(609f) Novel Charge Mosaic Membranes for Desalination

Membrane-based desalination has been extensively developed during the last 50 years as a promising solution for the growing concern of clean water scarcity in many parts of the world. In the same period, ion exchange membranes (IEM) have evolved from laboratory stage to industrial products with remarkable technical and commercial impacts. The evolution of ion exchange membranes has enabled their use in a variety of separation processes including electrodialysis for desalination. In contrast IEMs which possess either positive or negative fixed charges, a charge mosaic (CM) membrane consists of arrays of anion and cation exchange elements with fixed and mobile ions of both charges. Adjacent ionic channels of opposing charge provide a continuous pathway from one side of the membrane to the other. Negative osmosis and salt permeability occur in CM membranes much greater than non-electrolyte permeability.

This work describes a new formation technique to develop CM membranes, which offers the potential to increase the density of contact regions and thereby is expected to greatly enhance performance. The proposed membranes are prepared by adding Poly(sodium 4-styrenesulfonate) (PSS) and Poly(allylamine hydrochloride) (PAH) as two countercharge polyelectrolyte solutions to an ultrafiltration support. Diffusion of polymers inside the pores of the support layer provides the opportunity to build continuous channels, capable of flowing negative and positive ions through their respective pathways. The new method also seeks to maximize the already-achieved salt enrichment through CM membranes by operating under Gibbs_Donnan equilibrium condition. Therefore, one ionic polymer is added to the feed solution. Mathematical models are developed for quantification purposes of salt and polymer transport. The salt enrichment of outlet stream is calculated based on the developed models.

The challenges of producing these structures are discussed, and membrane performance results are reported illustrating the potential of the new membranes for desalination.