A Hybrid Sorbent Utilizing Nanoparticles of Hydrous Iron Oxide for Arsenic Removal from Drinking

Arsenic in drinking water, present primarily as inorganic As(III) (arsenite) or As(V) (arsenate), has been linked to a number of human ailments. This has prompted the United States Environmental Protection Agency (U.S. EPA) to lower the maximum contaminant level for arsenic in drinking water from 50 to 10 g/L. ArsenXnp was developed to satisfy the need for an efficient, reliable, and reusable material to meet this new arsenic standard. ArsenXnp is a hybrid sorbent consisting of nanoparticles of hydrous iron oxide distributed throughout a porous polymeric bead. This combines the excellent handling, flow char-acteristics and attrition resistance of conventional ion exchange resins with the well-documented arsenic affinity of hydrous iron oxides. In field tests, the resin maintained an effluent arsenic concentration be-low 10 g/L for 4 months of continuous operation with no mechanical problems and no pressure buildup across the resin bed. Arsenic is removed from solution due to the interaction with the nanoscale hydrous iron oxide surfaces rather than the anion exchange groups associated with the polymeric substrate, and the arsenic capacity is unaffected by common anions such as sulfate, chloride, or bicarbonate. Key words: arsenic; ArsenXnp; nanoparticles; drinking water; sorbent; hydrous iron oxide; hybri