Investigations on the reprocessing of fine particles from sulfidic tailings through flotation

In der Bergbauindustrie fallen jedes Jahr große Mengen an Bergbaurückständen an. Am häufigsten werden diese Bergematerialien in Bergeteichen gelagert, die enorme Ausmaße haben können. Das Management und die Lagerung solch großer Mengen an Material stellt viele Herausforderungen sowohl in Bezug auf die Stabilität der Dämme als auch an die Immobilisierung gefährlicher Schadstoffe dar, die ein Risiko für die menschliche Gesundheit und die Umwelt bergen, insbesondere bei sulfidhaltigen Rückständen. Außerdem können mit den Bergematerialien erhebliche Mengen an Edel- und Basismetallen verloren gehen. Aufgrund des wirtschaftlichen Wertes und der wachsenden industriellen Nachfrage nach diesen Edel- und Basismetallen können die Bergbaurückstände daher eine potenzielle Quelle für Sekundärrohstoffe sein. Im Rahmen dieser Forschungsarbeit wurden zwei Studien (aus einem aktiven und einem historischen Bergwerk) über die Wiederaufbereitung sulfidischer Bergematerialien mittels Flotation durchgeführt. Die erzielten Ergebnisse können zum Aufbau von Kenntnissen über die Wiederaufbereitung solch sulfidischen Bergematerialien beitragen. Der hier gewählte Ansatz konzentrierte sich auf die Entfernung sowohl wertvoller als auch gefährlicher Elemente sowie die Erzeugung saubererer Rückstände mit geringerem Schadstoffpotenzial und mit chemischen und mineralogischen Eigenschaften, die für weitere Anwendungen (z. B. in der Bauindustrie) geeignet sind. Die Bergematerialien aus dem aktiven Bergwerk wiesen eine breite Partikelgrößenverteilung auf, weshalb ein Flotationsansatz aus einer Kombination, bestehend aus klassischer Flotation und einer selektiven Flockung mit anschließender Flotation gewählt wurde. Das Material wurde sowohl im Originalzustand als auch nach einer Klassierung in zwei Fraktionen flotiert. Das Originalmaterial und die gröbere Fraktion (> 37 µm) wurden der klassischen Flotation zugeführt, während die feinere Fraktion (< 37 µm) entweder mit der klassischen Flotation aufbereitet oder nach der selektiven Flockung flotiert wurde. Die Flotation der gröberen Partikel führte zu höheren Sulfidausbringen, höheren Gehalten an Cu, Pb und Zn im Sammlkonzentrat (3,66 %), saubereren Rückständen (1,6 % S), schnelleren Flotationsraten und geringerem Reagenzienverbrauch. Die Ergebnisse der Feinpartikelflotation wiesen einen geringeren S-Gehalt in den Rückständen (3,4 % S) als im Vergleich zur Flotation des Originalmaterials auf. Die Ergebnisse des Kombinationsansatzes aus Flockung und Flotation der feineren Fraktion zeigte eine Erhöhung des Massenausbringens mit einem leichten Anstieg der Sulfidausbringen. Insgesamt erwies sich die Entwicklung eines Verfahrens zur Aufbereitung des Bergematerials als vielversprechend. Die Anwendung eines zweigleisigen Ansatzes zeigt hierbei Vorteile im Vergleich zu einem eingleisigen. Die Bergematerialien aus dem historischen Bergwerk enthielten neben den Sulfiden eine erhebliche Menge an Baryt. Aus diesem Grund wurde nach der Entfernung der Sulfide in einer weiteren Flotationsstufe der Baryt zurückgewonnen. Abschließend wurden Flotationsversuche im Pilotmaßstab (100-Liter-Flotationszelle) durchgeführt, um die Übertragbarkeit der erzielten Ergebnisse auf einen größeren Maßstab zu bewerten. Diese Ergebnisse zeigen, dass sowohl die Sulfide als auch der Baryt selektiv zurückgewonnen werden können, wobei der Baryt größere Probleme bereitet als die Sulfide. Die Flotation im Pilotmaßstab erzielte Konzentrate mit höheren Gehalten und erforderte längere Flotationszeiten, um die gleichen Ausbringen wie bei den Versuchen im Labormaßstab zu realisieren.The mining industry generates large amounts of tailings every year. The most common destination for the tailings is deposition in tailings storage facilities (TSFs), which can have enormous dimensions. The management and storage of such large volumes of material pose many challenges in terms of dam stability and immobilization of hazardous contaminants that represent human-health and environmental risks, particularly for sulfide-containing materials. In addition, considerable amounts of precious and base metals can be lost in the tailings. Due to the economic value and growing industrial demand for precious and base metals, tailings may therefore be potential sources of secondary raw materials. This research showed two case studies (from an active and a historical mine site) on the reprocessing of sulfidic mine tailings through flotation and the results obtained can contribute to the construction of knowledge about the reprocessing of sulfidic tailings. The approach adopted here focused on the removal of valuable and hazardous elements from the tailings and the generation of cleaner residues, with lower contaminant potential and with chemical and mineralogical characteristics more adequate for further applications (e.g. in the construction industry). The tailings from the active mine site presented a broad particle size distribution, therefore the flotation approach combined classic flotation and floc flotation (flotation of flocs of targeted minerals). Flotation of the material as received, as well as after classification into two fractions was performed. The samples as received and the coarser fraction (+37 µm) underwent classic flotation, while the finer fraction (-37 µm) was processed either by using the classic or the floc flotation approach. The flotation of the coarser particles provided higher sulfide recoveries, higher combined Cu-Pb-Zn grades in the concentrate (3.66%), cleaner residues (1.6% S), faster flotation rates, and reduced reagent consumption. Likewise, the results from the fine particle flotation allowed lower S content in the residues (3.4% S) as compared to the flotation of the original material. The results of the use of floc flotation for the finer fraction showed an increase in the mass pull with a slight increase in the recovery of sulfides. Overall the development of a route to process the tailings proved to be promising and the use of a two-route approach indicates advantages as compared to a single route. The tailings from the historical mine site, in addition to the sulfides, contained a relevant amount of barite. Therefore, flotation aiming for the separation of the barite was also performed after the sulfides removal. The tailings underwent classic flotation with several steps for the removal of sulfides and barite. Finally, trials in a pilot scale (100 L flotation cell) were performed to evaluate the transferability of the results to a larger scale. The results show that either the sulfides or the barite can be selectively recovered, with the barite posing more challenges than the sulfides. The flotation in the pilot scale enabled concentrates with higher grades and needed longer flotation times to achieve the same level of recovery as the bench-scale test

