Ultrasonically activated persulfate process for the degradation of phenanthrene in soil-washing effluent: Experimental, DFT calculation and toxicity evaluation

Soil-washing (SW) has been widely used to treat PHE in soil, but this has led to the problem of large quantities of contaminated soil-washing effluent (SWE) that are difficult to treat effectively. The primary objective of this study was to investigate the degradation of phenanthrene (PHE) in SWE with Alkyl glycoside (APG) as a surfactant through the implementation of ultrasound (US)/persulfate (PS) oxidation technique. The findings of the study demonstrated the effectiveness of the US/PS system in facilitating the degradation of PHE, with the degradation process accurately described by a first-order kinetic model. With the reaction conditions optimized, an impressive degradation efficiency of 79.8% was achieved for PHE. Notably, the presence of common water components such as Cl-, HCO3- , H2PO4- , and HA had an impact on the degradation process. The degradation mechanism and degradation pathways of PHE were determined by free radical burst test, electron paramagnetic resonance (EPR), density functional theory (DFT) calculations gas chromatography/mass spectrometry (GC/MS) tests, and the eco-toxicological evaluation of PHE and its intermediates was carried out by using ECOSAR software. Most importantly, physicochemical properties were analysed, structural characterisation and DFT calculations were carried out for the high concentration of APG compounds in the solution environment throughout the degradation process. The result showed that as the reaction progressed, the degradation radicals only opened the APG structure and degraded the PHE encapsulated in it. However, the APG compound itself showed little change. These comprehensive investigations contribute novel insights into the green and efficient treatment of PHE-containing SWE.