Deep removal of arsenite from water with no need for pre-oxidation or inline oxidation

摘要

Arsenite is toxic and labile in subsurface media. Oxidation of arsenite to arsenate is a widely used strategy to enhance the removal of arsenic from water. However, the formation of unwanted oxidation byproducts is a major concern in drinking water treatment. Herein, a titanium xerogel (TAX) was fabricated with abundant surface hydroxyl groups and anchored acetylacetone (AA) molecules that served as powerful capturing sites for arsenic. The resultant xerogel had high adsorption capacity for arsenic without the need for any pre-treatment (306 and 254 mg/g for arsenate and arsenite, respectively, at pH 7.0). Columns packed with TAX could effectively lower arsenite concentration from 200 mu g/L to less than 10 mu g/L for up to 6000 bed volumes, which is more than 10 times greater than those achieved by well-developed iron or zirconium-based nanocomposites. Besides the excellent arsenite capturing ability, the TAX was also effective in removing heavy metals and commonly co-existing iron and manganese species in arsenic-contaminated groundwater. Moreover, the TAX had good antibacterial activity toward Escherichia coli. These attributes make the TAX a promising point-of-use adsorbent for residents in arsenic-contaminated areas, especially areas lacking infrastructure for water treatment.