(355b) Synthesis of Polyamide Reverse Osmosis Membranes for Separating Small Neutral Charged Molecules

To meet the growing demand for potable and reusable water, numerous techniques are currently being employed, including filtration, sedimentation, distillation, and membrane-based separations. Among these techniques, reverse osmosis (RO) has gained significant attention due to its outstanding desalination performance. Even though RO membranes exhibit excellent performance rejecting monovalent and divalent salt ions, they do not reject small, neutral, and uncharged molecules (SNUs) to a level to produce potable water, especially at near-neutral pH. Because the top separation layer of RO membranes is a dense and non-porous polyamide layer, molecules pass through the free volume network and aggregate holes of the polyamide selective layer. The available free volume is a function of the monomers and polymerization conditions used to synthesize these polyamide layers. In this regard, the synthesis of RO membranes with novel chemistries for separating SNUs is required. We hypothesize that if the polyamide membranes can be made with small linear amine monomers, then the polyamide layer free volume hole size will be reduced increasing SNU rejection. In this work, we synthesized polyamide RO membrane separation layers via the interfacial polymerization reaction between an amine monomer (m-phenylenediamine and/or 1,3-diaminopropane) and an acid chloride monomer (trimesoyl chloride). The synthesized membranes were characterized using SEM and ATR-FTIR. Membranes were performance tested for water permeance and NaCl salt rejection using a dead-end stirred cell. Control and novel membranes showed moderate water permeance (~1.5 LMH/bar) and good salt rejection (~90%). SNU rejection tests using urea and boric acid are currently ongoing.