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 (β-Bi2O3, B) were embedded into the modified G to enhance its photocatalytic activity. The photocatalytic performance of the as-prepared composite (β-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 photochemical 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 degradation 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.