Three-dimensional porous graphene-like biochar derived from Enteromorpha as a persulfate activator for sulfamethoxazole degradation: role of graphitic N and radicals transformation

Abstract Three-dimensional graphene-like biochar derived from Enteromorpha (EGB) was prepared as a persulfate (PS) activator for sulfamethoxazole (SMX) degradation. The graphitic N in the EGB samples not only endowed the superior binding energy towards SMX adsorption, but also promote the PS binding with the EGB, which was crucial to the catalytic degradation of SMX in EGB/PS system. Different from the radical-based oxidation in biochar prepared at 400 °C via the persistent free radicals (PFRs), both 1O2 and surface electron transfer served as non-radical pathways in the EGB samples prepared above 500 °C, acting together with free radicals (O2∙-) on SMX degradation. Oxidation of SMX and its substructural analogues indicated that the selective oxidizing reaction occurred in the EGB/PS system and the isoxazole ring in SMX molecule was insensitive to be attacked 1O2. In addition, toxicity predication indicated that the overall biotoxicity of the intermediates during SMX degradation was decreased.