Progress of metal-loaded biochar-activated persulfate for degradation of emerging organic contaminants

In recent years, studies on the degradation of emerging organic contaminants by sulfate radical (SO4−·) based advanced oxidation processes (SR-AOPs) have triggered increasing attention. Metal-loaded biochar (Me-BC) can effectively prevent the agglomeration and leaching of transition metals, and its good physicochemical properties and abundant active sites induce outstanding in activating persulfate (PS) for pollutant degradation, which is of great significance in the field of advanced oxidation. In this paper, we reviewed the preparation method and stability of Me-BC, the effect of metal loading on the physicochemical properties of biochar, the pathways of pollutant degradation by Me-BC-activated PS (including free radical pathways: SO4−·, hydroxyl radical (·OH), superoxide radicals (O2–·); non-free radical pathways: singlet oxygen (1O2), direct electron transfer), and discussed the activation of different active sites (including metal ions, persistent free radicals, oxygen-containing functional groups, defective structures, etc.) in the SR-AOPs system. Finally, the prospect was presented for the current research progress of Me-BC in SR-AOPs technology. HIGHLIGHTS The characteristics of the preparation methods for metal-loaded biochar are summarized.; The effects of metals on the physicochemical properties of biochar are discussed.; The free radical and non-radical pathways for activation of persulfate by metal-loaded biochar are discussed.; The potential mechanisms of metal-loaded biochar catalysts are discussed.; The future blueprint for metal-loaded is described.;