Browsing by Subject "Solubility"
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Item Advannces in ion chromatograpy for environmental applications(Texas Tech University, 2003-08) Al-Horr, Rida SadekIon chromatography (IC) is a widely used analytical tool for the determination of many ionic species. Applications of ion chromatography extend over a wide range of chemical analyses. Introduction of eluent suppression in the mid-1970s extended the boundaries of conductometric detection into trace analysis. Current state-of-the-art IC systems require only water to operate, exhibit excellent reliabilities, and provide the ability of sample preconcentration and simultaneous multiple ion measurement, making them attractive for atmospheric analysis. Atmospheric particulate matter (PM) contains many inorganic and organic soluble ions. A number of those are weak acid anions that are largely undetectable in suppressed ion chromatography. An improved method that uses sequential suppressed and unsuppressed IC for the sensitive detection of both common anions and very weak acid anions has been investigated. After suppressed conductometric detection, the effluent is passed into a membrane device where KOH is passively introduced into the eluent stream using Donnan forbidden leakage. High temporal resolution measurement of atmospheric gases and constituents of atmospheric particulate matter (PM) is important to understand the chemistry and sources of atmospheric pollution. New continuous collection devices coupled with IC systems for fully automated measurement of soluble inorganic gases and soluble ionic constituents of atmospheric PM have been developed. Soluble gas collection is accomplished with a parallel plate wet denuder (PPWD). For particle collection, an automated alternating filter-based system was initially developed. This system uses two glass-fiber filters that alternate between sampling, and washing and drying. More recently, a continuous soluble particle collector (PC) of simpler design has been developed; this device does not use steam. Preceded by a denuder and interfaced with an ion chromatograph, this compact collector permits automated collection and continuous extraction of soluble anions and ammonium ion in atmospheric particulate matter. The systems have been deployed in a number of major field studies held in urban and suburban locations in the United States.Item Characteristics of foamed asphalt binders for warm mix asphalt applications(2014-08) Arega, Zelalem Alebel; Bhasin, Amit; Li, Wei, doctor of mechanical engineering; Prozzi, Jorge A; Zhang, Zhanmin; Juenger, Maria GAn increase in environmental awareness and energy concerns had recently prompted efforts to make pavement construction cheaper and more environmentally friendly. Warm mix asphalt (WMA) is an asphalt mixture production technology that promises to reduce production costs and greenhouse gas emissions. Foamed asphalt binder is increasingly being used to produce WMA. This dissertation addresses several issues related to the use of foamed asphalt binder for WMA applications. The first objective of the research presented in this dissertation is to develop a method and metrics to precisely quantify the characteristics of asphalt binder foams. Laboratory measurements were obtained using the newly developed method to evaluate the extent and stability of foams produced using different asphalt binders at different water contents and laboratory foaming devices. Results demonstrate that the method developed is promising in terms of its ability to provide a detailed history of the behavior of foamed asphalt binder as the foam collapses. In addition, results indicate that the method is sensitive to distinguish between foaming characteristics of different asphalt binders as well as different water contents and foaming devices. The second objective of this study was to relate intrinsic properties of the asphalt binder to its foaming characteristics. A physical model was developed for expansion of asphalt binder foam based on foam physics and fluid mechanics of micro-droplets. The model relates foamant water and asphalt binder mixing efficiency with the surface tension of the asphalt binder. The model can be used to predict which binder can be effectively foamed and used, and whether any chemical modification to the binder is necessary to achieve the same. Results indicate that only a small percentage of water is effective in foaming the asphalt binder. The last objective of this research was to evaluate the influence of foaming on asphalt binder residues and mixture workability and coatability. The influence of foaming process on the rheological properties of asphalt binder residue was investigated. In addition, the significance of foamed asphalt binder characteristics on mixture workability and coatability was evaluated. Results from this last part of the study can be used to optimize binder foaming such that the resulting mixture is coated and compacted without compromising performance.Item Characterization of an alkyl diamine surfactant for gas mobility control in gas enhanced oil recovery and conformance control(2016-05) Liebum, Madalyn Marie; Nguyen, Quoc P.; DiCarlo, DavidThe objective of this research is to characterize the properties and performance of an amine-based “switchable” surfactant, Duomeen TTM, at various environmental conditions. In particular, bulk characterization measurements namely, aqueous stability, solubility, partition, and rheological behavior were tested and applied in core flooding experiments using carbonate rock saturated in very saline brine. Aqueous stability provides insight about how Duomeen TTM solutions tolerate with changes in salt concentration, pH, and temperature. This surfactant becomes more hydrophilic as pH decreases and transforms into a viscoelastic solution at moderate to high salt concentrations. This viscoelasticity is intensified by changes in pH, temperature, and surfactant concentration of the solution, where surfactant concentration limits the aggregation density of the solution, pH influences the protonation process in the head group, and temperature controls the minimization of free energy by breaking, reformation, and branching of micellar networks. Furthermore, solubility measurements were conducted for a series of pressures and temperatures in pure CO2 as well as in gas mixtures composed of CO2 and CH4. It is shown that Duomeen TTM is very soluble in CO2, but becomes less soluble when methane is