Boosting selective degradation of refractory dissolved organic matter in landfill leachate: Morphology-tunable ZnO via magnetron sputtering-hydrothermal synthesis

Landfill leachate, a complex refractory wastewater rich in high-concentration dissolved organic matter (DOM), resists conventional biochemical treatment and threatens aquatic ecosystems and human health. Developing efficient, stable DOM remediation technologies remains urgent. Herein, four ZnO photocatalysts with distinct morphologies (rod-like ZnO-1, flower-like ZnO-2, needle-like ZnO-3, rod-like arrayed ZnO-4) were synthesised via magnetron sputtering pretreatment combined with hydrothermal reaction. Characterisations showed ZnO-1 had a high oxygen vacancy density (62.05 %) and efficient photogenerated electron-hole separation. After 90 min of photocatalysis, ZnO-1 achieved the highest TOC (36.84 %) and DOM (63.16 %) degradation efficiencies, outperforming other samples. All catalysts preferred fulvic-like substance degradation over protein-like ones. Hydroxyl radicals (·OH) were the primary active species, synergising with superoxide radicals (·O 2 – ) and photogenerated holes ( h + ) to degrade DOM via C=C cleavage, aromatic ring opening and mineralisation. ZnO-1 retained >30 % activity after four cycles. This work provides a high-performance catalyst for refractory DOM remediation and guides morphology-controlled semiconductor catalyst design for complex wastewater treatment.