Hypothesis: Superhydrophilic/underwater superoleophobic membrane constructed by hydrophilic polymers possesses great advantage in the separation of oily waste water, due to its intrinsic oil-repellent property. The formation of hydration layer to repel and block oil is considered as the mechanism of underwater superoleophobicity and subsequent oil/water separation. Constructing a stable hydrophilic polymer network on the substrate surface would significantly improve the robustness of hydration layer.
Experiments: In this work, a feasible and universal mussel-inspired dip-coating method was developed for constructing stable hydrophilic polymer network onto target substrate surface, via successively immersing substrate membranes into aqueous solutions of polydopamine (PDA) and catechol-functionalized hydrophilic polymer (CFHP). After pre-wetting with water, the polymer network would swell with water to form a thin and stable water film layer, serving as a barrier against oil penetration.
Findings: The as-prepared CFHP/PDA modified membranes exhibit outstanding performance in separating various oil/water mixtures and oil-in-water emulsions stabilized by surfactants, with separation flux up to 5641.1 L·m-2·h-1 and separation efficiency achieving 99.98%. The surface modification method developed in this work can be easily extended to various materials and membrane systems, for achieving a variety of practical applications such as industrial wastewater treatment.
Keywords: Mussel-inspired materials; Oil/water separation; Polymer network; Superhydrophilic surface.
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