Simultaneous photocatalytic redox removal of chromium(vi) and arsenic(iii) by hydrothermal carbon-sphere@nano-Fe3O4

Abstract

The coexistence of multiple-component contaminants, such as Cr(VI) and As(III) in acid mine drainage, brings more difficulties in the wastewater treatment. This study developed a novel strategy for simultaneous redox conversion and removal of Cr(VI) and As(III) in solution. By employing iron oxide encapsulated in a hydrothermal carbon sphere (HCS@Fe₃O₄), the synergistic photocatalytic reduction of Cr(VI) and oxidation of As(III) were markedly accelerated under simulated solar light irradiation. The transformed Cr(III) and As(V) were readily removed by forming Cr(OH)₃ and FeAsO₄ precipitates. The Fe(III)/Fe(II) cycle in the system, which was greatly reinforced by photocatalysis in the presence of HCS@Fe₃O₄, has been demonstrated to be critical in the redox of Cr(VI) and As(III). It can keep sufficient Fe(II) in solution to both directly reduce Cr(VI) and promote the generation of ˙OH for the oxidation of As(III). These findings provide an effectively synergistic conversion and removal strategy for implications in multiple-contaminated water treatment.