| Popis: |
Selenium has emerged as a contaminant of concern, which has natural and anthropogenic sources. Treatment of aqueous selenium levels to achieve stringent regulatory water limits in the range of from 5 to 50 μg Se/L poses a challenge. Two anionic forms of inorganic selenium are Se(IV) (selenite) and Se(VI) (selenate) which are the dissolved species of Se most commonly present in water sources. Se(IV) is present under reducing conditions while Se(VI) dominates in oxidizing environments. This chapter summarizes the chemical treatment methods for removing selenium from water, which include adsorption and reduction processes. Examples are given for adsorbing Se(IV) and Se(VI) onto solid surfaces of double hydroxides, activated alumina, chitosan, peanut shells, and biopolymers. Reduction techniques to remove Se(IV) and Se(VI) in water involve the application of zero-valent iron, iron(II) sulfide, and oxides of Fe(II) and Fe(III). Photocatalytic approaches can also be applied to reduce Se(IV) and Se(VI) to obtain removal of selenium from water. |
