A new apparatus for the determination of adsorption isotherms is described. The chief feature of this apparatus is that the gas under investigation is allowed to leak slowly, at a known rate, into the adsorbent. The rate at which the pressure increases in the system is recorded. From this data the amount of gas adsorbed by the solid can be calculated and with the measured pressure can be plotted as an adsorption isotherm. The adsorption of carbon dioxide on charcoal has been studied by the use of this apparatus. The reported presence of discontinuities in this adsorption isotherm has not been confirmed. / Science, Faculty of / Chemistry, Department of / Graduate

In this thesis various physicochemical factors which determine the characteristics of latex agglutination immunoassays are examined. A model of antibodies reacting with antigen (bovine serum albumin; BSA) adsorbed to the surface of polystyrene latex (PSL) beads was examined. The adsorption studies of BSA to PSL showed that the mass of BSA adsorbed at saturation depends on the type of polystyrene latex. Latexes with highly hydrophobic surfaces adsorbed more BSA molecules than those with lower hydrphobicity. Desorption studies showed that latexes that maximize adsorption lost the lowest fraction of their bound BSA molecules following extensive buffer wash. Partial desorption of BSA from PSL was achieved by the addition of detergent, whereas the addition of more BSA molecules or other macromolecules such as PEG or IgG did not displace the adsorbed BSA molecules. Examination of the material removed from the surface of the latexes by SDS-PAGE analysis showed that the composition of the adsorbed layer was enriched in the higher molecular weight oligomers of BSA, relative to their concentrations in the stock solution. A model in which adsorbed protein is assumed to undergo a polymerization reaction provides a general explanation of the observed results. Studies of polyclonal antibody (anti-BSA IgG) binding to antigen-coated PSL showed that the surface concentration of bound antibody depends on the surface concentration of antigen on the latex particles and on the availability of PSL surface area not occupied by antigen. Analysis of shear induced aggregation results show that for low surface coverage of latex particles by protein antigen in stable suspension, relatively low concentrations of specific antibodies are required to cause agglutination. Increasing surface density of antigen requires significantly higher concentrations of specific antibodies to produce agglutination. For a given surface coverage of antigen, results show that increasing the shear rate decreases the antibody concentration necessary to produce a given degree of agglutination. A remarkable structure formation and long range ordering exhibited by floes of latex coagulating in salt under intermediate shear rates was observed. This structure formation was not observed during antibody-induced agglutination under shear. / Science, Faculty of / Chemistry, Department of / Graduate

A single Fe³⁺ species has been introduced into Linde L zeolite and is identified as an iron oxyhydroxide from its Mössbauer relaxation properties. The effects of N₂, CO₂ and C₂H₆ on the ferric species and on the bulk behaviour of the sample are observed by Mössbauer Spectroscopy and adsorption studies under outgassing conditions. The ferric oxyhydroxide initially blocks the pores to gas adsorption but reducing it to Fe⁰ at 943⁰ K and reoxidizing it to α-Fe₂0₃ in air at 773⁰ K frees the pores. The bulk α-Fe₂0₃ is concluded to lie on the external zeolite surface. / Science, Faculty of / Chemistry, Department of / Graduate

The adsorption isotherm and the equation of state for the two-dimensional gas are derived from the grand canonical ensemble. Then the quantum statistical equation'of state is developed and applied to the two-dimensional second virial coefficient, B⁽²⁾, and the second gas-surface virial coefficient, B[subscript]AS, We compare theoretically the (12,6) and (12,6,3) potential models for B⁽²⁾. Finally the adsorption data for CH₄, CD₄, H₂ and D₂ on graphite are analysed quantally for the two-dimensional second virial coefficient and the second gas-surface virial coefficient. / Science, Faculty of / Chemistry, Department of / Graduate

The investigation of gas-surface interactions has been approached from two different aspects. Firstly, the design and construction of an apparatus to measure low coverage isotherms for argon on evaporated metal films in the region of liquid nitrogen temperature is discussed. Secondly, a detailed analysis of available second and third order gas-solid interaction data has been carried out. It is found that the existing theories for interpreting and calculating three-body forces in physical adsorption systems are incapable of explaining the observed values. / Science, Faculty of / Chemistry, Department of / Graduate

