A high-efficient and recyclable aged nanoscale zero-valent iron compound for V5+ removal from wastewater: Characterization, performance and mechanism.

An effective complex of nanoscale zero-valent iron (NZVI) supported on zirconium 1,4-dicarboxybenzene metals-organic frameworks (UIO-66) with strong oxidation resistance was synthesized (NZVI@UIO-66) for V5+ removal from wastewater. The results demonstrated that NZVI was successfully loaded on UIO-66 with a uniform dispersion, and then the composite was aged in the air which was named A-NZVI@UIO-66. V5+ could be removed quickly and completely using A-NZVI@UIO-66 in a wider pH range except for the pH = 1 condition. The reaction between A-NZVI@UIO-66 and V5+ was an endothermic process. Freundlich model with a better-fitted value showed the adsorption of V5+ on A-NZVI@UIO-66 was multi-layer heterogeneous adsorption and the adsorbed amount of V5+ was 397.23 mg V/g NZVI. Nitrate had a competitive inhibition on V5+ removal by A-NZVI@UIO-66. Mechanisms of vanadium elimination from the aqueous phase by A-NZVI@UIO-66 included physical adsorption, reduction, and complex co-precipitation, particularly the reduction dominated. The subsistent Zr-O bond in A-NZVI@UIO-66 provided a possible double reaction path by playing an electron donor, storage, or conductor role. After acid leaching, A-NZVI@UIO-66 represented good reusability in the removal of V5+ from the practical mine sewage.