Hydroxylamine-accelerated cobalt redox cycling enables peroxymonosulfate activation for sustainable water remediation

The practical application of cobalt-activated peroxymonosulfate (PMS) systems faces challenges of sluggish metal redox kinetics and environmental concerns. This study develops an innovative hydroxylamine (HA)-boosted Co(II)/PMS system that achieves rapid contaminant degradation based on the enhanced cobalt cycling. This system demonstrated exceptional performance, removing 90.02% of methylene blue within 15 min with a 5.8-fold increase in reaction rate compared to conventional Co(II)/PMS, while maintaining high efficiency across pH = 5-9 and in complex water matrices. HA functions through multiple concerted pathways: direct electron donation to PMS, rapid cycling of Co(II)/Co(III)/Co(IV) species, and a synergistic interaction with cobalt, and synergistic generation of multiple reactive species including SO₄·^-, ·OH, and Co(IV)=O. The system exhibited 46.78% mineralization efficiency and significantly suppressed toxic byproduct formation by 62%, addressing critical environmental safety concerns. Practical evaluations in real water samples (seawater and lake water) confirmed robust performance under environmentally relevant conditions. With its low cobalt requirement (2 μM) and excellent adaptability, this HA-enhanced system provides a sustainable and cost-effective solution for water treatment, aligning with green chemistry principles and industrial application requirements. The findings offer new insights into designing efficient metal-based advanced oxidation processes with minimized environmental impact.