Performance and mechanism of sulfite-activated metronidazole degradation by copper-aminoclay

Aminoclay (AC) is a promising and suitable choice of catalyst carrier due to its high water dispersibility and stability, but has not yet been applied in sulfite-based advanced oxidation systems. In our work, copper aminoclay (CuAC) was prepared and successfully applied to activate sulfite for efficient degradation of metronidazole (MNZ). In the CuAC structure, both aminoclay structure and hydroxyl copper nitrate structure coexists, the decrease in the ratio of copper to 3-aminopropyltriethoxysilane increases the proportion of the aminoclay structure in the CuAC structure, which does not significantly affect the resistance, Zeta potential, and electron transfer capabilities of CuAC, but inhibits the reaction activity of copper sites. Both heterogenous and homogenous Cu(II) sites were capable of activating sulfite to generate sulfate radical in CuAC-sulfite system, and CuAC maintains desirable structural stability, which chemical structure and catalytic performance did not show significant changes after 6 repeated reactions. This work reported a new type of sulfite catalyst with structural stability and dispersibility, and provided reliable experimental results using aminoclay as a carrier for sulfite-based advanced oxidation reaction catalytic sites.