Visible light-driven sustainable peroxymonosulfate activation over Mn(III)-rich NiMn-LDH for deep degradation of emerging organic contaminants at high salinity condition: Mechanistic insights and toxicity assessment.

Developing high-performance and stable heterogeneous catalysts for the continuous activation of peroxymonosulfate (PMS) is crucial to remediate emerging organic contaminants (EOCs) in complex aqueous environments. Herein, we successfully construct Mn(III)-rich NiMn layered double hydroxide (Ni1.5Mn1-LDH-5) with fast electron transfer rate to efficiently catalyze PMS for the generation of multitudinous reactive species under visible-light irradiation, enabling fast degradation of electron-rich EOCs. The Mn(III)-initiated photo-assisted Fenton-like system achieves near-100% bisphenol A (BPA) removal within 1 min and a high mineralization of 81.83% within 60 min, substantially surpassing the most state-of-the-art catalyst/PMS systems. Multiple experimental results suggest that reactive Mn(III) species dominate the PMS activation, enabling simultaneous PMS oxidation and reduction; Ni sites act as electron mediators to substantially promote the photo-excited electrons transport for Mn(IV)/Mn(III) cycle and accelerate electron transfer between Mn sites and PMS molecules. These attributes synergistically enhance the valence cycling of [Mn(II) ↔ Mn(III) ↔ Mn(IV)], thereby creating continuous PMS activation sites and boosting the production of SO4•-/•OH, and 1O2. Furthermore, NiMn-LDH maintains outstanding contaminants removing performance under high salinity conditions, and shows excellent cyclic stability with completed degradation of BPA for 15 h continuous operation. The toxicity assessment and sprout growth experiment demonstrate that this system achieves deep mineralization and even complete detoxification of organic contaminants. This work yields new insight into developing high-performance catalysts for efficient remediation of refractory organic contaminants in complex water matrices.