Persulfate activation by copper tailings with hydroxylamine: efficiency, mechanism and DFT calculations

• Hydroxylamine significantly enhances persulfate activation by copper tailings. • The leached Fe and Cu is below the limits of surface water standards. • Hydroxylamine and Cu(I) mediate the Fe(III)/Fe(II) cycle. • DFT calculations indicate enhanced adsorption of persulfate by hydroxylamine. Solid waste used as a catalyst to treat wastewater is a feasible solution to achieve “waste treating waste”, but its treatment efficiency needs to be further improved. This study used waste copper tailings (CT) as a catalyst and hydroxylamine (HA) as an intensifier to construct a new type of persulfate-based advanced oxidation process (CT/HA/PS) to achieve continuous and efficient degradation of organic pollutants. The introduction of HA significantly increased the degradation efficiency of organic pollutants in wastewater. Besides, the presence of HA increased the TOC removal efficiency from 32.55% to 68.26%, and the cyclic degradation efficiency increased from 43.7% to 87.41%. Density functional theory (DFT) calculation and experiments together confirmed that HA not only enhanced the adsorption efficiency of CT and the utilization of PS, but also accelerated the Fe(III)/Fe(II) and Cu(II)/Cu(I) cycling on the CT surface, thereby generating more SO 4 - . XPS analysis suggested that the sulfides on CT surface also provided active sites for PS activation. More importantly, the concentration of metal elements leached from CT is negligible and will not cause secondary pollution. Therefore, this research not only proposes a new type of advanced oxidation process that efficiently degrading organic pollutants in wastewater, but also a new possible way of resource utilization and stabilization of tailings.