Enhanced Removal of Phorate in Polluted Soil by Co-Solvent-Augmented Alkaline Activation of Persulfate

Organophosphorus pesticide contaminated sites have been categorized as a global priority contaminated site type for remediation due to the excessive accumulation of persistent organic pollutants. This study investigated the removal effect of phorate (PHR) in polluted soil through co-solvent-assisted alkaline activation of persulfate (PS) system, and evaluated the contribution of the co-solvent to the desorption behavior and solubilizing effect of PHR. Results showed that a high PHR degradation rate of 56.1% was obtained on the second day under the following conditions: 40% (v/v) acetonitrile (ACN) as co-solvent, C PS  = 382 mmol L –1 , pH 12, and a W L /W s ratio of 1:2. It was a significant improvement over the system without co-solvent (19.9%). Moreover, a degradation rate of PHR was up to 93.9% on the 21st day under the optimized operating conditions, which was significantly higher than that observed in the persulfate oxidation system (13.1%) and the alkaline hydrolysis system (33.6%). The critical active species, including sulfate radicals \(S{O}_{4}^{\bullet -}\) and hydroxyl radicals (•OH) for the oxidation of PHR in contaminated soil during the alkaline-activated persulfate system were identified using electron spin resonance (ESR) and radical quenching experiments. The degradation pathways involved both hydrolytic pre-activation and radical mineralization. Furthermore, the luminescent bacteria tests demonstrated that the luminescence inhibition rate of the PHR-contaminated soil decreased from an initial value of 100% (highly toxic) to 16.2% (low toxicity) after remediation. In summary, this study offers a promising approach for the remediation of organophosphorus pesticide-contaminated soils.