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Projeto de investigação
Thinking rough towards sustainability
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Optimization of Electric Field Assisted Mining Process Applied to Rare Earths in Soils
Publication . Pires, Carolina M. G.; Pereira, Jucélio T.; Ribeiro, Alexandra B.; Ponte, Haroldo A.; Ponte, Maria José J. S.; DCEA - Departamento de Ciências e Engenharia do Ambiente; CENSE - Centro de Investigação em Ambiente e Sustentabilidade; MDPI - Multidisciplinary Digital Publishing Institute
The extraction of rare earths has been studied worldwide, however some of these processes have a high cost and can cause negative environmental impacts. In order to mine these species from the soil, Electric Field Assisted Mining arises as an alternative to conventional mining processes. Therefore, the experimental parameters can be improved to obtain better results in the extraction of these species. The aim of this paper is to propose the optimization of the Electric Field Assisted Mining process of yttrium, to obtain the optimal experimental configuration to be applied in real soils. An optimization problem was defined to obtain the maximum extraction mass of yttrium ion (Y3+), considering the limitation for the quantity of electric current density. A hybrid optimization technique was used, based on the sequential application of genetic algorithms and non-linear programming. Different optimal process configurations were obtained, considering distinct limits for the electric current density. The best experimental configuration resulted in 0.5386 V cm−1 electric field strength and 0.10 mol L−1 electrolyte concentration. This condition was reproduced in real soil, which obtained a Y3+ electromining efficiency of 41.48%. The results showed that this technique is promising for the extraction of rare earth in real soils.
Electrodialytic Arsenic Removal from Bulk and Pre-treated Soil
Publication . Ferreira, Ana Rita; Couto, Nazaré; Ribeiro, Alexandra B.; Ottosen, Lisbeth M.; CENSE - Centro de Investigação em Ambiente e Sustentabilidade; DCEA - Departamento de Ciências e Engenharia do Ambiente; Springer Science Business Media
Arsenic (As) is a well-known highly toxic and carcinogenic element. A combination of electrodialytic remediation (EDR) after soil washing with flocculant addition targeting remediation of a soil polluted with As from wood preservation industry is the focus of this paper. The fine fraction (< 0.063 mm) from the washed soil after dry sieving was also considered. The EDR experiments were carried out in a 2-compartment cell applying 0.01 mA/cm2 during 14, 7 and 3 days. The suspended soil slurry was placed in cathode compartment separated by anion exchange membrane (AEM) of the anolyte where the pH was kept at 10. The soil was highly polluted with As, and the EDR was able to remove between 50 and 80% corresponding to 400–478 mg As/kg of soil. The major part of the As was removed within the first 3 days (63%), and approx. 10% more of As was released doubling the time of the experiment: 72% in 7 days and 80% in 14 days. The pre-treated soil showed higher As initial concentration, but did not show a clear advantage in terms of removal rate as the original soil (not washed or sieved) showed 80% of As removal comparing with 61% and 50% for washed and fine fraction, respectively (although the absolute removed concentration was similar). The sequential extraction results confirmed that As was bound into more mobile fractions in original soil, and the higher removal was mainly due to its larger exchangeable and reducible fractions compared to the oxidizable and residual fraction in pre-treated soil.
Electrodialytic hydrogen production and critical raw materials recovery from secondary resources
Publication . Almeida, Joana; Magro, Cátia; Mateus, Eduardo P.; Ribeiro, Alexandra B.; CENSE - Centro de Investigação em Ambiente e Sustentabilidade; DCEA - Departamento de Ciências e Engenharia do Ambiente; MDPI - Multidisciplinary Digital Publishing Institute
Electrodialytic technologies are defined as treatment processes that promote the removal/recovery of substances in a matrix, based on the application of low-level current intensities. Additionally, along these processes hydrogen is self-generated, allowing them to operationally produce clean energy. This energy carrier is produced due to electrolysis reactions occurring at the cathode end of the electrodialytic reactor, when using inert electrodes. Herein, hydrogen production during the electrodialytic treatment of sewage sludge and mining residues suspensions (coupled with effluent or sewage sludge), at 50 and 100 mA, was assessed. During the electrodialytic treatment of sewage sludge, hydrogen purity production achieved 33%. When effluent or sewage sludge were used as enhancements in mining residues suspensions, hydrogen purity reached 71% and 34%, respectively. Furthermore, a proton-exchange membrane fuel cell was connected to the cathode compartment of the electrodialytic reactor. The electrical energy generated from self-hydrogen produced at 100 mA achieved ≈1 V in all performed experiments. Simultaneously, critical raw materials extraction, namely phosphorus and tungsten, was evaluated. When the process was applied to mining residue suspensions combined with sewage sludge, the highest extraction ratio of phosphorus (71%) and tungsten (62%) was observed.
