PDA controllably-modified Janus membranes with high-permeability for oil/water separation

Janus membranes fabricated by polydopamine (PDA) can separate oil/water mixtures, but cause the problems of clogging microchannels and reducing permeability. In this work, a facile and easily approach of PDA controlled modification was developed to fabricate Janus membranes with asymmetric wettability, which show well separation selectivity and high permeability for various oil/water mixtures. Paraffin was first penetrated into the microchannels from the bottom surface of the PVDF membrane by adjusting the water infiltration time, and DA subsequently deposited on the opposite top surface. After removed paraffin, the microchannels in the membrane was released and PVDF/PDA Janus membrane could be obtained with one hydrophilic side and another oleophobic underwater side. The pure water permeability was much higher than that of PVDF@PDA membrane (0.5 × 104 L m2 h−1·bar−1) without paraffin pre-treatment, due to the microchannels was unclogged by PDA. The permeability of PVDF/PDA-20 was 1.23 × 104 L m2 h−1·bar−1 towards light oil/water and heavy oil/water mixtures. Moreover, the separation efficiency achieved above 99.7%. More importantly, this Janus membrane has high efficiency for both oil-in-water and water-in-oil emulsions. The membrane shows good reusability, which could be applicated in complex oil/water separation systems.