Adsorptive removal of arsenic from water by an iron-zirconium binary oxide adsorbent

Arsenate and arsenite may exist simultaneously in groundwater and have led to a greater risk to human health. In this study, an iron-zirconium (Fe-Zr) binary oxide adsorbent for both arsenate and arsenite removal was prepared by a coprecipitation method. The adsorbent was amorphous with a specific surface area of 339m²/g. It was effective for both As(V) and As(III) removal; the maximum adsorption capacities were 46.1 and 120.0mg/g at pH 7.0, respectively, much higher than for many reported adsorbents. Both As(V) and As(III) adsorption occurred rapidly and achieved equilibrium within 25h, which were well fitted by the pseudo-second-order equation. Competitive anions hindered the sorption according to the sequence PO₄^3->SiO₃^2->CO₃^2->SO₄^2-. The ionic strength effect experiment, measurement of zeta potential, and FTIR study indicate that As(V) forms inner-sphere surface complexes, while As(III) forms both inner- and outer-sphere surface complexes at the water/Fe-Zr binary oxide interface. The high uptake capability and good stability of the Fe-Zr binary oxide make it a potentially attractive adsorbent for the removal of both As(V) and As(III) from water.