Even at 3.3 ppb, seawater contains a uranium supply large enough to power the world’s nuclear fleet for 13,000 years. This large supply has prompted interest in technologies for recovering uranium from seawater. Since the 1960’s, economic models of such technologies have failed to produce an economically competitive strategy when compared to conventional uranium recovery from terrestrial mining. Thus, uranium from seawater is researched as a potential price ceiling because of the large supply but high recovery cost. Such an upper bound is still valuable research because it allows for more certainty in uranium prices for planning, research, development and deployment of nuclear power systems. This thesis explores past cost estimates for uranium recovery from seawater and adds a new cost estimate to the pool of literature. The past estimates showed a development from systems that actively moved seawater to systems that allowed adsorbent to sit passively in seawater. The adsorbent material changed from hydrous titanium oxide to the higher-capacity amidoxime ligand. Capacity was the strongest driver of cost. Early models with the amidoxime ligand used an acrylic substrate or backbone. This substrate was later replaced by polyethylene because of its increased durability and lower cost. However, each of those materials could contribute to the problem of plastics in the ocean. The new technology assessed for cost in this paper attempts to address the plastics concern by replacing the plastic with a high molecular weight chitin nanomat as the substrate for the amidoxime ligand. The cost assessment showed the technology is presently cost prohibitive largely due to the adsorption capacity and chitin nanomat production costs. To increase capacity, the grafting efficiency onto the chitin substrate must be improved in order to achieve capacities comparable to those observed for the amidoxime-polyethylene adsorbent. To reduce chitin nanomat production costs, the ionic liquid (IL) consumption must be reduced and the recyclability of IL must be achieved. / text

Thesis (doctoral)--Christian-Albrechts-Universität zu Kiel, 2002.

La leishmaniose est une maladie infectieuse due à Leishmania, responsable de plus de 50 000 décès par an en ce qui concerne la forme viscérale (LV). La plupart des médicaments antileishmaniens se révèlent inefficaces (apparition de résistances avec la molécule de référence : la pentamidine) ou trop onéreux pour les patients (incidence principale en Inde). Il existe donc un réel besoin de nouveaux médicaments ne manifestant aucune résistance parasitaire, moins chers et administrables par voie orale. Dans cet objectif, plusieurs séries de monoamidoximes (de structure similaire à celle de la pentadimine) ont été synthétisées, en utilisant des réactions radicalaires médiées par l'acétate de manganèse (III), et sous irradiation micro-ondes. Des réactions pallado-catalysées ont permis de diversifier les structures obtenues : couplages de Suzuki-Miyaura et couplages originaux avec des dérivés de structure allyl alcool. Plusieurs amidoximes ont ainsi montré une bonne activité in vitro sur les formes promastigote et amastigote de Leishmania et une faible toxicité sur des lignées de macrophages, leur indice de sélectivité étant meilleur que celui de la pentamidine, utilisée comme référence. / Leishmaniasis is an infectious disease due to Leishmania : there are more than 50,000 deaths a year due to visceral form (VL). Most of antileishmanial drugs are either inefficient (too many resistances with the main drug : pentamidin) or too expensive for people (most of patients live in India). Thus, there is a real need for new drugs, without parasitical resistances, less expensive and orally administered. In this aim, several series of monoamidoxime, derivatives (pentamidine structure-like) have been synthesized using a free radical mechanism mediated by manganese (III) acetate under microwave irradiation. Palladium-catalyzed coupling reaction were also carried out for extensions of potential drugs : Suzuki-Miyaura reactions and original cross-coupling reactions involving allyl alcohol derivatives. Several amidoximes showed valuable in vitro activities toward Leishmania promastigote and amastigote forms,and low toxicity on macrophages, exhibiting a better selectivity index than pentamidine used as a drug compound reference.

<p>To improve the adsorption capacity of polyacrylonitrile (PAN) fibres, hydrophilic amidoxime fibres were prepared by subsequent conversion of the cyano groups to an amidoxime group by reacting with hydroxylamine at 80&deg / C at an optimum amidoximation time of 2 hrs. The amidoxime fibre was hydrolyzed/alkali treated in a solution of sodium hydroxide to enhance or improve the adsorption properties. This was followed by characterization of the amidoxime and hydrolyzed fibres using Scanning electron microscopy (SEM) / Fourier transform Infrared Spectroscopy (FTIR) and exchange capacity (cationic and anionic). SEM showed that the hydrolysis process made the surface of Amidoxime fibre rougher than that of Polyacrylonitrile fibre. FTIR revealed that the hydrolyzed Amidoxime fibres contained conjugated imine (-C=N-) sequences. Functionalization enhanced the sorption of amidoxime fibres by an increase of 20 % in the cationic exchange capacity. This was achieved by the part conversion of the cyano groups into the carboxylic acid groups. The fibres showed faster kinetics largely due the available exchange sites on the surface of the fibres hence the equilibration was achieved much quicker.</p>

<p>To improve the adsorption capacity of polyacrylonitrile (PAN) fibres, hydrophilic amidoxime fibres were prepared by subsequent conversion of the cyano groups to an amidoxime group by reacting with hydroxylamine at 80&deg / C at an optimum amidoximation time of 2 hrs. The amidoxime fibre was hydrolyzed/alkali treated in a solution of sodium hydroxide to enhance or improve the adsorption properties. This was followed by characterization of the amidoxime and hydrolyzed fibres using Scanning electron microscopy (SEM) / Fourier transform Infrared Spectroscopy (FTIR) and exchange capacity (cationic and anionic). SEM showed that the hydrolysis process made the surface of Amidoxime fibre rougher than that of Polyacrylonitrile fibre. FTIR revealed that the hydrolyzed Amidoxime fibres contained conjugated imine (-C=N-) sequences. Functionalization enhanced the sorption of amidoxime fibres by an increase of 20 % in the cationic exchange capacity. This was achieved by the part conversion of the cyano groups into the carboxylic acid groups. The fibres showed faster kinetics largely due the available exchange sites on the surface of the fibres hence the equilibration was achieved much quicker.</p>

Magister Scientiae - MSc / To improve the adsorption capacity of polyacrylonitrile (PAN) fibres, hydrophilic amidoxime fibres were prepared by subsequent conversion of the cyano groups to an amidoxime group by reacting with hydroxylamine at 80°C at an optimum amidoximation time of 2 hrs. The amidoxime fibre was hydrolyzed/alkali treated in a solution of sodium hydroxide to enhance or improve the adsorption properties. This was followed by characterization of the amidoxime and hydrolyzed fibres using Scanning electron microscopy (SEM); Fourier transform Infrared Spectroscopy (FTIR) and exchange capacity (cationic and anionic). SEM showed that the hydrolysis process made the surface of Amidoxime fibre rougher than that of Polyacrylonitrile fibre. FTIR revealed that the hydrolyzed Amidoxime fibres contained conjugated imine (-C=N-) sequences. Functionalization enhanced the sorption of amidoxime fibres by an increase of 20 % in the cationic exchange capacity. This was achieved by the part conversion of the cyano groups into the carboxylic acid groups. The fibres showed faster kinetics largely due the available exchange sites on the surface of the fibres hence the equilibration was achieved much quicker. / South Africa

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