A new approach on visible light assisted oxygen doped g-C3N4/β-Bi2O3 direct Z-scheme heterojunction towards the degradation of bisphenol A: Degradation pathway, toxicity assessment, and continuous mode study

Graphitic carbon nitride (g-C3N4, G) was firstly doped with oxygen atom and then bismuth oxide nanoparticles (beta-Bi2O3, B) were embedded into the modified G to enhance its photocatalytic activity. The photocatalytic performance of the as-prepared composite (beta-Bi2O3/O-G, BOG) was evaluated towards bisphenol A (BPA) degradation under visible light irradiation in both batch and continuous-flow reactors. A series of catalyst characterization tests, including XRD, FTIR, FESEM, HRTEM, XPS, TGA, EDX, BET, DRS, PL, EIS, transient photocurrent, CV, and LSV, revealed the significant improvement in photocatalytic activity of G after oxygen doping and its combination with B. Under optimum conditions, 98.7% BPA and 76.8% total organic carbon (TOC) removals were achieved. A direct Z-scheme heterojunction system was described via a series of photo-chemical tests as well as the identified oxidizing reactive species. The visible light-assisted BOG system also exhibited excellent performance for purifying real BPA-laden water samples. Moreover, BOG composite showed noticeable reusability, implying its cost-effective potential for practical applications. The mechanistic degrada-tion pathway of BPA was proposed based on the identified transformation products (TPs). Furthermore, the toxicity of TPs was evaluated by the Ecological Structure-Activity Relationships (ECOSAR) predictive model. This study gives a new point of view on as-prepared BOG composite potential with highly-efficient photocatalytic performance towards degradation of emerging refractory contaminants and treatment of contaminated effluents.

Automated summary

In this study, oxygen-doped graphitic carbon nitride was prepared and bismuth oxide nanoparticles were embedded to enhance its photocatalytic activity. The resulting composite showed excellent performance in degrading bisphenol A under visible light irradiation and purifying BPA-laden water samples. Moreover, the composite exhibited good reusability and cost-effective potential for practical applications.