Mechanism study of ethyl xanthate degradation catalyzed by activated bentonite-based bismuth ferrites composite in visible-light-driven photo-Fenton process

Abstract

Ethyl xanthate (EX), a typical sulfide collector, has been widely used in froth flotation process and may cause serious environmental issues due to its toxicity. In the present study, using activated bentonite-based bismuth ferrites composite (A-BiFe/Bnet) as catalyst, the degradation of EX via a photo-Fenton process under visible light has been studied. The effects of initial pH, catalyst dosage, H2O2 dosage, reaction temperature, and coexisting anions on the removal ratio of EX were investigated. Moreover, the degradation of EX was analyzed by UV–visible, 1H NMR, LC-MS, FTIR and XPS spectral in detail. A possible mechanism of degradation EX catalyzed by A-BiFe/Bent was proposed based on the UV–visible, 1H NMR, LC-MS, FTIR and XPS techniques. It can be found that the sulfur atoms in ethyl xanthate were firstly adsorbed on the A-BiFe/Bent surface by the formation of Bi–S and Fe–S bonds. Then, EX molecules were transferred into some intermediates such as ethyl perxanthate (EPX), C2H5OH and S2O32−, finally degrading to even small inorganic molecules. Furthermore, a reasonable degradation pathway of EX was presented according to the results of characterization. Compare with that of the initial EX solution, the aquatic toxicity of the treated EX solution was weakened. Moreover, it was further found that A-BiFe/Bent exhibited high settleability, good magnetic property, remarkable reusability and stability in the photo-Fenton process. The present study provides a novel perspective on the degradation of EX in photo-Fenton process catalyzed by A-BiFe/Bent composite.