A hidrometalurgia na recuperação de metais contidos em resíduos ricos em zinco

Tese submetida à Universidade Técnica de Lisboa, Instituto Superior Técnico e aprovada em provas públicas para a obtenção do Grau de Doutor em Engenharia do Ambiente.Desenvolve-se um processo de lixiviação de poeiras siderúrgicas e de pilhas esgotadas do sistema electroquímico Zn-MnO2, para a recuperação de zinco e manganês. Na fase de caracterização físico-química verificou-se que ambos os resíduos têm elevados conteúdos metálicos, apresentando uma matriz química semelhante que justifica o desenvolvimento de um processo de reciclagem comum para os dois resíduos. As poeiras contêm 33% Zn, 21% Fe e 1,5% Mn, distribuídos entre as fases da zincite (ZnO) e da franklinite (ZnOFe2O3), e as pilhas 19% Zn, 7,5% Fe e 26% Mn, presentes na zincite, num óxido misto de zinco e manganês (ZnO.MnO2) e no óxido de manganês (IV) (MnO2). Do estudo sistemático da lixiviação do zinco em meio de ácido sulfúrico, conclui-se que em ambos os resíduos, o zinco na forma de zincite reage eficientemente, atingindo-se rendimentos de lixiviação totais usando concentrações de ácido próximas da estequiometria, à temperatura ambiente, com tempos de reacção reduzidos. Numa segunda fase, utilizando condições mais drásticas, recupera-se o zinco da franklinite (poeiras) e o manganês das pilhas. O estudo cinético da lixiviação da franklinite permitiu concluir que o processo é controlado pelo passo químico, enquanto no caso do MnO2 das pilhas existe um processo de controlo reaccional misto

Leaching behavior of several zinc rich residues in a hydrometallurgical recycling process

The leaching of metals contained in spent Zn-MnO2 batteries and electric arc furnace (EAF) dusts using sulfuric acid solutions was studied, in order to evaluate the feasibility of simultaneous treatment of both wastes by a hydrometallurgical process. In both residues, a substantial quantity of zinc was solubilized (about 100% in batteries and 70-80% in EAF dusts) in diluted acid solutions and room temperature, corresponding to the reaction of zinc oxide species. Other species were more refractory to the chemical attack, namely the manganese (III or IV) oxides in batteries and the zinc ferrite in dusts, requiring higher temperatures (e.g. 90ºC) and higher leachant concentrations. Lead present in EAF dusts was not solubilized in sulfate media, thus remaining in the leach residue. Results seem to confirm the possibility of treatment of both zinc-containing residues by the same hydrometallurgical process, eventually involving two leaching stages – diluted acid leaching and hot acid leaching – followed by solution purification through iron precipitation and Zn/Mn separation and recovery. Concerning lead, a second leaching circuit in chloride media could be developed for its potential recovery

Metals recovery from spent Zn-MnO2 batteries by Hydrometallurgy

A hydrometallurgical process for recycling spent Zn-MnO2 batteries was developed, involving leaching with sulfuric acid, purification by precipitation and metals separation for further recovery. Leaching of zinc oxide was easily attained while for manganese oxide was rather difficult depending on temperature and acid concentration. At 90ºC and with the liquid/solid ratio of 20 L/kg, more than 95% of zinc is recovered in 30 minutes with 0.5M H2SO4. To attain similar recovery for manganese, higher levels of acid concentration and time are needed (e.g 0.7 M and 2 hours). After leaching a purification step is necessary to remove iron co-dissolved through Fe(III) precipitation. Separation of zinc from manganese by solvent extraction with 1M DEHPA follows in the process route. The countercurrent multistage separation diagram developed allows the production of a zinc electrolyte with 120 g/L Zn and 0.005 g/L Mn, and a raffinate with 16 g/L Mn and 0.013 g/L Zn

Molten nitrate salts containing lithium as thermal energy storage media : a short review

