Origin of synergistic effect between Fe/Mn minerals and biochar for peroxymonosulfate activation

• The synergistic effect between biochar and mineral for PMS activation was explored. • The mechanism of mineral-biochar composites in PMS activation was explored. • A new insight into the electron transfer regime was provided. Biochar possesses attractive structural (highly porous) and chemical (abundant functional groups) properties, exhibiting promising future in diverse applications such as soil amendment and environmental remediation. However, the interaction between biochar and soil active minerals, especially the synergistic effect on peroxymonosulfate (PMS) activation is largely unknown. In this study, we focused on the origin of the observed synergistic effect between biochar and two typical soil active minerals, i.e., goethite (α-FeOOH) and birnessite (δ-MnO 2 ) on the activation of PMS by preparing four mineral-biochar composites, i.e., GBC 350 , BBC 350 , GBC 700 , and BBC 700 . Interestingly, BBC 350 , BBC 700 , and GBC 700 exhibited distinct synergistic effects for BPA removal, whilst no obvious synergistic effect was observed for GBC 350 . The theoretical calculations based on density functional theory (DFT) further confirmed the improved PMS adsorption affinity, ascribing to the delocalization of O electrons (in PMS) to the π bond in C-layer. Furthermore, non-radical regime was elucidated to dominate the BPA oxidation. Mineral species could establish an electron channel between oxidant and catalyst, thus accelerating the electron transfer process. The high-valent Mn species (Mn(V)) also contributed to BPA removal in BBC 350 /PMS process. Overall, this study uncovered the origin of synergistic effect between BC 700 and Fe/Mn minerals by exploring the electron transfer regime, which might provide new insights into PMS activation in practical applications.