Visible-light-driven photocatalytic reduction of Cr(vi) on magnetite/carboxylate-rich carbon sheets

Abstract

A solid state ferricarboxylate photocatalyst, magnetite/carboxylate-rich carbon sheets (MCRCSs), was synthesized in air via a low-temperature carbonization process. In the structure of MCRCSs, both Fe₃O₄ nanoparticles and EDTA are homogeneously dispersed into carbon sheets forming ferricarboxylate complexes. Abundant ferricarboxylate complexes endow the MCRCSs with marked visible light absorption properties. MCRCSs exhibit excellent visible-light-driven photoreduction activities of Cr(VI). Fe(II), O₂˙⁻, and carboxylate radicals (R-COO)_n³⁻ⁿ* produced from the Fe(II)/Fe(III) photoredox cycle of MCRCSs are the main reductants for the reduction of Cr(VI). After the photoreduction of Cr(VI), MCRCSs can be magnetically separated from aqueous solution easily. Unlike a conventional ferricarboxylate photocatalyst (homogeneous and heterogeneous) fabricated from two components, iron species (dissolved or solid) and dissolved low-molecular-weight carboxylic acids, MCRCSs exist in the all solid state and every particle of MCRCSs is an individual unit which can release active radicals O₂˙⁻ by itself. The special nature of the all solid state will simplify the operation process of MCRCSs.