Drinking water arsenic oxidation

Whereas studies have been carried out on the factors (surface coverage, residence time, pH) which influence the desorption of arsenate previously sorbed onto oxides, phyllosilicates and soils (O Reilly et al. 2001 Liu et al. 2001 Arai and Sparks 2002 Violante and Pigna 2002 Pigna et al. 2006), scant information are available on the possible desorption of arsenate coprecipitated with iron or aluminum. In natural environments arsenic may form precipitates or coprecipitates with Al, Fe, Mn and Ca. Coprecipitation of arsenic with iron and aluminum are practical and effective treatment processes for removing arsenic from drinking waters and might be as important as sorption to preformed solids. 

Thirunavukkarasu OS, Viraraghavan T, Subramanian KS (2003) Arsenic removal from drinking water using iron oxide-coated sand. Water Air Soil Poll 142 95-111... 

One way to remove arsenic from drinking water in Bangladesh is by coprecipitation with Fe(OH)3.6 Fe(ll) or Fe(s) is added to the water and allowed to oxidize in air for several hours to precipitate Fe(OH)3. After filtration through sand to remove solids, the wdter is drinkable. 

Sylvester, P., Westerhoff, P., Moller, T. et al. (2007) A hybrid sorbent utilizing nanoparticles of hydrous iron oxide for arsenic removal from drinking water. Environmental Engineering Science, 24(1), 104-12. 

EC is a simple, efficient, and promising method to remove arsenic form water. Arsenic removal efficiencies with different electrode materials follow the sequence iron > titanium > aluminum. The process was able to remove more than 99% of arsenic from an As-contaminated water and met the drinking water standard of 10p,gL 1 with iron electrode. Compared with the iron electrodes, aluminum electrodes obtained lower removal efficiency. The plausible reason for less arsenic removal by aluminum in comparison to iron could be that the adsorption capacity of hydrous aluminum oxide for As(III) is much lower in comparison to hydrous ferric oxides. Comparative evaluation of As(III) and As(V) removal by chemical coagulation (with ferric chloride) and electrocoagulation has been done. The comparison revealed that EC has better removal efficiency for As(ni), whereas As(V) removal by both processes was nearly same (Kumar et al. 2004). 

Chatteijee A, Das D, Mandal BK, Chowdhury TR, Samanta G, Chakraborti D (1995) Arsenic in groundwater in six districts of West Bengal, India The biggest arsenic calamity in the world. Part I. Arsenic species in drinking water and urine of affected people. Analyst 120 643-650 Cheah S-F, Brown GE Jr, Parks GA (1997) The effect of substrate type and 2,2 -bipyridine on the sorption of copper(II) on silica and alumina. In Voigt JA, Bunker BC, Casey W, Wood , Crossey LJ (eds) Aqueous Chemistry and Geochemistry of Oxides, Oxyhydroxides, and Related Materials, Mat Res Soc SympProc 432 231-236... 

Arsenic in drinking water supplies can be removed by a variety of treatment processes including those cited in Table 1, which also lists the typical applications of each process. All these processes do a much better job of removing As(V) compared with As(III). Thus, before using these processes, it will often be necessary to oxidize As(in) to As(V) using chlorine or an alternative oxidant. This chapter focuses arsenic treatment by metal-oxide adsorption (MOA), ion exchange (IX), and iron (III) coagulation-microfiltration (C-MF), because these processes have proven to be the most efficient and cost effective in bench- and pilot-scale studies, especially for point-of-use (POU), point-of-entry (POE), wellhead, and small community treatment systems. 

P Frank, DA Clifford. Arsenic III oxidation and removal from drinking water. U.S. Environmental Protection Agency Report, Cincinnati, OH, 1986. 

Arsenic contamination in drinking water is a global problem. It is usually present in water in two different oxidation states depending on redox and pH conditions. 

---