Construction of F-F@FeVO4/ZnCo2O4 photocatalysts with heterojunction interfacial enhancement and surface oxygen vacancies for the removal of tetracycline, sulfamethoxazole, ciprofloxacin and Cr(VI)

For the purpose of promoting application of green and sustainable photocatalytic materials in real-world com-posite wastewater remediation, developing stable, efficient and pollution-free treatment devices is necessary and actually urgent. We grew vertical nanosheets consisting of FeVO4/ZnCo2O4 directly on the surface of iron foam (F-F), which intertwined to form F-F@FeVO4/ZnCo2O4 p-n heterojunction catalysts with a three-dimensional framework structure. The F-F@FeVO4/ZnCo2O4 photocatalyst showed excellent photocatalytic performance achieving 96.32%, 92.85%, 95.92% and 97.17% removal efficiencies in the presence of tetracycline (TC), sul-famethoxazole (SMX), ciprofloxacin (CIP) and Cr(VI), respectively. In addition, the photocatalyst was assembled into a simulated photoreactor, enabling the continuous treatment of composite wastewater. The reactor achieved removal efficiencies of 94.81%, 90.02%, 94.17% and 97.15% for TC, SMX, CIP and Cr(VI), respectively, in a 100 min reaction. Furthermore, only after ten photocatalytic cycles under visible light does the catalytic efficiency of the reactor decrease slightly. The excellent performance may be attributed to unique structures that reduce visible light reflection and provide highly reactive reaction centers, as well as surface oxygen vacancies and heterojunctions to accelerate photocarrier separation and free radical generation. The high porosity of F-F also reduces the obstruction of visible light between branches. Moreover, the method of growing FeVO4/ZnCo2O4 active components on F-F overcomes a number of problems (increased interfacial charge transfer impedance, poor structural stability and nonuniform distribution, etc.) associated with conventional methods of combining nanomaterials with recyclable substrates (loading, introduction of adhesives and hybridization, etc.). Density functional theory (DFT) calculations explain the mechanism of interface enhancement.