Environmental Impact Variability of Copper Tailing Dumps in Fushe Arrez (Northern Albania): The Role of Pyrite Separation during Flotation

Acid mine drainage and potentially toxic elements release are a major source of pollution in sulfide-rich mining sites. Pyrite is the most impacting mineral due to its high acidification potential when it reacts with water under oxidizing conditions. At the Fushe Arrez dressing plant in Northern Albania, a volcanic massive sulfide copper mining district, pyrite was in past separated, with a double flotation process, to produce a pyrite concentrate and relatively-pyrite-poor tailings. In the last twenty years single flotation has replaced the double flotation process and pyrite has been deposited in pyrite-rich tailings stacked separately from the old ones. The study of the solid tailing materials and natural waters flowing through the dumping area, together with leaching tests show that waters interacting with single flotation tailings are slightly more acidic and much higher in total metal contents than those interacting with double flotation tailings. Also, the metal distribution is different, with the former being higher in sulfide-hosted metals and the latter higher in gangue-hosted metals. It is thus suggested that separation of pyrite can play an important role in the sustainable mining of pyrite-rich ores, either for dumping high hazardous pyrite concentrate separately or for marketing it as a by-product. An implementation of studies for the industrial uses of pyrite is pivotal in this last case.

Flotation extraction of elemental sulfur from gold-bearing cakes

Currently, in the development of the raw materials base of the gold mining industry, there is a tendency to reduce the quality of the initial mineral raw materials due to the depletion of reserves of rich gold-bearing ores. The article discusses the technology of extraction of refractory gold-bearing concentrates based on low-temperature leaching of pyrite concentrate. A decrease in the parameters of the autoclave oxidation of sulfide minerals, such as pyrite and arsenopyrite, leads to the incomplete extraction of gold into the solution and, consequently, its losses during subsequent cyanidation. As a possible option for a more complete extraction of gold using low-temperature oxidation technology, a method of flotation separation of elemental sulfur from leaching cakes is proposed. According to the basic process flow chart, the flotation process designed for gold extraction is carried out after autoclave oxidation, but before cyanidation. A series of experiments were carried out with varying reagent conditions and the dependence of gold losses on the extraction of elemental sulfur in the flotation tailings was established. As determining factors, pH and solid content in the initial pulp were considered. The paper justifies the separation of elemental sulfur from autoclave cake to enriched sulfur concentrate. The cake flotation modes after autoclave oxidative leaching of pyrite concentrate are investigated. The distribution of elemental sulfur and gold by flotation products makes it possible to conduct the tailings cyanidation process with acceptable indicators.

Investigation of Sulfatization Mechanism of Iron-Manganese Concretions in Fluidized Bed

The article presents the theoretical basis of sulfatizing roasting in the fluidized bed of oxidic and sulphidic polymetallic raw materials: iron-manganese concretions (IMC) containing non-ferrous metals and pyrite concentrate. The results of preliminary thermodynamic and thermogravimetric studies of IMC of Pacific Ocean and pyrite are described. The results of the laboratory-scale research of sulphatizing roasting of deep-water polymetallic IMC and pyrite concentrates are given. Based on the results obtained, the conclusion is made about the prospects of using the method of preliminary sulfatization for further production of marketable concentrates of manganese and non-ferrous metals.

Study on the extraction of metals from tails of flotation enrichment of copper sulfide ores

Flotation processing of copper-pyrite ores is accompanied by the formation of flotation tailings containing 0.2-0.7 % wt Cu and 0.6-1.4 g/t Au. Deeper extraction of these components into commercial products is of practical interest. The possibility of additional recovery of copper and gold using the example of tailings from the current processing of PJSC “Gaysky GOK” was studied. It was shown that thin emulsion impregnation of chalcopyrite (less than 10 μ) in pyrite prevented the copper and gold from being extracted from the tailings by ore dressing methods. A scheme for the deep extraction of valuable components, based on the preliminary concentration of gold and copper by pyrite flotation, was proposed. About 84.5% of gold and 60.9% of copper were extracted into pyrite concentrate, while the gold content in the chamber product was 0.25 g/t. The increase in the extraction of copper was impossible due to nature of copper phase in chamber product that consisted mainly of copper oxides. Further processing of the pyrite concentrate can be accomplished by the way based on oxidative roasting (550-600 °C), with subsequent sulfuric acid leaching of copper from the calcine, washing and cyanidation of washed cake. Acid leaching is recommended to be done without external heating with solutions of 10-20 g/l of sulfuric acid. Copper was precipitated from leachates by cementation with iron powder in the form of copper concentrate (22-32 % wt Cu), then the gold-containing solution is processed to produce ligature gold. The optimal conditions for the cyanidation of the calcine were determined as follows, L:S = 2, the initial concentration of NaCN was 2 g/l, the duration of cyanidation was 2 hours The possibility of achieving end-to-end extraction of 66% of gold, and 45% of copper in commercial products is shown. The proposed scheme makes it possible to reduce the specific consumption of NaCN during cyanidation from 2.5-2.8 to 0.8 kg/t of tailings. It is assumed to gain sulfuric acid from the burning gases.

