The main object of the present investigation has been to establish a titration curve for mohair keratin and to compare it with similar data for wool, to determine whether the differences in physical and chemical properties could be attributed in any way to the acidic and basic character of these fibres. As shown in subsequent discussion such measurements provide extremely useful information regarding the chemical structure of proteins in general, and in the technical fields involving processes such as wool scouring, carbonizing and dyeing. The study has been extended to include certain modified wools, i.e. photochemically damaged, and oxidized keratin. The most successful contribution to the titration data of wool keratin is the work of Steinhardt and Harris and subsequent authors have tended to adopt their procedures without modification. In the present study attempts have been made to obtain a clearer understanding of the fundamental processes. New techniques and analytical methods have been introduced to improve the accuracy of the measurements.

M.Tech. (Extraction Metallurgy) / For many decades, carbon nanotubes (CNTs) have been used as adsorbents for the removal of pollutants from wastewaters because of their unique properties such as inert surface, resistance to acid and base environment, rigidity and strength. Herein is a report of application of functionalised CNTs on the adsorption of metal ions from aqueous solutions and mine leachates. The CNTs were first synthesised in-house, purified, functionalised and characterised with various characterisation techniques: FTIR (Fourier Transform Infrared), SEM (Scanning Electron Microscopy, TEM (Transmission Electron Microscopy), EDS (Energy Dispersive Spectroscopy), Raman Spectroscopy, TGA (Thermal Gravimetric Analysis) and BET (Brunauer-Emmet-Teller). Together, these techniques gave substantiation for structure, surface and chemical modification of the synthesised moieties. After characterisation, the functional groups were attached to the walls of the tubes and this implies successful functionalisation...

De nombreuses espèces de moisissures (Aspergillus, Fusarium, Penicillium…) produisent des molécules toxiques appelées mycotoxines. Malgré des efforts agronomiques croissants, la contamination en mycotoxines dans les produits agricoles est toujours présente. Des stratégies de décontamination sont alors utiles pour limiter l’impact des mycotoxines sur la santé animale ou humaine. La première stratégie que nous avons étudiée est le piégeage par adsorption de mycotoxines sur des spores d’Aspergillus de la section Nigri. Nous avons démontré que les spores vivantes sont aussi efficaces que les spores inactivées à la chaleur, indiquant que les composés responsables de l’adsorption ne sont pas altérés par ce traitement. Le phénomène d’adsorption semble être principalement du à des interactions hydrophobes. Des études restent à faire sur l’efficacité d’un tel procédé in vivo et pour caractériser les composés responsables. La deuxième stratégie étudiée a été la biotransformation d’une mycotoxine particulière, la zéaralénone. Plusieurs microorganismes ont été testés. Parmi eux, il a été démontré que certaines espèces d’Aspergillus avaient la capacité de transformer la zéaralénone en zéaralénone-sulfate. La toxicité de ce composé a été évaluée par test de prolifération de cellules cancéreuses MCF-7. Ces cellules ont la particularité de proliférer en présence de composés oestrogéniques. Il a été montré que la zéaralénone-sulfate provoquait peu de prolifération chez ces cellules, suggérant une toxicité plus faible que la zéaralénone. Des études seront effectuées pour évaluer la stabilité d’un tel conjugué in vivo. / Several species of fungi (Aspergillus, Fusarium, Penicillium…) are producers of very hazardous mycotoxins. Despite the use of recommended agricultural practices to avoid mold development and mycotoxinogenesis during crop growth, harvesting and storage, contamination by mycotoxins still occurs. Decontamination procedures are useful to reduce the mycotoxin content of contaminated raw materials. The first strategy we studied was to decrease the bioavailability of mycotoxins trapping them with binding agents. For the first time, the adsorption of mycotoxins by conidia of black Aspergilli has been demonstrated. Heat-treated conidia are as efficient as living conidia, which demonstrates that the components involved in adsorption are not affected by heat-treatment. The adsorption phenomenon seems to involved hydrophobic interactions. Further in vivo studies are necessary to develop the application of such a decontamination process to contaminated raw materials and feeds. The second strategy studied was the biodegradation of zearalenone by microorganisms which could offer a pratical and efficient method to alleviate negative effects on animals. For the first time, some Aspergillus niger strains, isolated from grapes, have been shown to transform zearalenone to zearalenone-sulfate. To be sure that zearalenone biotransformation leads to a detoxification, the estrogenic toxicity of zearalenone-sulfate was determined by cell culture studies. An estrogen receptor positive breast cancer cell line (MCF-7) was used to confirm the lost of toxicity by E-screen assay. The test principle is based on the fact that MCF-7 cells proliferate in presence of estrogenic substances. Zearalenone-sulfate was less estrogenic than zearalenone. Further work will focus on the stability of the zearalenone-sulfate in vivo.

