Bio-based monomers are a more sustainable alternative to conventional oil-based monomers [1]. The bis-epoxide limonene dioxide from the epoxidation of the terpene limonene has shown potential for different applications [2]. One of those applications is the use of limonene dioxide as a crosslinking agent to improve the solvent resistance of nanofiltration membranes. Epoxidation of terpenes is conventionally done using meta-chloroperoxybenzoic acid (m-CPBA), using metal complexes with metals such as Tungsten, Titanium, and Cobalt, or different hydroperoxides. A greener method of epoxidation explored is the use of in situ generated dimethyldioxirane from the reaction of acetone and potassium peroxy-monosulfate (Oxone) [3]. The reaction uses sodium bicarbonate buffer in aqueous solution with a mixture of limonene and acetone. This project aims to synthesize different bis-, and tris-epoxides from different bio-derived terpenes including limonene, gamma-terpinene, geraniol, farnesol, and nerol using the reported method using Oxone and ultrasonication. Epoxidation using m-CPBA is also investigated to compare it to the Oxone method. In general, epoxidation using m-CPBA results in higher amount of epoxide, but the Oxone method presents a more sustainable alternative with good results. Successfully synthesized epoxides are used to crosslink polybenzimidazole nanofiltration membranes. Solvent testing in dimethylacetamide is used to inspect whether crosslinking is successful. Polyethylene glycol diglycidyl ether is a commercial bis-epoxide that was used to validate the crosslinking method. Crosslinking was successful, as confirmed by solvent testing and FT-IR analysis. Filtration testing showed that the permeance of the membrane was not affected by crosslinking, while the membrane’s rejection was increased from 10.29 ± 1.01 % to 17.23 ± 2.49 % after crosslinking using polyethylene glycol diglycidyl ether. Nerol and limonene bis-epoxides were successfully synthesized with high purity and were tested as crosslinkers. However, crosslinking was unsuccessful, as demonstrated by solvent testing. This project successfully synthesized bis-epoxides from different terpenes using a greener method of epoxidation. The possibility of successful crosslinking using the terpene-based crosslinkers should be further investigated.

<p> The nature of the coloured solutions of selenium and tellurium in sulfuric acid has been investigated using mainly cryoscopic, conductimetric, and spectrophotometric techniques. Evidence has been obtained for the new species Se₈²⁺ and Se₄²⁺ in the green and yellow solutions of selenium respectively. Evidence on red solutions of tellurium seems consistent with the formulation Te₄²⁺. Solid compounds analysing as Se₄S₄O₁₃, Se₄(HS₂O₇)₂ and TeO(HS₂O₇)₂ have been prepared and characterised. </p> <P> Solutions of some selenium(IV) and selenium(VI) compounds have been examined. It is shown that a number of phosphates and arsenates ionise in sulfuric acid to give the P(OH)₄⁺ and As(OH)₄⁺ ions respectively. Ammonium metavanadate and vanadium pentoxide ionise to give the complex acid H[VO(HSO₄)₄]. Potassium chromate and dichromate ionise to give the compound CrO₂(HSO₄)₂ and potassium permanganate ionises to give the non-electrolyte MnO₃∙SO₄H. </p> / Thesis / Doctor of Philosophy (PhD)

