Preparation of a Hydrophobic Attapulgite/Melamine Sponge Composite for Efficient Oil–Water Separation

To enhance the oil–water separation performance and stability of melamine sponge (MS), stearic acid-grafted attapulgite (SA-g-OATP) was synthesized via silanization and amidation grafting. The hydrophobic sponge (MS-POS) was fabricated by dip-coating MS in a polydimethylsiloxane (PDMS) solution containing SA-g-OATP. Characterization confirmed a grafting rate of 20.73%. The synergy between SA-g-OATP and PDMS constructed a hierarchical “micron skeleton-nanoparticle” rough structure. The optimal sample, MS-POS1-1, exhibited superhydrophobicity with a water contact angle of 159.34° and achieved high adsorption capacities for oils and solvents, reaching 112.33 g/g for palm oil. In gravity-driven tests, it showed separation efficiencies above 98.34% for oil–water mixtures and effectively separated water-in-oil emulsions. The sponge demonstrated robust stability, retaining hydrophobicity after 40 cycles of tape-peeling or sandpaper abrasion, and withstanding prolonged immersion in pH 2–12 solutions. The adsorption capacity remained above 89.70% after 20 consecutive adsorption-extrusion cycles. Developed from low-cost materials via a simple process, MS-POS exhibits high adsorption capacity, excellent selectivity, and robust stability, showing significant potential for oily wastewater remediation.