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Abstract: 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 543.7nm, a specific surface area of 151m2/g, and a pHzpc of 7. The sorbent has a rough surface and many pores developed on the surface. It has a molecular formula of ZrO(OH)2·1.6Fe3O4·2.5H2O, which was determined by the thermal gravimetric analysis, the elemental analysis, and the digestion experiments. The sorption equilibrium can be reached within 25h. 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 45.6mg-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. [Copyright &y& Elsevier]

Abstract: Arsenate removal by a calcium alginate-encapsulated magnetic sorbent was studied. The morphology, microstructure, and composition properties of the sorbent were explored using X-ray diffraction (XRD) and scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDX). The SEM study demonstrates that there are many protuberances and pores on the sorbent surface; the XRD analysis reveals that the sorbent consists of Fe3O4. The EDX analysis indicates that the adsorption on the surfaces of sorbent is highly location dependent. The interaction characteristics between the arsenic and the functional groups on the sorbent were studied by Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). These studies indicate that the lattice oxygen in magnetite and the oxygen in hydroxyl of the calcium alginate play important roles in the sorption of arsenate ions onto the sorbent. More importantly, the XPS analysis demonstrates that the arsenate is reduced to arsenite after its adsorption onto the sorbent. It is proposed that divalent iron and the alcoholic group in alginate provide electrons to arsenate. A conceptual model for the adsorption is proposed to illustrate the mechanisms. [Copyright &y& Elsevier]