Author

Wenyi Jiang

Date of Award

9-1999

Degree Type

Thesis

Degree Name

Doctor of Philosophy (PhD)

Department

Chemistry

Supervisor

Professor Ronald F. Childs

Abstract

Pore-filled cation-exchange membranes containing poly(styrene-sulfonic acid) have been prepared by thermally induced free radical polymerization of polystyrene and divinylbenzene (DVB) in the pores of a polyethylene (PE) microporous membrane followed by sulfonation of the incorporated poly(styrene-DVB). The mass increase of poly(styrene-DVB) incorporated in the PE substrate membrane can be controlled from 0 to approximately 600%. The degree of sulfonation ranges from 45% to 85% of the theoretical value calculated based on the mono-sulfonation of the incorporated poly(styrene-DVB). The formation of sulfones was been detected by Fourier transform infrared (FTIR). The Energy dispersive X-ray (EDX) spectroscopy, scanning electron microscope (SEM), and FTIR spectra show that the poly(styrene-sulfonic acid) incorporated is evenly distributed in the pores throughout the membranes. The membrane dimensions were examined during various manipulations, such as temperature and solvent, degree of incorporation of poly(styrene-DVB). These pore-filled membranes were characterized including ion-exchange capacity, ion-exchange concentration, water content, thickness, area electrical resistance, and transport number. These membranes have high water contents (up to 75%), ion-exchange capacities (up to 5.60 meq/g), and ion-exchange concentrations (up to 7.3 eq/kg of water). The electrical resistance of the membranes were found to be lower than 1.0 ohm·cm2 . The counter-ion (Na+ ) transport numbers were determined by an electromotive force (EMF) method and were found to range from 0.80 to 0.96. The cation-exchange membranes have been tested for the separation of sodium hydroxide and salts by diffusion dialysis. The membranes were capable of separating the base and salts in diffusion dialysis. The results have been discussed in terms of the different transport processes for sodium hydroxide and the salt. The membranes are capable of rejecting sodium chloride and separating NaCl/MgCl2 mixed solute solutions in pressure-driven processes. It was found that their rejections to NaCl were high but their fluxes were low. The effects of salt concentration on fluxes and rejections were determined. Negative rejections of sodium ions were observed for NaCl/MgCl2 mixed solute solutions. The negative cation rejection can be understood in terms of the combination effect of Donnan exclusion of the cation-exchange membranes and the diffusivity of the mobile ionic species in the pressure-driven processes. The results obtained in this work are consistent with the recent studies at McMaster University. It clearly demonstrated that gel polymer concentration within the pores is a crucial factor on membrane permeability. The findings of this work verified the pore-filled model developed at McMaster University. The work conducted in this thesis extends the understanding of properties and performance of polyelectrolyte-filled membranes for nanofiltration applications.

Files over 3MB may be slow to open. For best results, right-click and select "save as..."

Included in

Chemistry Commons

Share

COinS