La Seine est un écosystème profondément affecté par les activités humaines. Il a subi des changements améliorant le traitement des eaux usées parisiennes et les apports diffus de l'agriculture. Des campagnes de prélèvements en profils longitudinaux ont été menées à l'amont et à l'aval de la station d'épuration Seine-Aval (step SAV) pour décrire la dynamique de l'azote et des activités des micro-organismes nitrifiants et la comparer aux observations disponibles antérieures à l'implémentation d'un traitement de l'azote. Les résultats prouvent que la step SAV rejette moins d'ammonium et plus d'organismes nitrifiants mais avec un développement plus lent et moins important qui disparaissent en aval améliorant le déficit en oxygène en Seine. De plus, le bilan et le rôle du phosphore ont été démontrés avec des apports au milieu fluvial diminués d'un facteur 2.7 depuis le début des années 2000. La mesure expérimentale des paramètres de l'adsorption du phosphore sur la matière en suspension a permis d'affirmer que ceux-ci sont influencés par les rejets des stations d'épuration mettant en oeuvre un traitement du phosphore. Nous montrons, par modélisation, que la dynamique de développement des algues est sensible au processus d'adsorption du phosphore. Les changements apparus dans la fréquence et l'intensité des blooms algaux en Seine peuvent s'expliquer par la réduction de la charge ponctuelle en phosphore. Avec des concentrations en orthophosphates proches de la limitation dans les secteurs amont, une modélisation précise de l'apparition du phytoplancton à l'échelle du bassin versant reste cependant encore difficile avec les outils mécanistiques actuels que nous avons développés. / The Seine river system is an ecosystem deeply affected by human activities. The new water quality requirements have led to significant changes. We provided an overview of nitrogen transfers in the Seine basin. We conducted sampling campaigns in order to describe the dynamics of nitrogen and nitrification. Furthermore, we compared our results with the observations before the implementation of nitrogen treatment at the wastewater treatment plant Seine Aval (WWTP SAV). The results proved that the WWTP discharges less ammonium and more nitrifiers but with a slower development than before. These communities disappear downstream, without causing low oxygen concentrations in the lower Seine and its estuary, as they did before... A simplified modelling of nitrogen concentrations and nitrification before and after the implementation of nitrogen treatment helped to reproduce the past and the present trends.Moreover, the assessment of the fluxes and the analysis of the role of phosphorus were realized. The inputs to the river system have been reduced almost three times in the early year 2000. The experimental measurement of phosphorus sorption characteristics onto suspended solids has shown that particles could be affected by the discharges coming from the WWTP SAV after the introduction of an advanced treatment. We show also by modelling, that the algal growth is very sensitive to adsorption process. The changes in frequency and amplitude of algal blooms observed in the Seine can be explained by the reduction of point phosphorus loadings. The modelling of algal blooms throughout the entire basin remains difficult with the currently available mechanistic tools.

Dans cette thèse, on a étudié la formation de monocouches auto-assemblées de différentes molécules de chalcogénure et de films minces de semiconducteurs organiques. Leurs caractéristiques électroniques et structurelles ont été étudiées principalement par la spectroscopie de photoélectron à rayons X à base de rayonnement synchrotron, la spectroscopie d’adsorption de rayons X à proximité de seuil, la microscopie à force atomique et la diffraction d'électrons à faible énergie. En outre, les caractéristiques d'adsorption du sélénium et du soufre ont été étudiées comme complément à l'étude des adsorptions des molécules comportant des atomes de chalcogène. Le XPS à haute résolution a été utilisé pour enquêter sur les monocouches auto-assemblées de benzèneselénol et de sélénophène sur Cu (111). L'étude détaillée des pics caractéristiques des niveaux du coeur a démontré l'existence de différents sites d'absorption des molécules et aussi avec les mesures NEXAFS l'apparition du clivage de la liaison Se-C. Ces conclusions sont étayées par l'étude de l’adsorption de sélénium atomique montrant également différents sites d'absorption pour le sélénium atomique avec différents environnements chimiques basés sur une étude XPS haute résolution des spectres caractéristiques Se3d, Se3p et l'imagerie LEED. On a étudié les adsorptions de molécules de polythiophène (nT, n = 1-4, 6) ainsi que pour le α, ω-diquaterthiophène (DH4T) et le dihexylsexithiophène (DH6T) sur les films Au (111) et films de Au sur le mica. Les résultats indiquent que les pics