A novel synergy remediation of solubilization adsorption coupled with oxidation by cyclodextrin-magnetic biochar assisted persulfate for benzo(a)pyrene-contaminated soil

During biochar (BC) assisting persulfate (PS) in remediating organic contaminated soils, challenges include low electron transfer efficiency and a limited adsorption-oxidation interface, which hinder pollutant degradation under complex environmental conditions. This study prepared a biochar-based composite activator (CDMBC) by introducing iron oxides onto the biochar surface and grafting β-cyclodextrin (β-CD), and examined CDMBC's role in facilitating PS oxidation to remediate benzo(a)pyrene (BaP)-contaminated soil under mild conditions. Results showed that CDMBC had a loose surface structure with partially uniform active components, strong oxidative capacity, and enhanced electron transfer ability. Under the optimal conditions of 1.00 wt% of CDMBC addition, 0.75 wt% of PS addition, 35 °C of remediation temperature, 1:2.5 of solid-liquid ratio, and 800 °C of biochar preparation temperature, the BaP removal with a maximum of 98.97 % in contaminated soil was obtained after 120 min. Of this total BaP removed, 2.74 % was via the aqueous phase, 12.41 % through adsorption on the BC surface, and 83.82 % through oxidative degradation in the soil. CDMBC exhibited stable performance during repeated recycling and significantly reduced soil toxicity after remediation. CDMBC's loose structure, conductive magnetic particles, and solubilizing β-CD enhanced electron transfer and BaP adsorption, promoting BaP desorption from soil particles into the aqueous phase. Through the combined actions of solubilizing adsorption, reactive oxygen species (ROS) oxidation, singlet oxygen (¹O₂) - electron transfer - surface active groups oxidation, BaP in contaminated soil was decomposed into CO₂, H₂O, etc., hence facilitating significant remediation. Overall, this synergistic effect of solubilizing adsorption - oxidation provides a novel approach for BC-assisted PS remediation of organic-contaminated soils with substantial potential for practical applications.