3D g-C3N4/WS2/Agarose Aerogel Photocatalyst for Near-Complete Degradation of Broad-Spectrum Antibiotics in Batch and Continuous Flow Modes

Abstract

Heterojunction-based photocatalysts are receiving tremendous scientific attention for eliminating consumer-derived micropollutants from aqueous environments. However, the inherent difficulty in recovering photocatalysts following treatment, due to their application in powder form, precludes their widespread use. Herein, a self-supporting and lightweight three-dimensional (3D) graphitic carbon nitride (g-C₃N₄)/tungsten disulfide (WS₂)/agarose aerogel (GCWAA) was constructed via a facile and scalable radial freeze-casting approach. The as-synthesized 3D GCWAA proved extremely promising for the photocatalytic removal of three broad-spectrum antibiotic pollutants (ABPs), viz., tetracycline (94%), sulfamethoxazole (97%), and ofloxacin (96%), within 90 min of visible light irradiation in the batch regime. The enhanced photocatalytic performance of 3D GCWAA can be attributed to a Z-scheme electron flow from g-C₃N₄ to WS₂ in the aerogel, as inferred from electronic band structure characterization. To further demonstrate the practical utility of the composite aerogel in water and wastewater treatment systems, the continuous flow photocatalysis of ABPs over 3D GCWAA was systematically studied. Specifically, the influence of several noteworthy operational parameters, such as flow rate, solution pH, and the presence of interfering ions was comprehensively investigated. Interestingly, under optimized conditions, GCWAA achieved a remarkable average removal efficiency of 95% for ABPs in continuous mode, with minimal loss of activity over time. More attractively, GCWAA exhibited decent photocatalytic performance for treating a ternary mixture of ABPs in both freshwaters and wastewaters in the continuous flow reactor. The results of this study showcase the ultimate lab-scale demonstration of the photocatalytic potential of 3D GCWAA for the degradation of emerging contaminants, paving the way for future scale-up.