Game-Based Learning, Gamification in Education and Serious Games

Video games have become one of the predominant forms of entertainment in our society, but they have also impacted many other of its social and cultural aspects. The new forms of interaction and communication in online multiplayer games, the millions of viewers of professional e-sports competitions, the huge following of gaming streamers through channels such as Twitch, and the communities of players that are formed around a specific title are just some examples of the impact of games in everyday life today.[...]info:eu-repo/semantics/publishedVersio

Performance assessment in water supply and distribution

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Digital Startups Accelerators: Characteristics and Evolution Trends

In a period where economies face challenges on a global scale, entrepreneurship is an alternative and viable option for many people. Due to the considerable impact it has on the economic development of a region, many authors have studied this subject throughout the years, so the literature available is quite rich and complete. Entrepreneurial ecosystems include numerous entities that interact with each other in unique symbiosis relationships and these entities may be startups, universities, the government, investors and organizations that provide support to the startups in their development stages, such as accelerators, incubators and co-working spaces. However, some of these entities, especially the startup accelerators, are still very recent, since the first one was only launched in 2005. For that reason, there still is not an in-depth study on this subject and there are not many rigorous conclusions with regards to the nature and impact of these organizations, that are believed to play a very important role in the development of startups. Therefore, this dissertation is motived by that lack of rigorous knowledge on the subject of accelerators. The development of a research work of this kind may be a valuable contribution for the current knowledge on the subject, as well as for future research. The objective of this dissertation is to analyse the actual and future trends of accelerators, considering a worldwide scale, with a particular focus on their business models, acceleration programs, strategies, challenges and priorities for the future. This thesis is based on an in-depth literature review, which includes the most relevant concepts about entrepreneurship and accelerators. Following the literature review, there is an empirical study that is based on an online survey that was carried out amongst accelerators, which benefits from its strong statistical component. Moreover, there are Case Studies based on some organizations’ business models, that are relevant for the analysis. Throughout this research work, we concluded that accelerators are a worldwide phenomenon, due to the impact they have both in the development of the startups, as well as in the economic development of the region they operate in. Moreover, these organizations have different business models and, according to their nature and characteristics, they have distinct ways of facing the challenges and priorities for the future

