Thesis (Ph. D. in Physics)--University of California, Berkeley, Jan. 1961. / (UCRL-9346). TID-4500 (15th ed.). Includes bibliographical references (leaves 157-161).

Thesis (Ph. D.)--University of Wisconsin, 1967. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

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Made available in DSpace on 2014-06-11T19:23:05Z (GMT). No. of bitstreams: 0 Previous issue date: 2013-02-25Bitstream added on 2014-06-13T19:08:54Z : No. of bitstreams: 1 freitas_mgm_me_araiq_parcial.pdf: 235600 bytes, checksum: a5d1fd3c36700c6e060d46eb1cc56c59 (MD5) Bitstreams deleted on 2015-06-25T13:01:02Z: freitas_mgm_me_araiq_parcial.pdf,. Added 1 bitstream(s) on 2015-06-25T13:03:23Z : No. of bitstreams: 1 000721818_20160325.pdf: 223545 bytes, checksum: ad0525e605fb4a1d465a9470b87f6af3 (MD5) Bitstreams deleted on 2016-03-28T13:37:48Z: 000721818_20160325.pdf,. Added 1 bitstream(s) on 2016-03-28T13:38:50Z : No. of bitstreams: 1 000721818.pdf: 810955 bytes, checksum: ee2d029d7bb1ff4fc631c85e963a32ba (MD5) / Os metais terras raras têm adquirido grande importância tecnológica e econômica em função da diversidade de suas aplicações. A biossorção apresenta-se como uma tecnologia alternativa para a obtenção destes metais, apresentando vantagens econômicas, ecológicas e operacionais em comparação com métodos tradicionais de separação e concentração de terrasraras. Este trabalho propõe a utilização da biomassa melanizada e do pigmento produzido pela linhagem MEL1 do fungo Aspergillus nidulans como potenciais biossorventes (em sistemas livre e imobilizado) para a concentração de neodímio, lantânio e cério. Com os resultados obtidos foi possível estabelecer as condições ótimas de cultivo que proporcionam a maior melanização da linhagem estudada, que são: cultivo constituído de duas etapas, sendo a précultura suplementada com 1% de AMM e incubada por 48 horas, a 37 °C, sob agitação constante de 200 rpm, seguida de cultura suplementada com 0,2% de AMM, incubada por 3 dias, a 37 °C, sob agitação constante de 200 rpm. Também observamos que o grau de pigmentação da biomassa mostrou ter um efeito positivo na capacidade biossortiva da biomassa, porém não apresentou efeito na afinidade da interação metal-biossorvente. As condições ótimas para os ensaios de biossorção das terras-raras estudadas (Nd, La e Ce) são: tempo de contato (ou tempo de equilíbrio) de 90 minutos; concentração inicial de metal (ou concentração saturante) de 800 mg.L-1 dosagem de biossorvente de 0,1%; temperatura de 28 °C e pH inicial da solução monometálica igual a 5,6. Verificamos que a biomassa melanizada apresenta maior capacidade biossortiva do que o pigmento tipo melanina produzido pelo fungo e que quando imobilizada em alginato de cálcio, esta biomassa apresenta maior capacidade biossortiva do que se imobilizada em PVA-SA. Os... / The rare earth metals have gained great economical and technological importance due to the diversity of its applications. The biosorption process has been recognized as an alternative technology for obtaining these metals, with economical, ecological and operational advantages compared to the traditional methods of separation and concentration of rare earths. This work consists on evaluating the use of the melanized biomass and pigment produced by MEL1 strain of the fungus Aspergillus nidulans as potential biosorbents (in free and immobilized systems) for the concentration of neodymium, lanthanum and cerium. The results we obtained made it possible to determine the optimized culture conditions which can increase the fungus pigmentation, it consists of two stages, the pre-culture supplemented with 1% of corn steep liquor and incubated for 48 hours at 37 ° C under stirring constant 200 rpm, followed by culture supplemented with 0.2% of corn steep liquor, incubated for 3 days at 37 ° C under constant stirring of 200 rpm. The grade of pigmentation has shown a positive effect on the biosorption capacity, but had no effect on the affinity of the interaction metal-biosorbent. The optimum conditions of the biosorption process were: contact time of 90 minutes; initial concentration of metal (or saturating concentration) of 800 mg.L-1; biosorbent dosage of 0.1%, temperature of 28 ° C and an initial pH of 5,6 in the single metal solutions. We found that the melanized biomass presents greater maximum biosorption capacity than the pigment produced by the fungus. When immobilized in calcium alginate, this biomass has a higher biosorption capacity compared to the PVA-SA immobilized biomass. The evaluated desorption agents (HCl and EDTA) showed very similar performance in the recovery of metals for the same biosorbent. However desorption... (Complete abstract click electronic access below)

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