Efficient removal of bisphenol A from complex environments by Fe-Mn oxides loaded biochar: An innovative perspective of utilizing co-existing Cr(Ⅵ)

In the control process of complex pollution, coexisting heavy metals could promote the removal of organic pollutants by biochar. However, the unclear relationship between the synergistic effect and the properties of biochar limited the positive role of coexisting heavy metals in most studies. Herein, biochar derived from various of raw feedstock were prepared with different temperatures, and modified by loading ferrite-manganese oxides. By comparing the removal performance and characterization, this study found that part of the biochar could utilize Cr(Ⅵ) to enhance the Bisphenol A (BPA) removal. This was attributed to the abundance of C=O functional groups, conjugated aromatic structure, graphite properties and defects. Notably, the ferrite-manganese oxides loaded biochar (Fe-Mn/SC₅) was finally selected with the excellent BPA removal of 86.25 % in the single system (BPA) and 100 % in the binary system (Cr(Ⅵ) + BPA), respectively. Further, the results of characterization, quenching experiments and reactive oxygen species (ROS) measurement revealed that the mechanisms of BPA removal by Fe-Mn/SC₅ included adsorption (π-π interaction, hydrophobic interaction, hydrogen bond interactions and complexation) and degradation (radical and non-radical pathways). Cr(Ⅵ) played the positive role in the BPA removal by forming "BC-defect-HCrO₄^-" and participating in the redox reactions of C=O and Mn⁴⁺. Meanwhile, Cr(Ⅵ) was reduced and converted to Cr(Ⅲ). This study provided an excellent material that was derived from agricultural waste for the complex pollution removal, and offered a new perspective for binary pollution control based on the efficient utilization of the properties of biochar and pollutants.