A Study on the Adsorption Performance of Potassium Bicarbonate-Modified Biochar towards Benzo[a]pyrene in Aquatic Environments

Benzo[a]pyrene (BaP) is a highly carcinogenic and highly mobile polycyclic aromatic hydrocarbon, and there is an urgent need to develop remediation technologies for water bodies contaminated with it. In this study, porous biochar (PBC) was prepared from rice straw using co-pyrolysis with KHCO 3 as an activation agent, and its adsorption characteristics and mechanism of action towards BaP in water were investigated. High-temperature etching with KHCO 3 creates a rich microporous structure and enhances the aromaticity of the carbon framework; PBC800, prepared at 800℃, exhibits a saturated adsorption capacity of up to 55.41 mg/g; compared with the adsorption capacity of 25.47 mg/g for the original biochar, this represents an increase of 217.55%. Adsorption followed quasi-second-order kinetics and the Langmuir model. The adsorption process is predominantly characterised by spontaneous endothermic physical adsorption, accompanied by weak π-π and electron donor-acceptor interactions, with microporous filling and π-π interactions being the primary mechanisms. Response surface analysis indicated that the factors influencing performance, in order of significance, were: biochar dosage> temperature> initial BaP concentration. Under optimal conditions, the theoretical removal rate was 94.08%. The coexistence of carbonates was found to inhibit BaP adsorption; In practical applications involving water bodies, attention must be paid to the concentration of carbonate ions.. This potassium bicarbonate modified biochar provides a theoretical reference for the remediation of BaP pollution in water bodies.