Zr-modified Zn–Co hydroxyfluoride solid solution with enhanced oxygen-related defect signatures for peroxymonosulfate activation toward sulfamethazine degradation

A one-pot hydrothermal route was used to prepare a Zr-modified Zn–Co hydroxyfluoride solid solution for peroxymonosulfate (PMS) activation toward sulfamethazine (SMZ). Zr addition was associated with a transition from nanorod-built, urchin-like particles to nanosheet-assembled microspheres and with increases in BET surface area, surface Co 2+ fraction, and oxygen-defect-related XPS/EPR signals. Under otherwise identical conditions (0.1 g L −1 catalyst, 0.4 mM PMS, and 40 mg L −1 SMZ), 5% Zr-ZCHF2 removed nearly all SMZ within 7 min and gave k obs = 0.542 min −1 , compared with 0.402 min −1 for ZCHF2. The activity enhancement was associated with the combined effects of increased surface area and Zr-induced surface-chemical changes, although their individual contributions could not be quantitatively resolved. Concordant quenching, D 2 O, and EPR results support a predominant contribution from 1 O 2 under the tested conditions, with radical species also participating. Premixing and electrochemical measurements are consistent with interfacial charge transfer assisting PMS activation and ROS formation. An 8 h membrane experiment demonstrated short-term feasibility of immobilized continuous-flow operation under the tested conditions.