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Date submitted2022-05-20
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Date accepted2023-04-03
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Date published2024-02-29
Impact of carbon dioxide on the main geotechnical quality criteria and preparation cost of cemented paste backfill
There is a global upsurge in the use of cemented paste backfill (CPB) for various mining functions. However, the cost of the Portland cement binder is prohibitive, thus warranting strategies to reduce cement usage without overly diminishing the CPB quality. Since carbon dioxide is used for patented sand moulding processes, this study is premised on that physicochemical ability of CO2 to enhance the curing of consolidated inorganic materials. It evaluated the impact of carbon dioxide on the uniaxial compressive strength UCS and preparation cost of CPB standard samples (ASTM C109). The preparation cost was delimited to the purchase cost of the Portland cement. The backfill material was silica sand tailings with 4.5 wt.% Portland cement binder and a water-cement ratio of 7.6. Distilled water of pH 5.4 was used for the control samples while variable amounts of carbon dioxide were dissolved in distilled water to generate carbonated mixing water with pH values of 3.8; 4 and 4.2. The lower the carbonated water pH, the higher is the CO2 concentration. UCS tests were conducted on the samples after curing for 3, 7, 28, and 90 days. There was an observable increase in the UCSs and reduction in curing time with increasing carbon dioxide. Samples prepared with carbonated water of pH 3.8 had almost double the strength of those prepared with pure distilled water of pH 5.4, implying that more dissolved CO2 corresponds to higher CPB strength. This is supported by the trendline equations for the graphical simulation of strength on curing time. Thus, CPB with much less binder can be expected to attain the requisite UCS if carbon dioxide is incorporated. The average reduction in Portland cement consumption was 0.61 %, which translates to a cost saving of the same percentage points. If calculated over the operational life of a mine, this is a massive saving of millions of dollars.
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Date submitted2022-11-02
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Date accepted2023-03-02
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Date published2023-04-25
Environmental damage from the storage of sulfide ore tailings
The mining industry is one of the most challenging in ensuring environmental safety. During the last century, the Karabash Copper Smelting Plant was processing sulfide ores and depositing the tailings into storage facilities that now occupy an area of more than 50 hectares. To date, abandoned tailings are a significant source of natural water, air, and soil pollution in the Karabash city district. The article comprehensively examines the environmental impact of the Karabashmed copper smelter, one of the oldest metallurgical enterprises in Russia. The effects of seepage from the two Karabashmed tailings facilities on water resources were assessed. We revealed that even outside the area of the direct impact of processing waste, the pH of natural water decreases to values 4-5. Further downstream, the infiltration water from the tailings pond No. 4 reduces the pH of river water to 3.0-3.5. The presented results of environmental engineering surveys are derived from sampling water and bottom sediments of the Ryzhiy Stream and the Sak-Elga River, sample preparation, and quantitative chemical analysis. The study revealed significant exceedances of the maximum permissible concentrations for a number of chemical elements in the impact zone of the copper ore processing tailings.
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Date submitted2022-09-30
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Date accepted2023-02-13
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Date published2023-04-25
Hydrogeoecological conditions of technogenic groundwater in waste disposal sites
The specific hydrogeoecological conditions of aquifers of some technogenic formations, mainly iron ore skarn-magnetite and titanium-magnetite formations, are considered. The resulting wastes, which are stored in waste disposal sites during development of deposits, due to the impact of a number of factors (natural and technogenic) form technogenic waters. Waste disposal facilities are complex engineering structures (dumps and sludge storages), which in turn create their own hydrogeoecological conditions, which must be investigated in order to prevent and minimize environmental and economic damage caused by these objects to the aquatic environment. The paper presents long-term field and laboratory studies of the aquatic environment under the influence of a waste disposal facility in the Middle Urals – one of the largest tailings, representing a potential environmental and man-made hazard. This tailing dump contains tens of tons of waste – enrichment tailings and creates specific hydrogeoecological conditions on the territory. Based on many years of monitoring studies, an analysis of these conditions was carried out – the quality of groundwater affected by the tailings was assessed. It is shown that groundwater is of technogenic nature, i.e. are man-made waters that have a significant impact on the surface and underground hydrospheres of the territory.
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Date submitted2022-06-27
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Date accepted2022-09-09
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Date published2022-11-03
Study of the composition and properties of the beneficiation tailings of currently produced loparite ores
The increase in demand for rare earth metals and the depletion of natural resources inevitably causes the need to search for alternative unconventional sources of rare metal raw materials. The article presents the results of a study of the composition and properties of the beneficiation tailings of currently produced loparite ores. Sieve, mineralogical, chemical, and radionuclide analyses were carried out. The average content of loparite in tailings was determined. Using scanning electron microscopy, minerals-concentrators of rare earth elements in the loparite ore beneficiation tailings were diagnosed. The distribution of valuable components and thorium in the tailings was determined depending on the particle size class. The radium-thorium nature of radioactivity was established, the values of the effective specific activity of the samples were calculated. We concluded that it is necessary to develop an integrated technology for processing the beneficiation tailings of loparite ore, due to the complex and heterogeneous mineral and chemical composition of the tailings material.