Preparation and adsorption mechanism of rare earth-doped adsorbent for arsenic(V) removal from groundwater

Several types of rare earth metal-doped iron oxide adsorbents were prepared and their arsenic(As(V)) removal performance was evaluated. The cerium(Ce(IV))-doped adsorbent (CFA4) has the highest adsorption capacity. The crystalline properties (XRD), surface charge, FTIR and X-ray photoelectron spectroscopy (XPS) were determined for CFA. Based on the results of XRD, introduction of Ce(IV) ions into Fe(II)/Fe(III) systems results in the co-existence of Ce and Fe with the formation of minicrystals. The pHzpc (the pH value at which surface charge is zero) of CFA is 5.8 by the measurement of the acid-base titration method. By FTIR measurements, it is shown that the substitution of M-OH groups at CFA surface by As(V) ions plays an important role in the ad-sorption mechanisms of CFA. XPS spectra of CFA before and after adsorption of As demonstrate that Fe atom might be activated for As removal as a result of rare earth metal (Ce) doping.