XPS S2p ont des contributions de molécules intactes sur différents sites d'adsorption et des molécules cassées. Ces conclusions sont étayées par les calculs DFT existants. La dissociation spontanée apparaît dans une mesure variable dans différents cas, ce qui pourrait être lié à différentes morphologies de surface, à l'existence de défauts et à la réactivité différentes liés a ces défauts. Des films ultra-minces d'α-sexithiophène (6T) ont été déposés sur des surfaces planes de CaF2 (111) / Si (111) et sur des surfaces striées de CaF2 (110) / Si (001) par épitaxie par faisceau moléculaire. L'image AFM de 6T sur CaF2 (111) montre de grandes îles avec des terrasses plates sans préférence dans le plan, tandis que des îlots étroits et allongés suivant l'ondulation du substrat sont formés pour 6T sur CaF2 (110). Les spectres XPS et NEXAFS indiquent que les interactions entre 6T et les surfaces sont négligeables et que les molécules s'alignent avec leur long axe perpendiculaire aux surfaces pour les deux cas. / In this thesis, formation of self-assembled monolayers of different chalcogenide molecules and organic semiconductor thin films was investigated. Their electronic and structural characteristics have been investigated primarily by synchrotron based X-ray photoelectron, near edge X-ray absorption fine structure spectroscopy, Atomic force microscopy and low energy electron diffraction. In addition, the adsorption characteristics of selenium and sulfur were studied as a complement to the study of adsorptions of chalcogen headgroup molecules. The high resolution XPS was employed to investigate the self assembled monolayers of benzeneselenol and selenophene on Cu(111). The detailed study of characteristic core level peaks demonstrated the existence of different absorption sites of the molecules and also along with NEXAFS measurements the occurrence of Se-C bond cleavage. These conclusions are supported by the study of atomic selenium adsorptions showing also different absorption sites for the atomic selenium with different chemical environments based on high resolution XPS study of characteristic Se3d, Se3p spectra and LEED imaging. The adsorptions of polythiophene molecules (nT, n=1-4, 6) as well as for α, ω-diquaterthiophene (DH4T) and dihexylsexithiophene (DH6T) on Au(111) and Au films grown on mica was studied. The results indicate that the XPS S2p peaks have contributions from intact molecules on different adsorption sites and broken molecules complemented. These conclusions are supported by existing DFT calculations. Spontaneous dissociation appears to a variable extent in different cases, which could be related to different surface morphologies, existence of defects and ensuing differences reactivity.α-Sexithiophene (6T) ultrathin films were grown on CaF2(111)/Si(111) planar surfaces and on CaF2(110)/Si(001) ridged surfaces by molecular beam epitaxy. The AFM image of 6T on CaF2(111) shows large islands with flat terraces without in-plane preference, while narrow and elongated islands following the substrate corrugation are formed for 6T on CaF2(110). XPS and NEXAFS spectra indicate that the interactions between 6T and surfaces are negligible, and the molecules align with their long axis perpendicular to the surfaces for both cases.

>Magister Scientiae - MSc / Titanium dioxide (TiO2) has potential as an adsorbent within the 68Ge/68Ga generator context. To function effectively, three basic requirements are required: optimum 68Ga elution efficiency, stability and removal of the 68Ge breakthrough. After analysis of the 68Ga elution efficiency and the 68Ge breakthrough, two models are proposed, namely; surface modification and molecular imprinted polymer, to address factors influencing 68Ga elution efficiency and minimize 68Ge breakthrough. The surface modifiers that were investigated are 3-aminopolypropyltriethoxy silane (3-APTES), 3-mercaptopropyltrimethoxy silane (3-MPTMS), bis(3-aminopropyl)amine (BAPA) and 2-chloro-4,6-dimethoxy-1,3,5-triazine silane (CDMT). / 2023

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The discharge of poorly treated wastewater containing persistent organic contaminants, such as phenol, into water bodies is a major contributor to water pollution. This is of great concern as it poses health threats to human beings, aquatic species and the ecosystem as a whole. Amongst the water treatment technologies available, adsorption is highly recommended because of its ease of operation, simple design and economic viability. Commercial activated carbon (CAC) has previously been utilised as an adsorbent for remediation of recalcitrant pollutants from wastewater. However, high costs and the complexity of regenerating spent carbon has resulted in the need for economically viable adsorbents. The current research focused on the use of layered double hydroxide (LDH) clays for removal of phenol from contaminated water. The work