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- Corrosão de aços inoxidáveis austeníticos em sais fundidos ternários de cálcioPublication . Cunha Diamantino, Teresa; Gomes, A.; Paiva Luís, Teresa; Figueira, Isabel; Pedrosa, Fátima; Nogueira, Carlos; Guerreiro, L.; Collares-Pereira, M.RESUMO: O armazenamento de energia térmica (TES) é um fator chave para melhorar a eficiência e a despachabilidade dos diferentes sistemas energéticos, devido a um melhor ajustamento entre a procura e a oferta de energia, e ao permitir o desenvolvimento e a implementação de energias renováveis. Um exemplo claro é o TES em instalações de concentração de energia solar (CSP), onde o excesso de energia solar durante o período de luz solar é armazenado para ser utilizado durante os períodos em que a energia solar é necessária, mas não está disponível. Os sais fundidos têm sido amplamente utilizados como fluidos de transferência de calor (HTF) e para TES em instalações CSP. Uma das características fundamentais dos sais fundidos no que diz respeito à sua utilização como HTF e TES é a sua compatibilidade com os materiais de construção. Por esta razão, este trabalho apresenta a resistência à corrosão de dois aços inoxidáveis austeníticos AISI 316L e AISI 321H em contacto com sal ternário fundido com cálcio. Ambos os aços inoxidáveis demonstraram ter velocidades de corrosão aceitáveis para as centrais CSP. Entre os aços austeníticos estudados, o AISI 316L apresenta a menor velocidade de corrosão.
- Catalisadores de automóvel: Caracterização, Reciclagem e Recuperação de Metais PreciososPublication . Paiva, A. P.; Nogueira, Carlos; Costa, Ana M. Rosa da; Costa, M. ClaraOs catalisadores de automóvel desempenham um papel importante no tratamento dos gases de escape dos veículos, minimizando as emissões de substâncias nocivas para o ambiente. No final do seu ciclo de vida constituem resíduos que devem ser reciclados, não só por razões ambientais, mas também económicas e de conservação de recursos. Os agentes catalíticos destes dispositivos são os metais nobres do grupo da platina (Pt, Pd e Rh) cuja recuperação é crucial pelo seu valor e raridade. Neste artigo apresenta-se uma descrição do funcionamento, composição e de processos para a reciclagem de catalisadores de automóvel, bem como alguns resultados de um projecto de investigação em curso que visa contribuir para o desenvolvimento de operações hidro-metalúrgicas, como a lixiviação e a extracção por solventes, aplicáveis aos metais nobres contidos nestes resíduos. Estudou-se a lixiviação em meio de HCl, na presença de um oxidante, demonstrando-se o efeito de variáveis processuais como a concentração dos reagentes e a temperatura nos rendimentos de lixiviação dos metais. Foram também desenvolvidos extractantes (diamidas), que extraem eficiente e selectivamente os metais nobres de meios cloretados, possibilitando a sua separação e recuperação.
- End-of-life Zn–MnO2 batteries: electrode materials characterizationPublication . Cabral, Marta; Pedrosa, Fátima; Margarido, F.; Nogueira, CarlosPhysical and chemical characterization of several sizes and shapes of alkaline and saline spent Zn–MnO2 batteries was carried out, aiming at contributing for a better definition of the applicable recycling processes. The characterization essays included the mass balance of the components, cathode and anode elemental analysis, the identification of zinc and manganese bearing phases and the morphology analysis of the electrode particles. The electrode materials correspond to 64–79% of the total weigh of the batteries, with the cathodes having clearly the highest contribution (usually more than 50%). The steel components, mainly from the cases, are also important (17–30%). Elemental analysis showed that the electrodes are highly concentrated in zinc (from 48–87% in anodes) and manganese (from 35–50% in cathodes). X-Ray powder diffraction allowed for identifying several phases in the electrodes, namely zinc oxide, in the anodes of all the types of saline and alkaline batteries tested, while zinc hydroxide chloride and ammine zinc chloride only appear in some types of saline batteries. The manganese found in the cathode materials is present as two main phases, MnO·Mn2O3 and ZnO·Mn2O3, the latter corroborating that zinc migration from anode to cathode occurs during the batteries lifespan. A unreacted MnO2 phase was also found presenting a low crystalline level. Leaching trials with diluted HCl solutions of alkaline and saline battery samples showed that all zinc species are reactive attaining easily over than 90% leaching yields, and about 30% of manganese, present as Mn(ii/iii) forms. The MnO2 phase is less reactive and requires higher temperatures to achieve a more efficient solubilization.
- Recycling of zinc bearing residues: leaching behavior of spent batteries and eaf dusts in several aqueous mediaPublication . Pedrosa, Fátima; Cabral, Marta; Nogueira, Carlos
- The effect of shredding and particle size in physical and chemical processing of printed circuit boards wastePublication . Oliveira, Paula; Taborda, F. Charters; Nogueira, Carlos; Margarido, F.Circuit boards present in most electric and electronic devices are very important components, which should be removed during sorting and dismantling operations in order to allow further adequate treatment for recovering valuable metals such as copper, nickel, zinc, lead, tin and rare elements. This recovery can be made by physical and chemical processes being size reduction by shredding the first step. In this paper, the effect of particle size in physical and chemical processing of printed circuit boards is presented and discussed. Shredding using cutting-based equipment allowed the comminution of boards and the liberation of particles composed by different materials (mainly metals and resin). Particle sizes less than 1 mm seems to be appropriate to attain high liberation of materials, which is crucial for the physical separation using gravity or electrostatic processes. Concerning chemical treatment, hydrometallurgical processing involves a leaching operation which can be also influenced by particle size of shredded boards. Samples with different granulometries were leached with 1 M HNO3 solutions, being leaching yields evaluated. It was concluded that particle size can be an important factor for the solubilization of some metals, but the effect is not similar for all elements. When average diameters change from 2.0 to 0.20 mm, nickel, aluminium and tin reactivity were not significantly affected, being this effect important for copper. Zinc behavior was very dependent from extreme particle sizes but was less affected in intermediate granulometries. Lead leaching showed also a peculiar behavior, exhibiting high and almost constant yields (80-90%) for particle size of solids up to 1.2 mm, and decreasing suddenly for higher granulometries. The effect of time on chemical reactivity for samples with different granulometries demonstrated that particle size affects reaction rates but eventually similar efficiencies can be obtained for long time periods. Therefore the relationship between results from shredding operation and chemical leaching step needs to be optimized, considering the balance between factors like consumption of energy during grinding operation and residence time in leaching.
