Insight into the rapid degradation of antibiotic rifampicin by W-doped O-bridged g-C₃N₄via the coupling effect of electron replenishment in the dark degradation stage and electrophilic attack in the photocatalytic stage: experiments and DFT simulation calculations

High pressure wet ball milling and thermal polycondensation are used to prepare W-doped O-bridge carbon nitride (WOCN) for the rapid catalytic degradation of antibiotic rifampicin (RIF). The removal of rifampicin at a concentration of 150 mg L-1 in a dark environment reached 60% within 8 minutes and 92% after 40 minutes of visible light exposure. The rapid catalytic degradation of RIF benefits from the coupling effect of dark degradation with photocatalytic degradation, including the electron replenishment theory of dark degradation and the electrophilic attack under light irradiation. In the dark degradation reaction, the abundant delocalized electrons at the tungsten-oxygen insertion surface are captured by the dissolved oxygen to produce O2-, part of which directly participates in RIF degradation, whereas the other part is oxidized to O-1(2) by the holes at the carbon-rich cyano group surface and then participated in RIF degradation. The electrons consumed at the reaction site are continuously replenished through the O electron bridge, allowing RIF degradation to continue. In the photocatalytic degradation reaction, photogenerated electron holes are excited using visible light, which partly participate in the degradation of RIF through the above dark reaction pathway. Meanwhile, some photogenerated holes oxidize OH- to (OH)-O-center dot and degrade RIF by electrophilic attack.