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 339 m2/g. It was effective for both As(V) and As(III) removal; the maximum adsorption capacities were 46.1 and 120.0 mg/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 25 h, which were well fitted by the pseudo-second-order equation. Competitive anions hindered the sorption according to the sequence PO43->SiO32->CO32->SO42-. 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.

Graphical abstractArsenate is removed by Fe–Zr binary oxide through formation of inner-sphere surface complexes, while As(III) is removed by formation of both inner- and outer-sphere surface complexes.Figure optionsDownload full-size imageDownload high-quality image (76 K)Download as PowerPoint slideHighlights► The Fe–Zr binary oxide has high adsorption capacity toward both As(V) and As(III). ► Co-existing anions did not significantly influence the arsenic adsorption. ► As(V) is adsorbed by formation of inner-sphere surface complexes. ► As(III) is adsorbed by formation of both inner- and outer-sphere surface complexes.