Peroxymonosulfate activation by NiCoFe-layered double hydroxides for enhancing contaminant elimination in water

Peroxymonosulfate (PMS)-based advanced oxidation processes (AOPs) have emerged as promising technologies for water purification. The development of multi-metal catalysts has attracted considerable attention in recent years due to the limited efficiency of single-metal catalysts. Herein, a novel trimetallic layered double hydroxide (NiCoFe-LDH) was rationally designed to boost PMS activation for the removal of emerging contaminants. It was found that the NiCoFe-LDH/PMS system achieved a total organic carbon removal of 43.5 % for oxytetracycline (OTC), which was twice that of unary-metal LDHs and surpassed most reported data. Mechanistic studies revealed a dual-pathway PMS activation mechanism: (1) surface Ni(II)/Co(II)/Fe(III/IV) sites decomposed PMS into free and surface-bound sulfate radicals and hydroxyl radicals, and (2) PMS bound to the NiCoFe-LDH surface to generate active complexes (PMS*) and subsequently electrons were transferred from OTC to PMS* thereby being oxidized by electron-transfer pathways. The wide pH adaptability (3-11) and high efficiency in real water matrices indicate the high potential of NiCoFe-LDH in practical applications. This work provides new insights into the rational design of multi-metal catalysts and their application in AOPs-based sustainable water treatment.