Ultrathin in situ silicification layer developed by electrostatic attraction forced strategy for ultrahigh-performance oil-water emulsions separation
Membrane fouling caused by oil or other pollutants is one of the major challenges for membrane separation technology used for the emulsified oil/water purification. Aiming at the realization of comprehensive fouling-resistant/fouling-releasing property, and further achieving long-term cyclic separation, an ultrathin silica (SiO2) layer is conformally engineered onto a porous polyketone (PK) substrate, via the electrostatic attraction forced silicification process. This in situ silicification forms an ultrathin and superhydrophilic/underwater superoleophobic interface structure that allows the realization of ultrahigh water permeance up to 7533 Lm-1h-1bar-1, an exceptional high emulsion fluxes up to 6000 Lm-1h-1bar-1 (close to the pure water permeance), and incorporated with a high rejection of > 99.9% against various of oily emulsions. The unique design of the superhydrophilic silicification layer grown onto the hydrophilic PK substrate also endowed the membrane with a thoroughly antifouling property against the comprehensive oily emulsions containing various of pollutants such as proteins, surfactants, and other natural organic materials (NOM), from which a nearly 100% recovery ratio of permeating flux could be obtained after several cycles of oily emulsions filtration. The use of inorganic SiO2 modification incorporated with highly chemical inert PK substrate (SiO2-d-PK membrane) also enabled the application of SiO2-d-PK membrane under more challenging conditions, where the great tolerance and long-term stability toward salty, strong acid/alkaline solutions, and various organic solvents were further demonstrated. Overall, this study provides an insight into engineering the ultrathin membrane with ultralow fouling-propensity in treating challenging oily emulsions.