Inaug.-Diss.--Bonn, 2000. / Includes bibliographical references (p. [119]-124).

Layered metal sulfides MoS2 and WS2 exhibit highly anisotropic surface chemistry. Adsorption of molecules is stronger on the atomic layer edges than on atomic planes. The edges are catalytically active in the petroleum hydrodesulfurization, while the layer planes are inert. Dispersing MoS2 and WS2 on the nanometer scale can also lead to the onset of photocatalytic properties due to the bandgap tuning by quantum confinement. In this work, we aim at determining how the adsorption on surface sites is altered for the nanoparticles compared to the bulk sulfides (micron-sized particles). A comparative study of the MoS2 and WS2 nanoparticles and bulk materials is done by attempting the adsorption of small molecules (N2, CO, acetone, and acetonitrile) to probe the surface sites. MoS2 and WS2 nanoparticles were synthesized by thermal decomposition of the metal hexacarbonyls in presence of sulfur in high-boiling solvents. The size range is 5-30 nm from Transmission Electron Microscopy. Transmission Infrared Spectroscopy was used to monitor the spectra of the probe molecules. A dedicated experimental setup has been constructed that consists of a high-vacuum chamber with a base pressure of 5×10-7 Torr. At the lowest achievable temperature of the sample (-145°C), N2, CO, and acetone were found to not adsorb strongly enough to be retained in vacuum on these materials. Acetonitrile was found to adsorb on these materials at -145°C and to desorb between -90°C and -50°C. The nanomaterial samples adsorbed significantly more acetonitrile than the corresponding bulk sulfides, as judged by the infrared signals intensity. Qualitatively, adsorbed acetonitrile species on nanodispersed and bulk sulfides are the same. It is likely that most of the adsorbed acetonitrile observed is physisorbed as ice or adsorbed on the sulfur-terminated terraces. At the final stages of desorprtion, distinctly different adsorbed species are seen whose CN stretching IR bands are shifted to higher frequencies. It is likely that these minority species are at monolayer or submonolayer coverages. The exact nature of the species requires further studies. / Department of Chemistry

Access to abstract permanently restricted to Ball State community only / Construction of experimental setup -- Synthesis of MoS₂ and WS₂ fullerene like structures -- Synthesis of MoS₂ and WS₂ nanotube like structures -- Infrared spectroscopy of acetonitrile adsorption on synthesized MoS₂ materials. / Access to thesis permanently restricted to Ball State community only / Department of Chemistry

A series of bench-scale experiments was carried out to determine the rate and efficiency with which benzene and p-xylene, components of gasoline, could be removed from an unsaturated soil by air stripping. Glass columns, 30 cm in length, were packed with soil and wetted to volumetric moisture contents of 10 and 18 percent. Air saturated with one of the volatile organic compounds (VOCs) was used to load the column. Clean air was used to strip the contaminant from the soil. Benzene and p-xylene concentrations in the soil water and air were reduced four orders of magnitude after a few hours (2-8) of stripping. Benzene was removed faster than p-xylene. Air flow was the rate-limiting step early in the stripping, however slow desorption from the soil became rate-limiting as the stripping progressed. As moisture content increased the rate of removal of both contaminants decreased.

Solutions of poly(2-ethyl-2-oxazoline) and poly(2-methyl-2-oxazoline) in water and several alcohols were characterized by light scattering and cloud point measurements. The second virial coefficients in water were found to decrease with increasing temperature, reflecting lower critical solution behavior, which is consistent with the cloud point measurements. The temperature dependence of the second virial coefficients revealed that specific interactions between polymer and water dominated the free energy of mixing. The Flory-Huggins x parameter determined from light scattering was in the range 0.48 - 0.49 in water and 0.32 - 0.41 in ethanol. The Kuhn length for PEOX was determined to be 0.77 nm which corresponds to less than two monomer units, indicating relatively flexible chains of PEOX. The segmental adsorption energy, x_s^po, of PEOX was measured using a desorption/displacement technique. PEOX was desorbed from silica with five low molecular weight organic displacers in two solvents - water and ethanol - to obtain values of the critical volume fraction of the displacer at which desorption was complete, Φ_cr. The high adsorption energy parameters are consistent with the polymer adsorbing principally by hydrogen bonding between the carbonyl groups on the polymer and surface silanol groups. The difference in adsorption energies in water and ethanol reflect specific solvent effects that may be related to the formation of hydrogen bond bridges between PEOX and silanol groups in water. Adsorption of PEOX from water, alcohols and chlorobenzene onto silica was investigated by measuring PEOX adsorption isotherms using a depletion method. A linear relationship of the plateau adsorption amount, Γ_p vs. log (molecular weight) was obtained, which agreed qualitatively with the Scheutjens-Fleer (S-F) mean field adsorption theory. The values of Γ_p, varied significantly with solvent type as well as with pH and electrolyte concentration in water. These variations in Γ_p, were due to changes of the polymer solvency and the silanol density on the silica particles. Competitive adsorption experiments of PEOX with various polymers were performed, including poly(ethylene oxide) (PEO), poly(propylene oxide) (PPO) poly(vinyl methyl ether) (PVME), and poly(dimethyl siloxane) (PDMS). PEOX showed a higher affinity to the silica surface than other polymers. This suggested that PEOX had good potential for serving as an anchor block for diblock copolymer stabilizers for metal oxides in water. The solubility of homopolymers PEOX, PEO, PPO, PVME, and PDMS and copolymers PEOX-PDMS and PEOX-PVME was investigated in water, alcohols, and chlorobenzene using static light scattering (SLS). The steric stabilization effect of silica dispersions in chlorobenzene by PEOX-PDMS was measured by dynamic light scattering (DLS). The stability was qualitatively related to the average particle hydrodynamic diameter against time. The adsorbed amount and layer thickness of diblock copolymer poly(dimethyl amino ethyl methacrylate-b-n-butyl methacrylate) (DMAEM-BMA) on silica surfaces from isopropanol was measured. The linear dependence of the adsorbed amount and thickness with respect to the tail block length was obtained. This is consistent with the Marques-Joanny model. / Ph. D.

M. Tech. Engineering Chemical. / Aims to investigate how the addition of impurities in a CO2 stream affects the adsorption capacity of CO2 on South African coals. To achieve this aim, the following objectives were carried out. 1. To measure the adsorption isotherms and adsorption capacities of pure CO2 and flue gas mixtures on various South African coals under in-seam conditions including pressures up to 88 bar and isothermal temperature of 35 &#x00BA%x;C; 2. To evaluate the effects of coal rank on the adsorption isotherms and adsorption capacities of pure CO2 and flue gas mixtures; 3. To do a comparative study to evaluate the effects of CO2 impurities on the adsorption capacity of pure CO2 on coal; 4. To study the degree of preferential sorption of the individual flue gas mixtures components on coal; 5. To determine the suitability of the Langmuir, Freundlich, and Temkin adsorption isotherm models in representing pure CO2 adsorption onto coal; and 6. To determine the suitability of Extended Langmuir (EL) adsorption models in representing the flue gas mixture adsorption onto coal.

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Call number: LD2668 .T4 1938 R62

Call number: LD2668 .T4 1984 S22 / Master of Science

Call number: LD2668 .T4 1985 L56 / Master of Science