Thesis ... of the University of Pennsylvania by Anna Lockhart Flanigen.

Thesis (Ph. D.)--University of Wisconsin, 1967. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (PH. D.)--University of Pennsylvania, 1913.

Thesis (Ph. D.)--University of Texas at Austin, 2004. / Supervisor: Allen J. Bard. Vita. Includes bibliographical references.

No description available.

Thesis (Master of Engineering in Chemical Engineering)--Cape Peninsula University of Technology, 2018. / Electrochemical and non-enzymatic fructose detection has evoked keen interest in the scientific literature. Several authors have reported on different methods of electrode preparation for fructose sensors. However, little systematic study has been conducted to design a cheap, efficient method of depositing metal oxides to detect fructose. To address the challenge, a Co3O4 thin film was fabricated using a simple solution step deposition on Fluorine doped Tin oxide (FTO) glass electrode. In this study, a report on the selective oxidation of fructose on Co3O4 thin film electrode surface is presented. Electrode characterization was done using X-ray diffraction (XRD), High Resolution Transmission Electron Microscopy (HR-TEM), Scanning Electron Microscope (SEM), Atomic Fluorescence Microscopy (AFM), and Electrochemical Impedance Spectroscopy (EIS). All cyclic voltammetry (CVs) and chronoamperometry tests were carried out by the use of an AUTOLAB POTENTIOSTAT 302 N, controlled by Nova 2.0 software instrumentation using a customized 50 cm3 electrochemical cell. The cell consisted of a graphite rod as the counter electrode (CE), 3 M Ag/AgCl reference electrode (RE) and the fabricated Co3O4/FTO as the working electrode (WE). All experiments were carried out at 25±2 ⁰C. From the results, the constructed sensor exhibited two distinctive linear ranges in the ranges of 0.021 – 1.74 mM and from 1.74 - ~15 mM, covering a wide linear range of up to ~15 mM at an applied potential of +0.6V vs. Ag/AgCl in 0.1M NaOH solution. The sensor demonstrated a high, reproducible and repeatable sensitivity of 495 (lower concentration range) & 53 (higher concentration range) μA cm-2 mM-1 for a low R.S.D of 5 %. The Co3O4 thin film produced a low detection limit of ~1.7 μM for a signal to noise ratio of 3 (S/N = 3); a fast response time of 6s and long term stability. The repeatability and stability of the electrode resulted from the chemical stability of Co3O4 thin film. The study showed that the sensor was highly selective towards fructose compared to the presence of other key interferences i.e. AA, AC, and UA. Because of such a favourable electrocatalysis of the Co3O4 sensor towards fructose, the ease of the electrode fabrication and reproducibility makes it a future candidate for commercial applications in the food and beverages sector.

