Methods In this paper， CuO-kaolinite composite was fabricated using a hydrothermal calcination method. Initially，1. 0 g of sepiolite was mixed with 50 mL of distilled water and stirred for 0. 5 h. Then， different amounts of Cu （NO₃）₂ ·3H₂O were added to the solution and stirred for 10 min. Subsequently， an ammonia-water solution （v：v=1：1） was added drop-wise to adjust the pH value to 7. 5~8 at room temperature. After stirring for 15 min， the mixture was transferred into a 100 mL Teflon-lined stainless-steel autoclave and heated at 150 ℃ for 5 h. The resulting products were washed， dried， ground， and then calcined in a muffle furnace at 250 ℃ for 3 h. Finally， after simple grinding， the CuO-kaolinite composite with different mass ratios of CuO and kaolinite was synthesized. The crystal structure， surface chemical state， microstructure， specific surface area，

Results and discussion The effects of different mass ratios of CuO and kaolinite， catalyst dosages， PMS dosages， initial concentration of norfloxacin （NOR）， initial pH of the solution， and coexisting anions on the degradation efficiency of NOR were investigated. The experimental results indicated that higher NOR degradation efficiency was achieved with the CuO-kaolinite-PMS system compared to other oxidation systems. Specifically， when the mass ratio of CuO and kaolinite was 40%， the CuO-kaolinite composite exhibited optimal catalytic performance. At a catalyst dosage of 1. 5 g/L， a PMS dosage of 1. 0 mmol/L， and an initial NOR concentration of 10 mg/L， the degradation efficiency of NOR after reacting for 60 min was about 76. 21%. An increase in catalyst dosage initially led to a significant enhancement in NOR degradation efficiency， followed by a slight increase， while excessive PMS had an inhibitory effect. A higher initial concentration of NOR gradually decreased its degradation efficiency. Within a wide pH range， high NOR removal efficiency was achieved in the composite-PMS system， demonstrating its good practical application potential. The coexisting Cl^-， HCO₃^-， and H₂PO₄^-in this system exhibited inhibitory effects on the NOR degradation， while NO₃^- had a relatively minor impact. In addition， the catalytic mechanism of the CuO-kaolinite composite for NOR degradation was systematically analyzed， revealing that the valence cycle between the Cu²⁺ and Cu⁺ in CuO-kaolinite composite was involved in the activation of PMS. The main active species in the reaction system were singlet oxygen （¹ O₂）， while superoxide radicals （O₂ ^•-）， sulfate radicals （SO₄ ^•-）， and hydroxyl radicals （^• OH） also contributed to the NOR degradation.

Conclusion The introduction of kaolinite carriers allows for the formation of CuO nanosheets with smaller grain sizes， which are dispersed and deposited on the surface of kaolinite. The specific surface area and pore volume of the composite are greater than those of pure CuO. In CuO-kaolinite composite， CuO nanosheets are uniformly dispersed and deposited on the surface of kaolinite carriers， significantly reducing their self-aggregation and exposing more reactive sites， thereby enhancing the activation efficiency of PMS. As a result， more active species， such as¹O₂， O₂ ^•-， SO₄ ^•-， and^•OH， are continuously produced， which contributes to the NOR degradation. In summary， this work provides a new approach for the structure design and preparation of mineral-based PMS catalysts with efficient catalytic performance and adsorption capacity， guiding their application in antibiotic wastewater treatment.

Keywords：CuO； kaolinite； peroxymonosulfate； norfloxacin