Removing BaP from soil by biochar prepared with medicago and corn straw using batch and solid-phase extraction method

Low-cost materials with a highly efficient adsorption capability prepared from corn straw and medicago (abbreviated to CB and MB), which can effectively remove benzo(a)pyrene (BaP) from contaminated soil, were prepared at a temperature of 350 °C under limited-oxygen conditions. The appearance traits, contents of C, H, N and functional group types of CB and MB were obtained by SEM, elemental analysis and FT-IR. Through the batch method, it was found that the adsorption of BaP by CB and MB was in accordance with pseudo-secondary kinetics because the correlation coefficients are 0.855 with CB and 0.948 with MB, respectively, and the maximum adsorption capacity in the fitting (CB: 78.2 mg kg^-1, MB: 88.8 mg kg^-1) was consistent with the actual measurement (CB: 79.8 mg kg^-1, MB: 89.3 mg kg^-1). Freundlich and Langmuir equations can well describe the isothermal adsorption data of CB and MB due to the correlation coefficients all being greater than 0.87. Soil samples treated with ASE were separated by solid-phase extraction (SPE) with different biochar contents in packed columns. It was found that the contributions of CB and MB to the removal of BaP increased from 58.5% and 60.4% to 80.6% and 82.1%, respectively, which could effectively reduce BaP in polluted soil.