Enhanced non-radical activation of persulfate with pompon-like NiO microspheres for removing sulfamethoxazole in water

The development of efficient heterogeneous catalyst for non-radical activation of persulfate (PS) is highly desired for removing organic pollutants in water. Herein, four NiO samples were prepared by different methods, and their performance for PS activation was investigated using sulfamethoxazole (SMX) as the target pollutant. The structure, surface chemical state, and redox ability of these samples were measured by various characterization techniques, and the key property affecting PS activation efficiency was explored. The results showed that the degradation of SMX by these samples all followed the non-radical mechanism, and the activated PS was the dominant active species. Among them, pompon-like NiO microspheres exhibited the highest activity due to its large surface area and especially high oxidation ability. Catalyst with high oxidation ability or reducing ability should facilitate the non-radical or radical activation of PS, respectively. SMX was completely removed by pompon-like NiO microspheres within 10 min, and the reaction rate constant was calculated to be 0.4199 min−1. An adsorption–degradation experiment was designed to verify the high stability and oxidation potential of the adsorbed PS on NiO surface. Pompon-like NiO microspheres exhibited good reusability, and its performance was barely affected by water quality, demonstrating its potential application in water treatment.