Increased public awareness, stricter legislation standards, and environmental and health effects associated with water pollution are driving the development of improved wastewater treatment techniques. In order to meet these challenges, a novel and cost effective process has been developed at the University of Manchester to treat water contaminated with dissolved organics by exploiting a combination of adsorption and electrochemical regeneration. Adsorption of organics takes place on the surface of a non-porous and highly electrically conductive graphite adsorbent, followed by anodic electrochemical regeneration leading to oxidation of the adsorbed organic contaminants. The mechanism of degradation of adsorbed organics during electrochemical regeneration is particularly important from the point of view of the breakdown products. Ideally, complete oxidation of the adsorbed organics to CO2 and H2O should occur, but it is also possible that intermediate by-products may be formed. These breakdown products could be released into the water, be released as gases during the regeneration process or may remain adsorbed on the surface of the adsorbent. Information about the breakdown products is an important requirement for the commercial application of the process. This PhD project focused on an investigation of the formation of intermediate oxidation products released into the water (liquid phase) and with the regeneration gases. Phenol was chosen as a model pollutant and a graphite intercalation compound (GIC) adsorbent, Nyex®1000 (Arvia® Technology Ltd) was used. The main oxidation products formed during both batch and continuous adsorption with electrochemical regeneration were 1,4-benzoquinone, maleic acid, oxalic acid, 4-chlorophenol and 2,4-dichlorphenol. These compounds were detected in small concentrations compared to the overall concentration of the phenol removed. Two mechanisms of organic oxidation during electrochemical regeneration of the GIC adsorbents were identified. The first was the complete oxidation of the adsorbed species on the surface of the adsorbent and the second involved the indirect electrochemical oxidation of organics in solution. Breakdown products were found to be formed due the indirect oxidation of organics in solution. The formation of (chlorinated and non-chlorinated) breakdown products was found to be dependant on current density, pH, initial concentration, chloride content and the electrolyte used in the cathode compartment. The concentrations of chlorinated breakdown products can be minimized by using low current density, low initial concentrations, a chloride-free environment and/or treating the water over a number of adsorptions and regeneration cycles. On the other hand, non-chlorinated breakdown products can be minimized by applying higher current density and treating the solution over several cycles of adsorption and regeneration. Therefore, selection of optimum conditions is important to reduce the formation of undesirable breakdown products. The formation of free chlorine during batch electrochemical regeneration was also investigated under a range of operating conditions including the initial concentration of chloride ions, current density and pH. The outcomes of this study have important implications in optimising the conditions for the formation of chlorinated breakdown products and in exploring the role of electrochlorination for water disinfection. Analysis of the regeneration gases has revealed that the main components of the gases generated during the electrochemical regeneration of GIC adsorbents were CO2 and H2O. A preliminary mass balance has suggested that about 60% of the adsorbed phenol was oxidised completely to CO2. However, further work is needed to determine the fate of the remaining phenol. The surface characterization of the GIC adsorbent during adsorption and electrochemical regeneration was carried out using surface techniques including Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, Energy dispersive X-ray spectroscopy (EDS) and Boehm titration. FTIR and Raman spectroscopy were found to be unsuitable for determining the concentration changes at the surface of the adsorbent during adsorption and regeneration. However, Boehm titration has shown that the GIC adsorbent has phenolic, carboxylic and lactonic groups. The concentrations of phenolic groups were found to be higher after phenol adsorption and to decrease during electrochemical regeneration. The results of EDS analysis gave results which were consistent with these observations. Another important aspect of this PhD project was to explore the potential application of adsorption and electrochemical regeneration using GIC adsorbents to water disinfection. A model microorganism E. coli was selected for adsorption and electrochemical regeneration studies under a range of experimental conditions. This study has provided evidence that the process of adsorption and electrochemical regeneration using GIC adsorbents can be used for disinfection of water. Disinfection of water was found to be a combination of two processes: the adsorption of microorganisms followed by their deactivation on the surface; and electrochemical disinfection in solution due to indirect oxidation. The possible disinfection mechanisms involved in these processes include electrochlorination, pH changes and deactivation by direct oxidation of microorganisms. Scanning electron microscopy was found to be a useful tool for investigating changes in surface morphology of microorganisms during adsorption and electrochemical regeneration. The disinfection of a variety of bacteria, fungi and yeasts was tested and evaluated. However, disinfection of protozoa including C. parvum was not demonstrated successfully. It was also demonstrated that the process of adsorption with electrochemical regeneration using GIC adsorbents can be used to simultaneously remove organics and to disinfect microorganisms.

