Optimization of Reduced Graphene Oxide/Titanium Dioxide-Coated Polyurethane Foams as Novel Floating Photocatalysts for Water Decontamination

Titanium dioxide (TiO2) photocatalysis is a promising sustainable solution for water decontamination; however, the industrial application of TiO2 is hindered by its wide band gap and high handling and recovery costs. This work proposes to overcome these issues by developing a composite coating of nanopowder TiO2 and reduced graphene oxide (rGO) applied onto commercial polyurethane (PU) foams by means of a simple, low-energy dip-coating process designed to enhance pollutant adsorption and photocatalytic activity. The rGO-TiO2 coating was optimized by exploring different surface pre-treatments of the PU foams, the deposition of rGO-TiO2 multilayers, and the variation in the rGO-TiO2 mass ratio (1:3, 1:4, and 1:5). The prepared materials were characterized by optical microscopy, SEM-EDX, DSC, and thermogravimetry, while the stability of the coating was preliminarily evaluated through ultrasonic tests. The water decontamination capability of the coated foams was investigated by adsorption and UV-Vis photodegradation tests using a 3 mg/L aqueous solution of Rhodamine B (RhB) as a model contaminant. The results demonstrated that the rGO-TiO2 1:3-coated samples achieved complete RhB photodegradation within 90 min, with a pseudo-first-order kinetic constant of 0.0446 1/min. Moreover, pre-treating the foam with a 3 M NaOH solution improved coating adhesion onto the PU substrate while maintaining comparable decontamination efficiency.