ABSTRACT PELCHEM, the chemical division of NECSA, produces the fluorocarbon hexafluoropropylene (HFP) onsite. In 2005 PELCHEM initiated research into the wet oxidation of HFP to produce the higher value fluorocarbon hexafluoropropylene oxide (HFPO). Although successful in the conversion of HFP to HFPO, the product stream contained both the product and the unreacted HFP. As a result, PELCHEM contracted the Thermodynamics Research Unit at the University of KwaZulu-Natal to investigate the separation of HFP and HFPO. A solvent selection procedure was used to identifY potential solvents and an initial list of two hundred and seven candidate solvents compiled. Utilising the UNIFAC group contribution method, the initial list was narrowed down to thirty solvents using the criterion of selectivity at infinite dilution. Through the comparison of specific solvent properties such as recoverability, safety, environmental factors and economic considerations, a final list of ten solvents was generated. The list of ten solvents was proposed to PELCHEM who identified four solvents for further studies. The work involving the two solvents, toluene and hexafluoroethane (RI 16), is presented in this dissertation. The solvent toluene has been previously used by the du Pont company for the separation of HFP and HFPO, while R116 is a novel solvent for this application. The solvent selection procedure was performed in collaboration with a member of the Thermodynamics Research Unit, and the work on the remaining two solvents is presented in the dissertation of (Nelson 2008). Experimental binary high pressure vapour liquid equilibrium data were measured for the HFP + toluene, HFPO + toluene, R116 + HFP, and R116 + HFPO systems at two temperatures: 273.15 and 3 13.15 K. Pure component vapour pressure data for HFPO in the temperature range of 271.90 to 318.20 K were also measured. The HPVLE measurements were performed at the Thermodynamics Energy and Phase Equilibria laboratories at Ecoles des Mines de Paris using two experimental techniques and equipment. The binary systems involving toluene were measured on a static synthetic Pressure Volume Temperature apparatus equipped with a variable volume cell. The binary systems involving RI16 were measured on a static analytic apparatus equipped with a Rapid On-line Sampler Injector. None of the systems measured for this project have been reported in the literature. The four binary systems and the pure component vapour pressure measurements thus constitute new data sets. All experimental data were modelled via the direct method using the computer software Thermopack. Three model combinations were used to represent the data: the Peng-Robinson equation of state with the Wong-Sandler mixing rules, the Peng-Robinson equation of state with the Modified-Huron-Vidal first order mixing rules, and the Soave-Redlich-Kwong equation of state with the Wong-Sandler mixing rules. The Mathias-Copeman alpha function was used in conjunction with the equation of state models, and the NRTL activity coefficient model was incorporated into the mixing rules. Due to time constraints, experimental data for the binary system HFP + HFPO were not measured. Data for this system was predicted at two temperatures, 273.15 and 313.15 K, via the PSRK-UNIFAC method. The critical line for the supercritical systems R116 + HFP and R116 + HFPO were calculated in Thermopack. PELCHEM required a commercial grade HFPO product stream of purity greater than 99 % (mole), and a purified HFP product stream of purity greater than 95 % for the recycle and conversion of HFP into HFPO. Using the regressed experimental high pressure vapour liquid equilibrium data, two preliminary separation processes were designed in Aspen Plus to achieve these objectives. The first scheme involved toluene and utilised the process of extractive distillation with toluene introduced as a liquid solvent. The toluene bonded to the HFP and was removed as a bottoms product which allowed a purified HFPO stream to be recovered as a distillate. The second scheme involved RI16 and utilised the process of gas stripping, with a liquid mixture of HFP and HFPO contacted with a gaseous stream of R116. The R116 removed the HFP from the liquid mixture, resulting in a purified HFPO stream. The toluene process resulted in an overall HFPO product recovery of 98.46 % and HFPO product purity of99.88 % (mole). The RI16 process resulted in an overall HFPO product recovery of96.57 % and HFPO product purity of99.71 %. For the component HFP, the toluene process resulted in an overall HFP product recovery of 99.42 % and product purity of96.41 %. The RI16 process resulted in an overall product recovery of99.36 % and product purity of93.45 %. From a comparison of the preliminary design of the separation processes on the basis of patent issues, performance, and other miscellaneous factors, it was concluded that the RI16 process compared favourably to the process involving the solvent toluene. The preliminary process designs were presented to PELCHEM in 2007, and pending further experimental work PELCHEM plans to patent the RI16 separation process. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2008.