ABSTRACT: Energy storage plays a crucial role in the development and progress of renewable energy sources. In the case of thermal energy, storage has been a step ahead since storage solutions already exist, unlike other conversion energy technologies. In this sense, the utilization of molten salts, mainly composed of mixtures of alkali/alkaline earth metals, in nitrate forms (sometimes also with nitrite), have been proposed and successfully applied. Molten salts have recognized advantages over other solutions namely in what concerns simultaneous use as heat transfer fluids and as storage media. Commercial utilization of molten salts has been tested essentially with the Na/K salt mixtures. Introduction of lithium nitrate in these formulation has been proposed, since can allow decreasing the melting point of the mixtures, thus providing safety concerning the risks of freezing in the tubes or tanks of the storage plant. This paper provides a short review on the utilization of lithium in molten salt mixtures used for thermal energy storage. Physical, chemical and thermal properties, as well as stability and decomposition issues are evaluated. Corrosion of stainless steels in contact with the salts is another crucial question that is also addressed.info:eu-repo/semantics/publishedVersio

Escolha de marca: O papel do influenciador digital.

This article presents the opinion of the role of the digital influencer by social media, thus influencing the purchasing power of clients, since most people have access to the internet.UFU - Universidade Federal de UberlândiaTrabalho de Conclusão de Curso (Graduação)O presente artigo apresenta o quanto julga a opinião do papel do influenciador digital pelas mídias sociais, assim influenciam o poder de compra de clientes, na medida em que maioria das pessoas tem acesso a internet

Integration of physical operations in the hydrometallurgical processing of spent Zn-MnO2 batteries

The recycling of spent Zn-MnO2 batteries by hydrometallurgy involves the leaching of material previously treated by physical processing to allow the liberation of electrode particles and the separation of unwanted scrap. The integration of these physical operations with leaching is therefore crucial for the optimization of the process, allowing achieving high recovery yields of zinc and manganese and minimizing reactants consumption and iron contamination. In this paper, several options involving physical processing and leaching with sulphuric acid are presented and discussed. After batteries shredding and disaggregation, the separation of steel scrap was performed by sieving or magnetic separation, and the remaining solids were treated by leaching. These options were compared, in terms of metals recovery and contamination, with the alternative of direct leaching of all the shredded fractions without physical treatment. The separation of the steel scrap by sieving or magnetic separation allowed the removal from the circuit of 37 or 49% of iron, respectively, with losses of 15 or 6% of zinc and 2 or 4% of manganese. Therefore more than 50% of iron remained in the process, which was attributed to the presence of iron oxides formed by the corrosion of the battery cases. In the leaching operation, zinc dissolution was very effective (yields above 97%) while manganese is strongly depended from the process option, being its leaching proportional to the presence of scrap (yields of 80%, 56% and 43%, respectively in direct leaching, sieving / leaching and magnetic separation / leaching). These results showed that iron plays an important role in the reductive leaching of manganese species (III or IV), and so the presence of steel scrap in leaching, besides disadvantages concerning solutions contamination, contributes positively for the leaching efficienc

High-temperatures corrosion of AISI 316L and AISI 430 steels in dynamic conditions with molten solar salt

ABSTRACT: Potassium nitrate and sodium nitrate in mixing proportion of KNO3–NaNO3 40-60 wt% (also called solar salt) has been successfully used for over a decade as a heat storage medium for concentrated solar power plants. At temperatures of 550 ºC, reached in state-of-the-art solar tower systems, corrosion of metallic components in contact with solar salt can become an issue and has caused leaks and plant shut-downs in recently built tower projects. While the corrosion rates of several materials have been determined for different temperatures in static molten salt immersion experiments, there is a lack of corrosion data for dynamic inservice conditions. Fluid dynamics and scale-up are two factors that can influence the corrosion phenomena. In this work, corrosion studies were carried out on austenitic stainless steel (SS) (AISI 316L) and ferritic steel (AISI 430) under dynamic conditions, with long-term immersion in solar salt, on a pilot scale. It was found that AISI 316L steel forming more adherent oxides, presented a significantly lower corrosion rate than the AISI 430 steel, due to the formation of a protective FeCr2O4 layer, making it less susceptible to corrosion. The measured corrosion rates are presented and compared to static corrosion tests.info:eu-repo/semantics/publishedVersio

