Synthesis of g-C3N4/BiVO4 heterojunction composites for photocatalytic degradation of nonylphenol ethoxylate

The g-C3N4/BiVO4 heterojunction composites were successfully synthesized by ultrasound assisted method for better photocatalytic degradation of nonylphenol ethoxylate (NP-9, Tergitol) in water under the irradiation of visible light. The band gaps of BiVO4 doped with 0–10 wt% g-C3N4 were calculated from the absorption edge position ranges of 2.43–2.46 eV. The specific surface area of BiVO4 composites increased from 1.6 m2/g to 16.3 m2/g by the increased doping of g-C3N4 from 0 wt% to 40 wt%. In addition, the photocatalytic activity of g-C3N4/BiVO4 for NP-9 degradation was evaluated under visible light irradiation. The results show that g-C3N4/BiVO4 composites had higher activity than pristine BiVO4 to give an excellent catalytic activity for NP-9 degradation. The improvement of activity after the recombination of g-C3N4 and BiVO4 is mainly due to the structure in heterojunctions with better visible light absorption and lower electron-hole pairs recombination rate. Furthermore, the 10 wt% g-C3N4/BiVO4 with the highest activity gives the best photocatalytic performance when the initial pH of the solution is at 3 and the dosage of the catalyst is 0.5 g/L. At the same time, it exhibits sufficient catalytic stability in the cycled test. It is indicated that this heterogeneous photocatalyst has huge potential for the removal of organic pollutants. Moreover, it is demonstrated that hVB+ and O2− are the main radicals in the photocatalytic reaction through the radicals trapping experiments.