- Liquid-Liquid Extraction of Platinum from Chloride Media by N,N'-Dimethyl-N,N'-DicyclohexyltetradecylmalonamidePublication . Costa, M. Clara; Assunção, Ana; Costa, Ana M. Rosa da; Nogueira, Carlos; Paiva, A. P.Liquid-liquid extraction of platinum(IV) from chloride media was carried out using N,N'-dimethyl-N,N'-dicyclohexyltetradecylmalonamide (DMDCHTDMA) in 1,2-dichloroethane. Platinum can be effectively extracted by DMDCHTDMA without addition of tin(II) chloride, since extraction percentages (%E) of 88% and 99% have been achieved from 6 M and 8 M HCl, respectively. Moreover, platinum can be successfully stripped through a simple contact with a 1 M HCl solution. The effect of some experimental parameters such as equilibration time, diluent, extractant and HCl concentrations was systematically investigated. The loading capacity of DMDCHTDMA was also evaluated. Data obtained from successive extraction-stripping cycles suggest a good stability pattern of DMDCHTDMA. Preliminary extraction data achieved with single metal ion solutions pointed out to a possible separation of platinum(IV) from palladium(II).
- Recovery of platinum(IV) and palladium(II) from complex hydrochloric acid matrices by a thiodiglycolamide derivativePublication . Paiva, A. P.; Carvalho, G. I.; Costa, M. Clara; Costa, Ana M. Rosa da; Nogueira, CarlosThe solvent extraction performance of N,N’-dimethyl-N,N’-dicyclohexylthiodiglycolamide (DMDCHTDGA) towards Pt(IV) and Pd(II) in HCl solutions has recently been published. It was shown that these two platinum-group metals (PGMs) are efficiently extracted from 8 M HCl aqueous phases, being subsequently separated by sequential strippings: 1 M HCl allows Pt(IV) recovery, whereas Pd(II) is only back-extracted by thiourea in HCl. In this work, selectivity tests were carried out to evaluate the performance of DMDCHTDGA towards the recovery of both PGMs, from 8 M HCl aqueous phases, when in presence of Rh(III), Fe(III), Ni(II), Zn(II), Al(III), Ce(III) and Zr(IV), simulating the leaching solutions that may result from the hydrometallurgical treatment of spent automobile catalytic converters. It was generally observed that the additional metal ions do not affect the recovery of Pd(II) and Pt(IV) by DMDCHTDGA. Fe(III), Zn(II) and Zr(IV) are co-extracted with Pt(IV) and Pd(II); Fe(III) and Zn(II) were efficiently scrubbed with water, whereas Zr(IV) was removed by an acidified aqueous solution. Inversely, Ni(II) is not extracted, and Rh(III) and Ce(III) appear only traceably in the loaded organic phase. Al(III) is a concern, as it is appreciably extracted, and none of the tested backextraction solutions was able to strip it.
- Separation of non-ferrous frations of shredded end-of-life vehicles for valorising its alloysPublication . Margarido, F.; Santos, R. Novais; Durão, F.; Guimarães, C.; Nogueira, Carlos; Oliveira, Paula; Pedrosa, Fátima; Gonçalves, Ana MariaWorldwide the end-of-life vehicles (ELV) generate millions of tons of waste, requiring an adequate and efficient management. The non-ferrous fraction contains essentially aluminium, magnesium and copper alloys, being valorised by metallurgical processors to obtain new metals and alloys. However most of the recovered metals are downcycled, as is the case of aluminium where the recycled products are essentially used to produce less purity casting alloys. New or improved separation technologies are therefore necessary in order to allow an accurate separation of alloys or alloy groups, increasing the value of the non-ferrous streams. In this paper, the composition of the non-ferrous fractions of ELV shredders are assessed with particular relevance for the aluminium and magnesium alloys. Essentially, the main cast and wrought alloys are characterized and their markets and applications are discussed. Based on waste composition, several physical separation and sorting technologies can be applied to improve the products quality, which are here depicted and discussed. Physical processing includes operations such as eddy current and heavy media separations. For sorting alloys contained in the non-ferrous stream, other sensor-based technologies are being developed, such as electromagnetic sensing and novel laser induced breakdown spectroscopy systems, constituting an important contribution for boosting the non-ferrous metals recycling rates.
- Lithium metallurgical processing from primary resources [Comunicação oral]Publication . Nogueira, Carlos
- Molten nitrate salts containing lithium as thermal energy storage media : a short reviewPublication . Pedrosa, Fátima; Marcelo, Teresa; Nogueira, Carlos; Gomes, A.; Cunha Diamantino, TeresaABSTRACT: 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.