(324c) Zwitterionic Hydrogels Modified By Gel-Liquid Interfacial Polymerization with Improved Water/Salt Selectivity

Zwitterionic hydrogels have been intensively investigated for membrane water/salt separation, such as forward osmosis (FO) for water purification. Herein we demonstrate that the hydrogels can be modified with highly cross-linked polyamides by gel-liquid interfacial polymerization (GLIP) to further improve the water/salt selectivity without reducing water flux. Specifically, the hydrogels are prepared using sulfobetaine methacrylate (SB) and poly(ethylene glycol) diacrylate (PEGDA) via photopolymerization. Then the hydrogels were swollen by piperazine solutions and then exposed to trimesoyl chloride for interfacial polymerization to form a skin layer of polyamides. The surface morphology and mechanical properties significantly change after surface modification. For example, the average surface modulus of a hydrogel is ~8.7 MPa, and after modification, it increases to 200 MPa. The modification also increases the surface roughness. The effect of hydrogel compositions and the GLIP conditions on the water/salt separation properties is thoroughly investigated. For example, the modified hydrogel exhibits water permeance of 0.25 liter/(m² h) (LMH) and Na₂SO₄ rejection of 90% or higher. Such performance is more superior to commercial membranes such as NF90 (with water permeance of 0.10 LMH) and SW30-XLE (0.046 LMH). The effect of foulants (such as sodium alginate) on the long-term water flux will also be presented. This work demonstrates a facile approach to modify hydrogels to improve mechanical properties and water/salt separation properties.