The threats of global warming attributed to fossil fuel combustion, combined with increasing energy demands and a growing population, have generated interests in diversifying the world energy mix. Biofuels from microalgae offer a sustainable renewable option and do not suffer the sustainability issues associated with early forms of bioenergy. However, research efforts of nearly 5 decades have not resulted in any significant gains and have motivated further investigation into novel techniques. The dilute nature of microalgae suspensions often requires dewatering and drying, which adds to energy intensity and costs associated with recovery processes. Curiously, the conventional recovery techniques do not consider the characteristic tendency of microalgae cells for surface attachment. This behaviour of cells, coupled with the discovery of a non-porous adsorbent material, NyexTM particles, has brought to the fore an exciting prospect. This has motivated the underpinning question behind this research; does the non-porous characteristic of the NyexTM particles presents an opportunity to recover microalgae cells from suspension using an adsorption technique?Using Chlamydomonas reinhardtii as a model microalgae strain, preliminary batch studies revealed a rapid recovery of the cells onto the NyexTM particles; nearly 90% recovery was attained within one minute, which depends on suspension concentration. At a correlation coefficient, R2 = 0.99, the Freundlich isotherm was found to give a better description of batch systems than the Langmuir isotherm, which suggests that cell coverage onto the NyexTM particles may not be a simple monolayer adsorption. Although a low adsorptive capacity of 0.55 mg/g was measured, the equilibrium parameter (1⁄) of about 0.6 was well within the range for favourable adsorption (i.e. 0 - 1). Further studies undertaken suggest that the recovery of cells could be driven by a hydrophobic-hydrophobic interaction, electrostatic forces of attraction and the flocculating behaviour of the NyexTM particles. Fixed bed studies showed that the lack of pores led to an early breakthrough. However, findings demonstrated that unlike most column studies, the bed capacity was a more valuable parameter to assess the column performance. Unexpectedly, depressed breakthrough curves, where bed exhaustion never attained Ct/C0 = 1.0, were observed. Nonetheless, the modified dose response (MDR) model was found to predict the experimental bed capacity to a greater degree of accuracy than other models. Furthermore, this research exploited the logistic features of the Bohart-Adams and the Clark models to adapt them to the experimental data. The adapted models significantly improved the accuracy of predictions with R2 values > 0.99 for the depressed breakthrough curves. The conductive nature of NyexTM particles was explored to electrochemically regenerate the adsorbent and reuse it to recover more cells. A current density of 32 mA.cm-2 was sufficient to inactivate the cells, regenerate the adsorbent and attain a maximum percentage recovery. Interestingly, scanning electron micrograph showed that the membranes of the adsorbed cells were ruptured, during NyexTM regeneration, potentially leading to lipid release. The maximum lipids extracted into a hexane solvent was estimated as 30 μg/mL at a current density of 64 mA.cm-2.Overall, the potential to recover microalgae cells onto a non-porous adsorbent has been demonstrated. The prospect of rupturing membranes of adsorbed cells offers the opportunity to use this technique to recover microalgae cells for potential biofuel applications. The results obtained from this research can serve as the impetus to further exploit this novel procedure. Future work should consider high lipid producing varieties of microalgae strains, develop a robust protocol to account for all forms of lipids released and undertake an energy and cost analysis to develop the technology further.

No description available.

In this work, several materials possessing a layered structure were investigated using a technique of exfoliation in liquid phase to produce few- to mono-layers of the material. Materials exfoliated in such a way included graphite, boron nitride, molybdenum disulfide and tungsten disulfide. Subsequent transmission electron microscopy and accompanying electron diffraction patterns revealed that few and mono layer forms of these materials have been realized through this exfoliation method. Ultraviolet-visible spectroscopy confirmed the shifting of the band gaps in molybdenum and tungsten disulfides that is predicted in reducing the number of layers of these materials and was also used to confirm the band gap of the boron nitride. As a potential application, exfoliated molybdenum disulfide was used in the construction of electrodes for electrical charge storage in an electrochemical double layer capacitor, or supercapacitor, style device. Cyclic voltammetry, galvanostatic charge discharge, and electrochemical impedance spectroscopy measurements were performed using three different electrolytes, which showed good capacitive behavior for these devices. Using the data from electrochemical impedance spectroscopy, equivalent circuit models were generated to represent the systems in different electrolytes. From this, it was determined that the capacitive behavior of these systems was partially diffusion limited.