manuf. Syst. 2004, 23, 373–381.
554
Downloaded by [UQ Library] at 13:16 03 November 2014
[32] Valerdi-Perez, R.; Berna-Amoros, L.M.; Ibanez-Mengual, J.A. Determination of working optimum parameters for an electrodialysis reversal plant. Separ. Sci. Technol. 2000, 35(5), 651– 666. [33] Lee, H.-J.; Strathman, H.; Moon, S.-H. Determination of limiting current density in electrodialysis desalination as a function of linear velocity. Desalination 2006, 190, 43–50.
Mendoza et al. [34] Tanaka, Y. Water dissociation in ion-exchange membrane electrodialysis. J. Membrane Sci. 2010, 350, 347–360. [35] Chao, Y.-M.; Liang, T.M. Feasibility study of industrial wastewater recovery using electrodialysis reversal. Desalination 2008, 221, 433–439. [36] Robinson, R.A.; Stokes, R.H. Electrolyte Solutions, 2nd Ed.; Academic Press, Inc.: New York, 1965.
Journal of Environmental Science and Health, Part A: Toxic/Hazardous Substances and Environmental Engineering Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/lesa20
Feasibility studies on arsenic removal from aqueous solutions by electrodialysis Rose Marie O. Mendoza d
a f
b
c
, Chi-Chuan Kan , Shih-Shing Chuang , Sheila Mae B. Pingul-Ong e
, Maria Lourdes P. Dalida & Meng-Wei Wan
f
a
General Education Department , Far Eastern University-Nicanor Reyes Medical Foundation , Quezon City , Philippines b
Institute of Hot Spring Industry, Chia Nan University of Pharmacy and Science , Tainan , Taiwan (R. O. C.) c
Shell Kwong Sir Enterprise Co., Ltd. , Tainan , Taiwan (R. O. C.)
d
Environmental Engineering Program, National Graduate School of Engineering , University of Philippines Diliman , Quezon City , Philippines e
Department of Chemical Engineering , University of Philippines Diliman , Quezon City , Philippines f
Department of Environmental Engineering and Science , Chia Nan University of Pharmacy and Science , Tainan , Taiwan (R. O. C.) Published online: 10 Jan 2014.
To cite this article: Rose Marie O. Mendoza , Chi-Chuan Kan , Shih-Shing Chuang , Sheila Mae B. Pingul-Ong , Maria Lourdes P. Dalida & Meng-Wei Wan (2014) Feasibility studies on arsenic removal from aqueous solutions by electrodialysis, Journal of Environmental Science and Health, Part A: Toxic/Hazardous Substances and Environmental Engineering, 49:5, 545-554, DOI: 10.1080/10934529.2014.859035 To link to this article: http://dx.doi.org/10.1080/10934529.2014.859035
PLEASE SCROLL DOWN FOR ARTICLE Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) contained in the publications on our platform. However, Taylor & Francis, our agents, and our licensors make no representations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of the Content. Any opinions and views expressed in this publication are the opinions and views of the authors, and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be relied upon and should be independently verified with primary sources of information. Taylor and Francis shall not be liable for any losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use of the Content. This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden. Terms & Conditions of access and use can be found at http:// www.tandfonline.com/page/terms-and-conditions
Journal of Environmental Science and Health, Part A (2014) 49, 545–554 C Taylor & Francis Group, LLC Copyright ISSN: 1093-4529 (Print); 1532-4117 (Online) DOI: 10.1080/10934529.2014.859035
Feasibility studies on arsenic removal from aqueous solutions by electrodialysis ROSE MARIE O. MENDOZA1,6, CHI-CHUAN KAN2, SHIH-SHING CHUANG3, SHEILA MAE B. PINGUL-ONG4, MARIA LOURDES P. DALIDA5 and MENG-WEI WAN6 1
General Education Department, Far Eastern University-Nicanor Reyes Medical Foundation, Quezon City, Philippines Institute of Hot Spring Industry, Chia Nan University of Pharmacy and Science, Tainan, Taiwan (R. O. C.) 3 Shell Kwong Sir Enterprise Co., Ltd.,Tainan, Taiwan (R. O. C.) 4 Environmental Engineering Program, National Graduate School of Engineering, University of Philippines Diliman, Quezon City, Philippines 5 Department of Chemical Engineering, University of Philippines Diliman, Quezon City, Philippines 6 Department of Environmental Engineering and Science, Chia Nan University of Pharmacy and Science, Tainan, Taiwan (R. O. C.)
