Insights into O₂ Activation via Mn^IIIOOH Species on Mn-Rich Biochar

Although metal-rich biochar (M-BC) is widely used in soil remediation and pollution control, the activation mechanism of molecular oxygen (O-2) by M-BC still needs to be clarified due to the low metal loading. In this study, we enhanced the manganese content of low-temperature manganese-rich biochar (Mn-BC) by treating it with hydrogen peroxide (H2O2), resulting in the formation of MnBC-Hx (where x represents the volume of H2O2 used in mL). MnBC-H5 was particularly effective in activating O-2, leading to the successful degradation of phenol and dyes. Characterizations showed that the Mn-II in the outer layer of MnC2O42H(2)O nanoparticles evenly dispersed over Mn-BC was oxidized to Mn-III by H2O2. This process was accompanied by the removal of coordinated H2O, resulting in the formation of (MnC2O4)-C-III on MnBC-H5. Under visible light irradiation, Mn-III can bind to O-2 to form (MnOOH)-O-III species, which facilitates the transfer of charges and generates superoxide radicals (O-(2)-) that effectively degrade organics. Notably, Mn-III of MnBC-H5 remains stable after the organic degradation reaction. This study will not only provide a theoretical basis for developing environmentally friendly biochar-based catalysts but also promote the study of the environmental effects of biochar.