Preparation and evaluation of Zr-beta-FeOOH for efficient arsenic removal

A Zr-beta-FeOOH adsorbent for both As(V) and As(III) removal was prepared by a chemical co-precipitation method. Compared with beta-FeOOH, the addition of Zr enhanced the adsorption capacities for As(V) and As(III), especially As(III). The maximum adsorption capacities for As(III) and As(V) were 120 and 60 mg/g respectively at pH 7.0, much higher than for many reported adsorbents. The adsorption data accorded with Freundlich isotherms. At neutral pH, for As(V), adsorption equilibrium was approached after 3 hr, while for As(III), adsorption equilibrium was approached after 5 hr. Kinetic data fitted well to the pseudo second-order reaction model. As(V) elimination was favored at acidic pH, whereas the adsorption of As(III) by Zr-beta-FeOOH was found to be effective over a wide pH range of 4-10. Competitive anions hindered the adsorption according to the sequence: phosphate > silicate > bicarbonate > sulfate > nitrate, while Ca2+ and Mg2+ increased the removal of As(III) and As(V) slightly. The high adsorption capability and good performance in other aspects make Zr-beta-FeOOH a potentially attractive adsorbent for the removal of both As(III) and As(V) from water.