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The effectiveness of electrodialysis (ED) in removing inorganic arsenic (As) from aqueous solution was investigated. A tailor-made ED stack was used to perform current-voltage and optimization experiments in a recirculating batch mode. Samples were pre-oxidized with NaClO using 1:2 sample to oxidant weight ratio (RS :O) to transform 100% of As(III) to As(V) in 180 seconds. A high feed water conductivity of 1500 µS/cm and a low feed water conductivity of 800µS/cm had limiting currents of 595 mA and 525 mA, respectively. Optimum experimental conditions that provided maximum As separation were applied potential (E) of 12 V, feed flow rate (Q) of 0.033 L/s, feed concentration (C) of 662.0 µg L−1, and operating time (t) of 45 min, the most significant ones were applied potential, feed concentration and operating time. Model confirmation experiments showed a good agreement with experimental results with only 0.031% error. The total As in the diluate stream was 4.0 µg L−1, consisting of an average of 3.0 µg L−1 As(V) and 1.0 µg L−1 As(III). Keywords: Electrodialysis, arsenic removal, limiting current density.
Introduction The problem of high arsenic concentrations in groundwater systems is evident in many countries all over the world. Smedley and Kinniburgh [1] noted that major As-related incidents have been reported in Argentina, Bangladesh, Chile, Hungary, India, Mexico, the United States, Romania, Vietnam, China and Taiwan. By far, the largest effect was evident in the Ganges Delta between Bangladesh and India, where about 40 million people were at risk to As exposure.[2] Studies have discovered that As exposure causes many negative effects to human health, such as blackfoot disease (BFD), ischemic heart disease, hyperpigmentation, hyperkeratosis, diabetes, meningioma, and cancers of liver, kidney, bladder, prostate, lymphoid tissue, skin, lung, colon, and nasal cavity.[3–5] In fact, As is classified as a Group Address correspondence to Meng-Wei Wan, Department of Environmental Engineering & Science, Chia-Nan University of Pharmacy & Science, 60, Erh-Jen Rd., Sec.1, Jen-Te, Tainan 71710 Taiwan; E-mail: [email protected] Received July 9, 2013.
1 Human Carcinogen by the International Agency for Research on Cancer (IARC).[3,6] To control the damage caused by As contamination, World Health Organization has set a guideline value of 10 µg L−1 for arsenic in drinking water, which is the same value set by the European Union, the United States of America, Japan, and Taiwan. Common methods used for As removal from contaminated water are adsorption,[7–13] chemical oxidation,[14–15] phytoremediation,[16] photochemical,[17] and photocatalytic oxidation.[18] Membrane separation technologies such as reverse osmosis (RO), nanofiltration (NF), and ultrafiltration (UF) are also used to separate and transport ions such as As and yield a high-quality filtrate that is suitable for discharge or reuse.[19] However, UF is limited to physical sieving, which makes it less suitable for As removal, and NF allows changes in As speciation upon prolonged stay of treated water inside the filter.[20] Electrodialysis (ED) is an electrically driven membrane process that uses an applied electrical potential difference to transport ions through alternating cationic and anionic membranes arranged in parallel between an anode and a cathode,[21,22] resulting in two flow regimes—one
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stream concentrated with ions, and another more diluted stream.[23,24] ED has many advantages, such as it can tolerate feed waters with high chloride and sulfates, it does not need additional chemicals, and the recirculation promotes turbulent flow within the stack, requiring less applied potential for the system. In addition, ED utilizes highly cleanable, recoverable, and durable membranes.[25] With these many advantages, ED has the potential to remove ionic pollutants such as As from contaminated water. This study aimed to determine the capacity of a tailor-made ED stack in removing As from synthetic contaminated water down to the maximum contaminant level (MCL) of 10µg L−1, and optimize significant parameters for the most efficient As removal.
