Boosting photocatalytic degradation of antibiotics: The role of alcohol solvent on the morphology and bandgap structure of FeWO4 used for peroxymonosulfate activation

Abstract

Advanced oxidation process based on persulfate activation has been considered as a proven and effective means of rapidly removing organic pollutants from sewage. However, the low efficiency of heterogeneous catalysts still hinders its widespread application. Herein, FeWO₄ synthesized by solvothermal method, using different water/alcohol mixed solvents, is employed to photocatalytically activate peroxymonosulfate (PMS) for antibiotics degradation. Due to differences in solvent polarity, dissolution kinetics and physicochemical properties of different alcohols (ethanol, ethylene glycol, glycerol), the morphology, specific surface area, pore structure, photoelectric properties, band gap structure, and consequently the photocatalytic activity of FeWO4, are significantly affected. It is found that as the alcoholic hydroxyl groups increase, the FeWO₄ morphology gradually changes from nanorods to rice-grain-like nanoparticles, accompanied by an increase in specific surface-area and pores, an extension of the reaction-interface and light-absorption area, and an exposure of more active sites. Among them, FeWO₄ (DZ:GI = 2:8), synthesized in a deionized water/glycerol mixed solvent with a volume ratio of 2:8, exhibits the highest photocatalytic activity for activating PMS. Within 15 mins, the removal rate of tetracycline (TC) catalyzed by FeWO₄ (DZ:GI = 2:8) reaches 100 %. Free radical trapping experiments and electron paramagnetic resonance (EPR) spectra confirm that oxygen singlet (¹O₂) has a key role in TC degradation. Whereas hydroxyl radicals (•OH), holes (h⁺), superoxide radicals (•O₂^–), and sulfate radicals (SO₄^•−) play only a minor role.