| A REVIEW OF ARSENIC INTERACTIONS WITH ANIONS AND IRON HYDROXIDES |
| Sunbaek Bang†, and Xiaoguang Meng |
| Center for Environmental Systems, Stevens Institute of Technology Hoboken, NJ 07030, USA |
Corresponding Author:
Sunbaek Bang ,Tel: 201-216-8994, Fax: 201-216-8303, Email: sbang@stevens.edu
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Received: December 6, 2003; Accepted: August 3, 2004. |
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| ABSTRACT |
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Interactions between anions and iron hydroxides and effects of anions such as silicate, phosphate, and bicarbonate on arsenic adsorption by iron hydroxides, are discussed in this review paper. Arsenic is strongly adsorbed on the surface sites of iron hydroxides through the formation of inner-sphere complexes. When arsenic coexists with silicate or phosphate in the suspension of iron hydroxides, arsenic adsorption to iron hydroxides decreases due to competitive adsorption of the anions. Especially phosphate and arsenic exhibit similar chemical behavior and compete for the adsorption sites. Carbonate decreases the sorption capacity of arsenite [As(Ill)] on iron hydroxides. The affinity of the anions for the adsorption site of iron hydroxides decreases in the following order: arsenate [As(V)] > phosphate > As(lll) > silicate > bicarbonate. Silicate, phosphate, and bicarbonate in separate solutions decrease As(Ill) adsorption at relatively low concentrations and surface site coverage whereas the anions have none or moderated effects on As(V) adsorption. However, As(V) adsorption is dramatically decreased in multi-anions solution. |
| Keywords:
arsenic | iron hydroxides | anion effect | adsorption | interaction |
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