Materials and methods Arsenic solution Initial As concentrations of 700, 600, 500 and 50 µg L−1 were prepared from 1000 mg L−1 As stock solution formulated using 0.1320 g of (99.5% assay) arsenic trioxide (As2 O3 ) obtained from Acros Organics (Pittsburgh, PA, USA). Solid As2 O3 was dissolved in 10 mL of 4% (w/v) NaOH and 2 mL of 37% (w/w) HCl, and the solution was diluted to 100 mL using Ultrapure 18.2 m deionized water. The As solution was pre-treated with Merck sodium hypochlorite (NaClO) contaning 10% active Cl, 1.22 kg/L density and 1:2 sample to oxidant weight ratio (RS :O)[26] before it enters the ED stack, with a theoretical dose of 7.79 mL NaClO per mg As based on a stoichiometric reaction proposed by Ghurye and Clifford.[14] The pH of the solution was adjusted to 7.4–7.6 using NaOH and HCl. The chemical reaction for As (III) oxidation to As (V) follows:[26] H3 As O3 + NaCl O → H2 As O4− + Na + + Cl − + H+
Electrodialysis (ED) system The ED system, supplied by Shell Kwong Sir Enterprise Co., Ltd. (Tainan City, Taiwan), was composed of a single hydraulic and a single electrical stack with 20 cell pairs situated 0.9 mm apart. It was equipped with a control panel and a DC source of 500 W LD 66500 rectifier with a maximum input power of 300 V. The cationic (SKS-C) and anionic (SKS-A) membranes have a dimension of 40 cm × 20 cm and effective area of 11,200 cm2. The anode and cathode were made of titanium coated with ruthenium and iridium. A summary of the ED specifications is shown in Table 1. In addition, two 320 rpm IWAKI magnetic pumps (Saitama, Japan) were used to introduce the feed water and electrode rinse solution into the ED stack. The concentrated stream was used as electrode rinse and recirculated at a rate of
Mendoza et al. Table 1. The SKS electrodialysis (ED) stack specifications. Parameter
Values/Material
Number of hydraulic stages 1 Volume of stack 4,240 cm3 Anode Titanium coated with mixed oxides of ruthenium and iridium Cathode Titanium coated with mixed oxides of ruthenium and iridium Current 0–2 A Voltage 0–30 V Maximum Flow Rate 5 L/min Anion exchange membrane SKS-A (quarternary ammonium) Cation exchange membrane SKS-C (sulfonic acid group) Number of cell pairs 20 Membrane size 200 mm × 400 mm Spacer Polypropylene (PP) with 170 mmoˆ 360 mm flow pass length Spacer thickness 0.9 mm Effective membrane area 11,200 cm2 (sq.cm)
0.042 L s−1, as shown in Figure 1. The system was operated at 25 ± 1◦ C.
Experimental methods Conductivities of 1500 µS cm−1 and 800 µS cm−1 were used for the current-voltage experiments, while desalination tests used feed concentrations of 50, 500 and 1000 µg L−1. The following parameters were held constant: initial feed volume of 2 L, feed flow rate of 0.033 L s−1 or 2.0 liters per minute (LPM), and electrode flush volume of 4.5 L of tap water, the characteristics of which are indicated in Table 2. The electrode flush flow rate was kept at 0.042 L s−1 (2.5 LPM) to prevent formation of chlorine or hypochlorite in the electrode compartments.[23] The product/diluate stream and the concentrate stream were initially separated and recirculated into the ED stack until the conductivities of the two streams were constant. The rectifier was turned on, and current was initially set at 150 mA and increased stepwise, in increments of 50 mA, up to a maximum of 800 mA. After each increase, the system was allowed to reach steady state for 5 min, and the potential and conductivity of the diluate were recorded.[27] For optimization and model confirmation experiments, the controlled experimental parameters were the same as those used in the previous experiments. Applied voltage ranged from 5 to 20 V. The rectifier was turned off when a constant conductivity and current reading was observed continuously for 5 min. Total As in the feed, concentrate, and diluate streams, current and voltage values, and operating time were monitored throughout each experimental run.
