Superhydrophilic and antifouling PDA/TA-MOF nanocomposite PTFE membranes for efficient and sustainable treatment of dissolved oil-containing wastewater

PTFE membranes are desirable for oil-water separation due to their excellent chemical and mechanical stability. However, because of their inherently strong hydrophobicity, they experience severe membrane fouling, significantly compromising filtration efficiency. To address membrane fouling of PTFE membranes, we developed a superhydrophilic nanocomposite PTFE membrane by performing in-situ polymerization of dopamine with the simultaneous incorporation of tannic acid (TA)-functionalized MOF nanoparticles to simultaneously address the low water permeability and severe membrane fouling stemming from the high intrinsic hydrophobicity of the PTFE membrane. The TA-MOF incorporation dramatically improved the hydrophilicity of PTFE membranes, as evidenced by the significantly reduced contact angle (138° to 42.6°). The enhancement in hydrophilicity was achieved even with half of the MOF amount (10 mg) due to the large number of hydrophilic catechol groups provided by TA. As a result, the TA-MOF incorporation increased the water permeance by 418-fold and 2.44-fold in short-term filtration using 450 ppm vacuum pump oil and soybean oil emulsions, respectively, compared to the ethanol-treated PTFE membrane. Furthermore, the TA-MOF nanocomposite membrane proved its excellent antifouling properties and membrane regeneration capabilities during the 72-h long-term cyclic filtration test by recovering water permeance to 1.6–5 times higher levels than before washing, in contrast to the control PTFE membrane that suffered from severe flux decline of more than 95% and no flux recovery. We hope this paper will provide insights into a strategy to develop superhydrophilic and antifouling nanocomposite PTFE membranes using a minimum amount of nanomaterials for effective and sustainable oil-water separation using polymeric membranes.