Inert magnesium-doped Co₃O₄ spinel assembling catalytic membrane for instantaneous peroxymonosulfate activation and contaminants elimination

The practical application of heterogeneous Fenton-like processes in wastewater treatment is limited by inadequate catalyst recovery and limited mass transfer in traditional batch mode. Consequently, a catalytic membrane composed of inert magnesium (Mg)-doped Co₃O₄ spinel (MCO) was crafted to activate peroxymonosulfate (PMS) for the elimination of organic contaminants. The incorporation of the less electronegative Mg induced electronic polarization on the MCO surface, resulting in the generation of sufficient electron-rich Co centers, thereby amplifying its electron-donating properties in PMS activation and enhancing the inherent catalytic activity of the spinel. Regarding the catalytic membrane, the stacked porous structure of the MCO layer achieved reactive sites exposure, mass transfer enhancement, and reactive species availability. Remarkably, the MCO@polyethersulfone (PES) membrane/PMS system instantaneously activated PMS, displaying an elimination kinetic constant of 0.039 ms⁻¹ for tetracycline. The MCO@PES membrane exhibited exceptional catalytic performance and stability in long-term operational studies. Mechanistic investigations elucidated that the highly accessible SO₄[rad]⁻, [rad]OH, and ¹O₂ within the catalytic membrane facilitated the immediate elimination of contaminants. This study serves as a valuable reference for the application of transition metal spinel-based catalytic membranes in wastewater treatment.