Constructing an Antifouling Sulfonated Dopamine/Chitosan Hydrogel Layer onto Two-Type Membrane for High-Efficiency...

Developing the anticrude oil-fouling membrane separation technology can enhance separation and cycling performance for efficient treatment of wastewater containing crude oil. Here, a superhydrophilic hydrogel with -SO₃, -OH, and -NH₂ functional groups was constructed onto stainless steel (SSM) and polyvinylidene fluoride (PVDF) membrane surface by oxidant-induced codeposition strategy of sulfonated dopamine (SDA) and chitosan (CS). The hydrogel surface promotes the underwater superoleophobic property of the modified SSM and PVDF membrane and achieved the outstanding anticrude oil adhesion performance. Faced with a crude oil/water mixture, SSM@SDA/CS can demonstrate 2350 L·m^-2·h^-1 under a 20 cm liquid column pressure after 10 separating cycles. For different stabilized crude oil-in-water emulsions (oil concentration: 1%; surfactant: SDS, CTAB, Tween 80), PVDF@SDA/CS membrane also achieved above 99% rejection rate. After long-term and multicycle experiments, the SDA/CS hydrogel surface demonstrated excellent antifouling and separation stability for the nonionic Tween 80-stabilized emulsions. Importantly, compared to a single PVDF@SDA/CS membrane, faced with high-concentration crude oil/water emulsions containing 20% oil, a comprehensive separation system by combining the SSM@SDA/CS and PVDF@SDA/CS membranes can demonstrate obviously higher separation efficiency (∼99.63%) and flux (457.0 L·m^-2·h^-1). Moreover, when exposed to a corrosive environment for 8 days, the SDA/CS hydrogel surface exhibited outstanding stability in acid and salt environments. Thus, we believe that the SDA/CS hydrogel antifouling strategy can provide a theoretical reference for further achieving the separation of crude oil wastewater.