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Arsenic removal from aqueous solutions by electrodialysis
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Fig. 1. Process flow diagram for the electrodialysis (ED) system.
Laboratory analysis The ORP and pH of the solution were monitored using Suntex pH-ORP meter SP-300 (Suntex Instruments Co., Ltd., Kaohsiung, Taiwan). Current and voltage measurements were performed using Hao Ling HL 833 digital ammeter and voltmeter. The conductivities of the diluate and concentrated streams were determined using Suntex EC410 digital conductivity meter. All the laboratory standards were freshly prepared to ensure proper standard calibration. Separation of As(III) and As(V) was done using a solid phase extraction membrane, Supelco LC-SAX strong anion resin (Shanghai, China), at an elution time of 1 min.[28] Table 2. Composition of tap water used as an electrode flush solution. Cations Na+ K+ Mg2+ Ca2+ Mn2+ Fetot Astot
Concentration mg/L 12.89 1.27 16.26 50.99 ND ND ND
Anions
Concentration Mg L−1
Cl− NO3 − SO4 2− HCO3 − PO4 3−
0.08 ND 74 131.75 2.17
Others: Eh = 463 mV; pH = 7.63; T = 24◦ C; EC = 490 µS cm−1. ND: none detected (700 µg L−1, SN and S were observed to vary inversely with C. This translates to high values of S when C is below 700 µg L−1, which was verified by optimization studies that showed maximum S was achieved at 662 µg L−1. According to ANOVA, Q does not significantly affect As separation percentage. This is due to the turbulence generated using a recirculated batch mode, where the thickness of the stagnant layer near the membrane-solution interface was reduced. High Q in the turbulent flow regime has no
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S (%)
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SN S
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Table 5. Signal-to-noise ratio of the controllable factors and their levels based on a LTB criteriaa. Level
Applied Potential
Feed Concentration
Feed Flow Rate
Operating Time
Low Middle High Deltaa Rank
38.903 39.672 39.858 0.955 1
39.211 39.527 39.579 0.394 4
39.249 39.644 39.540 0.483 3
39.132 39.548 39.753 0.621 2
a Delta is the amount of information in the design that is attributed to the factor or term. High delta means higher effects.
92
39.2
91 30
45
60
Operating Time (min.)
Fig. 6. Effects of (a) E, (b) Q, (c) C and (d) t on SN and S.
effect on E and t, as verified by Chandramowleeswaran and Palanivelu in their work.[23, 32] As shown in Figure 7, E has the greatest effect on S, followed by t and C. Therefore, based on the maximization of S and SN, numerical and
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Mendoza et al. Table 7. Characteristics of the feed, diluate and concentrate streams. Feed Water
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Parameters
Fig. 7. Contribution of each factor on As separation percentage.
graphical optimization yielded the same optimum conditions: E = 12 V, Q = 0.033 L s−1, C = 662 µg L−1 and t = 45 min.
pH EC, µS cm−1 Cations, mg L−1 Na+ K+ Mg2+ Ca2+ Mn2+ Fe (total) As (total) As (V) As (III) Anions, mg L−1 Cl− NO3 − PO4 3− SO4 2−
(Synthetic As solution)
Diluate Stream
Concentrated Stream
7.63 1489
4.8 35
5.3 1603
139.87 ND ND 2.858 ND ND 660 µg L−1 625 µg L−1 35 µgL−1
2.473 ND ND ND ND ND 4 µg L−1 3 µg L−1 1 µg L−1
686.20 349.30 33.90 12.65 ND ND 724 µgL−1 180 µg L−1 543 µg L−1
228 ND ND ND
0.11 ND ND ND
299.00 2.68 5.22 167.09
Synthetic As water solution concentration = 660 µg L−1. ND: None detected (< 5–10 ppb).