is divided into two sections whereby the initial phase focuses on the use of commercial LDH clays, while the second phase is based on the in-house synthesised LDH clays guided by the performance of the commercial clays. Six commercial clays were sourced from different suppliers for the first phase, namely: DHT ̵ 4A and Alcamizer 1 from Kisuma Chemicals (Netherlands), Sorbacid 944, Sorbacid 911 and Hycite 713 from Clariant (Germany) and GF ̵ 450 from Greenfield additives (South Africa). Sorbacid 944 was the only clay which had three metallic constituents, magnesium Mg), zinc (Zn) and aluminium (Al) and was quantified to be 100% hydrotalcite; other clays had a substantial amount of impurities, such as calcite, boehmite and silica. Screening tests on the commercial clays were done by contacting 10 g L-1 of each clay with 40 mg L-1 synthetic phenol solution over 108 h. All the clays produced an adsorption efficiency of less than 10%. However, three clays which showed better adsorption efficiencies, namely: GF ̵ 450 (9%), Sorbacid (6%) and DHT ̵ 4A (3%) were utilised for further assessment. The three clays were thermally treated at 500°C for 4 h to produce mixed metal oxides (MMO), which are known to be good adsorbents. Calcination of the clays resulted in an increase in phenol adsorption efficiency over 24 h on Sorbacid 944 (87%) and DHT ̵ 4A (52%) while GF ̵ 450 remained below 10%. Having produced a higher adsorption efficiency, Sorbacid 944 was further assessed for optimisation of phenol removal process. The initial pH of the solution was established to have an inverse proportionality relationship with phenol adsorption. Elevated pH resulted in an increase in the concentration of hydroxyl ions (OH-) which increased the reformation rate of calcined LDH (CLDH) and reduced the adsorption efficiency, while acidic pH was not evaluated as it is known to cause dissolution of LDH. Neutral pH was established to be the optimum pH for phenol adsorption. An increase in operational temperature resulted in a faster phenol adsorption rate from 2 x 10-4 g mg-1min-1 at 25 °C to 3.8 x 10-3 g mg-1min-1at 65 °C. The optimum clay loading was 10 g L-1 and the clay proved to be effective over three cycles. The Freundlich equilibrium isotherm best fitted the phenol adsorption equilibrium data, with a maximum adsorption capacity of 16.6 mg g-1. The change in enthalpy of the adsorption process was determined to be ca.20 kJ mol-1 indicating an endothermic process dominated by physical adsorption. The changes in Gibbs free energy over the evaluated temperatures ranged between -12 kJ mol-1 and -16 kJ mol-1. This showed that the adsorption process was spontaneous irrespective of the operating temperature. The second phase of the study involved the synthesis of eight LDH clays containing varying compositions of Mg, Zn and Al with a carbonate interlayer anion. The clay which contained molar ratios of Mg (60%), Zn (20%) and Al (20%) (Mg0.6Zn0.2Al0.2) was found to possess higher adsorption efficiencies upon calcination at 450 °C for 4 h. Clays which had a Zn/Mg molar ratio greater than 1, Mg0.4Zn0.4Al0.2, Mg0.25Zn0.5Al0.25 and Zn0.75Al0.25 showed lower phenol adsorption efficiencies of 63%, 65% and 50% respectively. Clays with a Zn/Mg ratio less than 1, Mg0.6Zn0.2Al0.2 and Mg0.5Zn0.25Al0.25 showed optimal ratio of acidic and basic sites hence higher phenol adsorption efficiencies of 89% and 80% respectively. A higher aluminium content in the clay increased the spinel content (MgAl2O4) upon calcination resulting in a decrease in phenol adsorption. Phenol adsorption equilibrium data and kinetics for clay Mg0.6Zn0.2Al0.2 were comparable with those of Sorbacid 944. Column reactor configurations should be investigated for industrial applications. Furthermore, real wastewater matrices containing multi-contaminants should be used instead of synthetic wastewater with a few pollutants. This will provide insight in the applicability of LDH for impurity removal from wastewater on an industrial scale. / Dissertation (MEng (Water Utilisation))--University of Pretoria, 2021. / Technology and Human Resources for Industrial Support (THRIP) / Chemical Engineering / MEng (Water Utilisation) / Unrestricted