<p> Approximately 80 percent of all synthetic polymers used are cross-linked polymers, unfortunately the characterization of cross-linked polymers has not kept up with their use. This study tries to help in the characterization of cross-linked polymer systems. More specifically the interactions of cross-linked polymer systems with solvents will be probed. Nuclear Magnetic Resonance (NMR) spectrometric techniques will be used to characterize solvent-polymer interactions.</p> <p> The cross-linked polymer system studied was the polymer ethylene glycol dimethacrylate (EGDMA) with methylmethacrylate (MMA). A splitting of the solvent signals was observed in the NMR spectrum which can be used to understand these solvent-polymer interactions. Several NMR parameters and swelling of the polymers were measured in order to understand these interactions. The chemical shift differences between the solvent types and the peak linewidths were measured. As the polymer becomes more highly cross-linked the chemical shift differences and the linewidths increases. This compactness can be monitored by measuring the degree of swelling of the polymer. In addition the possibility of an isotope effect was explored by monitored by placing the polymer in solvent mixture of CHCl3/JCDCl3 and varying the temperature. No isotope dependence was found to exist for chloroform over the temperature range analyzed. The degree of splitting and the occurrence of splitting was found to be dependent on the solvent system. In general, solvent splitting is present for solvents that are able to cause the polymer to swell appreciably. For 4.8 weight percent EGDMA in EGDMA/MMA polymer a splitting is usually observed for a solvent that is able to swell the polymer to twice its dry size. The association between the solvents and the polymers can be best explained by breaking the interactions into a number of components.</p> <p> The explanation is based on the presence of three interactions. A weak chemical interaction exists between the solvent and the polymer to account for the field dependent linewidths. A second chemical interaction that results is a binding between the solvent and the polymer and causes the solvent splitting to occur. The third interaction is a result of the increased rigidity and compactness of the polymer as the weight percent EGDMA in EGDMA/MMA polymer increases. Alternatively as the polymer becomes more compact the chemical shift difference between the two types of solvents increases.</p> <p> Ultimately, it is shown that NMR is a useful aid in understanding solvent-polymer interactions.</p> / Thesis / Master of Science (MSc)

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A new solvent extraction method has been developed for the extraction of metal and organic ions from very dilute aqueous solutions. The new method, which has been named Predispersed Solvent Extraction (POSE), is based on the principle that 1 there is no need to comminute both phases. All that is necessary is to comminute the solvent phase prior to contacting it with the feed. This is done by converting the solvent into aphrons, which are micron-sized globules encapsulated in a soapy film. Since the aphrons are so small, it takes a long time for the solvent to rise to the surface under the influence of gravity alone. Therefore, the separation is expedited by piggy-back flotation of the aphrons on specially prepared gas bubbles, which are somewhat larger than aphrons and are called colloidal gas aphrons (CGA). Copper, uranium and chromium ions, and alizarin yellow were extracted from very dilute aqueous solutions using PDSE. Tests were performed in a vertical glass column in both batch and continuous modes, and in a continuous horizontal trough. The new solvent extraction procedure worked very efficiently and very quickly under laboratory conditions. Higher than 99% extraction was achieved in many of the tests performed. / Master of Science

In this work, we present two open literature databases, the VT-2005 Sigma Profile Database and the VT-2006 Solute Sigma Profile Database, that contain sigma profiles for 1,645 unique compounds. A sigma profile is a molecular-specific distribution of the surface-charge density, which enables the application of solvation-thermodynamic models to predict vapor-liquid and solid-liquid equilibria, and other properties. The VT-2005 Sigma Profile Database generally focuses on solvents and small molecules, while the VT-2006 Solute Sigma Profile Database primarily consists of larger, pharmaceutical-related solutes. We design both of these databases for use with the conductor-like screening model−segment activity coefficient (COSMO-SAC), a liquid-phase activity-coefficient model. The databases contain the necessary information to perform binary and multicomponent VLE and SLE predictions. We offer detailed tutorials and procedures for use with our programs so the reader may also use their own research on our research group website (www.design.che.vt.edu). We validate the VT-2005 Sigma Profile Database by pure component vapor pressure predictions and validate the VT-2006 Solute Sigma Profile Database by solid solubility predictions in pure solvents compared with literature data from multiple sources. Using both databases, we also explore the application of COSMO-SAC to solubility predictions in mixed solvents. This work also studies the effects of conformational isomerism on VLE and SLE property prediction. Finally, we compare COSMO-SAC solubility predictions to solubility predictions by the Non-Random Two-Liquid, Segment Activity Coefficient (NRTL-SAC) model. We find UNIFAC is a more accurate method for predicting VLE behavior than the COSMO-SAC model for many of the systems studied, and that COSMO-SAC predicts solute mole fraction in pure solvents with an average root-mean-squared error (log10(xsol)) of 0.74, excluding outliers, which is greater than the RMS error value of 0.43 using the NRTL-SAC model. / Master of Science

Yes / A systematic study of the influence of solvent on the crystal packing behaviour of Reichardt's dye demonstrates that the structure of the assembly formed in the solid state depends on the nature of the solvent–solute interactions present in the solution phase. Apolar aprotic solvents lead to solvates with a hexagonal channel topology, but this supramolecular assembly is perturbed by the presence of aromatic or polar protic solvents.