Västerås is a city with an industrial heritage. One of the larger companies in Västerås is ABB AB, which has multiply businesses located at the area Finnslätten. High concentrations of trichloroethene (TCE) were found in the soil and groundwater at Finnslätten 1 during a phase II environmental site assessment. Due to the result of the assessment a supplementary investigation and a site specific risk assessment were made of building 358. The source zone and plume of trichloroethene have not been characterized even after several investigations at the site. The aim of this study was to make a risk assessment of three other buildings inside the area were degreasing with TCE have historical taken place. The collected information resulted in a risk class 2 of the three objects and shows that the buildings might be potential pre-emission sources of trichloroethene. The second aim contains a comparison between traditional and alternative approaches to enlighten the importance of effective characterization methods. Two potential characterization strategies were chosen; TRIAD approach and CMF approach. The result showed the importance of systematic project planning, dynamic work planning strategy and the use of multiple techniques to form the best “hybrid” during characterization of DNAPL. In order to bring the investigation to a successful conclusion it is of great importance to consider the uncertainties or diminish the uncertainties by collecting essential information.

Persistent organic pollutants and heavy metals are released into the environment through different anthropogenic processes. They are of concern because they tend to bioaccumulate in the food chain and show adverse health effects ranging from acute to chronic toxicity. These pollutants need therefore to be monitored to conserve the environment. Conventionally, samples are sent to a laboratory for analysis by standard techniques such as chromatography and spectroscopy. Although these conventional techniques display high accuracy and low detection limits, they are expensive, require the use of highly trained personnel and tedious sample preparation. In comparison, electrochemical methods such as biosensors are sensitive, low cost and simple to operate. In this thesis, the determination of selected persistent organic pollutants (polybrominated diphenyl ethers, polybrominated biphenyls and polychlorinated biphenyls) and heavy metals (Cd, Pb and Cu) was achieved by the use of amperometric inhibition biosensor based on horseradish peroxidase (HRP) immobilized on the surface of platinum-polyaniline modified electrode. Polyaniline (PANI) film was electrochemically deposited on the platinum electrode surface. The film was characterized by cyclic voltammetry and spectrometric techniques. The CV results proved that the PANI was electroactive and exhibited a fast reversible electrochemistry. Characteristic Ultraviolet–Visible and Fourier Transform Infrared features of the polymer film were identified. They revealed that PANI film synthesized in this study is the conductive emeraldine salt. Horseradish peroxidase based biosensor was constructed by electrostatic attachment of the enzyme onto Pt-PANI electrode surface. Spectrometric and cyclic voltammetric results indicated that the immobilized HRP retained its bioelectrocatalytic activity towards the reduction of hydrogen peroxide. The Pt/PANI/HRP biosensor showed a linear response over a concentration range of 0.05 to 3.17 mM with a detection limit of 36.8 nM. Apparent Michaelis- Menten constant ( app M K ) was calculated as 1.04 mM. This implied that the HRP biosensor had a high affinity for H2O2. Furthermore, the fabricated biosensor showed high sensitivity, good reproducibility, repeatability and long-term stability. The Pt/PANI/HRP biosensor was applied to the determination of selected persistent organic pollutants and heavy metals. The latter was found to inhibit the HRP enzyme’s activity. The percentage inhibition of the investigated persistent organic pollutants decreases in the following order: 2,2´4,4´,6-pentabrominated diphenyl ether> 2-brominated biphenyl> 2-chlorinated biphenyl> 2,2´,4,5,5´-pentachlorinated biphenyl> 2,4,4´-trichlorinated biphenyl. In the case of heavy metals, the degree of inhibition of heavy metals was highest for Cd2+, followed by Cu2+ and then Pb2+. Kinetic study for the amperometric response to H2O2, recorded in the absence and presence of persistent organic pollutants and heavy metals revealed that for polybrominated diphenyl ethers, the inhibition process corresponded to a competitive type whereas for polybrominated biphenyls, polychlorinated biphenyls and heavy metals, it corresponded to the on-competitive type. The biosensor exhibited high sensitivity towards the determination of the metals and persistent organic pollutants as pollutants in real water samples, namely tap water and landfill leachate samples. / Thesis (M.Sc.)-University of KwaZulu-Natal, Durban, 2010.

Membrane technology is a potential method for upgrading gasoline quality, with respect to its tendency to promote fouling of engine inlet-systems. This thesis investigates the transport and separation mechanisms of dense polydimethylsiloxane (PDMS) membranes in nanofiltration applications relating to the filtration of gasoline fuels. Simulated fuels were created which comprised representative organic solvents with organometallic and poly-nuclear aromatic solutes. The flux and separation behaviour of the solvent-solute systems were studied using several apparatus and a range of operating regimes. Tests were performed with real fuels and refinery components to verify the mechanisms observed with the model solvent-solute systems, and several strategies were developed by which the process could be optimised or improved. Parallel to this work, a project was undertaken to assess the suitability of the technology on an industrial scale and to identify any scale-up issues. The key factors influencing flux were found to be the viscosity and swelling-effect of the solvent or solvent mixture. The dense membrane was shown to exhibit many characteristics of a porous structure when swollen with solvents, with the separation of low-polarity solutes governed principally by size-exclusion. It is postulated that swelling causes expansion of the polymer network such that convective and diffusive flow can take place between polymer chains. In general terms, a higher degree of swelling resulted in a higher flux and lower solute rejection. The separation potential of the membrane could be partly controlled by changing the swelling-effect of the solvent and the degree of membrane crosslinking. The transport of polar/non-polar solvent mixtures through PDMS was influenced by swelling equilibria, with separations occurring upon swelling the membrane. Separation of the more polar solvent occurred in this manner, and the solute rejection in multicomponent polar/non-polar mixtures deviated significantly from the behaviour in binary mixtures. The results obtained from a pilot-plant scale apparatus were largely consistent with those from laboratory-scale equipment, and engine tests showed that fuel filtration with PDMS is a technically-viable means of upgrading gasoline quality.

