Photoreduction of Cr(VI) on B4C/AgFe2O4 composite

Abstract

The present study aimed to couple boron carbide (B4C) and silver ferrite (AgFe2O4) in the composite structure for the Cr(VI) photoreduction application. B4C was synthesized through a heat treatment process of a polymer precursor, polyvinyl borate (PVB). B4C/AgFe2O4 composites were obtained by the synthesis of AgFe2O4 using a auto-combustion technique in the presence of the as-prepared B4C. Fourier-transform infrared spectroscopy and X-ray powder diffraction analyses revealed that pure B4C, pure AgFe2O4, and the B4C/AgFe2O4 composites were synthesized successfully. Field emission scanning electron microscopy and N-2 adsorption-desorption studies exhibited that the as-prepared samples had similar surface morphology. The B4C/AgFe2O4 composites can absorb a significant part of the visible light and can be used as visible-light-driven photocatalyst, shown by UV-Vis absorption spectroscopy. Coupling B4C with AgFe2O4 in the composite structure provided enhancement in the Cr(VI) photoreduction efficiency. The Cr(VI) removal rate of pure B4C increased from 65.1% to 98.0% within 120 min. of visible light irradiation. The resulting enhancement in the Cr(VI) photoreduction efficiency was attributed to the suppression of the recombination of the photoexcited charge carriers on the composites, which was shown by photoluminescence spectroscopy. Under acidic conditions, the Cr(VI) removal rate in the presence of B4C/AgFe2O4 increased to almost 99%. The Cr(VI) photoreduction efficiency decreased to 89.9% when real wastewater spiked with Cr(VI) ions was used instead of the simulated Cr(VI) solution. It was observed that the prepared composites were reusable for the Cr(VI) removal process and magnetically separable from the Cr(VI) solution.[GRAPHICS].