Synergy between ultrasound irradiation and mechanical agitation driving persulfate activation for efficient degradation of organic pollutants

Advanced oxidation processes (AOPs) based on persulfate (PS) have been widely applied in environmental remediation owing to their ability to generate strong oxidizing reactive species. However, the traditional homogeneous and heterogeneous PS activation systems are prone to cause secondary pollution problems such as the leaching of toxic metals or the formation of sludge. To overcome these technical bottlenecks, this study constructed a ternary catalyst-free system coupling mechanical stirring (MA), ultrasonic irradiation (US), and PS, aiming to efficiently degrade organic contaminants in water bodies. In the proposed MA/US/PS system, peroxymonosulfate (PMS) demonstrates a significantly higher removal rate of Rhodamine B (RhB) than those of sodium persulfate (PDS), ammonium persulfate (PNS), and hydrogen peroxide (H 2 O 2 ) under the same conditions, which could be associated with the asymmetry structure of PMS, potentially facilitating its activation. Moreover, the MA/US/PMS system maintains stable catalytic activity over a broad pH range (3.09–10.52) and demonstrates excellent degradation efficiency in the presence of various coexisting anions and in actual water matrices. The effects of key operational parameters such as PMS dosage, agitation speed, ultrasonic power, and temperature on the degradation efficiency is comprehensively investigated. By combining radical quenching tests and electron paramagnetic resonance (EPR) techniques, the dominant reactive species responsible for RhB removal are identified. This work proposes an efficient, green, and catalyst-free activation strategy for PMS, which holds great potential for the advanced treatment of actual wastewater.