Adding CuCo2O4-GO to inhibit bromate formation and enhance sulfamethoxazole degradation during the ozone/peroxymonosulfate process: Efficiency and mechanism

Abstract

In this work, a new type of catalyst CuCo₂O₄-GO was synthesized as a heterogeneous catalyst, and its control effect on bromate (BrO₃^-)generation and sulfamethoxazole (SMX) degradation in O₃/PMS process was studied. When 100 mg/L CuCo₂O₄-GO was added to the reaction system, the BrO₃^- concentration generated was 0.25 μM at pH = 7.0, 100 μM PMS addition and 1.30 mg/min ozone injection after 30 min reaction. Compared with the 6.58 μM BrO₃^- produced in the control group, the addition of CuCo₂O₄-GO prominently inhibited the generation of BrO₃^- and the inhibition efficiency reached 96.17 %. The addition of CuCo₂O₄-GO inhibited the conversion of hypobromous acid, thereby inhibiting the formation of BrO₃^-. Meanwhile, the first-order kinetic constant of the degradation of SMX by O₃/PMS and O₃/PMS/CuCo₂O₄-GO was 0.163 and 0.422 min^-1, respectively. The addition of CuCo₂O₄-GO promoted the degradation of SMX and the removal efficiency was reached above 98 % after 10 min reaction. According to the optimization of the GO loading ratio, it was found that CuCo₂O₄-GO with 20 % GO loading had the best promotion effect on the degradation of SMX, and almost completely inhibited the formation of BrO₃^-. Finally, in the repeated cycle experiment, CuCo₂O₄-GO could maintain its high catalytic activity and still had a high removal effect on SMX after three repeated uses. Besides, the BrO₃^- inhibition efficiency was above 80 % after two repeated uses. Therefore, adding synthetic CuCo₂O₄-GO is an effective way to control the formation of BrO₃^- and enhance the degradation of SMX in the O₃/PMS process.

Keywords: Bromate inhibition; CuCo(2)O(4)-GO catalyst; Ozone; Peroxymonosulfate; Sulfamethoxazole degradation.