Enhanced in-situ remediation of VOCs-contaminated soil using alkaline activated persulfate with co-solvent assistance for improved removal efficiency

The development of efficient and sustainable remediation strategies is critical for treating volatile organic compound (VOCs)-contaminated soil. This study investigated the removal of methylbenzene (MB) and ethylbenzene (EB) from contaminated soil through co-solvent-assisted alkaline activation of persulfate (PS) system, The effect of the co-solvent in enhancing the desorption and solubilization of MB and EB was also evaluated. Under optimal conditions (C PS = 382 mmol L –1 , pH 12, 40% (v/v) acetonitrile (ACN) as co-solvent), the removal rates of MB and EB reached 41.5% and 50.9% on the 1 st day, significantly higher than those without ACN (11.4% and 16.2%, respectively). Moreover, the removal rates further increased to 91.7% for MB and 94.5% for EB on the 21 st day. The higher degradation rate of EB was attributed to the relatively weak benzylic C–C bond (76.4 kcal mol –1 ) and C–H bonds (85.4 kcal mol –1 ) at the ethyl site. Electron spin resonance (ESR) and quenching experiments confirmed that •OH and were the dominant reactive oxygen species, contributing 52.0% and 35.2% to MB degradation, respectively. The degradation of MB and EB proceeded via hydrogen abstraction, hydroxylation, electron transfer, and dealkylation, culminating in complete mineralization. Toxicity assessments using T.E.S.T. and bioluminescent bacteria assays indicated a significant reduction in ecological risk, with bioluminescence inhibition for MB and EB decreasing from 70.7% (very toxic) and 98.3% (very toxic) to 8.2% (low toxicity) and 5.6% (low toxicity), respectively. In summary, this study presents a promising strategy for the remediation of VOCs-contaminated soils.