Performance and mechanism of Bi2WO6/AgI/ZnFe2O4 double Z-scheme heterojunction photocatalyst for tetracycline hydrochloride degradation under visible light

Recent studies on the effective degradation of antibiotics in water bodies have attracted extensive attention in wastewater treatment. In this paper, a novel AgI/Bi₂WO₆/ZnFe₂O₄ catalyst has been synthesized with double Z-scheme heterojunction by ultrasonic assisted coprecipitation-mechanical mixing, and the degradation properties of tetracyclin hydrochloride (TC-HCl) have been studied. It was found that the degradation rate of TC-HCl by the AgI/Bi₂WO₆/ZnFe₂O₄ catalyst could reach 92.22 % within 90 min under visible light, and its pseudo-first-order reaction rate constant is 0.02016 min⁻¹, which is 3.17, 1.52, 2.23 and 1.09 times higher than AgI, Bi₂WO₆, ZnFe₂O₄, AgI/Bi₂WO₆ respectively. Meanwhile, the catalyst likewise exhibited good salt resistance, wide applicability and water adaptability to antibiotics. Through a series of characterization experiments, it is observed that the principal reason for the advancement of photocatalytic activity of AgI/Bi₂WO₆/ZnFe₂O₄ may lie in that the combination of AgI and ZnFe₂O₄ on Bi₂WO₆ enhances the visible light absorption capacity and adsorption performance of the catalyst, and forms a heterojunction with it to accelerate the separation of photogenerated carriers. In conclusion, this experiment has put forth a mechanism involving a dual Z-scheme heterojunction for electron transfer, which accounts for the photocatalytic degradation of TC-HCl under visible light illumination using the AgI/Bi₂WO₆/ZnFe₂O₄ composite material.