Immobilizing a visible light-responsive photocatalyst on a recyclable polymeric composite for floating and suspended applications in water treatment

A visible light responsive TiO2/Ag3PO4 (10 : 1) nanocomposite was prepared and successfully immobilized (12 wt%) in a spherical polymeric matrix consisting of polysulfone and alginate (10 : 6). The resulted beads featured a sponge-like structure with interconnected macrovoids and micropores, and showed high adsorption and visible-light photocatalytic activity towards various wastewater pollutants, including the widely used dye – methylene blue (k = 0.0321 min−1), and two emerging pharmaceutical contaminants – diclofenac (k = 0.018 min−1) and triclosan (k = 0.052 min−1). As determined, the ˙OH radical and h+ are the primary reactive oxygen species responsible for the photodegradation. The composite photocatalytic beads are also effective in bacterial inactivation and degradation of acyl-homoserine lactones (AHLs), the bacterial quorum sensing autoinducers triggering biofilms, thus exhibiting a promising future in wastewater disinfection and biofilm retardation. Additionally, these beads could be used in inter-switchable suspended or buoyant forms, and be effectively regenerated by H2O2 treatment, and used for multiple cycles without any significant loss in photoactivity. With these unique features, the prepared visible-light photocatalytic beads could be easily applied in large-scale water and wastewater treatment systems.