Wastewater effluent from industries (e.g., shale oil and gas) are often highly saline, beyond the treatment limit of reverse osmosis processes. Instead, water reclamation from industrial wastewater via membrane distillation technology (MD) has emerged as a promising technique to reduce the burden of freshwater supply. However, the complex nature of these industrial wastewaters with the presence of organic foulants, surfactants, and low-surface-tension compounds pose challenges of fouling and wetting in the MD technology. Janus membrane, which comprises a hydrophilic antifouling layer on a wetting-resistant membrane substrate, has emerged as a promising approach to simultaneously prevent fouling and wetting. Despite the recent exploration of Janus membrane fabrication, most methods are material specific and lack a universal technique for robust Janus MD membrane.<br/>In our study, we develop a non-substrate specific universal modification technique to fabricate Janus membranes using polydopamine-assisted, surface-initiated atom-transfer radical-polymerization (ATRP) for grafting antifouling zwitterionic polymer brush layer that can be applied to any hydrophobic/omniphobic substrate. The tunability of the zwitterionic polymer layer structure is characterized by electron microscopy, profilometry, and Fourier-transform infrared spectroscopy. The fabricated omniphobic base layer resists wetting against various low-surface-tension liquids as well as water. The excellent antifouling functionality by the zwitterionic polymer layer is confirmed by static oil-fouling test. We show the long-term, simultaneous resistance of the fabricated Janus membrane against wetting and fouling in the MD experiments. Our modification technique is further applied to commercial omniphobic membranes to demonstrate the universal applicability of the developed technique for Janus membrane fabrication.

Developing a non-substrate specific technique of Janus membrane fabrication for hypersaline wastewater desalination

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