Rapid electron transfer-promoted tetracycline hydrochloride degradation: Enhanced activity in visible light-coupled peroxymonosulfate with PdO/g-C3N4/kaolinite catalyst

•PdO anchoring on CNK could achieve rapid transfer between electrons.•The plentiful hydroxyl groups on kaolinite surface can accelerate the self-decomposition of PMS.•The valence state of Pd in 4 %P/CNK were close to + 2.•The degradation mechanisms under the vis/PMS system were proposed.