present in the system. Partition experiments amongst brine and CO2 reveal Duomeen TTM is very water soluble at low pH, in agreement with the aqueous stability results. Finally, these bulk characterization results were applied in core flooding experiments where in-situ viscoelasticity or gel development capabilities were tested with surfactant dissolved in solution at different salinities. In-situ viscosification is mainly dependent on the salinity contrast between the injective solution and resident brine as well as the rheological behavior of the surfactant solution at different salinities. This in-situ gel development provides mobility control by blocking thief zones and high permeable regions in porous media. In all, this ability to viscosify in-situ makes Duomeen TTM applicable for near-wellbore conformance control and CO2 mobility control in CO2 enhanced oil recovery.Item Improved bioavailability and site specific delivery of poorly water soluble drugs through the production of stabilized drug nanoparticles(2005-08) Vaughn, Jason Michael; Williams, Robert O., 1956-Bioavailability enhancement of poorly water soluble active pharmaceutical ingredients (API) is key for improving existing therapies and allowing for formulation of certain new chemical entities. The rate limiting step for absorption of these APIs is dependent on the dissolution rate and the APIs apparent solubility. Particle engineering processes such as evaporative precipitation into aqueous solution (EPAS) and spray freezing into liquid (SFL) were developed to enhance API dissolution and bioavailbality through the production of amorphous and nanoparticulate API. The morphology, primary API domain size and miscibility of particles produced by EPAS and SFL were investigated by several complementary and novel techniques. It was found that the SFL composition displayed amorphous character, a primary danazol particle size of 30 nm and was consistent with a solid solution. The EPAS composition was mostly amorphous with slight crystallinity, a primary danazol particle size of 500 nm and was consistent with a solid dispersion. The ability of the nanoparticulate and amorphous particles to supersaturate dispersions and how this impacts oral bioavailability was tested through in vitro and in vivo models. Through the use of a testing method for supersaturation, it was found that EPAS and SFL compositions achieve higher apparent solubilities when compared to the physical mixture and commercial Danocrine® capsules. This improvement in solubility allowed for more danazol to be available for absorption in vivo. Pulmonary delivery of SFL nanoparticulate itraconazole was evaluated for pharmacokinetic parameters and steady state trough levels compared to oral delivery of an SFL oral composition and the commercial product. Inhalation of ITZ compositions is an effective method of antifungal therapy for the treatment and prophylaxis of invasive fungal infections. High and sustained lung tissue concentrations are achieved via inhalation of an amorphous ITZ pulmonary composition while maintaining serum levels which are above the minimum lethal concentration for A. fumigatus. Histology, macrophage uptake and IL-12 induction was evaluated for aerosolized amorphous ITZ nanoparticles. Pulmonary administration of amorphous ITZ nanoparticles or excipient placebo does not cause inflammation or changes in alveolar and airway histology. Uptake of ITZ by alveolar and airway macrophages occurs following inhalation of an amorphous ITZ composition.Item Monte Carlo studies of polymer chain solubility in water(2005-12) Lu, Ying, 1972-; Sanchez, Isaac C., 1941-Poly (Ethylene Oxide) (PEO, with a general formula (CH₂-CH₂-O)[subscript pi] ) is completely soluble in water at room temperature over an extremely wide molecular weight range and has been widely studied by experiment and theory. The objective of our work is to study the solubility behavior by the method of Monte Carlo simulation. The insertion factor lnB, which is equivalent to the infinite dilute Henry's Law Constant, is used to represent the solubility of various molecules in water. Our research started with simple fluid and aqueous solutions of small molecules including hard spheres, inert gases, hydrocarbons and dimethyl ether (DME, as a precursor for PEO). Solubility consists of a favorable energy term and an unfavorable entropy term. Against the common belief of entropy-dominating-hydrophobicity effect, it is actually the ability of the solute to interact with solvent (or the energetic factor) that dominates solubility. The solubility minimum appearing for both hydrophobic and hydrophilic solutes along the water coexistence curve is the result of competition between the favorable energy contribution and the unfavorable entropy contribution. Normal alkanes with carbon number from 1 to 20 have been modeled by LJ chains to study the solubility of non-polar polymer chains in water. Various constraints have been put on the LJ model to evaluate their effect on solubility. No significant difference was observed for LJ chain with or without fixed bond angles, but torsional interaction changed the chain solubility dramatically. The temperature and chain-length effect on chain solubility has been examined and it can be explained by the balancing between the intra-chain interaction and entropy penalty. By choosing the right torsional interaction parameters we may be able to reproduce by simulations the solubility minimum of normal alkanes at C₁₁. PEO was modeled by united atom chains with length up to 30. The most probable distance between two nearest ether oxygens in both vacuum and aqueous solutions matches the hydrogen bond length in bulk water. Hydrogen bonding plays an important role in the unique water solubility behavior of PEO since the water-PEO interaction effectively increases the total number of hydrogen bonds and results in a favorable change in energy. A trans-gauche-trans conformation along the O-C-C-O bonds does enable hydrogen bond formation between one water molecule and two nearest or next nearest ether oxygens. A helix structure is not required for the PEO to have favorable interactions with water. Two polymers with similar structure as PEO but are insoluble in water: Poly (methylene oxide) (PMO) and Poly (propylene oxide) (PPO) have been studied to compare with PEO. Their difference in structure from PEO, though slight, reduces the chance of hydrogen bond forming between water and chains so as to decrease the solubility.