3D rGO and rGO/TiO₂-Modified Melamine Sponges: Sorbents for Oil and Emerging Organic Pollutant Removal

Environmental disasters resulting from the exploitation of natural resources, such as oil spills, have severe and lasting impacts on ecosystems. In this work, melamine sponges were modified with reduced graphene oxide (rGO) and titanium dioxide nanosheets (TiO₂) to develop multifunctional materials for environmental remediation. Prior to TiO₂ modification, the sponges were coated with rGO of different sheet sizes to evaluate the influence of rGO dimensions on surface coverage and material properties. Graphene oxide was reduced using ascorbic acid as a green reducing agent, and the process was accelerated in a microwave reactor. The resulting 3D material exhibited hydrophobic and oleophilic characteristics, enabling efficient and selective oil absorption from water. Structural and morphological characterizations confirmed the successful modification of the sponge, which displayed an outstanding oil uptake capacity of approximately 85 times its own weight. In addition to oil sorption, the material demonstrated high adsorption efficiencies for various organic contaminants, including methylene blue (95%), rhodamine B (99%), ibuprofen (75%), bisphenol A (71%), and tetracycline (73%). It also exhibited excellent photocatalytic activity toward methylene blue (95%) and maintained remarkable reusability, preserving high removal efficiencies after nine consecutive cycles for RhB (97%), IBP (71%), and TC (70%). These results highlight the potential of rGO/TiO₂-modified melamine sponges as versatile and sustainable platforms for oil-water separation and the remediation of organic pollutants in aqueous media.