One-pot synthesis of C-doping and defects co-modified g-C3N4 for enhanced visible-light photocatalytic degradation of bisphenol A

Doping and defects were often used for g-C3N4 modification to improve its photocatalytic performance. In this work, modified g-C3N4 (CE) was successfully synthesized by a simple one-pot thermal polymerization using urea as precursor and EDTA-2Na as modifier. The results showed that the addition of EDTA-2Na increased the carbon content and formed defects in the modified g-C3N4, but excessive EDTA-2Na might lead to disorder of the g-C3N4 structure. The co-modification of C-doping and defects can narrow the energy band gap of g-C3N4 and improve the photogenerated carrier mobility, which enables it to utilize visible light more efficiently. The modified g-C3N4 (0.02CE) synthesized by adding 0.02 g EDTA-2Na exhibited the best catalytic activity and it was 8.68 times higher than that of the original g-C3N4 for the degradation of BPA (10 mg/L). In addition, it was able to completely degrade BPA (0.2 mg/L) in aqueous solution within 40 min and reach 83.1% degradation rate for BPA (0.2 mg/L) in municipal sewage. 0.02CE showed the best photocatalytic activity at pH 11. Superoxide radicals (center dot O-2(-)) and photogenerated holes (h(+)) were proved to be the dominant active species in the reaction process of catalytic degradation of bisphenol A by free radical scavenging experiments and ESR testing.