Made available in DSpace on 2014-06-11T19:31:00Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-03-25Bitstream added on 2014-06-13T21:01:53Z : No. of bitstreams: 1 oliveira_rc_dr_araiq.pdf: 2354887 bytes, checksum: 89c5b192793995d9542d4827f06031b1 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O processo de biossorção tem sido reconhecido como alternativa potencial na concentração de metais pesados e radioisótopos a partir de corpos d’água que recebem ação antropogênica (indústria, mineração, etc.). A biossorção é um processo que se baseia na remoção de íons metálicos em solução aquosa através de interações entre o metal e determinados sítios ativos presentes em revestimentos celulares, provenientes de biomassas como algas, bactérias e fungos. Na última década, há na literatura um crescente interesse na aplicação deste processo para concentração, recuperação e separação de metais de alto valor agregado e/ou de grande demanda tecnológica, tais como as terras-raras (TR) – essenciais para fabricação de um sem-número de produtos, a citar: laseres, supercondutores, equipamentos miniaturizados, etc. Apesar de apresentarem uma considerável disponibilidade na natureza, as TR possuem alto valor agregado devido aos dispendiosos e complexos processos de separação e purificação de misturas de TR, resultado da alta similaridade química entre os elementos do grupo. Poucos países detêm processos industriais completos de separação destes metais, dessa forma, o domínio dessa tecnologia determina uma importância considerável nos aspectos geopolíticos, estratégicos e econômicos, visto a extensão de investimentos em P&D envolvidos e as descobertas geológicas nas últimas décadas das jazidas chinesas, que abrangem 80% das reservas mundiais. Este trabalho consiste em uma avaliação preliminar da utilização do processo de biossorção na biomassa Sargassum sp. para a concentração, recuperação e separação de misturas de metais TR a partir de soluções sintéticas. As interações metal-biomassa seguem uma cinética de pseudo-segunda ordem e são descritas pelo modelo de adsorção de Langmuir... / The biosorption process has been recognized as potential alternative to concentrate heavy metal and radioisotopes from wastewaters of the anthropogenic activities (industry, mining, etc.). The biosorption is a process based on removal of metallic ions in aqueous solution from interactions among the metal and determined active sites on cellular envelope of biomasses as such algae, bacteria, and fungus. In last decade, there are in the literature a crescent interest to apply this process for the concentration, recovery, and separation of metals of high aggregated value and/or high technologic demand as the rare earth metal (RE), which are essential for the manufacturing of a great number of products; e.g. lasers, superconductors, miniaturized equipments, etc. Despite of the RE present a relevant availability, they have high aggregated value due to expansive and complicate processes of separation and purification of RE mixtures, which is resulted of the high chemical similarities of the group. Few countries have complete industrial processes of separation of these metals, so the domain of this technology determines a considerable importance in geopolitical, economic, and strategic aspects because the extension of R&D investments involved and the geological discoveries of the Chinese ore deposits in the last decades, which comprise 80 % of world reserves. This work consists on evaluation of the biosorption process by Sargassum sp. biomass for the concentration, recovery, and separation of RE metals from synthetic solutions. The metalbiomass interactions follow the pseudo-second-order kinetics and they are described by the Langmuir adsorption model. Potentiometric and spectroscopic (SEM/EDX, FTIR e XPS) analyses indicate that the biomass is bounded to the RE by oxygenated groups via ionexchange and complexation mechanisms... (Complete abstract click electronic access below)

Abstract not available

This work describes detailed convergent beam electron diffraction (CBED) studies of GdAlO3 and LaAlO3 perovskites. CBED patterns tilted away from major zone axes have been found to have high sensitivity to the presence of mirror or glide mirror symmetry. Such patterns confirm to high accuracy that the space group of GdAlO3 is orthorhombic, Pnma. Tilted patterns from this well characterised structure also serve as benchmarks against which similar patterns may be compared. In the case of LaAlO3, tilted patterns enable the space group to be confirmed as rhombohedral R3c, previously claimed to be cubic (Fm3c) by CBED. Furthermore, no evidence for the low symmetry (I2/a or F1) phases proposed for LaAlO3 has been observed. The LaAlO3 study also gives a careful assessment of the influence of tilted specimen surfaces on the CBED data. Within the qualitative scope of these experiments, no symmetry degrading effects could be observed. Some preliminary Quantitative CBED (QCBED) data from LaAlO3 is also presented. This shows it will be possible to make a detailed study of the bonding charge density (Δρ) in this material when combined with X-ray diffraction data. Also included is a brief CBED study of LaFeO3, a material that is isostructural with GdAlO3. Although this is restricted to exact zone axis patterns, it is noted that tilted patterns have significant potential to improve the quality of the symmetry determination.

Bibliography: leaves 132-147 / ix, 147 leaves : ill ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Physical and Inorganic Chemistry, 1987

Thesis (M.S.)--West Virginia University, 2007. / Title from document title page. Document formatted into pages; contains xiii, 119 p. : ill. (some col.), col. maps. Includes abstract. Includes bibliographical references (p. 105-110).

Thesis (Ph. D.)--Ohio State University, 2006. / Title from first page of PDF file. Includes bibliographical references (p. 194-202).

The synthesis of yttrium phenalenide complexes 129-132 was achieved by salt metathesis reactions between ligand anions and YCI3. Ytterbium phenalenide complexes 133-137 were synthesized by protonolysis reactions between neutral ligands and Yb[N(SiMe3)2]2(THF)2. The solid state structure of (Pni1Bu)2Yb(THF) 136 reveals a unique n3 bonding pattern, however the electrons of the phenalenide ligand remain delocalized even when bonded to the metal center. Mono-alkyl complexes (PCpR)2Y(CH2SiMe3)(THFSiMe3)(THF) 147-149 (R = Me. Ph. H) and bis-alkyl complexes (PCp*)Y(CH2SiMe3)2(THF) 150 and (sCp)Y(CH2SiMe3)2(THF) 152 were synthesized by direct protonolysis reactions between Y(CH2SiMe3)3(THF)2 and neutral ligands. When treated with phenylsilane, complex 148 generated the crowded hydride dimer [(PCpPh)2Y(u-H)]2 161. Complexes 150 and 152 undergo acid-base. metallation. insertion reactions and polymerization of small substrates. A variable temperature `H NMR study of 150 and 152 at low temperature reveals an equilibrium between 150/152-THF and 1501152. The THF-free complexes. 150/152-THF. appear to undergo inversion of a pyramidal ground state structure to generate a C2 symmetric intermediate. The X-ray structures of 136, 147, 150. 152, (sCp)Y(CH2SiMe3)2(bipy) 154, 161. [PCp*Y(CCSiMe3)(THF)]2(u2-CCSiMe3)2] 167, acetylide cluster 169 and bis-(Me3Si)2Cp yttrium chloride dimer 176 were determined and structural features discussed.

Thesis (M.S.)--Ohio State University, 2008. / Title from first page of PDF file. Includes bibliographical references (p. 64-66).

Thesis (Ph.D.)--University of Texas at Dallas, 2005. / Includes vita. Includes bibliographical references.

Thesis (M.S.)--University of Missouri--Rolla, 2007. / Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed June 17, 2008) Includes bibliographical references.