π-π stacking derived from graphene-like biochar/g-C3N4 with tunable band structure for photocatalytic antibiotics degradation via peroxymonosulfate activation

Enteromorpha biochar modified g-C3N4 (BC/CN) was synthesized and applied to degrade tetracycline by activating PMS under visible light, obtaining around 90% removal rate within 1 h. The Enteromorpha biochar can provide electron-withdrawing groups to adjust the electronic structure of g-C3N4, and induces more pi-pi interaction to decline the recombination of photocarriers. The environmental adaptability of the BC/CN/PMS/vis system was confirmed by the TC degradation in different initial pH, coexisting ions, and natural organic materials. In most cases, the system maintained over 78% degradation rate. The kinetics and mechanism of the system indicating that center dot O-2(-), O-1(2) contributed more to the TC photocatalytic degradation than center dot OH, SO4.-, and h(+). During the process, TC underwent serials hydroxylation, demethylation, and ring-opening processes, and produced more than 40 intermediates in three pathways. Moreover, the BC/CN/PMS/vis system was proved to have at least a 50% degradation rate for more tetracyclines and quinolone antibiotics with the same condition.