Hydroxylamine enhanced zero-valent copper/persulfate oxidation systems: Rapid corrosion of Cu(0) and reduction of Cu(II)

Zero-valent copper (Cu(0))-activated peroxodisulfate (PDS) generates reactive oxygen species (ROS) that effectively degrade azo dyes, but its application is limited by low Cu(I) conversion and narrow pH range. To overcome these barriers, this study introduced hydroxylamine (HA) to the Cu(0)/PDS system, boosting its oxidative capacity by accelerating the Cu(I)/Cu(II) redox cycle. Under the optimal conditions, the Cu(0)/PDS/HA system achieved a 78.5 % improvement in the degradation efficiency of orange II (AO7) within 10 min. UV-Vis spectroscopy, electron spin resonance (ESR) analysis, and scavenging experiments confirmed SO4 center dot- and center dot OH as the primary reactive species in the Cu(0)/PDS/HA system, with minimal Cu(III) formation. A Systematic investigation of operational parameters (initial pH, Cu(0) dosage, HA concentration, and PDS concentration) and water matrix components (Cl-, NO3-, SO42-, HCO3-, and humic acid) revealed their impact on AO7 removal. Furthermore, experiments in real water samples (tap, lake, and river water) validated the practicality of the Cu(0)/PDS/HA system, which was also demonstrated to effectively degrade other common pollutants. In conclusion, the present study provided an efficient strategy to bolster the oxidizing capacity of Cu(0)/PDS system, broadening its application potential for treating refractory organic pollutants.