NEW TECHNOLOGY OF COMPLEX PROCESSING OF PYRITE CONCENTRATE

The paper discusses the benefits of processing pyrite concentrates using a new technology that uses roasting in an atmosphere of water vapor. There are various technologies for the processing of pyrite concentrates containing precious and non-ferrous metals, Au, Ag, Cu and other elements. These technologies often have such disadvantages as undesirable release of sulfur dioxide into the environment, incomplete extraction of useful metals. The optimal modes of technological processes, such as firing temperature, the ratio of steam and solid phases, the duration of the process, the size of the particles, etc. are given. Special attention was paid to the desulfurization of pyrite concentrate with the prevention of the release of sulfur dioxide into the atmosphere, and its transfer into the phase of solid elemental sulfur or sodium sulfide. The developed technology makes it possible to obtain an iron cinder, and with subsequent magnetic separation and reduction in a hydrogen atmosphere to obtain iron in the form of a sponge–a high-quality product for smelting steel or cast iron. The proposed technology provides a closed loop cycle and waste-free with minimal environmental pollution. The technology was tested in a pilot laboratory setup using concentrates from the Kajaran deposit inArmenia.

A Geometallurgical Approach to Tailings Management: An Example from the Savage River Fe-Ore Mine, Western Tasmania

At the Old Tailings Dam (OTD), Savage River, Western Tasmania, 38 Mt of pyritic tailings were deposited (1967 to 1982) and have since been generating acid and metalliferous drainage (AMD). Mineral chemistry analysis confirmed high concentrations of refractory cobalt in pyrite (up to 3 wt %). This study sought to determine, through a series of bench scale tests, if Co could be liberated using biohydrometallurgical techniques. Four bulk tailings samples were collected across the OTD, from up to 1.5 m depth, targeting three sulphide-bearing facies. The study was conducted in four stages: (1) bacterial adaption using BIOX® bacteria; (2) biooxidation optimization with pH, temperature and Fe medium parameters tested; (3) flotation test work to produce a sulphide concentrate followed by biooxidation; and (4) Fe and Co precipitation tests. The BIOX® culture adapted to the bulk composite (containing 7 wt % pyrite) in ~10 days, with biooxidation occurring most efficiently at pH 1.5–1.6 and 40 °C whilst the Fe medium concentration was identified as a less-controlling parameter. Flotation produced a 71% pyrite concentrate with total oxidation occurring after 14 days of biooxidation with 99% of Co leached. At pH 3, Co was effectively separated from Fe, however Ni and Cu were also present in the pregnant liquor solution and therefore required refining before production of cobalt hydroxide, the intermediate saleable product. This study shows that adopting a geometallurgical approach to tailings characterisation can identify if mine waste has commodity potential and how best to extract it therefore unlocking the potential for unconventional rehabilitation of AMD affected sites.

Iron Recovery by Two-Stage Roasting the Gold-Bearing Pyrite Concentrate and Gold-Leaching from the Pyrite Cinder by Thiourea

Pyrite cinders, which are the waste products of sulphuric acid manufacturing plants, contain hazardous but valuable heavy metals. This passage introduced that iron recovery by two-stage roasting the pyrite concentrate and gold-leaching from the pyrite cinder by thiourea. After re-floating and two-stage roasting of the gold-bearing low-grade pyrite concentrate, the final cinder contains about 0.056% As and 61% Fe and high grade gold and silver. The thiourea gold-leaching experiment for the pyrite cinder shows the gold-leaching rate is up to 90.4% in the case of grinding fineness of 60%-0.074mm, pH = 1~2, R=1:2, thiourea dosage of 10g / L, ferric sulfate dosage of 3g / L, leaching time of 6h.