Model confirmation Based on the optimum conditions, namely E = 12 V, Q = 0.033 L s−1, C = 662 µg L−1 and t = 45 min, model confirmation runs were conducted using synthetic As water. In addition to the optimized conditions, electrode flush solution was maintained at 0.042 L s−1 and the stack was operated under the limiting current. The recirculation process and high electrode flush solution flow rate prevented significant deposition of Cl– ions and gases in the electrodes.[23, 34–36] Table 6 shows that an average of 99.471% As separation was obtained, with 4.0 µg L−1 total As in the diluate stream. The model prediction on S was 99.500%, where the total As was 3.0 µg L−1. A 0.031% error indicates a very good agreement between the model and experimental values for As separation percentage, implying that the Table 6. Results of the model confirmation experiments on As separation percentagea.
model can adequately predict the value of S. In terms of the inorganic As species, it was found that an average of 3.0 µg L−1 As(V) and 1.0 µg L−1 As(III) were detected in the diluate stream, values which are lower than the MCL of As in drinking water set by WHO and US EPA. Other characteristics of the feed, diluate and concentrate stream are listed in Table 7. Since a considerable amount of Na+ and Cl– were present in the feed stream during sample preparation and pre-oxidation stage, the amount of Na+ and Cl– in the feed and concentrate streams at the end of desalination were extremely important. Table 7 shows that Na+ and Cl– were depleted from the diluate stream and transported to the concentrate stream. Na+ was reduced from 139.875 to 2.473 mg L−1, while Cl– decreased from 228 to 0.110 mg L−1.
Conclusion
Experimental Results
Parameter
Run 1
Run 2
Average
Model Predicted S
Total As S (%)
3.992 99.399
3.036 99.543
3.514 99.471
3.301 99.500
Error % 6.453 0.031
Performed at optimum experimental conditions: E = 12 V; Q = 0.033 L s−1; C = 660 µg L−1; t = 45 min. Other ED settings: Electrode flush = 0.042 L s−1; Vfeed = 2 L; Vrecir. stream = 4.5 L. Recirculation ratio: Feed = 1.15; Concentrate = 0.85; Electrode flush solution = 1.0.
a
Inorganic As was efficiently removed from contaminated water using a tailor-made ED stack operated in recirculated batch mode. Limiting current was 595 mA for high conductivity As (1500 µS cm−1) and 525 mA for low conductivity As solution (800 µS cm−1), corresponding to an average LCD of 0.0455 mA cm−2 for the entire process. Taguchi L9 OA design with LTB criteria was used to obtain optimum experimental conditions, which were found to be as follows: 12 V applied potential (E), 0.033 L s−1 feed flow rate (Q), 662 µg L−1 feed concentration (C), and
Arsenic removal from aqueous solutions by electrodialysis 45-min operating time (t). ANOVA illustrated that the E, C and t were the significant factors that affect As separation (P = 0.0344). Predicted values were consistent with experimental values, with only 0.031% error for S when the operation was performed under optimum experimental settings. Total As in the diluate stream was 4.0 µg L−1, with an average of 3.0 µg L−1 As(V) and 1.0 µg L−1 As(III). Results indicate that ED operated under recirculated batch condition is an efficient process in removing As from contaminated water, achieving As concentrations below the 10 µg L−1 provisional guideline for treated water. The durability of the membranes makes an ED unit effective up to over 20 years, making the system an economical investment.
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Funding The authors would like to thank the Taiwan National Science Council for financially supporting this research under Contract No. NSC 101-2221-E-041-010-MY3, in collaboration with the Commission on Higher Education–Higher Education Development Program (CHED-HEDP) of the Republic of the Philippines.
