Facile coating of floating polyurethane foams using reduced graphene oxide and TiO2 for pollutant adsorption and photodegradation in water

Developing effective and sustainable technologies for wastewater treatment is challenging in materials engineering. Photocatalysis based on TiO2 is a promising solution for removing organic contaminants. However, the large bandgap and predominant use of TiO2 nanoparticles hinder the industrial scalability of the process owing to the requirement of UV light, recovery issues, and potential environmental concerns. This study developed a simple and low-energy consuming strategy to combine TiO2 nanopowder and reduced graphene oxide (rGO) in a water-based coating for polyurethane (PU) foams. The addition of rGO provides multiple synergistic functions including (i) immobilization of TiO2 particles, (ii) adsorption of organic pollutants, improving the contact with catalytic sites, and (iii) partial bandgap narrowing, as reported in the literature. Commercial PU foams (20 PPI; 5.5 cm diameter; 0.5 cm thickness) were dip-coated with formulations at rGO:TiO2 mass ratios of 1:1, 1:2, and 1:3. Photocatalytic activity was assessed via Rhodamine B (RhB) degradation (3 mg L−1 aqueous solution) under UV-Vis irradiation. Complete removal was achieved within 90 min by using rGO-TiO2 1:3-coated samples, as evidenced by the subsequent RhB release experiments. Coated foams were fully characterized, both before and after decontamination tests, through thermal (TG and DSC), spectroscopic (EDX, UV-Vis, and ICP-OES) and morphological (optical microscopy and SEM) analyses, which confirmed coating stability. The proposed binder-free strategy provides a scalable route to design multifunctional photocatalytic foams. Moreover, by bridging materials engineering with environmental applications, it opens perspectives for the development of sustainable, easily deployable wastewater treatment systems.