Interfacial chemical behaviors and petroleum hydrocarbon removal performances of the biochar-mineral composites prepared by one-step pyrolysis

Three biochar-based adsorbents, namely, original ecological biochar (BC), attapulgite-biochar composite (ABC), and FeCl3-attapulgite-biochar composite (FABC), were successfully prepared by one-step pyrolysis in an oxygen-deficient atmosphere in the study. The as-prepared samples were applied to remove petroleum hydrocarbons from soil. The characterization results of interfacial chemical behaviors of the adsorbents indicated that Fe-O-C metallic-organic complexes were generated on the surface of biochar when FeCl3 and ATP was added in the pyrolysis process of biochar. FABC performed best in improving the stability and oxidation resistance of biochar. The adsorption experiments of petroleum hydrocarbons indicated that the maximum removal efficiency of FABC was 86.75%, which was 1.39 times of that of ABC and 1.56 times of that of BC. The composition changes of petroleum hydrocarbons before and after adsorption experiments were analyzed with UV–vis diffuse reflectance spectroscope (UV–vis DRS) and gas chromatography-mass spectroscopy (GC-MS). Primary adsorption mechanisms of petroleum hydrocarbons onto FABC were attributed to surface adsorption, micropore filling, hydrogen bonding, π-π interactions, and chelating effects and oxidation-reduction reactions were also involved in the adsorption process. Therefore, as a low-cost, efficient, and environmentally friendly adsorbent, FABC is significant in removing organic pollutants from soil.