Negatively charged pore-filled membranes

Negatively charged pore-filled membranes based on homogeneous poly(2-acrylamido-2-methylpropanesulfonic acid), PAMPS, gels have been studied for nanofiltration applications. The properties of these membranes such as Darcy permeability and salt separation have been investigated and compared with other gel-filled membranes. It was found that PAMPS gel-filled membranes have lower permeabilities due to the very hydrophilic nature of the gel polymer. The salt separation profiles were typical of that expected for negatively charged membranes based on the Donnan exclusion separation mechanism.; Fundamental work on the calculation of membrane permeability and salt separation has also been conducted. The Darcy permeabilities of PAMPS gel-filled membranes have been theoretically calculated using the sphere model developed at McMaster University. It was shown that an accurate prediction of Darcy permeabilities of PAMPS gel-filled membranes can be made using the Odjik's theory of semi-dilute polyelectrolyte solutions combined with the Happel's cell model. The salt separation of PAMPS gel-filled membranes were calculated using both Teorell, Meyer and Sievers (TMS) and Donnan-Steric Pore (DSP) models with either measured or calculated membrane structural parameters. The results showed that salt separations of membranes with a wide range of gel polymer volume fractions could be accurately calculated. The model predictions also showed that Donnan exclusion is the predominant separation mechanism with these membranes; steric effect only plays an important role in very dense gel-filled membranes. The effective charged densities of the membranes are governed by counterion condensation.; To obtain better nanofiltration membranes, two novel methodologies have been developed. First, pore-filled membranes based on copolymer hydrogels were prepared by co-polymerization of AMPS with neutral co-monomers within the pores of a microporous substrate. Compared with the PAMPS gel-filled membranes, AMPS copolymer gel-filled membranes exhibited larger Darcy permeabilities and smaller dimensional changes. The salt separations were unchanged with these improvements in performance. Second, bipolar gel-filled membranes consisting of a PAMPS gel-filled layer on top stacked with a poly(3-acrylamidopropyltrimethylammonium chloride), PAPTAC, gel-filled layer have been studied for nanofiltration. These bipolar membranes showed high rejections of salts with both bivalent cations and bivalent anions (e.g., MgCl2 and Na2SO 4). However, the separation characteristic of these bipolar gel-filled NF membranes were found to be strongly affected by structural parameters such as the thickness of the top layer relative to that of the bottom layer and the gel density in the top layer.; Most importantly it is shown in the thesis that macroporous gels can be anchored within a microporous substrate by using a polymerization induced phase separation technique. These macroporous gel-filled membranes represent a new class of microporous membranes which have both a porous structure and a functionalized pore surface. It was found that the incorporated polymer networks were soft in nature and that the hydrodynamic properties of membranes could be controlled by manipulation of preparation conditions and gel chemical compositions. These membranes were examined in terms of protein purification. They were shown to have very high lysozyme binding capacities (up to 192mg/ml), more than four times the capacity of any commercially available S-membrane adsorbent. A three-dimensional protein adsorption mechanism has been proposed to explain these high capacities. Effect of preparation conditions and chemical compositions on protein adsorption has also been studied.; This thesis demonstrates clearly the possibility to construct gel-filled membranes with the pore sizes ranging from nanometer to micrometer using a single gel polymer. The structures and functionality of membranes can be effectively man...