Photocatalytic reduction performance and mechanisms of Cr(VI) by illite-g-C3N4 under visible light

Abstract

Cr(VI) has great solubility and mobility in water, and is a class of highly toxic heavy metals. Illite modified g-C3N4 (IL-CN) materials were successfully synthesized and their photocatalytic activities for Cr(VI) reduction under visible light irradiation were tested in this study. Due to carbon and oxygen vacancies and defects by IL-CN, the modified IL-CN materials exhibited larger specific surface area and pore volume, and stronger electron-hole pair separation capacities. As a result, the IL-CN catalysts exhibited excellent catalytic activity for Cr(VI) reduction. Approximately 91.8 % of Cr(VI) was reduced to Cr(III) after 60 min of treatment under photocatalytic reaction of 2/IL-CN, which was much higher than those of the single g-C3N4 and single illite materials. There existed an optimum ratio of illite/g-C3N4 to realize the greatest Cr(VI) reduction efficiency. Acidic conditions and relatively higher dosage of IL-CN were conducive to Cr(VI) reduction. Cr(VI) reduction was mainly initiated by free electron in the photocatalytic system of modified IL-CN materials, while the role of O2− was quiet weak. Furthermore, the stability and recycling of the IL-CN catalysts were evaluated.