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

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), O-2(center dot-), and carboxylate radicals (R-COO)(n)(3-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 O-2(center dot-) by itself. The special nature of the all solid state will simplify the operation process of MCRCSs.