Persulfate activation with sawdust biochar in aqueous solution by enhanced electron donor-transfer effect

In addition to its strong adsorption capacity, the biochar-induced catalytic degradation of contaminants has attracted considerable attention recently. However, the mechanism and influential factors are poorly understood. This study investigated the persulfate (PS) activation performance of sawdust biochar (SBC) pyrolyzed at different temperatures (SBC-300 to SBC-700, respectively.) in acid orange 7 (AO7) degradation and found the main activation mechanism of it. The results demonstrated the degradation efficiency of PS/SBC system increased with the increasing SBC pyrolysis temperature. Moreover, the degradation rates of AO7 in the system could be even increased from 7% (SBC-300) to over 90% (SBC-700) under the optimum dosage of PS (9 mmol/L) and SBC (1.5 g/L). The reaction mainly took place in the pore and near the surface of SBC which was defined as graphite electron donor-transfer complex in this study, and graphite holes played a decisive role in the reaction. Besides, SO₄^- and OH were the active radicals participating in the reaction. It was found that comparing with the oxygen function groups and persistent free radicals (PFRs) of SBC, the electrical conductivity and electron donor ability were playing the main roles in enhancing PS activation with biochar pyrolyzed at high temperature for AO7 degradation.