Evaluation of the quantitative and qualitative aspects of pain in the fibromyalgia sydrome

OBJETIVO: Avaliar a percepção da dor na fibromialgia por meio de técnica metodológica quantitativa e qualitativa. MÉTODOS: Foram avaliadas 30 pacientes mediante entrevista apreciada por meio de análise de conteúdo temática e do Instrumento de Descritores de Dor, porquanto para os dados resultantes foram calculados a média aritmética e o desvio-padrão para determinar quais descritores caracterizam a dor na fibromialgia. RESULTADOS E DISCUSSÃO: A análise de conteúdo resultou a construção de categorias de análise referentes às percepções de diagnóstico, motivações, doença, sentimentos, pensamentos e repercussões na qualidade de vida. Já o Instrumento de Descritores de Dor revelou que os descritores de maior atribuição na caracterização da dor foram: incômoda, que espalha, latejante, desconfortável e persistente, e os de menor atribuição foram: desgraçada, demoníaca, maldita, aterrorizante e assustadora. Os dois instrumentos mostraram tendência das pacientes em perceber e relatar a dor mais relacionada às características sensorial-discriminativas. Além disso, apresentaram dados relativos à importância do papel da família e do profissional de saúde no manejo da dor. CONCLUSÃO: Percebeu-se a necessidade de estimular a percepção e a expressão das pacientes em relação à dor, abarcando sua multidimensionalidade e, que o manejo da dor deve ser realizado levando-se em conta a tríade equipe de saúde, paciente e família, em face da complexidade do fenômeno.OBJECTIVE: Evaluate the perception of pain in the fibromyalgia through the quantitative and qualitative methodological technique. METHOD: A total of 30 patients were assessed through an interview analyzed by the thematic content and through the instrument Descriptors of Pain. Arithmetic mean and standard error were used to determine which descriptors better characterize the pain in the fibromyalgia. RESULTS AND DISCUSSION: The result of the content analysis was the construction of categories of analysis regarding the perceptions of: diagnosis, motivation, disease, feelings, thoughts and repercussions on the quality of life. The Descriptors of Pain instrument revealed the descriptors of higher attribution in the characterization of pain were inconvenient, spreading, pulsating, uncomfortable and persistent and the descriptors with the lower attribution were miserable, demoniac, cursed, terrifying and frightening. The two instruments showed the patients' tendency in perceiving and reporting the pain regarding to the sensorial-discriminating characteristics. In addition, data related to the importance of the family's and the health professional's roles in managing the pain were presented. CONCLUSION: The need to stimulate the perception and expression of patients regarding the pain in its multidimensionality was perceived. It is concluded that the management of pain must be performed considering the complexity of the phenomenon in terms of the triad health team - patient - family

ELV recycling steps up a gear: development of improved sorting technologies for the non-ferrous fraction of auto-shredders

Although the number of end of life vehicles (ELVs) needing recycling is growing, due to processing limitations aluminium recycling rates are being hindered. A European-funded project - ShredderSort - aims to contribute to new solutions to the aluminium recycling industry. More than 10 million tons of automotive waste from end of life vehicles (ELV) are generated yearly in the EU and the values are continuously increasing. ELV wastes are managed by the auto-shredder plants which process ELVs through a series of mechanical and physical operations in order to separate the materials into different streams: ferrous, non-ferrous, heavy non-metal and fluff. Ferrous materials, constituting more than 60wt% (percentage by weight), are sent to steel-making plants, while the non-ferrous (NF) fraction, rich in aluminium and representing slightly less than 10wt%, is processed to separate some alloys