Electron paramagnetic resonance techniques have been used to investigate the nature and possible effects of adsorption of gaseous species on several adsorbents, in particular several synthetic zeolites, at temperatures from 77°K upwards. Analysis of the spectra obtained has been aided through computer simulation of the various spectra and comparison of these to the actual observed spectra. The molecule chlorine dioxide ( C10₂ ) has been studied in various low temperature matrices but little has been published for C10₂ in the adsorbed state. An attempt was made to find an adsorbent such that an inert matrix might be approximated, to give a base from which to make comparisons. To this end, adsorbents including silica gel, synthetic zeolites 13X, 10X, 4A, 5A, Na-mordenite and H-mordenite were investigated. The results vary between those from silica gel, where spectra yielding EPR parameters similar to other matrices were obtained, to those from 13X where it was evident that two distinct adsorption sites of the C10₂ were present. In the 13X as in the other synthetic zeolites, EPR parameters markedly different from other studies were found and were attributed to the intense electrostatic fields present in these zeolites. Results obtained at room temperature for these adsorbents ranged from C10₂ molecules freely rotating in the cages of the zeolites to other molecules having hindered rotations. Nitrogen dioxide ( NO₂ ) was also investigated with a view to finding similar interactions. Although changes as marked as for C10₂ compared to other studies were not observed, the synthetic zeolite H-mordenite yielded spectra closely approximating those obtained in solid N₂O₄ matrices. It is proposed the NO₂ molecules are caged in the numerous side pockets emanating from the main channels in this zeolite and are effectively isolated from other NO₂ molecules. The resulting spectra are strikingly more resolved than those obtained using other adsorbents and enabled accurate computer simulations to be made. The adsorption of nitric oxide ( NO ) produced an effect not found with the other molecules. A new species was formed from a reaction of the NO with H-mordenite and could not be removed at room temperature, indicating a strong bond to the surface. The new species does not contain nitrogen as identical spectra were obtained from adsorption of ¹⁴NO and ¹⁵NO. Attempts to observe spectra which could be assigned to the difluoroamino radical from adsorption of tetrafluorohydrazine were unsuccessful. The spectra observed were assigned to a species having no hyperfine structure and an anisotropic g tensor. / Science, Faculty of / Chemistry, Department of / Graduate

This study examined the adsorption of elemental S onclean Si(lOO) surfaces and Cs on s- covered Si(lOO) surfaces. The study was performed in an UHV system using LEED, AES and WF measurements. The objective was the protection of the\ surface against degradation. The s adsorption process may be enhanced by the addition of Cs. Results indicate that S adsortion forms: a hemisulfide, (~0.5 ML) with a (2xl) structure and a monosulfide, (~1 ML) with a (lxl) structure. Adsorption of Cs on clean Si(100)2xl reduces the WF to a minimum value with a subsequent increase towards the value of metallic Cs. Preadsorption of Son Si(100)2xl lowers the WF to a final plateau without the increase. The presence of S increases the binding energy and the maximum amount of Cs that can be deposited on the Si(lOO) surface. Structural models for S and Cs on Si(lOO) surfaces have been given in the text.

This investigation involved the production of specific antisera against known International Streptomyces project strains of Streptomyces.

The adsorption of different fractions of organic matter on the surface of Al2O3 and ZrO2 were investigated. The aim was to study the affinity of these fractions on the surface of metal oxide and the effect of several factors. Batch adsorption experiments were conducted with Low molecular weight oxygenated compounds. These chemical compound have been chosen to investigate:1) the aliphatic and aromatic structurer;2)contribution of hydroxyl group and; 3) the number of carboxyl group. HPLC and IC analysis used for determent the concentration of these chemical in the working solution. ATR-FTIR used to distinguish the type of coordination structure with the surface of metal oxide. The results fitted with Langmuir equation. The results showed that the chemical structure and the type and number of attached functional have an impact on the adsorption. Which it was proved via ATR-FTIR where the result showed that each chemical have different coordination structure on the surface of ZrO2 and Al2O3. Different fractions and sources of NOM were used (hydrophobic fraction of Suwannee and Colorado River, biopolymers extracted for the exuded of 2 species of algae, and low molecular acids that do not adsorb in XAD-8 resin). Results showed that these different fractions have different affinity with the surface of Al2O3 and ZrO2. These adsorption behaviors were varying according to the difference in the component of each NOM. Biopolymers showed significant adsorption at acidic pH. These biopolymers are mainly comprised of polysaccharides and this result proved that polysaccharide adsorb on the surface of ZrO2 more than Al2O3.

archives@tulane.edu / 1 / Yang Wang