References [1] Smedley, P.L.; Kinniburgh, D.G. A review of the source, behaviour and distribution of Arsenic in natural waters. Appl. Geochem. 2002, 17, 517–568. [2] Alam, M.G.; Allinson, G.; Stagnitti, F.; Tanaka, A.; Westbrooke, M. Arsenic contamination in Bangladesh groundwater: a major environmental and social disaster. Int. J. Environ. Health Res. 2002, 12(3), 235–253. [3] Chen, Y.-C.; Su, H.-J.J.; Guo, Y.-L.L.; Hsueh, Y.-M.; Smith, T.J.; Ryan, L.M.; Lee, M.S.; Christiani, D.C. Arsenic methylation and bladder cancer risk in Taiwan. Cancer Cause Contr. 2003, 14, 303–310. [4] Chan, P.C.; Huff, J. Arsenic carcinogenesis in animals and in humans: mechanistic, experimental, and epidemiological evidence. Environ. Carcin. Eco. Res. 1997, C15, 83–122. [5] Chiou, H.Y.; Hsueh, Y.M.; Liaw, K.F. Incidence of internal cancers and ingested inorganic arsenic: a seven-year follow-up study in Taiwan. Cancer Res. 1995, 55, 1296–1300. [6] International Agency for Research on Cancer (IARC). Arsenic and its compounds; In Monographs on the Evaluation of Carcinogenic Risk of Chemicals to Humans: Some Metals and Metallic Compounds; Author: Lyon, 1980; 23. [7] Mohan, D.; Pitmann, C.U. Jr. Arsenic removal from water/wastewater using adsorbents–A critical review. J. Hazard. Mater. 2007, 142, 1–53. [8] Lin, T.F.; Wu, J.K. Adsorption of arsenite and arsenate with phosphate and molybdate on oxide minerals. J. Soil Sci. Soc. Amer. 2001, 60 (1), 121–131. [9] Reed, B.E.; Vaughan, R.; Jiang, L. As(III), As(V), Hg and Pb removal by Fe-oxide impregnated activated carbon. J. Environ. Eng. 2000, 126 (9), 869–873. [10] Genc-Fuhrman, H.; Tjell, J.C.; McConchie, D. Increasing the Arsenate adsorption capacity of neutralized red mud (Bauxol). J. Coll. Interf. Sci. 2004, 27 (2), 313–320.
553
[11] Thirunavukkarasu, O.S.; Viraraghavan, T.; Subramanian, K.S.; Chaalal, O.; Islam, M.R. Arsenic removal in drinking water-impacts and novel removal technologies. Energ. Sour. 2005, 27 (1–2), 209–219. [12] Guibal, E. Interactions of metal ions with chitosan-based sorbents; A review. Sep. Purif. Technol. 2004, 38(1), 43–74. [13] Boddu, V.M.; Abburi, K.; Talbott, J.L.; Smith, E.D.; Haasch, R. Removal of Arsenic (III) and Arsenic (V) from aqueous medium using chitosan-coated-biosorbent. Water Res. 2008, 42 (3), 633–642. [14] Ghurye, G.; Clifford, D. As(III) oxidation using chemical and solidphase oxidants. J. Am. Water Works Ass. 2004, 96 (1), 84–96. [15] Ferguson, M.A.; Hoffmann, M.R.; Hering, J.G. TiO2 photocatalyzed As(III) oxidation in aqueous suspensions: reaction kinetics and effect of adsorption. Environ. Sci. Technol. 2005, 39, 1880–1886. [16] Dickinson, N.M.; Baker, A.J.M.; Doronila, A.; Laidlaw, S.; Reeves, K.D. Phytoremediation of inorganics: realism and synergies. Int. J. Phytorem. 2009, 11, 97–114. [17] Emett, M.T.; Khoe, G.H. Photochemical oxidation of arsenic by oxygen and iron in acidic solutions. Water Res. 2001, 35, 649–656. [18] Dutta, D.K.; Pehkonen, S.O.; Sharma, V.K.; Ray, A.K. Photocatalytic oxidation of Arsenic(III): evidence of hydroxyl radicals. Environ. Sci. Technol. 