Rapid synthesis of amorphous CoO nanosheets: Highly efficient catalyst for parachlorophenol degradation by peroxymonosulfate activation

Amorphous CoO nanosheets (CoO-A) were prepared in a short time and large scale for the first time via NaBH4 reduction, and applied as a catalyst for PMS activation to remove parachlorophenol (4-CP). Approximately 100% of 4-CP (10 mg/L) was degraded by PMS (0.25 mM) activated with CoO-A (0.03 g/L) with the kinetic constants of 0.428 min−1, which was 5.7 and 214.0 times higher than crystalline CoO/PMS and Co3O4/PMS systems, respectively. The superior catalytic performance was ascribed to the synergy of large surface area and amorphous structure of CoO nanosheets. Moreover, the effects of water matrix species and reaction parameters on 4-CP degradation were systematically investigated. The hydroxyl radicals and sulfate radicals were detected and involved in CoO-A/PMS system for 4-CP oxidation, and sulfate radicals made the primary contribution. The redox circles of Co2+/Co3+ on CoO-A surface were mainly responsible for the catalytic activation of PMS, and the possible activation mechanism and degradation pathway were proposed.