Hollow BiOI/Bi5O7I hierarchical microsphere with S-scheme heterostructure for efficiently removal of tetracycline hydrochloride

Abstract

The problem of environmental pollution caused by the frequent use of antibiotics has attracted extensive attention. The heterojunction composed of various bismuth oxyiodide (such as BiOI, Bi4O5I2, Bi5O7I, etc.) were widely used in the treatment of antibiotic wastewater. Herein, a hollow BiOI/Bi5O7I hierarchical microsphere was constructed in-situ by annealing BiOI precursors synthesized by the solvothermal method. The phase transition temperature for the formation of heterojunctions has been investigated in detail. The obtained products were characterized by various technologies including transmission electron microscope (TEM), X-ray photon-electron spectroscopy (XPS), and so on. Experimental results suggested that 390-BiOI/Bi5O7I microsphere with hollow structure exhibits the optimal performance and maximum photocurrent response under visible light irradiation. The efficiency for degradation of tetracycline hydrochloride (TH) was up to 83 % in 100 min. The value still maintained at 95 % after the catalyst has been reused for four times. The capture experiment indicates that produced ·O2− played the most important role. But formed h+ and ·OH played a secondary role. The degradation intermediates were analyzed by Liquid Chromatography-Mass Spectrometry (LC-MS). Accordingly, the possible degradation pathways are proposed. An S-scheme based heterostructure photocatalytic mechanism is proposed aiming to explain the enhanced catalytic performance. The BiOI/Bi5O7I heterojunction with exceptional activity and stability is bound to expand applications in the field of water treatment.