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.