Thin film composite polyamide membrane on polydopamine layer containing stabilized particles for reverse osmosis
September 11-16, 2016
Ultrathin, crosslinked, aromatic polyamide (PA) thin film composite (TFC) membranes, which are interfacially polymerized onto microporous polysulfone support membranes, are extensively utilized in the state of the art reverse osmosis systems. The dense, ultrathin, crosslinked PA layer enables high water permeability with high selectivity. However, the performance of these membranes in desalination applications is currently limited by an “upper bound”, the permeability/selectivity trade off inherent in polymeric membranes and polyamide membranes are susceptible to damage from biological fouling and free chlorine. Therefore, to break through the performance upper bound of polymeric membranes, a class of mixed matrix membranes called thin film nanocomposite (TFN) membranes has been developed. In these membranes, fillers (typically inorganic nanoparticles) are dispersed in aqueous or organic phase casting solutions during interfacial polymerization process. The addition of nanoparticles to TFC membranes is a promising technology to reduce energy costs and increase the performance in desalination processes. Nevertheless, there may be some “non-ideal effects” in the membrane such as particle aggregation at higher zeolite loadings and void or rigidified polymer formation at the polymer/particle interface. Furthermore, there might be particle loss under high pressure during cross-flow desalination process which may decrease the membrane performance. In addition to the performance improvement efforts, researchers have developed thin film composite membranes functionalized with surface coating to enhance the antifouling resistance of membranes. However, due to addition of transport layer into structure, the membrane may have lower water permeability. To overcome these drawbacks, our overall goal is to develop highly permeable, antifouling thin film composite membranes with polydopamine/molecular sieve layer and anti-fouling surface coatings. The performance of these novel membranes’ will be demonstrated by desalination through reverse osmosis processes. To achieve this goal, our first research objective is to develop highly permeable polydopamine-molecular sieve/polyamide membranes without antifouling coating, which will be added later. Therefore, we developed a method to enhance membrane performance and filler particle stability in TFN membranes. First, we stabilized particles on microporous polysulfone support by thin bio-inspired polydopamine layer, and then we interfacially synthesized polyamide on top of this layer. This method also minimizes the expensive particle usage compared with the common TFN synthesis procedure (particle addition into polyamide casting solution). In this work, we present our results for development of thin film composite polyamide membranes on polydopamine layer with molecular sieves particles on polysulfone support membrane. First, we synthesized dopamine layer with different particle content and different particle size. Then, we synthesized a series of polyamide membranes via interfacial polymerization. For comparison, we also synthesized regular TFC and TFN polyamide membranes. Then we measured the permeability and selectivity performance using dead-end filtration and cross-flow testing system. We report the synthesized membrane surface and morphology result with contact angle, Fourier transform infrared spectroscopy, scanning electron microscopy, and atomic force microscopy.
Pinar Cay Durgun, Mary Laura Lind, Francois Perreault, and Rafael Verduzco, "Thin film composite polyamide membrane on polydopamine layer containing stabilized particles for reverse osmosis" in "Advanced Membrane Technology VII", Isabel C. Escobar, Professor, University of Kentucky, USA Jamie Hestekin, Associate Professor, University of Arkansas, USA Eds, ECI Symposium Series, (2016). http://dc.engconfintl.org/membrane_technology_vii/83