Comparação entre as técnicas de modelação implícita e modelação explícita: um caso de estudo com o software Leapfrog Geo na Mina de Neves Corvo
Publication . Malagón Aguirre, Camilo Andrés; Almeida, José; Gonçalves, Miguel
O aperfeiçoamento gráfico e computacional, no campo da exploração mineira, tem permitido reconstruir a morfologia dos corpos geológicos por modelos de maior resolução espacial.
Historicamente, a delimitação explícita de estruturas geológicas, era feita pela interpretação bidimensional por peritos em secções sensivelmente paralelas. Mais recentemente, o aprimoramento de funções volumétricas, capazes de construir superfícies equipotenciais, promoveu o desenvolvimento das técnicas implícitas para a modelação do fenómeno geológico.
Na presente dissertação pretende-se comparar os fundamentos e resultados das técnicas de modelação explícita e implícita, aplicados a um depósito mineral com geometria complexa. Foi utilizada uma base de dados com 365 sondagens, procedentes do depósito mineral do Zambujal, Mina de Neves-Corvo, e que regista as características qualitativas e quantitativas da geologia e geoquímica, respetivamente.
Todos os modelos morfológicos 3D foram gerados com recurso ao software Leapfrog Geo™. É de salientar que este software só está concebido para a construção de modelos geológicos por meio técnicas implícitas, com auxílio de ferramentas de interpolação de distâncias designadas Fast RBF. De acordo com este pressuposto, para a modelação explícita, foi aplicada uma abordagem híbrida mantendo o desenho tradicional dos limites do corpo geológico, interpolando-os a partir de linhas poligonais para gerar o sólido final.
O resultado deste estudo enfatiza as vantagens da modelagem implícita, nomeadamente o tempo de processamento que é bastante inferior ao da modelagem explícita, bem como a eficiência para atualizar o modelo e a sua imparcialidade. Em contrapartida, a modelação explícita, embora mais tediosa, consegue resultados mais realistas em zonas de maior complexidade estrutural e onde a intervenção de um perito seja pertinente.
Electrodialytic removal of tungsten and arsenic from secondary mine resources – Deep eutectic solvents enhancement
Publication . Almeida, Joana; Craveiro, Rita; Faria, Paulina; Silva, A. Santos; Mateus, E. P.; Barreiros, Susana; Paiva, A.; Ribeiro, Alexandra B.; CENSE - Centro de Investigação em Ambiente e Sustentabilidade; DCEA - Departamento de Ciências e Engenharia do Ambiente; DEC - Departamento de Engenharia Civil; CERIS - Polo NOVA; LAQV@REQUIMTE; DQ - Departamento de Química; Elsevier
Tungsten is a critical raw material for European and U.S. economies. Tungsten mine residues, usually considered an environmental burden due to e.g. arsenic content, are also secondary tungsten resources. The electrodialytic (ED) process and deep eutectic solvents (DES) have been successfully and independently applied for the extraction of metals from different complex environmental matrices. In this study a proof of concept demonstrates that coupling DES in a two-compartment ED set-up enhances the removal and separation of arsenic and tungsten from Panasqueira mine secondary resources. Choline chloride with malonic acid (1:2), and choline chloride with oxalic acid (1:1) were the DES that in batch extracted the average maximum contents of arsenic (16%) and tungsten (9%) from the residues. However, when ED was operated at a current intensity of 100 mA for 4 days, the extraction yields increased 22% for arsenic and 11% for tungsten, comparing to the tests with no current. From the total arsenic and tungsten extracted, 82% and 77% respectively were successfully removed from the matrix compartment, as they electromigrated to the anolyte compartment, from where these elements can be further separated. This achievement potentiates circular economy, as the final treated residue could be incorporated in construction materials production, mitigating current environmental problems in both mining and construction sectors.
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Entidade financiadora
European Commission
Programa de financiamento
H2020
Número da atribuição
778045