Bioremediation of chlorinated contaminants in groundwater can be achieved by reductive dechlorination by anaerobic dechlorinating cultures. However, at sites impacted with multiple different chlorinated contaminants, reductive dechlorination is often inhibited by co-contaminants. The inhibitory effects of trichloroethene, cis-dichloroethene and vinyl chloride on chloroform dechlorination were studied using a Dehalobacter-containing chloroform dechlorinating mixed culture (ACT-3). The inhibitory effect of chloroform on chlorinated ethene dechlorination was studied in a Dehalococcoides-containing trichloroethene dechlorinating mixed culture (KB-1). Vinyl chloride was found to be the strongest inhibitor of chloroform in ACT-3. Chloroform exerted a complex and strong inhibitory effect on chlorinated ethene dechlorination in KB-1. The potential for microbial reductive defluorination was also examined in the enrichment cultures. Quantifying the substrates and substrate interactions in dechlorinating cultures is necessary to most efficiently use these cultures to remediate contaminated sites.

Bioremediation of chlorinated contaminants in groundwater can be achieved by reductive dechlorination by anaerobic dechlorinating cultures. However, at sites impacted with multiple different chlorinated contaminants, reductive dechlorination is often inhibited by co-contaminants. The inhibitory effects of trichloroethene, cis-dichloroethene and vinyl chloride on chloroform dechlorination were studied using a Dehalobacter-containing chloroform dechlorinating mixed culture (ACT-3). The inhibitory effect of chloroform on chlorinated ethene dechlorination was studied in a Dehalococcoides-containing trichloroethene dechlorinating mixed culture (KB-1). Vinyl chloride was found to be the strongest inhibitor of chloroform in ACT-3. Chloroform exerted a complex and strong inhibitory effect on chlorinated ethene dechlorination in KB-1. The potential for microbial reductive defluorination was also examined in the enrichment cultures. Quantifying the substrates and substrate interactions in dechlorinating cultures is necessary to most efficiently use these cultures to remediate contaminated sites.

Several pseudopolymorphic forms of sodium naproxen were crystallized from methanol-water and ethanol-water solutions, including hydrated and alcohol-solvated forms. Results showed that the transitions of the pseudopolymorphic forms occur at temperatures that depend upon the solvent concentration. Results also revealed that water activity is a controlling factor for the transitions because regardless of which alcohol solvent mixture was used. The heats of solution for each pseudopolymorph were estimated by fitting the solubility data with the van't Hoff equation. The stability of hydrated forms over solvated forms at higher temperatures was proven for enantiotropic systems from a thermodynamic cycle. A 1:1 methanol-solvated form of sodium naproxen was discovered and fully characterized using a variety of analytical techniques. For further analysis, a single crystal was performed and revealed a two to three ratio solvate of sodium naproxen to methanol. The 1.5 solvate was shown to not be representative of the entire sample, but still provided insight into the bonding of the methanol solvent in sodium naproxen. Additionally, the ability of sodium naproxen to solvate with other alcohol solvents was explored, specifically looking at comparisons between pure ethanol, 1-propanol, 2-propanol, 1-butanol, and isobutanol solvents. It was shown that as the size of the alcohol increases and/or branching increases the ability to solvate decreases in relation to the molar amount of the alcohol present in the crystal structure. Additionally larger, branched alcohols required more energy to desolvate.

Thesis (Ph.D.)--Chemical Engineering, Georgia Institute of Technology, 2008. / Committee Chair: Charles A. Eckert; Committee Co-Chair: Charles L. Liotta; Committee Member: J. Carson Meredith; Committee Member: Rigoberto Hernandez; Committee Member: William J. Koros

Thesis (M. Ed.)--University of Hong Kong, 1988. / Includes bibliographical references (leaf 135-144).

Thesis (Ph.D.)--Chemical Engineering, Georgia Institute of Technology, 2008. / Committee Chair: Charles A. Eckert; Committee Co-Chair: Charles L. Liotta; Committee Member: Christopher W. Jones; Committee Member: Facundo M. Fernandez; Committee Member: Thomas F. Fuller.