Enhanced photocatalytic reduction of Cr(VI) in aqueous solution by UV/TiO2 process in the presence of Fe(III): Performance, kinetic, and mechanisms

Photocatalytic reduction of Cr(VI) in aqueous solution was investigated using fabricated TiO2 film under UV irradiation with the presence of Fe(III). Effects of solution pH, UV light intensity, initial concentrations of Cr(VI) and Fe(III), and competitive inorganic ions on Cr(VI) photoreduction efficiency were discussed in this study. The presence of Fe(III) promoted the photoreduction of Cr(VI) by 34% in acidic medium through the Fe(III)/Fe(II) redox cycle. The Cr(VI) reduction rate was two times higher than that with the absence of Fe(III) in aqueous solution. Furthermore, the photonic efficiency was significantly promoted for experiments conducted with decreasing light intensity due to the inhibition of charge carrier recombination. A dual-site kinetic model based on the Langmuir-Hinshelwood mechanism for Cr(VI) photoreduction by UV/TiO2/Fe(III) process is first proposed and well fitted with the experiment data.