The low-cost and high-efficient photoreduction of Cr(VI) by oxalic acid synergized with the iron-loaded rice straw

Abstract

In the view of the possible synergy between the Fe(III)-induced photochemical reduction and the photocatalytic role of agriculture waste rice straw(RS), the iron-loaded rice straw (Fe-RS) was firstly prepared and successfully used in the photoreduction removal of Cr(VI) by oxalic acid (Ox). 1 mM of Cr(VI) in aqueous solution was completely removed in 6 min in Fe-RS/Ox/UV system. The Cr(VI) removal of Fe-RS/Ox/UV system was investigated through the effect of Ox concentration, initial Cr(VI) concentration, Fe-RS dosage and reusability of Fe-RS. The Cr(VI) removal mechanism of Fe-RS/Ox/UV system was discussed in detail, and the role of Fe-RS in Fe-RS/Ox/UV system was further revealed. The results showed that Fe-RS significantly enhanced the Cr(VI) photoreduction by Ox, and the loaded Fe component and the contained Si components on Fe-RS played an important synergized photocatalytic action for Cr(VI) removal in Fe-RS/Ox/UV system. The continuously photo-generated Fe(II) and CO2·- in the system reduced most Cr(VI). The separated electron (e-) and the produced CO2·- from the oxidation of Ox by hole (h+), which was due to the photocatalyzed SiO2 on Fe-RS, reduced some Cr(VI).