Ruthenium (hydr)oxides have recently been identified as high capacity sorbent materials for sequestration of contaminant oxyanions and organic ligands including: arsenic (III and V), chromate, tungstate, and dissolved organic matter analogs (oxalate and ascorbate). The sorption capacity of these oxides exceeds traditional sorbent materials (iron, aluminum, and manganese oxides) by 1 to 2 orders of magnitude. XAFS and pressure-jump relaxation measurements indicate that oxyanions form predominately bidentate surface complexs. Desorption data with arsenate indicates less than 0.5% of the adsorbed arsenate is removed during desorption with 0.1 M sodium hydroxide indicating the stability of adsorbed complex.