Cellulose derived biochar: Preparation, characterization and Benzo[a]pyrene adsorption capacity

Edible oil is prone to be contaminated by Benzo[a]pyrene (BaP) during production and processing. Adsorption is an important technology for the removal of BaP from edible oil, and biochar as a new type of adsorbent for the treatment BaP has received extensive attention. In this study, we prepared unmodified biochar and ZnCl₂-modified biochar from sesame straw cellulose (SSB and SSZ) and sesame capsule cellulose (SCB and SCZ), carried out structure characterization by Fourier Transform Infrared (FT-IR), Brunauer-Emmett-Teller (BET) and Scanning Electron Microscope (SEM), and finally evaluated their potential effectiveness in BaP removal from sesame oil. FT-IR results revealed that SSZ and SCZ showed higher peak intensities, indicating that they could provide more active sites for adsorption. The results of XRD presented that SSZ and SCZ had a higher graphitization degree than the unmodified biochar. SEM results showed that the SSZ and SCZ had more complex pore structure, which is beneficial to adsorption. BET analysis results showed that SSZ and SCZ had a higher specific surface area of 1622.83–1797.39 m²/g and a better developed porous structure (the total pore volume V_total was 0.9434–1.0023 cm³/g) than the SSB and SCB (specific surface area was 350.55–352.59 m²/g, and V_total was 0.1907–0.1918 cm³/g), indicating that modification promoted the formation of porous structure and thus improved the adsorption capacity of biochar. Adsorption experiments confirmed once again that the BaP removal rates of SSZ and SCZ (92.67%–96.13%) were much higher than that of unmodified biochar (3.34%–4.28%), and the BaP content in the sesame oil treated by SSZ and SCZ were far below the current EU maximum levels (2 μg/kg). Therefore, the modified biochar from cellulose is a promising adsorbent for BaP removal. In future studies, the influences of bichar on the nutritional quality of edible oil should be taken into consideration so as to find an ideal active carbon substitute for BaP removal in edible oil.