Using a Surface-Response Approach to Optimize the Photocatalytic Activity of rGO/g-C3N4 for Bisphenol A Degradation

Although environmental and clean energy research has identified graphitic carbon nitride impregnated with reduced graphene oxide (rGO/g-C3N4) as a potential, efficient non-metallic photocatalyst, its efficacy against Contaminants of Emerging Concern (CECs) is relatively unknown. This study reports an optimized photocatalyst (response surface methodology, RSM) to remove the plasticizer and endocrine disruptor bisphenol A (BPA) from water. The synthetic procedure included sonication of prepared particles of g-C3N4 and graphite oxide (rGO), followed by reduction with hydrazine (24 h reflux), increasing specific surface areas, and improving synthesis reproducibility. In optimal conditions, the produced photocatalyst (50 mg L-1) removed 90% of BPA (100 mL, 100 & mu;g L-1) in 90 min (30 min in the dark + 60 min irradiated) using a UV source (centered at 365 nm, 26 W) and exhibiting pseudo-first-order kinetics. For comparison purposes, under the same experimental conditions, pure g-C3N4 removed 50% of the BPA solution. Radical scavenging tests identified the superoxide radical as the main reactive oxygen species involved in the degradation. Two major degradation products were identified by mass spectrometry, both of them less ecotoxic than BPA to a variety of test organisms, according to in silico estimations (ECOSAR 2.0).