<p> The mechanism by which PVC particles remained stable in n-butylchloride was investigated.</p> <p> The PVC particles were made by aqueous emulsion polymerization with benzoyl peroxide initiator and polyvinyl alcohol surfactant. The particles were cleaned by ion exchange and their surface charge was found to be 0.068 ± 0.005 C/m^2. Dispersions of PVC in n-butylchloride were prepared by two methods. In the first, the particles were dried in an oven. The dried particles were redispersed in n-butylchloride via sonication. This produced a dispersion consisting of 0.26 kg/m^3 of PVC particles with an arithmetic volume average diameter of 317 nm and a standard deviation of 93 nm. The second method involved dialyzing the cleaned aqueous latex with methanol and then with n-butylchloride. The dialysis method was inferior to the sonication method. The dialysis method was time consuming, it produced a dispersion with large particle diameter, the dispersion was contaminated with water and methanol and surface species were removed by the methanol.</p> <p> The particles were found to be stabilized by an electrostatic mechanism. This was verified by observing that the particles migrated to the positive electrode when exposed to a potential difference of 1000 V. A surface potential of 0.203 V was calculated for the particles from mobility measurements and the Huckel equation.</p> <p> The charge separation that must occur to allow the particles to have the negative charge is hypothesized to be a result of organic molecules such as PVC-PVA oligomers that dissolve from the particles and form micelles. These molecules were readily soluble in methanol and only slightly soluble in n-butylchloride. As a result, when the dispersion was washed with methanol, the particles flocculated. The presence of these species in the dispersant was supported by evidence from ultra-violet, infra-red and nuclear magnetic resonance spectroscopy. The electronegative groups in the micelles provide a reasonably polar environment for hydrogen ions to exist. These hydrogen ions became the countercharge for the negatively charged particles.</p> / Thesis / Master of Engineering (MEngr)

<p> The ultimate objective of this research project was to establish an HPLC method that allows the quantification of most of the major components of a circulating Stretford process liquor using one sample. The criteria that had to be met were reasonable retention times, resolution approaching 1.0 and quantitative results (ie. with an uncertainty in the accuracy and precision of the results less than ± 10%). Ion chromatography was the route chosen since the major components of the circulating liquors are present as either inorganic or organic anions. Ion pair chromatography and ion exchange chromatography were the general methodologies investigated during the study.</p> <p> Ion pair chromatography, specifically soap chromatography, was successful in the isolation of the NaSCN, Na2SO4 and Na2S2O3 species of the circulating Stretford liquors. It was unsuccessful in the quantitative separation of these species. The method was abandoned in order to find a method which could quantify these species as well as the other components of the circulating liquors.</p> <p> The ion exchange chromatography studies fell into two categories, that being columns with a silica based packing and columns with a polymer based packing. The silica based columns had a limited operating range of pH for the analysis and the backbone of these columns degraded at pH values exceeding pH 5.5. The polymer based ion exchange columns had a much wider operating pH range and allowed for the analysis of the Stretford liquors without the need to change the pH of the solution.</p> <p> The best possible method of analysis was the polymer based technique. All of the components of the Stretford liquors, with the exception of the ADA (anthraquinone disulfonic acid) could be quantified in under 15 minutes. The method provided quantitative results and very good resolution between the species eluted.</p> / Thesis / Master of Science (MSc)

Electrodialysis is a membrane separation process that uses an electrical potential to drive the separation. The performance of these systems is largely based on the performance of their ion exchange membranes (IEMs). This research focused on enhancing the performance of IEMs for electrodialysis through surface modification techniques involving chitosan bonded to the surface of commercially available cation exchange membranes (CEMs). The surface functionalization techniques resulted in membranes with improved electrodialysis performance. This research also explored the processing framework to produce functionalized sulfonated PEEK (sPEEK) nanofibers for future consideration as cation exchange membranes. Chitin was deacetylated to form the functionalized biopolymer chitosan, then applied to the surface of CEMs, rendering them more hydrophilic. These membranes were evaluated across several electrodialysis performance metrics. Results demonstrate that adjusting the degree of deacetylation of chitosan to enhance membrane hydrophilicity positively impacted electrodialysis performance. Furthermore, this research evaluated the effectiveness of similarly functionalized membranes to extract Lithium from brine solutions. The chitosan-coated membranes showed improved electrodialysis performance, including enhanced flux, limiting current density, system resistance, selectivity, and fouling resistance. Lastly, the sPEEK nanofibers were produced for the fabrication of ion exchange membranes by manipulating operational parameters to assess their impact. This research presents the successful functionalization of PEEK via sulfonation and electrospinning of the resulting sPEEK. These nanofibers were then pressed to form a solid sPEEK membrane. It was observed that changes in electrical potential and rotational speed influenced fiber diameter and spinnability. A correlation was established between membrane surface hydrophilicity and electrodialysis performance metrics in desalination and lithium extraction applications. This research advanced the understanding of structure-property relationships for CEMs. The research herein proposes techniques for industries such as desalination and lithium extraction that can meet growing demands for clean water and sustainable methods for producing high-value raw material streams.

