Synergistic Superhydrophobicity and Photocatalysis in SA@CNZ/PMS Sponge for Sustainable Oily Wastewater Remediation: High-Efficiency Oil–Water Separation and Visible-Light-Driven Organic Dye Degradation

With the rapid development of petroleum resources and the chemical industry, the release of oily wastewater has increased dramatically and environmental pollution has become increasingly serious. In this study, an inexpensive, simple, and environmentally friendly technique was established to synthesize a multifunctional melamine sponge (MS) with both superhydrophobic and photocatalytic properties through polydopamine (PDA) functionalization, followed by the immobilization of CNZ (C3N4@ZnO) nanoparticles and the grafting of stearic acid (SA). The prepared SA@CNZ/PMS sponge exhibited outstanding superhydrophobicity with a water contact angle (WCA) of 150.5°. The sponge possesses superior hydrophobic–oleophilic selectivity, which can effectively separate various oil/water mixtures as well as oil-in-water emulsions. Meanwhile, the sponge exhibits high oil sorption capacity (11.55–52.76 times its own weight) and oil–water separation efficiency (99.3% after 10 cycles). In addition, superhydrophobic SA@CNZ/PMS is resistant to chemical corrosion and demonstrates good mechanical stability. Moreover, SA@CNZ/PMS exhibits a rapid removal efficiency for organic dyes (96.4% for methylene blue) through synergistic adsorption and visible light photocatalysis. This research provides new insights into the design of multifunctional materials for treating oily and dye-containing wastewater.