Identificação de possíveis recursos em três tipos distintos de resíduos mineiros da Faixa Piritosa Ibérica com técnicas de fluorescência de raios-x

O conceito de economia circular consiste num sistema de produção e consumo que promove o uso sustentável dos recursos, em ciclos fechados energizados por fontes renováveis, de forma a eliminar desperdícios. Na economia circular, os resíduos são materiais que devem ser considerados com o potencial de serem reintroduzidos (reciclados) nos circuitos da cadeia de valor, sendo conside rados como Matérias-Primas Secundárias (SRM-Secondary Raw Materials). Atualmente, e de forma geral, apenas uma pequena percentagem dos resíduos é reciclada e é integrada neste grupo compa rativamente às necessidades reais de consumo. De acordo com sua definição tradicional, SRM’s são materiais que foram usados em produtos e são recicláveis e, portanto, podem ser injetados de volta na economia como novas matérias-primas. A definição do EIT (European Institute of Technology) consi dera igualmente SRM’s como todos os materiais de origem mineral que ainda não foram processados ou usados, mas já foram extraídos da crosta terrestre. Nesta perspetiva, os resíduos mineiros são potencialmente recursos de minerais metálicos e minerais, ou seja, os resíduos mineiros são SRM’s. De facto, e de acordo com suas características, os resíduos mineiros podem ser considerados inclusi vamente como fontes múltiplas de matérias-primas distintas e/ou matérias-primas críticas (CRM's). Nesta perspetiva, o principal objetivo deste estudo foi proceder à identificação dos elementos metálicos presentes em três tipos distintos de resíduos de uma antiga minada Faixa Piritosa Ibérica (FPI), localizada na Região Sul do Alentejo em Portugal (São Domingos). Para tal, foram consideradas análises de fluorescência e microfluorescência de raios-X para identificar elementos químicos presen tes nos distintos tipos de resíduos mineiros. Em resíduos de períodos da história mineira distintos, os métodos de exploração variaram ao longo dos anos, tendo alterado a composição e potencialidades das escombreiras resultantes da exploração mineira. De referir, que a riqueza de história mineira desta área faz com que alguns desses resíduos fossem classificados como património arqueológico-industrial. As análises realizadas no XRF-Fluorescência de raios-x permitiram concluir sobre o potencial económico existente quanto aos elementos Sb, Sn, Bi, Pb, P, Au e Ag nos resíduos de cinzas piríticas, Zn, Cu e Mn em escórias das décadas 50/60 (60’s) e Al, Ti, Cr e Pb em antigos escoriais Romanos (Roman), sendo que nestes últimos esta informação será mais propriamente uma curiosidade do que uma potencialidade em termos de exploração em virtude do valor arqueológico associado. Com as análises no µ-XRF (micro-fluorescência de raios-x) foi possível concluir o potencial económico dos ele mentos Sb, Pb e Sn nos resíduos do tipo Greywaste, Cu e Zn nos 60’s e Ti nos Roman. As análises realizadas permitiram concluir sobre a ocorrência de diferentes tipos de elemen tos que poderão representar algum potencial económico devendo este estudo ser entendido como um contributo na aplicação do conceito de economia circular à atividade mineira.The concept of circular economy consists of a production and consumption system that promotes the sustainable use of resources, in closed cycles powered by renewable sources, in order to eliminate waste. In the circular economy, wastes are materials that have the potential to be reintroduced (recycled) in value chain circuits, being considered as Secondary Raw Materials (SRM-Secondary Raw Materials). Currently, and in general, only a small percentage of waste is recycled and is included in this group compared to real consumption needs. According to their traditional definition, SRM's are materials that have been used in products and are recyclable and therefore can be injected back into the economy as new raw materials. The definition of the EIT (European Institute of Technology) also considers SRM's as all materials of mineral origin that have not yet been processed or used, but that have already been extracted from the earth's crust. In this perspective, mining residues are potentially resources of metallic minerals and minerals, that is, mining residues are SRM's. In fact, and according to its characteristics, mining residues can even be considered as multiple sources of different raw materials and/or critical raw materials (CRM's). In this perspective, the main objective of this study was to identify the metallic elements present in three different types of waste from an old mined Iberian Pyrite Belt (FPI), located in the southern region of Alentejo in Portugal (São Domingos). To this end, X-ray fluorescence and microfluorescence analyzes were considered to identify chemical elements present in different types of mining waste. In residues from different periods of mining history, exploration methods have varied over the years, having changed the composition and potential of the heaps resulting from mining. It should be noted that the richness of the mining history of this area means that some of this waste is classified as archaeological-industrial heritage. The analyzes carried out in XRF-X-ray fluorescence allowed to conclude on the existing economic potential for the elements Sb, Sn, Bi, Pb, P, Au and Ag in pyritic ash residues, Zn, Cu and Mn in slag from decades 50/60 (60's) and Al, Ti, Cr and Pb in ancient Roman slags (Roman), and in the latter this information will be more a curiosity than a potential in terms of exploration due to the associated archaeological value. -adopted. With the analysis in µ-XRF (X-ray micro-fluorescence) it was possible to conclude the economic potential of the Sb, Pb and Sn elements in Greywaste, Cu and Zn in 60's and Ti in Roman residues. The analyzes carried out allowed us to conclude on the occurrence of different types of elements that could represent some economic potential and this study should be understood as a contribution to the application of the concept of circular economy to mining activit

The Dual Paradigm of Mining Waste: “From Ecotoxicological Sources to Potential Polymetallic Resources” - An Example from Iberian Pyrite Belt (Portugal)

GeoBioTec/NOVA UIDP/GEO/04035/2020The main goal of this study was to identify potential chemical elements present in three types of polymetallic mine waste, stored in the old mine site of São Domingos, located in the Iberian Pyrite Belt, Alentejo, Southern Region of Portugal. This study involves the characterization of potential resources in those mine residues, bearing in mind that its reprocessing can facilitate the environmental remediation and rehabilitation activities which are underway at the site. X-ray Fluorescence (XRF) and micro (μ)-XRF 2D mapping surveys were performed. Univariate and multivariate data analysis reveal that differences in compositions are mainly related with element concentration per type of waste. Image processing and clustering analysis allowed the recognition of distinct elemental spatial distribution patterns. Some of these residues, although classified as archeological-industrial heritage materials may present toxicity to the ecological environment and to human health. This fact enhances, therefore, geoethical doubts regarding its remining and exploitability. In this context, a multi-criteria decision analysis considering two geoethical alternatives was performed.publishersversionpublishe

Characterisation of microbial attack on archaeological bone

As part of an EU funded project to investigate the factors influencing bone preservation in the archaeological record, more than 250 bones from 41 archaeological sites in five countries spanning four climatic regions were studied for diagenetic alteration. Sites were selected to cover a range of environmental conditions and archaeological contexts. Microscopic and physical (mercury intrusion porosimetry) analyses of these bones revealed that the majority (68%) had suffered microbial attack. Furthermore, significant differences were found between animal and human bone in both the state of preservation and the type of microbial attack present. These differences in preservation might result from differences in early taphonomy of the bones. © 2003 Elsevier Science Ltd. All rights reserved