Solvent extraction techniques have been used to determine formation constants for molecular silver chloride and dichloro silver (I) ion in unsaturated aqueous solutions. Nitrobenzene was used to extract the molecular silver chloride from the aqueous silver chloride solution. The total concentration of silver in each phase was determined by radioassay techniques and related by an expression involving the equilibrium constants. The reciprocal of the distribution ratio times the activity of the chloride ion was plotted versus the activity of the chloride ion and portions of the curve were analyzed by the method of least squares to obtain values for the constants involved. The values obtained for K1, K2 and Kd were 1.96 X 103, 3.00 X 105, and 0.243 respectively. A second analysis of the experimental data was made by a least squares analysis of a plot of the logarithm of the reciprocal of the distribution ratio versus the logarithm of the activity of the chloride ion. The analyis was performed over the entire range of experimental points and the values obtained for K1, K2, and Kd were 1.62 X 103, 2.80 X 105, and 0.285 respectively.

The complex species in silver chloride solutions have been investigated by solubility measurements and by ion exchange methods in this work. The solubility of silver chloride in solutions of varying chloride ion concentrations was determined by radioassay techniques. The method of least squares was used to evaluate the constants for the formation of the aqueous silver chloride and the dichloro-complex species; the values being 1.99 x 103 and 2.98 x 104, respectively, at 25.00°C. Aqueous solver chloride has been shown to be sorbed by Amberlite IR-120 from silver chloride solutions which have an ionic strength of 0.2. This sorption has been found to follow the Freundlich, as well as the Langmuir adsorption equations. The sorbed species is postulated to be associated silver chloride molecules, the degree of association being about 4, 5, or 6.

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In our previous studies, uncross-linked large diameter cellulose beads were optimized for solids content, bead size, pressure-flow limits, molecular accessibility and performance as an immunosorbent. Here, anion exchange (DEAE) cellulose beads were derivatized by two different procedures (defined as A and B) and the changes in bead morphology were correlated with transport and sorption kinetics. The kinetic characteristics clearly defined a minimum of two different types of protein binding site architecture. DEAE cellulose beads exhibited molecular exclusion of BSA near the edge of the bead in contrast to greater permeability seen in underivatized beads. Thus, accessible BSA binding sites are present only on the surface of the derivatized beads. DEAE cellulose beads derivatized by procedure B gave higher density of DEAE ligand as compared to beads derivatized by procedure A, as well as higher static and dynamic capacity for BSA. Even though DEAE cellulose beads (DP 2070, 450 μm diameter derivatized by procedure B) have lower small ion capacity than DEAE cross-linked agarose beads, as well as 1/4 the surface area, they exhibit equivalent binding capacity for BSA per volume of support. Thus, DEAE cellulose beads possess more sites per surface area as well as have lower ligand density per BSA site. Furthermore, BSA adsorption sites on DEAE cellulose beads derivatized by procedure B exhibit slow binding kinetics as compared to those derivatized by procedure A and also compared to DEAE crosslinked agarose beads. Thus, the rate limiting step for the adsorption of BSA on DEAE cellulose beads was not diffusion as suggested by the large diameter of the bead. Feasibility studies were performed for process scale applications to fixed and expanded bed anion exchange purification. The large diameter DEAE cellulose beads of this study maybe useful for process scale anion exchange as evident from purification of immunoglobulins from hybridoma cell culture in fixed bed. The balance of large diameter and density of these DEAE cellulose beads enable stable expanded bed purification of proteins such as recombinant human protein C from transgenic porcine whey. / Ph. D.

The main goal of this project was to compare the changes in statistical variation and Weibull characteristics of the strength of glass rods as modified by heat treatment with and without an ion exchange bath. Several sample groups of 30 sodium borosilicate glass rod specimens were heat treated at various temperatures in air and in a potassium nitrate salt bath to induce an ion exchange process. All samples were then tested to failure in 4-point bending to assess the resulting Modulus of Rupture (MOR). Statistical analysis techniques and Weibull analysis were used to study the variations which occur within and between strength distributions of each sample group. A smaller sampling of test groups was subjected to fractographic analysis to study the effect of ion exchange on fracture features. The data shows that the ion exchange process caused a statistically significant increase in the strength of the glass rods. Samples which were heat treated do not show any significant changes in average strength. The fractographic analysis suggests that no changes in fracture morphology occurred as a result of ion exchange process, and that the critical flaw size population was not significantly different. / Master of Science