Chemical Composition Data of the Main Stages of Copper Production from Sulfide Minerals in Chile: A Review to Assist Circular Economy Studies

Experimental investigation on dynamic deformation characteristics of the overlying strata in backfilling strip mining at different time scales

The dynamic subsidence disaster caused by underground mining of coal resources is a complex spatiotemporal process, which is a common disaster in mining areas. The backfilling strip mining technology is a green and sustainable coal mining method, which has been commonly used to reduce the subsidence disaster of the overlying strata and protect surface buildings. The transient deformation is the main reason of surface buildings damage; therefore, in this study, the similar material model was used to research dynamic deformation characteristics of the overlying strata in backfilling strip mining at different time scales, and the optical image method was employed to monitor and obtain the movement data of the overlying strata automatically. The data analysis shows that there is a time-scale effect in mining subsidence. The deformation of the overlying strata increases instantaneously at a certain time under the monitoring of small time scale, and this phenomenon gradually disappears as time scales increase. According to the subsidence velocity of small time scale, the subsidence state of the overlying strata can be further divided into the abrupt subsidence state and the gentle subsidence state. This is really significant for promoting the development of the backfilling strip mining technology and preventing the damage of surface buildings.

Socio-Environmental Risks Linked with Mine Tailings Chemical Composition: Promoting Responsible and Safe Mine Tailings Management Considering Copper and Gold Mining Experiences from Chile and Peru

There is a need to define mine tailings in a clear, precise, multidisciplinary, transdisciplinary, and holistic manner, considering not only geotechnical and hydraulic concepts but also integrating environmental and geochemical aspects with implications for the sustainability of mining. This article corresponds to an independent study that answers questions concerning the definition of mine tailings and the socio-environmental risks linked with mine tailings chemical composition by examining the practical experience of industrial-scale copper and gold mining projects in Chile and Peru. Definitions of concepts and analysis of key aspects in the responsible management of mine tailings, such as characterization of metallic-metalloid components, non-metallic components, metallurgical reagents, and risk identification, among others, are presented. Implications of potential environmental impacts from the generation of acid rock drainage (ARD) in mine tailings are discussed. Finally, the article concludes that mine tailings are potentially toxic to both communities and the environment, and cannot be considered as inert and innocuous materials; thus, mine tailings require safe, controlled, and responsible management with the application of the most high management standards, use of the best available technologies (BATs), use of best applicable practices (BAPs), and implementation of the best environmental practices (BEPs) to avoid risk and potential socio-environmental impact due to accidents or failure of tailings storage facilities (TSFs).

The microbial world in copper sulfide flotation plants (CSFP): Novel insights into bacterial communities and their application as potential pyrite bioreagents

Operations in copper sulfide flotation plants (CSFP) are complex and governed by several variables such as available technologies, reagents, and environmental conditions. However, few investigations are related to studying the microbial communities. These aspects provide a reason to compare the bacterial communities of two CSFP operated with freshwater (FwFlo) and seawater (SwFlo), and study whether indigenous bacteria could be used as pyrite bioreagents. Analyses were determined through next-generation sequencing by Illumina MiSeq System and conducted throughout the entire process: (i) minerals before and after grinding; (ii) final concentrate and concentrate thickener overflow; (iii) final tailings and tailings thickener overflow; and (iv) intake water. Bacterial strains from both plants were tested as potential bioreagents, given their tendency to adhere to pyrite after 5 min. In both CSFP, Proteobacteria (relative abundance from 45.48% to 79.22%), followed by Bacteroidetes (9.37%-44.7%), were the most abundant phyla. Regarding species, Algoriphagus olei (11.35%-43.52%) was present exclusively in FwFlo samples in contact with process water and absent in the mineral before grinding, where Cupriavidus metallidurans (16.05%) and Pseudomonas_uc (11.79%) predominated. In SwFlo samples, Marinobacter flavimaris (3.47%-41.1%), and GU061212-s (10.92%-27.63%), were the most abundant microorganisms. All of them were also detected in intake seawater. The strains with the highest adhesion rate (from 29.84% ± 0.14-100%) were phylogenetically identified as species of the genera Marinobacter, Pseudomonas, Idiomarina, Halomonas, Bacillus, Aerocuccus, and Peribacillus. Our results reveal that bacterial communities are critically dependent on process waters during mining activities, and our data depicted that indigenous bacteria could be used as potential pyrite bioreagents, evidenced by a high adhesion rate. It is thus possible to propose that different indigenous bacterial strains could be considered as new bioreagents to reduce the impact of conventional flotation reagents on health from an environment friendly perspective.

Ore Processing Technologies Applied to Industrial Waste Decontamination: A Case Study

The correct management of industrial waste, as well as being an environmental obligation, can also be used as an opportunity to reduce costs in terms of energy and raw material consumption. A large amount of waste sand is generated in foundries with a high content of pollutants adhering to its surface structure. In this study, the material utilized consists of a silicic sand that comes from a casting process, with a thin layer of fixed carbon on the surface of the particles. The objective is to remove this contaminant, in order to have clean sands for use in alternative processes, such as in glass raw material, green concrete, or in the recirculation of these in the same process. The mechanical action that is best for eliminating surface attached contaminants is abrasion. In this regard, two specific devices, commonly used in ore processing operations, were utilized to apply energy in a material in order to reach abrasion by attrition, but with different kinetic approaches: stirring in a slurry media and using a light milling, in both cases reducing the grinding media in order to avoid material fracture. The test performance evaluation is mainly focused on the decontamination efficiency, the sand mass recovery ratio, and the energy consumption. The results show that in all cases, liberation is reachable in different levels at different residence times. We were able to decrease the LOI content from 4% to less than 1%, combined with a near 85% recovery rate of clean sand in the case of stirring. In the case of light milling, the results are even better: the final product reached near 0.5% of LOI content, despite mass flow recovery potentially being less than 80%. Finally, we discuss whether energy consumption is the factor which decides the best alternative. The energy consumed ratio when comparing light milling with stirring is near 9:1, which is a significant amount when taking into account the importance of reducing energy consumption in today’s industry due to its economic and environmental impact.