Preparation and characterization of superhydrophobic melamine and melamine-derived carbon sponges modified with reduced graphene oxide–TiO2 nanocomposite as oil absorbent materials

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The spillage of oil and hydrophobic volatile organic compounds (VOCs) has become a global challenge that removing them from the environment is essential to the health of living organisms. The superhydrophobic sponges are considered as an excellent absorbent to clean up oil/solvent spills due to high absorption capacity and elasticity. The most important challenges in creating superhydrophobic sponges are to increase absorption capacity, selectivity, and thermal stability by developing the surface area, water contact angle, and coated materials, respectively. In this study, in order to enhance surface area, reduced graphene oxide–titanium dioxide (TiO2) nanocomposite was applied on a substrate of raw and carbonized melamine sponge by a simple dip coating method. The results show that better bonding of synthesized nanocomposite to carbonized sponge fibers leads to a greater increase in surface area than modified raw sponge. Besides, hydrophilicity property of raw sponge varies to superhydrophobicity after modification to the contact angle of 161.5° and 165.1° for raw and carbonized sponge, respectively. Modified sponges with high thermal stability reduce the risk of fire. The maximum oil/organic solvents absorption capacity for modified melamine sponge was reported 169 times of its weight, which is increased for carbonized sponge due to higher porous volume and lower density. They also demonstrated good recycle ability after 15 times, repeating the absorption–squeezing process. These outstanding features make them an exceptional candidate absorber for various oils and hydrophobic VOCs.