A study of adsorption equilibria of oxygen, nitrogen and oxygen-nitrogen mixtures on types 4A, 5A, 13X and Na-Mordenite molecular sieve pellets has been made. Pure component isotherms, using a volumetric apparatus, have been measured for each gas on each adsorbent at pressures up to 9 bar and for temperatures of 278.15,293.15 and 303.15 K. Curve fitting of the pure canponent isotherms has been attempted using the kinetic model of Gonzalez and Holland, the vacancy solution model, the statistical thermodynamic model and a mathematical equation similar to the Hill-de Boer model. With the exception of the kinetic model, good curve fitting was obtained. Binary equilibria data have been measured, using a constant volume method, for mixtures of oxygen and nitrogen at pressures of 1.7 and 4.4 bar and at temperatures of 278.15,293.15 and 303.15 K for each of the adsorbents. These results have been presented graphically as equilibrium phase compositions and corresponding total adsorption loadings. The binary experimental equilibria data have been examined against values predicted by mixture models (kinetic model, the extended vacancy solution model, the statistical thermodynamic model, the Cook and Basmadjian model, and the ideal adsorbed solution theory) using regression parameters obtained from the pure component isotherms. The statistical thermodynamic model and the ideal adsorbed solution theory gave the best representation of the experimental data. The activity coefficients of the adsorbed phase for the binary experimental data have been calculated and the results showed no appreciable deviation of the adsorbed phase from ideality. / British Council and the University of Gezira (Sudan)

<p> Rate of adsorption data for gases on molecular sieve·s and coals have been interpreted using equations for unsteady state diffusion derived from Fick's law for spheres usually, ignoring the amount adsorbed and the shape of the adsorption isotherm. These inappropriate equations result in calculated diffusivities that are too low and activation energies that are too large. </p> <p> Numerical. solutions of Fick's law were made for diffusion and adsorption in a porous sphere of radius R by finite difference methods for the following conditions: a. Diffusion is the rate-controlling step, and the diffusivity, D, is constant. b. Within an increment of the particle the total amount of adsorbate per unit volume, T is related to the "effective" concentration, c, by a Langmuir-like isotherm T = abC/(1 + bC). c. At zero tine the particle containing no adsomate is surrounded by adsozbate of concentration, Co, which remains constant throughout the rate process, and d. Equilibrium is established immediately at the periphery of the sphere. </p> <p> The solutions are obtained in terms of Z = Q/Q and T=(DCo/QR^2) t = kt, where t is time, k is a constant equal to the term within the brackets, and Q and Q are the amounts adsorbed per unit volume at time t and at equilibrium. The quantity within brackets is also a valid expression for linear and Freundlich-like adsorption isotherms and probably holds for other isotherms. Plots of z as a function of T shift systematically as the parameter B = bCo increased from 0, corresponding to a linear adsorption isotherm, to large values; the value of Z at a given T increasing with increasing values of B. For B = 0 the numerical solution is identical with analytical solution for the linear adsorption isotherm which for values of z <0.87 is given by kt = (2/π) { (-1 - πZ/6) - (1 ~πZ/3) ^1/2 } where k = DCo/R^2Q. For large values of B the numerical solutions approach as a limit the parabolic law kt = (1/2) {(1- 2Z/3) - (1- Z) } The value of (1/k~) o.zidt~ at short times increases fran 3.385 for B = 0 to 4 .. 243 for very large values of B.. From experimental data the value of k derived using the equation for B = 0 is 1.56 larger than for the parabolic equation. Hence the values of D obtained from the initial linear portions of t.he rate curve change by only a factor of 1.56 when the type of isotherm is changed from linear to rectangular. </p> <p> Rates of adsorption and the adsorption isotherm were determined for N2 , CH4, co2 , and C2H6 on samples of Linde 4A molecular sieve at several temperatures from -78° to +50°C in a manostatic volumetric aborption apparatus. The Langmuir equation satisfactorily approximatedthe isotherms and the values of B were moderately large at the lower temperatures of each series of experiments, eg., for N2 at -78°C, 10.6; for CH4 at -78°C, 7.3; for co2 at 0°C, 64; for Ci!6 at 0° and 30°C, 37 and 10.3. </p> <p> The rate data plotted as Z against t^1/2 were not linear at short times but curved upward initially before becoming linear. The initial (, nonlinear portion persisted significantly longer than the brief uncertain period at the beginning of the experiment. This phenomena could result from the equilibration at the periphecy of the particles requiring a finite time rather than being instantaneous. </p> <p> An equation based on the parabolic law model and a first order equilibration process was derived, which fits. the experimental data for 0.05 < Z < 0.95. This equation is appropriate only to data with a large value of B, but is probably a reasonable approximation for other rate data. </p> <p> The rates of adsorption for different molecules were co2 > N2 > CH4 > c2H6 · The activation energies for the diffusivity were found to be 4.1 and 6.0 kcal./nole for methane and ethane. The _heats of adsorption were found to be 7.2 and 8.3 kcal/mole for methane and ethane. </p> / Thesis / Master of Engineering (MEngr)