Synergistic photocatalysis of Cr(VI) reduction and 4-Chlorophenol degradation over hydroxylated α-Fe2O3 under visible light irradiation

Abstract

A series of Fe2O3 materials with hydroxyl are synthesized in different monohydric alcohol (C2–C5) solvents by solvothermal method and characterized by XRD, BET, XPS, TG and EA. The amount of hydroxyl is demonstrated to be emerged on the surface of the as-synthesized Fe2O3 particles and their contents are determined to be from 7.99 to 3.74wt%. The Cr(VI) reduction experiments show that the hydroxyl content of Fe2O3 samples exacts great influence on the photocatalytic activity under visible light irradiation (λ>400nm) and that the Fe2O3 sample synthesized in n-butyl alcohol exhibits the optimal photocatalytic activity. The synergistic photocatalysis for 4-Chlorophenol (4-CP) degradation and Cr(VI) reduction over above Fe2O3 sample is further investigated. The photocatalytic ratio of Cr(VI) reduction are enhanced from 24.8% to 70.2% while that of 4-CP oxidation are increased from 13.5% to 47.8% after 1h visible light irradiation. The Fe2O3 sample keeps good degradation rates of mixed pollutants after 9 runs. The active oxygen intermediates O2−, OH and H2O2 formed in the photoreaction process are discovered by ESR measurement and UV–vis test. The photocatalytic degradation mechanism is proposed accordingly.