Mechanochemically tailored Cu(I)-rich catalyst triggers Cu(III) generation in ozone activation for hypersaline wastewater decontamination.

The performance of conventional heterogeneous catalytic ozonation (HCO) is severely impaired in hypersaline wastewater due to the scavenging of hydroxyl radicals (HO•) by chloride ions (Cl⁻). Herein, we fabricate a mechanochemically tailored Cu(I)-rich CuxO/MnOx catalyst to steer ozone activation toward a Cu(III)-mediated non-radical pathway. Ball milling promotes the formation of interfacial Cu-O-Mn linkages, enabling electron transfer from MnOx to Cu sites and stabilizing surface Cu(I). Using oxalate as a model recalcitrant contaminant, the CuxO/MnOx/O3 system achieves 93.2 %-100 % oxalate removal over a pH range of 4.0-9.0 and retains 81.7 % removal at 300 mM Cl-. Multiple lines of evidence confirm that Cu(III), rather than HO•, acts as the dominant oxidant. Notably, this system exhibits oxidative stability owing to continuous Cu(I)/Cu(III) redox cycling, which could be attributed to the electron replenishment to Cu sites from MnOx and O2•⁻ mediated by Cu-O-Mn bonds. Furthermore, when applied to real hypersaline wastewaters with total dissolved solids of 8.1-24.1 g L-1, the CuxO/MnOx membrane catalytic system attains 56.7 %-76.8 % TOC removal, representing a 1.6- to 2.7-fold enhancement over ozonation. This work provides a robust strategy for developing salt-resistant non-radical HCO systems for hypersaline wastewater treatment.