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

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 (alpha-FeOOH) and birnessite (delta-MnO2) on the activation of PMS by preparing four mineral-biochar composites, i.e., GBC350, BBC350, GBC700, and BBC700. Interestingly, BBC350, BBC700, and GBC700 exhibited distinct synergistic effects for BPA removal, whilst no obvious synergistic effect was observed for GBC350. 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 pi 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 BBC350/PMS process. Overall, this study uncovered the origin of synergistic effect between BC700 and Fe/Mn minerals by exploring the electron transfer regime, which might provide new insights into PMS activation in practical applications.

Automated summary

This study uncovered the synergistic effect between biochar and soil active minerals in the activation of peroxymonosulfate (PMS). The mineral-biochar composites exhibited notable synergistic effects in BPA removal, possibly due to the improvement in electron transfer mechanism.