Preparation and characterization of zirconium-based magnetic sorbent for arsenate removal

In this study, a zirconium-based magnetic sorbent is developed by a coprecipitation technology. The characterization of the sorbent and its adsorption behavior are systematically investigated. It is shown that the sorbent has a small mean diameter of 543.7 nm, a specific surface area of 151 m(2)/g, and a pH(zpc) of 7. The sorbent has a rough surface and many pores developed on the surface. It has a molecular formula of ZrO(OH)(2) x 1.6 Fe(3)O(4) x 2.5 H(2)O, which was determined by the thermal gravimetric analysis, the elemental analysis, and the digestion experiments. The sorption equilibrium can be reached within 25 h. Better adsorption can be obtained at lower pH, and the optimal initial pH is from 2.6 to 3.3. The maximum adsorption capacity of 45.6 mg-As/g is achieved, which is much higher than many reported sorbents. FTIR spectra analysis indicates that -OH groups play an important role in the uptake. Some of the arsenate are reduced to arsenite after its adsorption onto the magnetic sorbent; the divalent iron in the sorbent may provide electrons for the reduction. A conceptual model for the adsorption of arsenate by the magnetic sorbent is proposed to illustrate the mechanism.