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

Silylated thiol-containing cellulose nanofibers as a bio‑based flocculation agent for ultrafine mineral particles of chalcopyrite and pyrite

A considerable amount of very fine particles can be found, e.g., stored in tailing ponds, and they can include valuable or hazardous minerals that have the potential to be recovered. Selective flocculation, i.e., the formation of larger aggregates from specific minerals, offers a promising approach to improve the recovery of ultrafine particles. This study focuses on the use of a new bio-based flocculation agent made of silylated cellulose nanofibers containing a thiol-functional moiety (SiCNF). Flocculation was performed in separated systems of ultrafine mineral dispersions of pyrite, chalcopyrite, and quartz in aqueous alkaline medium. The flocculation performance of SiCNF was addressed in terms of the turbidity reduction of mineral dispersions and the floc size, and the results were compared with the performance of a commercial anionic polyacrylamide. SiCNF exhibited a turbidity removal efficiency of approximately 90%–99% at a concentration of 4000–8000 ppm with chalcopyrite and pyrite, whereas the turbidity removal of quartz suspension was significantly lower (a maximum of approximately 30%). The sulfide particles formed flocs with a size of several hundreds of micrometers. The quartz in turn did not form any visible flocs, and the dispersion still had a milky appearance after dosing 12,000 ppm of the flocculant. These results open a promising path for the investigation of SiCNF as a selective flocculation agent for sulfide minerals

A study on the desulfurization of sulfidic mine tailings for the production of a sulfur-poor residue

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 contribution investigates the flotation of pyrite-rich tailings, containing residual chalcopyrite, galena, and sphalerite, and high amounts of ultrafine particles. Flotation was used to recover the sulfide minerals and generate tailings with low sulfur content. The Cu-Pb-Zn-rich product could go to further treatment (e.g. (bio)hydrometallurgy) to recover the metals, while the low sulfur fraction could be used in the civil construction industry. Automated mineralogy (MLA) was used to provide quantitative mineralogical and textural data. Bench-scale experiments were performed by combining 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 show 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

Influence of the storage time of saponified Amazonic vegetable oils on the floatability of apatita / Influência do tempo de armazenamento de óleos vegetais Amazônicos saponificados na floatabilidade de apatita

This study's main objective is verifying the influence of the storage time of collectors reagents, obtained from Amazonian vegetable oils (Buriti and Babassu Coconut), in the apatite's floatability. Collectors were obtained by the oils' alkaline hydrolysis (saponification), made with aqueous and alcoholic solutions of sodium hydroxide at room temperature. The floatability of the apatite was evaluated through microflotation tests, done in a modified Hallimond tube, using a height extender to avoid entrainment. Approximately 1 g of the pure mineral (apatite) was used, with granulometry between 300 and 106 ?m, pH 9.5, conditioning time of 4 minutes and aeration time of 1 minute. These microflotation tests were done every 2 days, from time 0, after the oils' saponification, up to 30 days of storage. The collector concentration used was 6 mg / L, defined from previous experiments. The results showed that the collector reagent, obtained from buriti oil’ saponification in an alcoholic solution of NaOH, presented better results.This study's main objective is verifying the influence of the storage time of collectors reagents, obtained from Amazonian vegetable oils (Buriti and Babassu Coconut), in the apatite's floatability. Collectors were obtained by the oils' alkaline hydrolysis (saponification), made with aqueous and alcoholic solutions of sodium hydroxide at room temperature. The floatability of the apatite was evaluated through microflotation tests, done in a modified Hallimond tube, using a height extender to avoid entrainment. Approximately 1 g of the pure mineral (apatite) was used, with granulometry between 300 and 106 ?m, pH 9.5, conditioning time of 4 minutes and aeration time of 1 minute. These microflotation tests were done every 2 days, from time 0, after the oils' saponification, up to 30 days of storage. The collector concentration used was 6 mg / L, defined from previous experiments. The results showed that the collector reagent, obtained from buriti oil’ saponification in an alcoholic solution of NaOH, presented better results

