ABSTRACT
Sorption onto iron oxides is a major determinant of arsenic concentrations in oxic aquatic systems. Silicic acid (H4SiO4) has a high affinity for the surfaces of iron oxides and many properties of iron oxides are altered by H4SiO4. As the iron (Fe) oxide surface concentration of H4SiO4 (ΓSi in moles Si adsorbed per mole Fe) increases the Point of Zero Charge (PZC) decreases, transformation to more stable phases is inhibited and the morphology can be altered (Swedlund et al. 2010). Numerous studies of natural and engineered aquatic systems have shown that H4SiO4 adsorbed on iron oxide surfaces can cause elevated solution concentrations of potentially toxic oxyanions of arsenic (As), chromium (Cr) and selenium (Se).
