Floating TiO2 nanotube-polyurethane foam composite for photocatalytic removal of contaminants of emerging concerns

Floating photocatalysts represent a promising class of immobilized semiconductor systems engineered to overcome the limitations of conventional photocatalysis. By forming an air/solid/water triphase interface in buoyancy-driven configurations, these systems facilitate photocatalyst recovery, improve light harvesting, and enhance oxygen transfer. In the present study, we fabricated TiO 2 nanotubes (TNTs) by ultrasound-assisted hydrothermal synthesis and deposited the photocatalyst onto floating polyurethane foam (PUF) through wet chemical deposition. The synthesis method yielded TiO 2 nanotubes with a surface area of 110 m 2 /g and a bandgap energy of 3.0 eV. TNTs photocatalyst exhibited a biphasic anatase/TiO 2 (B) structure with a crystallite size of 26 nm and a photocurrent density of 0.2 mA/cm 2 . The photocatalytic activity of floating TNTs@PUF was evaluated for the removal of contaminants of emerging concerns (CECs) under simulated sunlight irradiation. When individual contaminants were treated, removal efficiencies were 98% for bisphenol A (BPA), 98% for methyl orange (MO), 85% for methylene blue (MB), 98% for bentazon (BZ), 98% for isoproturon (IPU), 98% for sulfamethoxazole (SMZ), and 97% for carbamazepine (CBZ) after 4 h of irradiation. The presence of natural organic matter and inorganic anions in the BPA solution was also examined. Water matrix components had inhibitory effects on the photocatalytic activity of floating TNTs@PUF, decreasing BPA removal to 80%, 86%, and 30% for humic acid, citric acid, and oxalic acid, respectively. Similarly, inorganic anions reduced BPA removal to 80% with bicarbonate, 86% with chloride, and 90% with sulfate. In a mixture of CECs, the removal of BPA was 80%.