Synthesis of CuWO4/Bi2S3 Z-scheme heterojunction with enhanced cephalexin photodegradation

Abstract

Herein, a new visible-light driven CuWO4/Bi2S3 Z-scheme composite was synthesized by a hydrothermal method. The photocatalyst was specified by XRD, FT-IR, EDX, SEM, TEM, HRTEM, BET, UV–vis DRS and PL analyses. The prepared heterojunction greatly improved the CFX photodegradation performance compared with pristine Bi2S3 and CuWO4 under LED illumination. The enhanced degradation efficiency was assigned to the higher visible-light adsorption spectrum, higher redox ability, effective separation and reduced recombination of photoinduced electron-hole pairs due to the Z-scheme construction. The point of zero charge (pzc) pH for the binary CuWO4/Bi2S3 heterojunction was calculated as 6.2 through pH drift method. The maximum degradation efficiencies in batch (76 %) and continoues flow (81.7 %) reactor were achieved at optimum values of the operating parameters as follows: irridation time = 150 min, CFX concentration = 10 ppm, pH = 3 and 0.8 g/L of catalyst dose. The optimum values for temperature and light intensity were 25 °C and 400 W/m2, respectively. According to the kinetic studies, the photocatalytic degradation of CFX followed the first order kinetic. The new Z-scheme composite indicated desirable reusability and chemical stability after five cycles. According to the trapping tests, the Z-schematic construction was proposed for the photocatalytic mechanism and superoxide and hydroxyl radicals were found to be the main active species in the degradation process. This work recommended a novel Z-scheme heterojunction as a new idea for CFX removal. © 2020