Regeneration of deactivated ozone catalysts in the treatment of high-alkalinity industrial wastewater

The deactivation of catalysts during actual operation is a critical issue. This study focuses on the deactivated catalyst generated from the prolonged treatment of genuine high-alkalinity wastewater. The acid washing and regeneration test of the deactivated catalyst were conducted utilizing acetic acid at several pH levels (pH = 3, 4, 5, 6, 7), followed by an assessment of catalytic performance and structural analysis. The regeneration of the deactivated catalyst at pH 3 yielded optimal performance results. The radical yield returned to 90.5 % of the original catalyst, which was 2.5 times greater than that of the deactivated catalyst. The degradation rate of the model pollutant (oxalic acid) approached that of the original catalyst, attaining 71.20 %, whereas the deactivated catalyst exhibited just 21.37 % degradation. The consistency of the regenerated catalyst's performance was validated by five consecutive experiments. The catalyst's structural characteristics were characterized using SEM, BET, and XRD techniques. The elevated alkalinity of the wastewater led to the precipitation of calcium carbonate on the catalyst surface, diminishing the pore size (from 17.27 nm to 12.99 nm) and obstructing the active sites by pore filling, ultimately resulting in its deactivation. Acid washing with acetic acid can efficiently eliminate the calcium carbonate layer on the catalyst's surface. The etching effect results in a modest increase in pore size relative to the original catalyst (18.54 nm), re-exposing the active sites and restoring catalytic activity. The acid regeneration catalyst has significant cost advantages over traditional replacement.