Unraveling the mechanism and the key role of amorphous structure C-O-Fe in tetracycline degradation by activation of persulfate in lotus leaf-based red mud-modified biochar

In the present study, red mud modified lotus leaf biochar was synthesized using a low-cost and concise method. The experimental results showed that when RM-HBC=0.4 g/L, PDS=4 mM, pH=5.0, the RM-HBC-PDS system exhibited the best degradation effect on TC, with the highest removal rate of 98.61 %, the highest degradation kinetics of 0.0229 min(-1). Advanced characterization and density functional theory have demonstrated that the emergence of the C-O-Fe structure led to the redistribution of the surface charge of RM-HBC. This charge redistribution caused the electrons on the surface of RM-HBC to transfer from C to Fe through the C-O-Fe structure, forming an electron-rich center centered on Fe. The C-O-Fe structure facilitated the transformation of the Fe valence state within the RM-HBC while transmitting electrons, thus maintaining the regeneration of Fe(II). This further promoted the adsorption and activation ability of RM-HBC for PDS, thereby improving the degradation effect of TC in the system. XRD detection showed that the Fe3O4 crystal strength in RM-HBC after the reaction was significantly enhanced. This was due to the C-O-Fe present on the surface of RM-HBC in the process of degradation of TC, which accelerated sustained electron transfer at C-O-Fe, leading to structural fracture, recombination, and ultimately the formation of Fe3O4 crystals. Intermediate detection and toxicity prediction showed that the toxicity of TC was significantly reduced. All the above results confirmed that this study not only achieved the efficient treatment of antibiotic wastewater but also realized the rational utilization of lotus leaf and red mud resources.