Experimental study on soil contamination degradation of pentachlorophenol at a chemical site

Pentachlorophenol (PCP) contamination in soil poses severe environmental risks due to its persistence and toxicity. While various remediation technologies exist, efficient and cost-effective in-situ degradation remains a challenge. In this study, a persulfate (PS) oxidation system activated by calcium oxide (CaO/Lime) was employed to remediate PCP-contaminated soil at a chemical site. The specific inorganic and organic free radicals, primarily sulfate radicals (SO4⋅−) and hydroxyl radicals (⋅OH), generated by the alkaline activation of PS were utilized to degrade PCP. The effects of key operating parameters—reaction time, PS dosage, water content, and lime dosage-were systematically investigated using response surface methodology (RSM). The results demonstrated that under alkaline conditions (pH > 12) maintained by CaO, a dosage of 0.25 g sodium persulfate per 50 g soil achieved a removal efficiency of 99.4% within 3 days, reducing PCP concentration from 1000.9 mg/kg to 6.1 mg/kg. The degradation mechanism involves the activation of PS by OH− released from lime, generating strong oxidizing radicals that dechlorinate and mineralize PCP. This study confirms that the lime-activated persulfate system is a promising, feasible strategy for the remediation of high-concentration organic contaminated sites.