Efficient Remediation of p-chloroaniline Contaminated Soil by Activated Persulfate Using Ball Milling Nanosized Zero Valent Iron/Biochar Composite: Performance and Mechanisms

In this study, efficient remediation of p-chloroaniline (PCA)-contaminated soil by activated persulfate (PS) using nanosized zero-valent iron/biochar (B-nZVI/BC) through the ball milling method was conducted. Under the conditions of 4.8 g kg⁻¹ B-nZVI/BC and 42.0 mmol L⁻¹ PS with pH 7.49, the concentration of PCA in soil was dramatically decreased from 3.64 mg kg⁻¹ to 1.33 mg kg⁻¹, which was much lower than the remediation target value of 1.96 mg kg⁻¹. Further increasing B-nZVI/BC dosage and PS concentration to 14.4 g kg⁻¹ and 126.0 mmol L⁻¹, the concentration of PCA was as low as 0.15 mg kg⁻¹, corresponding to a degradation efficiency of 95.9%. Electron paramagnetic resonance (EPR) signals indicated SO₄•⁻, •OH, and O₂•⁻ radicals were generated and accounted for PCA degradation with the effect of low-valence iron and through the electron transfer process of the sp² hybridized carbon structure of biochar. 1-chlorobutane and glycine were formed and subsequently decomposed into butanol, butyric acid, ethylene glycol, and glycolic acid, and the degradation pathway of PCA in the B-nZVI/BC-PS system was proposed accordingly. The findings provide a significant implication for cost-effective and environmentally friendly remediation of PCA-contaminated soil using a facile ball milling preparation of B-nZVI/BC and PS.