Bimetallic modified sludge biochar for enhanced peroxodisulfate activation and radical induction

Abstract

The development of water treatment technologies had been advanced through the induction of directional radical generation. However, despite their promising potential, the uncertain selectivity and structural complexity of these systems have continued to affect the efficiency of pollutant degradation. In this study, peroxodisulfate (PDS) activation and degradation were achieved by combining different bimetallic systems (FeAl, FeNi and FeCu). The results demonstrated that the FeAl-SBC, FeNi-SBC and FeCu-SBC systems achieved degradation rates of over 90 % for tetracycline (TC). And it was confirmed by EPR results that the main contributing radicals in the degradation systems of FeAl-SBC, FeNi-SBC and FeCu-SBC were ¹O₂, O₂•⁻, •OH and SO₄•⁻. Density Functional Theory (DFT) studies revealed that the constructed Fe-O-Al, Fe-O-Ni and Fe-O-Cu structures exhibited energy gaps of 1.069 eV, 0.423 eV and 0.138 eV, respectively. These energy gaps induced distinct electron-rich environments, which played a critical role in generating different radicals. Under the synergistic effects of the bimetallic systems, the Fe³⁺/Fe²⁺ redox cycle was found to promote radical formation. Notably, these systems exhibited a broad scope of application, demonstrating wide adaptability to various organic pollutants and water environments. Based on LC-MS and Fukui function calculations, the degradation pathways of TC were proposed. Overall, these insights significantly enhanced the understanding of bimetallic systems in advanced oxidation processes.