Recently, many efforts to enhance separation performance of the reverse osmosis (RO) membranes have been made. Among them, the post treatment with organic solvent, so called solvent activation, has been recognized as an effective method to improve membrane performance. However, solvent activation enhances water flux along with the loss of NaCl rejection. Furthermore, there have been no clear mechanisms and reliable criteria of the solvent activation effects. In this study, we demonstrate that a new type of organic solvent, benzyl alcohol, can effectively activate the RO membrane to significantly enhance water permeation without deteriorating NaCl. Based on this results, we elucidate the underlying solvent activation mechanism and propose a reliable indicator of the solvent activation effect.

Growing demands for reducing energy consumption have raised interest to design advanced materials for thin film composite (TFC) desalination membranes with high permselectivity and low fouling. Here, we synthesized a star-shaped polymer as a new building block material, which can be assembled into selective layer of the TFC membrane via a facile interfacial polymerization (IP). Star polymer with compact globular structure and high density amine functional groups enabled to fabricate higher permselectivity and lower fouling propensity membrane compared to commercial membranes. In addition, star polymer assembled TFC membrane can function as either nanofiltration or reverse osmosis membrane by simply adjusting IP process conditions, which cannot feasible in conventional materials, demonstrating remarkable versatility of our star polymer.

The highly performing polyamide (PA) thin film composite (TFC) reverse osmosis (RO) membrane was prepared using the commercialized porous polyolefin (PO) membrane as a support. The PO-supported TFC (PO-TFC) membrane was fabricated via a conventional interfacial polymerization process. The highly permselective PA layer was formed by optimizing membrane fabrication parameters such as monomer/additive composition and post-treatment. The uniform pore structure and high surface porosity of the PO support are beneficial for improving the membrane permselectivity. As a result, the prepared PO-TFC membrane showed ~30% higher water flux and ~0.4% higher NaCl rejection compared to a commercial RO membrane. In addition, the PO-TFC membrane exhibited excellent mechanical properties and organic solvent resistance.

In this study, we present a unique surface modification method for a water desalination membrane to control the surface fouling via titanium dioxide (TiO2) nanopillar pattern imprinting. The patterned membranes showed significantly improved fouling resistance for both organic protein and bacterial foulants compared to the nonpatterned membranes. The hydrophilicity of TiO2 used as a pattern material affects the improvement of chemical antifouling resistance of the membrane. Fouling behavior was also interpreted in terms of the topographical effect depending on the relative size of foulants to the pattern dimension. Moreover, the computational fluid dynamics simulation intimates that the overall and local shear stress enhancement on the patterned surface could affect the foulant deposition behavior on the membrane.

Thin-film composite (TFC) membrane is currently the most widely used membrane structure for reverse osmosis (RO) process. Most commercial membrane for RO consisted of porous support layer and dense polyamide permselective layer, yet the polyamide layer has a very rough surface morphology and considerable thickness, and these features are intrinsic properties of current RO membrane fabrication process. In this study, we present the new membrane fabrication, named layered interfacial polymerization (LIP). LIP could control the roughness and thickness of permselective layer without complicated process or significant membrane performance loss, and the performance itself was comparable to conventional IP membrane. Moreover, the fabricated membrane has a remarkable antifouling ability possibly due to the unique smooth morphology.