Tuning the heterostructure of Zn–Fe–O nanoparticles for highly efficient photocatalytic removal of U(vi) under different light intensities

Abstract

Fe₂O₃ has received a lot of attention due to its low cost, easy doping regulation, and convenient recovery. However, the low utilization of visible light, and higher transition energy and electron hole recombination rate make it difficult to be used in photocatalysis. Herein, ZnFe₂O₄ with different Zn/Fe ratios (Z_xFO, x is the ratio of zinc atoms to iron atoms) was synthesized by a co-precipitation method, and applied to reduce U(VI) under visible light irradiation. Different ratios of zinc were deposited on iron oxide nanospheres to precisely regulate the growth of the ZFO spinel. ZFO exhibits a lower interfacial charge transfer resistance, meaning that it has a faster electron transfer rate at the solid–liquid interface. The uranium removal rate of ZFO can reach more than 94% within 80 h under sunlight (intensity = 88 000–95 000 LUX), and can even reach more than 90% at 28 h and 103 h on cloudy (intensity = 20 000–30 000 LUX) and rainy days (intensity < 10 000 LUX). The broadened visible light response enables ZFO to effectively absorb a wider spectrum of light, which is favorable for photocatalysis even under low light intensity. This study is of great significance for designing potential high efficiency photocatalysts to eliminate U(VI) pollutants in different weathers.