Deep oxidation and removal of arsenite in groundwater by rationally positioning oxidation and adsorption sites in binary Fe-Cu oxide/TiO2

摘要

Integration of oxidation and adsorption of adsorbents is highly desired to deep remove As(III) in groundwater. In this study, a superparamagnetic Fe3O4@SiO2@Fe2O3-CuO/TiO2(Mag@Fe-Cu/TiO2) adsorbent was synthesized using step-by-step precipitation process. The TiO2 nanoparticles were rationally positioned onto the shell of Fe2O3-CuO for oxidization of As(III). The Fe2O3-CuO binary oxide significantly improved As(III, V) adsorption compared to individual oxide (Fe2O3 or CuO). The ingenious design of the adsorbent could give full play to oxidation and adsorption functions. As a result, Mag@Fe-Cu/TiO2 showed much better As(III) removal performance than Mag@Fe-Cu-TiO2 prepared by co-precipitation. The maximal adsorption capacity of Mag@Fe-Cu (7)/TiO2(8.74) for As(III) reached to 17.49 mg/g under UV irradiation. The removal of As(III) in groundwater was tested using Mag@ Fe-Cu/TiO2 adsorbent. Almost all the As(III) were removed under UV irradiation (t = 24 h for C-0 = 1-5 mg/L or 12 h for C-0 = 20-1000 mu g/L, adsorbent dose = 1 g/L, pH = 7.0, T = 25 degrees C). Moreover, it could be easily separated from treated water with an external magnet and well reused maintaining a high As(III) adsorption capacity. Furthermore, the adsorbent could effectively treat arsenic spiked natural groundwater. The adsorption followed the inner-sphere complex mechanism via the chemical interactions between metal (M: Fe and Cu) and arsenic species (As) forming M-O-As bonds.