Relato de caso: atonia uterina / Case report: uterine atony

A atonia uterina corresponde a um estado de perda da contratilidade da musculatura uterina no período pós-parto imediato o que aumenta o risco de hemorragia pós-parto (HPP). É fundamental que os sinais de atonia uterina sejam identificados de forma precoce para prevenir complicações. Além disso é imprescindível uma equipe multidisciplinar que realize a monitorização da paciente e que esteja apta para atuar em casos de complicações Objetivos: Identificar os sinais de gravidade nos quadros de atonia uterina e como realizar o manejo dessa paciente. Métodos: Revisão bibliográfica, cujo levantamento de referências ocorreu entre os meses de fevereiro a abril de 2018. Foi realizada busca nas The Lancet e Scielo, empregando-se os termos: atonia uterina; hipotonia uterina; hemorragia pós-parto, prevenção para atonia. Os critérios de inclusão foram artigos cujas abordagens contivessem aspectos pertinentes ao trabalho, com ano de publicação entre 2015 e 2018. Foram descartadas as fontes que não continham conteúdo adequado para a confecção deste trabalho. Foram utilizadas 10 referências bibliográficas incluído livros físicos sobre o assunto abordado.  Discussão: Existem diversas causas para HPP, dentre elas a atonia uterina. É fundamental observar as todas as pacientes após o parto, uma vez que, a maioria das pacientes que desenvolvem o quadro não possuem fatores de risco prévio. Além disso, a principal formar de prevenção é adotar uma conduta ativa no terceiro estágio do trabalho de parto, que consiste na administração de droga uterotônica após o desprendimento do ombro anterior e tração controlada do cordão umbilical. Conclusão: É sempre importante observar os sinais vitais, bem a quantidade de sangue perdida pela paciente para tomar medidas o mais precoce possível. Além disso é fundamental uma equipe multiprofissional apta para atuar no manejo adequado. Por fim é de extrema importância a realização de medidas preventivas para evitar complicações e até mesmo o óbito materno

Pervasive gaps in Amazonian ecological research

Biodiversity loss is one of the main challenges of our time,1,2 and attempts to address it require a clear un derstanding of how ecological communities respond to environmental change across time and space.3,4 While the increasing availability of global databases on ecological communities has advanced our knowledge of biodiversity sensitivity to environmental changes,5–7 vast areas of the tropics remain understudied.8–11 In the American tropics, Amazonia stands out as the world’s most diverse rainforest and the primary source of Neotropical biodiversity,12 but it remains among the least known forests in America and is often underrepre sented in biodiversity databases.13–15 To worsen this situation, human-induced modifications16,17 may elim inate pieces of the Amazon’s biodiversity puzzle before we can use them to understand how ecological com munities are responding. To increase generalization and applicability of biodiversity knowledge,18,19 it is thus crucial to reduce biases in ecological research, particularly in regions projected to face the most pronounced environmental changes. We integrate ecological community metadata of 7,694 sampling sites for multiple or ganism groups in a machine learning model framework to map the research probability across the Brazilian Amazonia, while identifying the region’s vulnerability to environmental change. 15%–18% of the most ne glected areas in ecological research are expected to experience severe climate or land use changes by 2050. This means that unless we take immediate action, we will not be able to establish their current status, much less monitor how it is changing and what is being lostinfo:eu-repo/semantics/publishedVersio

Pervasive gaps in Amazonian ecological research

Biodiversity loss is one of the main challenges of our time,1,2 and attempts to address it require a clear understanding of how ecological communities respond to environmental change across time and space.3,4 While the increasing availability of global databases on ecological communities has advanced our knowledge of biodiversity sensitivity to environmental changes,5,6,7 vast areas of the tropics remain understudied.8,9,10,11 In the American tropics, Amazonia stands out as the world's most diverse rainforest and the primary source of Neotropical biodiversity,12 but it remains among the least known forests in America and is often underrepresented in biodiversity databases.13,14,15 To worsen this situation, human-induced modifications16,17 may eliminate pieces of the Amazon's biodiversity puzzle before we can use them to understand how ecological communities are responding. To increase generalization and applicability of biodiversity knowledge,18,19 it is thus crucial to reduce biases in ecological research, particularly in regions projected to face the most pronounced environmental changes. We integrate ecological community metadata of 7,694 sampling sites for multiple organism groups in a machine learning model framework to map the research probability across the Brazilian Amazonia, while identifying the region's vulnerability to environmental change. 15%–18% of the most neglected areas in ecological research are expected to experience severe climate or land use changes by 2050. This means that unless we take immediate action, we will not be able to establish their current status, much less monitor how it is changing and what is being lost