Thesis (Ph. D.)--University of Michigan, 1934. / Reprint of an article, by F.E. Bartell and George B. Hatch, published in the Journal of physical chemistry, v. 39, no. 1, January, 1935. eContent provider-neutral record in process. Description based on print version record. Bibliography: p. 19.

M.Tech. (Extraction Metallurgy) / Please refer to full text to view abstract

The electrochemical oxidation and reduction of galena (PbS) was studied in aqueous solutions of perchloric acid between pH 0 and 4. The wide variation of rest potential as reported in the literature was explained on the basis of stoichiometric variations of this material as well as the activities of ionic and molecular species involved in the PbS equilibria. The stoichiometry of the anodic and cathodic reactions was determined to be primarily PbS ↦ Pb⁺⁺+ S° + 2e⁻ and PbS + 2H⁺ + 2e⁻↦ Pb° + H₂S respectively. The irreversibility of anodic oxidation to lead sulphate was observed, with no sulphate produced below about 0.7 to 1.0 volt, depending on the pH. Polarization experiments revealed that ohmic, concentration, and activation polarization effects all contributed to the non-equilibrium behavior of PbS. Reaction of Pb0₂ and MnO₂ with PbS was rapid and interpreted as a "galvanic" effect, relying on the conductivity of the reactants as a necessary condition for its success. / Applied Science, Faculty of / Materials Engineering, Department of / Graduate

Thesis (PhD) -- University of South Australia, 1998

Thesis (B.S.)--University of Missouri, School of Mines and Metallurgy, 1913. / The entire thesis text is included in file. Typescript. Illustrated by author. Title from title screen of thesis/dissertation PDF file (viewed April 27, 2009) Includes bibliographical references.

Thesis (M.A.)--Eastern Illinois University, 1976. / Includes bibliographical references (leaves 87-89).

Programa de Pós-Graduação em Engenharia Mineral. Departamento de Engenharia de Minas. Escola de Minas, Universidade Federal de Ouro Preto. / Submitted by Marise Leite (marise_mg@yahoo.com.br) on 2016-04-15T14:57:32Z No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) DISSERTAÇÃO_AgregaçãoHidrofóbicaFlotação.pdf: 2126943 bytes, checksum: cbca3c5ff8e9a197695a4c63e2a645bd (MD5) / Approved for entry into archive by Oliveira Flávia (flavia@sisbin.ufop.br) on 2016-04-15T15:27:37Z (GMT) No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) DISSERTAÇÃO_AgregaçãoHidrofóbicaFlotação.pdf: 2126943 bytes, checksum: cbca3c5ff8e9a197695a4c63e2a645bd (MD5) / Made available in DSpace on 2016-04-15T15:27:38Z (GMT). No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) DISSERTAÇÃO_AgregaçãoHidrofóbicaFlotação.pdf: 2126943 bytes, checksum: cbca3c5ff8e9a197695a4c63e2a645bd (MD5) Previous issue date: 2015 / A evolução da atividade mineradora têm impulsionado a aplicação de novos conceitos para o eneficiamento de minérios com teores baixos e com granulometria de liberação cada vez menor. Várias técnicas alternativas têm sido desenvolvidas, dentro das quais se destaca o processo de agregação hidrofóbica seletiva. Neste processo, as partículas dos minerais de interesse são seletivamente hidrofobizadas pela ação de coletores gerando agregados capazes de aderirem às bolhas de ar e serem recuperados através da flotação. Apesar do grande potencial, este processo ainda possui aplicação restrita na indústria mineral, o que pode ser atribuído a grande complexidade e pouca compreensão a respeito do assunto. Este fato motivou o desenvolvimento desta pesquisa, que teve como objetivo estudar a aplicabilidade da agregação hidrofóbica para auxiliar a flotação dos minerais sulfetados de zinco e de chumbo com granulometria inferior a 16μm, presentes na planta de beneficiamento da unidade de Vazante da Votorantim Metais. Primeiramente, foram feitos estudos fundamentais com amostras dos minerais galena e esfalerita. Em seguida, foram realizados ensaios, em escala de bancada, com o minério sulfetado. Foram utilizados o amil xantato e propil xantato como reagentes coletores e o MIBCOL como espumante. Para cada reagente coletor foi analisada a influência da velocidade de agitação e do pH. Os resultados mostraram que a agregação hidrofóbica relacionou-se com a hidrofobicidade das partículas e não diminui com o aumento das cargas superficiais, fato que contraria a teoria DLVO. Além disso, a agregação das partículas de galena aumentou em meio básico. Nos testes de flotação não convencional com o minério, observou-se um aumento significativo na recuperação metalúrgica do chumbo, sendo a diferença para a flotação convencional chegou a 73,6% no teste realizado com amil xantato, 2200 rpm e 10 minutos. Dentre as variáveis analisadas, a velocidade de rotação foi a variável que teve maior efeito na recuperação tanto do chumbo quanto do zinco. A adição de óleo diesel prejudicou a recuperação do chumbo e o tempo de condicionamento do coletor foi o fator que menos influenciou os resultados. A análise dos resultados, permitiu concluir que a agregação hidrofóbica é uma técnica promissora para a recuperação de particulas finas de sulfeto de zinco e chumbo. ______________________________________________________________________________________ / ABSTRACT: The mining activities evolution has driven implementation of new concepts to process ores with low grades and small size particle liberation. Several alternative techniques have been developed, among which the hydrophobic aggregation should be emphasized. In this process selective hydrophobization is induced by collectors that adsorb onto desired minerals forming aggregates able to adhere to air bubbles and to be recovered by flotation. Despite the great potential, this process still has restricted application in the mineral industry, due to the great complexity and little understanding about this technique, thus motivating the development of this research, which aimed to study the applicability of hydrophobic aggregation to assist flotation of sulphide minerals of zinc and lead with particle size below 16μm, present in the pulp of the the processing plant unit of Votorantim Metais Zinc. The experiments were conducted at the University of Ouro Preto. Firstly, fundamental studies were performed with samples of galena and sphalerite minerals. Then, bench tests were carried out with the sulfide ore. Amyl xanthate and propyl xanthate and diesel were used as collector and MIBCOL as frother. For each collector reagent were analyzed the influence of pH and agitation speed. The experimental results showed that the hydrophobic flocculation was closely correlated with the particle hydrophobicity, but was not lowered upon increasing the particle surface charges due to collector adsorption, which is contrary to the DLVO theory. This flocculation has been observed to increase in alkaline media. From the ore flotation results, it was observed a significant increase in metallurgical recovery of lead, the difference to conventional flotation reaching 73.6 % in the test performed with amyl xanthate, 2200 rpm and 10 minutes. Among the variables analyzed, the speed of rotation was the variable that had greater effect on recovery of lead and zinc. The addition of diesel oil has lowered lead recovery and conditioning time was the factor that less influenced the results. The analysis of the results allowed concluding that the hydrofobic aggregation is a promising technique for recovering fine particles of zinc and lead sulfide.

No description available.

No description available.

Thesis (PhDApSc)--University of South Australia, 2003.