Constructing porous beads with modified polysulfone-alginate and TiO2 as a robust and recyclable photocatalyst for wastewater treatment

The availability of suitable support material for immobilizing photocatalyst, without loss of photoactivity, is a bottleneck for photocatalytic wastewater treatment in real-world applications. Here we report a facile method for the preparation and pore structure modification of highly stable and porous polymer composite consisting of polysulfone (PSF) and alginate (Alg) for immobilizing TiO2 nanoparticles. Compared to its constituents alone, this newly identified polymer composite has much higher stability as well as adsorption capacity towards the pollutant molecules, acting as an ideal matrix for immobilizing the photocatalyst. Various combinations of PSF, Alg, and TiO2 were tested in the form of beads, with the final ratio of 10:6:12, for the best adsorption and photodegradation capacity. With surface modification, these beads (denoted as PAT-12 M) showed superior photocatalytic activity toward methylene blue (MB) and the two pharmaceuticals - triclosan (TCS) and diclofenac (DCF), which were almost completely removed within 50, 40 and 120 min, respectively. The reactive oxygen species scavenging experiments confirmed the center dot OH radicals played the primary role in photodegradation. The robustness of these beads allowed their use for at least 25 cycles under batch mode and 30 days in continuous mode with over 99% MB degradation. Thanks to the large size (3 mm) and excellent mechanical stability, these beads can be effortlessly dispersed in polluted solutions, in interswitchable suspended or floating form, and easily recovered. With these advantageous properties, PAT-12 M beads could be effectively employed for a wide range of applications at large scales.