2005, 39, 1827–1834. [19] Harisha, R.S.; Hosamani, K.M.; Keri, R.S.; Aminabhavi, T.M. Arsenic removal from drinking water using thin film composite nanofiltration membrane. Desalination 2009, 300, 1–6. [20] US Environmental Protection Agency (US EPA). Drinking Water Regulation for Arsenic and Clarification to Compliance and New Source Monitoring; In National Primary Drinking Water Regulations; Implementation Guidance for Arsenic Rule; Author: Washington, DC, 2004; 6975–7066. [21] Smara, A.; Delimi, R.; Chainet, E.; Sandeaux, S. Removal of heavy metals from diluted mixtures by a hybrid ionexchange/electrodialysis process. Separ. Purif. Technol. 2007, 57(1), 103–110. [22] Sadrzadeh, M.; Rami, A.; Mohammadi, T. Separation of monovalent, divalent and trivalent ions from wastewater at various operating conditions using electrodialysis. Desalination 2007, 205, 53–61. [23] Chandramowleeswaran, M.; Palanivelu, K. Treatability studies on textile effluent for total dissolved solids reduction using electrodialysis. Desalination 2006, 210, 164–174. [24] Zhong, K.W.; Zhang, W.R.; Hu, Z.Y.; Li, H.C. Effect of characterization spacers in electrodialysis cells on mass transfer. Desalination 1983, 46, 243–252. [25] Valerdi-Perez, R.; Loez-Rodriquez, M.; Ibanez-Mengual, J.A. Characterizing an electrodialysis reversal plant. Desalination 2001, 137, 199–206. [26] Sorlini, S.; Gialdini, F. Conventional treatments for the removal of arsenic with chlorine dioxide, hypochlorite, potassium permanganate and monochloramine. Water Res. 2011, 31(2), 289–297. [27] Kocherginsky, N. Mass transport and membrane separations: Universal description in terms of physicochemical potential Einstein’s Mobility. Chem. Eng. Sci. 2010, 65, 1474–1489. [28] Lu, K.L.; Liu, G.W.; Wang, S.W.; Jang, C.S.; Lin, K.L.; Liao, V.H.C.; Chang, F.J. Assessing the characteristics of groundwater quality of aquifers in the black foot disease endemic area. J. Hazard. Mater. 2011, 185(2–3), 1458–1466. [29] Mohammadi, T.; Moheb, A.; Sadrzadeh, M.; Razmi, A. Modelling of metal ion removal for wastewater by electrodialysis. Separ. Purif. Technol. 2005, 41, 23–82. [30] Montgomery, D.C. Design and Analysis of Experiments, 3rd Ed.; John Wiley & Sons: New York, 1991. [31] Maghsoodloo, S.; Ozdemir, G.; Jordan, V.; Huang, C.H. Strengths and limitations of Taguchi contributions to quality, manufacturing, and process engineering. J. Manuf. Syst. 2004, 23, 373–381.
554
Downloaded by [UQ Library] at 13:16 03 November 2014
[32] Valerdi-Perez, R.; Berna-Amoros, L.M.; Ibanez-Mengual, J.A. Determination of working optimum parameters for an electrodialysis reversal plant. Separ. Sci. Technol. 2000, 35(5), 651– 666. [33] Lee, H.-J.; Strathman, H.; Moon, S.-H. Determination of limiting current density in electrodialysis desalination as a function of linear velocity. Desalination 2006, 190, 43–50.
Mendoza et al. [34] Tanaka, Y. Water dissociation in ion-exchange membrane electrodialysis. J. Membrane Sci. 2010, 350, 347–360. [35] Chao, Y.-M.; Liang, T.M. Feasibility study of industrial wastewater recovery using electrodialysis reversal. Desalination 2008, 221, 433–439. [36] Robinson, R.A.; Stokes, R.H. Electrolyte Solutions, 2nd Ed.; Academic Press, Inc.: New York, 1965.
