Photocatalytic degradation of sulfonamides in suspensions of coral-like graphene carbon nitride with nitrogen vacancies.

Sulfonamides (SNs) belong to a category of broad-spectrum antibiotics, which have attracted growing concerns owing to the adverse effects on ecosystem. In this paper, coral-like graphitic carbon nitrides with nitrogen vacancies were prepared by polymerization of melamine in the presence of NH4Cl, and the effect of NH4Cl amount on the structure and photocatalytic performance of g-C3N4 in degradation of sulfonamide antibiotics such as sulfamethoxazole (SMX), sulfadiazine (SDZ) and sulfathiazole (STZ) was systematically studied. It was found that the addition of NH4Cl results in the formation of coral-like g-C3N4 with nitrogen vacancies, and optimal photocatalyst (PCN-1 sample) prepared with a melamine to NH4Cl mass ratio of 1:1 showed the highest photocatalytic activity towards SNs degradation due to the quick electron-hole migration, efficient separation capacity and excellent photoelectric properties. The electron paramagnetic resonance (EPR) technique was used to determine the reactive oxygen species (ROSs) that are responsible for the degradation of SNs, and the detailed degradation pathway of STZ was proposed according to the identification of the intermediates by liguid chromatography-high resolution mass spectrometry (LC-HRMS).