Fabrication of novel ZnO@BiOBr/UiO-66-NH2 core-shell heterojunction for improved tetracycline degradation

A novel ternary heterojunction of ZnO-nanorods/BiOBr/UiO-66-NH2 Z-scheme with improved charge separation ability was prepared and characterized by XRD, FTIR, XPS, FE-SEM, EDX, TEM, HRTEM, BET, UV–vis DRS, PL, EIS, and TGA analyses. The degradation of the tetracycline (TC) by the synthesized photocatalyst was investigated at the optimal molar ratio of ZnO: BiOBr: UiO-66-NH2 = 3: 1: 0.17. The ternary heterojunction showed significant development in photodegradation compared with ZnO/BiOBr, and pure UiO-66-NH2. The optimal operational conditions were determined by the Box-Behnken design at pollutant concentration = 20 ppm, catalyst dose = 0.48 g/L, pH = 7.2 and irradiation time = 90 min. The maximum degradation efficiency reached 96.6 % at the optimum conditions. In addition, at optimal conditions, the effect of immobilization of the ternary photocatalyst was investigated on FTO, and the TC degradation efficiency was about 98.2 %. The new ternary heterojunction showed good chemical stability and recoverability after 4 cycles. Based on the trapping experiments, O2–• and OH• improved the degradation process of TC. The toxicity test was studied by the growth of Escherichia coli bacteria and confirmed the rapid toxicity removal process by ZnO-nanorods/BiOBr/UiO-66-NH2 photocatalysis.