Polyetheramine-modified polyurethane sponge for interfacial demulsification-enhanced coalescence separation of O/W emulsions.

A material-preparation and separation strategy integrating interfacial demulsification with coalescence separation was proposed for efficient O/W emulsion treatment. Demulsification-functionalized coalescence materials (PEA-PDA@PU) were prepared by depositing a polydopamine (PDA) interlayer on polyurethane (PU) sponges and grafting different polyetheramine (PEA) demulsifiers. Their surface morphology, chemical composition, grafting amount, wettability, separation performance, operating characteristics, and underlying mechanism toward nonionic surfactant-stabilized emulsions were systematically investigated through experiments and XDLVO analysis. PEA-PDA@PU increased oil removal by 6-10 percentage points over unmodified materials. PEA2.8 and PEA13.8 showed the best overall performance, achieving approximately 97% oil removal, steady-state pressure drops of 3-5 kPa, and stable operation for 20 h. This advantage mainly originated from PEA-enabled interfacial demulsification and chain-structure effects, thermodynamically manifested as enhanced Lewis acid-base (AB) interactions, the dominant short-range component of material surface-interfacial film interactions. Among the investigated PEA structural parameters, molecular weight emerged as a key molecular-design parameter governing interaction strength, chain spatial availability, and interfacial demulsification capability. Consequently, interfacial demulsification destabilized emulsified droplets, while the coalescence layer converted this destabilization into sustained droplet coalescence and separation enhancement, establishing an efficient interfacial demulsification-coalescence synergistic mechanism and superior overall separation performance.