Insights into the rapid elimination of antibiotics from aqueous media by tunable C3N4 photocatalysts: Effects of dopant amount, co-existing ions and reactive oxygen species.

Conventional photocatalytic nanomaterials are not environmentally sustainable since these are usually produced from scarce mineral and metal precursors. Moreover, high pollutant removal efficiencies by conventional photocatalysts are only attained after several hours of reaction with light. In this study, novel visible light-active photocatalysts were synthesized from environment-friendly carbon precursors and applied for the rapid degradation of sulfamethoxazole (SMX) in aqueous solutions. The photocatalysts were prepared via the co-pyrolysis of urea with varying doping temperature and dopant amount. These variations played a vital role in improving the performance of the photocatalysts and resulted in up to >99% SMX removal within 45 min of visible light irradiation. Characterization of the photocatalysts showed that potassium and iodine dopants were responsible in the red shift and broadening of the light absorption spectrum to the visible region. In addition, the band gap energy narrowed by 0.23 eV resulting in faster charge transfer but slower recombination of the photo-generated electron and hole pairs. Effects of varying concentrations of inorganic salts (NO3-, SO42-, Cl-, PO43-) on SMX removal were also examined. Lastly, the mechanism of SMX photodegradation was elucidated.