Functional photoelectrocatalytic membrane fabricated from ZnIn₂S₄, PVDF and carbon fibre for continuous removal of tetracycline

In this work, a functional photoelectrocatalytic membrane (PEM) electrode was prepared by loading polyvinylidene fluoride (PVDF) layer onto one side of carbon fibre felt (CF) and ZnIn₂S₄ microparticles onto the other side. The ZnIn₂S₄/CF/PVDF membrane was characterised by scanning electron microscope (SEM) equipped with an energy dispersive spectroscopy detector (EDS), Fourier transform infrared spectrometer (FT-IR) and BET surface area. The cyclic voltammetry (CV) and the photocurrent response measurements were also tested. The ZnIn₂S₄/CF/PVDF membrane had good electrical conductivity for photoelectrocatalytic degradation of tetracycline (TC). The optimized degradation condition with applied voltage of -0.3 ​V, pH of 6.5 and electrolyte concentration of 50 ​mmol ​L^-1 was determined in operating mode with effluent circulating to reactor, which can realize the TC removal efficiency of 87% and mineralization of 52% under reaction time of 3 ​h. The PEM remained stable during 4 days of continuous influent and effluent experiments. The yield of superoxide radical (·O₂^-) and hydroxyl radical (·OH) was 4.17×10^-5 ​mol ​L^-1 and 1.04×10^-5 ​mol ​L^-1, respectively. The degradation pathways of TC by photocatalysis, electrocatalysis and photoelectrocatalysis were compared and proposed, respectively. The generated intermediates during the continuous influent and effluent process were also identified.