Evaluation of an ecosystem service in restored quarry areas: pollination

Ecological restoration allows for accelerated recovery of a degraded ecosystem’s biodiversity, function, and ability to provide ecosystem services. However, the issues of when active restoration is necessary and how restoration effectiveness should be measured are still subject to considerable debate. Here we evaluate plant-pollinator networks in actively and passively restored quarries, comparing structure and composition to a natural area representing the reference ecosystem, to determine which restoration approach holds higher effectiveness on the rehabilitation of this ecological process. We found that while both approaches allowed for the restoration of pollination function, active restoration allowed for faster recovery. Nevertheless, the distinct strategies generated key structural vegetation differences, which influenced distinct pollinator communities providing the service in different areas. These results support the idea that restoration might be attained by distinct biological communities, and that both composition and function should be taken into account when evaluating restoration outcomes; RESUMO: O restauro ecológico permite acelerar a recuperação da biodiversidade, função e serviços de um ecossistema degradado. No entanto, existe bastante debate sobre as situações em que é realmente necessário o restauro ativo e como deve ser avaliado. Neste estudo, avaliamos redes plantapolinizador em pedreiras restauradas ativamente e passivamente, comparando a sua estrutura e composição com uma área natural que representa o ecossistema de referência, para determinar a abordagem mais eficiente na reabilitação da polinização. Verificámos que, apesar de ambas permitirem o restauro desta função, o restauro ativo permite uma recuperação mais rápida. No entanto, estratégias distintas geraram diferenças estruturais na vegetação, o que influenciou o estabelecimento de comunidades de polinizadores distintas a polinizar as diferentes áreas. Estes resultados apoiam a ideia de que o restauro pode ser atingido com comunidades biológicas distintas, e que a composição e a função devem ambas ser tidas em conta na avaliação do restauro ecológico

Health-related quality of life in hereditary transthyretin amyloidosis polyneuropathy: a prospective, observational study

Background Hereditary Transthyretin Amyloidosis Polyneuropathy is a rare life-threatening neurologic disease that imposes considerable mortality and it is associated with progressive related disabilities. In this study, we aimed to assess the effect of the disease across health-related quality of life dimensions, in both carriers of the mutation and patients, to compare health-related quality of life with general population, as well as to explore health-related quality of life prognostic factors among patients, including disease progression and treatment. Methods This study was a multi-institutional, longitudinal, prospective, observational study of hereditary Transthyretin Amyloidosis Polyneuropathy Portuguese adult subjects (621 asymptomatic carriers and 733 symptomatic patients) enrolled in the Transthyretin Amyloidosis Outcomes Survey. Health-related quality of life was captured with the preference-based instrument EQ-5D-3 L. For general population the dataset included all subjects enrolled in a representative national study (n = 1500). Different econometric models were specified; multivariate probit, generalized linear model and generalized estimating equations model; including demographic and clinical covariates. Results Hereditary Transthyretin Amyloidosis Polyneuropathy patients have their health status severely impaired in all quality of life dimensions and more anxiety/depression problems were found among asymptomatic carriers. No differences on utility were found between carriers and general population (p = 0.209). Among patients, the utility value is estimated to be 0.51 (0.021), a decrement of 0.27 as compared with general population utility. Higher disease duration, advanced disease stage and not receiving treatment are associated with impaired health-related quality of life. No differences were found between genders (p = 0.910) or between late (≥50 years) and early-onset patients (p = 0.254). The utility estimate ranged from 0.63 (0.009) in stage I to 0.01 (0.005) in stage IV. Conclusions Hereditary Transthyretin Amyloidosis Polyneuropathy symptoms and progressive associated disabilities substantially decrease patient’s health-related quality of life. Clinical strategies focused on health-related quality of life preservation such as close follow-up of asymptomatic carriers, prompt diagnosis and adequate, early treatment would benefit patient’s long-term outcomes, slowing the progressive decline in health-related quality of life.info:eu-repo/semantics/publishedVersio

Educação e formação de adultos em Portugal: desafios e estratégias no início do século XXI

No contexto da globalização, a educação e a formação, em geral, são o eixo da aprendizagem ao longo da vida; e a educação e formação de adultos constitui um dos grandes desafios na União Europeia. Para atingir os objectivos da Estratégia de Lis-boa, Portugal é chamado a «apreciar o valor social e económico» da educação e formação, abrindo o seu sistema educativo, desenvolvendo a certificação de competências e reforçando no programa “Novas Oportunidades” a vertente de indução na vida ativa e do empreendedorismo.In the globalization/globalisation context, education and training are the axle of life-long learning process and in EU adult education and training constitute a major challenge. For achieving the Lisbon goals, Portugal is called to appreciate the social and economic value of education and training, opening the education system, developing the certification of competences and applying the ‘New Opportunities’ Initiative