Degradation of tetracycline using persulfate activated by a honeycomb structured S-doped g-C3N4/biochar under visible light

In this work, a novel S-doped g-C3N4/biochar (SCNBC) nanocomposite was fabricated to activate persulfate (PS) under visible light for tetracycline (TC) abatement. The maximum photocatalytic degradation efficiency of TC by the SCNBC/PS system exhibited 2.34 and 2.32 times of individual biochar (BC) and g-C3N4, respectively. This was mainly because the honeycomb tubular structure facilitated electrons transfer along the linear direction, favoring electron-hole (e−-h+) pair separation. Meanwhile, BC could serve as an electron reservoir to further inhibit e−-h+ recombination. Radical scavenging tests and electron paramagnetic resonance measurement revealed that h+ and O2− were the dominant oxidizing radicals in TC removal. Three possible degradation pathways of TC were proposed, the mechanism of which mainly included dealkylation, deamidation, dehydration, hydroxylation and ring-cleavage reactions. Overall, this work provides a facile photocatalyst to activate PS for removal of organic pollutants.