Highly efficient removal of bisphenol A by a three-dimensional graphene hydrogel-AgBr@rGO exhibiting adsorption/photocatalysis synergy

Abstract

The increasing extent of environmental pollution by industrial chemicals necessitates the development of facile methods of their removal. Among the various techniques employed for this purpose, photocatalytic degradation is particularly attractive, since it does not require the use of other chemicals, achieving pollutant mineralization by the action of light and atmospheric oxygen only. However, most photocatalysts suffer from poor stability and recyclability, which limits their practical applications. This study describes the encapsulation of AgBr by reduced graphene oxide to form a composite (AgBr@rGO) that can be incorporated into graphene to form hydrogels (rGH-AgBr@rGO) with three-dimensional (3D) network structures. The core-shell structure of AgBr@rGO inhibited the growth of AgBr particles, achieving excellent control over their size (500-600nm), while hybridization with graphene promoted the rapid migration and separation of photogenerated charges. Bisphenol A (BPA) were rapidly adsorbed by the 3D graphene nanosheets of rGH-AgBr@rGO and promptly degraded by AgBr@rGO nanoparticles under visible-light irradiation, showing that the synergy between adsorption and photocatalytic degradation could significantly improve pollutant removal efficiency. Moreover, the micron-sized 3D mesh structure could be regenerated using a simple filter without the need for a complex catalyst filtration system. The obtained results revealed a superior synergy between photocatalytic and adsorption-based pollutant degradation by rGH-AgBr@rGO, which achieved a 1.5-fold higher BPA removal degree than pure AgBr, exhibiting values above 90% after five consecutive cycles. Finally, the degree of BPA degradation was maintained at 100% during the first 6h under continuous flow conditions.