No abstract

Bor, Krivelj, and Bela Rivers belong to the watershed of Timok River, which is a tributary of transboundary Danube River. These rivers receive metal-rich acidic wastewater from metallurgical facilities and acid mine drainage (AMD) from mine wastes around Bor copper mines. The aim of this study was to determine the mobility and natural attenuation of metals and arsenic in rivers from Bor copper mines to Danube River during the year 2015. The results showed that metallurgical facilities had the largest impact on Bor River by discharging about 400 t of Cu per year through highly acidic wastewater (pH = 2.6). The highest measured concentrations of Cu in river water and sediments were 40 mg L and 1.6%, respectively. Dissolution of calcite from limestone bedrock and a high concentration of bicarbonate ions in natural river water (about 250 mg L) enhanced the neutralization of acidic river water and subsequent chemical precipitation of metals and arsenic. Decreases in the concentrations of Al, Fe, Cu, As, and Pb in river water were mainly due to precipitation on the river bed. On the other hand, dilution played an important role in the decreases in concentrations of Mn, Ni, Zn, and Cd. Chemically precipitated materials and flotation tailings containing Fe-rich minerals (fayalite, magnetite, and pyrite) were transported toward Danube River during the periods of high discharge. This study showed that processes of natural attenuation in catchments with limestone bedrock play an important role in reducing concentrations of metals and arsenic in AMD-bearing river water.

Sulfide copper mineral, typically Chalcopyrite (CuFeS), is one of the most common minerals for producing metallic copper via the pyrometallurgical process. Generally, flotation tailings are produced as a byproduct of flotation and still consist of un‒recovered copper. In addition, it is expected that more tailings will be produced in the coming years due to the increased exploration of low‒grade copper ores. Therefore, this research aims to develop a copper recovery process from flotation tailings using high‒pressure leaching (HPL) followed by solvent extraction. Over 94.4% copper was dissolved from the sample (CuFeS as main copper mineral) by HPL in a HO media in the presence of pyrite, whereas the iron was co‒dissolved with copper according to an equation given as C = 38.40 × C. To avoid co‒dissolved iron giving a negative effect on the subsequent process of electrowinning, solvent extraction was conducted on the pregnant leach solution for improving copper concentration. The result showed that 91.3% copper was recovered in a stripped solution and 98.6% iron was removed under the optimal extraction conditions. As a result, 86.2% of copper was recovered from the concentrate of flotation tailings by a proposed HPL‒solvent extraction process.

No abstract

Hydrometallurgical processes for copper revalorization from overburden of abandoned mine Cerovo in Eastern Serbia were studied. Paper contain results of percolation leaching tests, performed with acidic mine waters accumulated in the bottom of the former open pit, followed by solvent extraction (SX) and electrowinning (EW) processes on achieved copper pregnant leach solutions. Usage of accumulated waste waters was objected to minimizing the environmental hazard due to uncontrolled leaking of these waters in nearby creeks and rivers. Chemical composition of acidic mine waters used for leaching tests was: (g/dm3): Cu - 0.201; Fe - 0.095; Mn - 0.041; Zn - 0.026; Ni - 0.0004; pH value - 3.3. Copper content in overburden sample used for leaching tests was 0.21% from which 64% were oxide copper minerals. In scope of leaching tests were examined influence of leaching solution pH values and iron (III) concentration on copper recovery. It was established that for 120 hours of leaching on pH=1.5 without oxidant agents, copper concentration in pregnant leach solutions enriched up to 1.08g/dm3 which was enough for copper extraction from solution with SX-EW treatment. As extraction reagent in SX circuit was used LIX-984N in a kerosene diluent. Cathode current density in electrowinning cell was 220Am-2 while electrolyte temperature was kept on 50±2oC. Produced cathode copper at the end of SX-EW process has purity of 99.95% Cu

Mining activities in the Bor and Majdanpek mining areas in Eastern Serbia started in 1903 and 1961, respectively. Environmental problems in the Bor mining area began after the opening of the Bor mine. Long‐term pollution of river water in the Bor and Majdanpek mining areas has an environmental impact on East Europe because all of the river water from these mining areas flows into the Danube River. However, the sizes of areas with pollution and the differences between the environmental impacts of the Bor and Majdanpek mining areas are not clear. In order to determine the effects of mining activities on river water in the study area, creation of geochemical maps showing the distributions of sulfate, heavy metals, and arsenic; estimation of threshold values to discriminate anomalous values from background values; and comparison of the environmental impacts of the two mining areas were carried out. High concentrations of SO42−, Fe, As, Cu, and Mn were found in the Bor River, Krivelj River, and Bela River located in the Bor mining area. These rivers are characterized by acidic pH ranging from 2.9 to 6.2. High concentrations of these components were also measured in the Small Pek River and the upper reach of the Pek River. These rivers are located in the Majdanpek mining area and are characterized by weakly alkaline pH (7.3–8.4). The acidic river water in the Bor mining area transports large quantities of heavy metals and arsenic downstream (6,900 t/year of Fe, 42 t/year of As, 910 t/year of Cu, and 187 t/year of Mn). On the other hand, the weakly alkaline river water in the Majdanpek mining area transports smaller quantities of heavy metals and arsenic downstream (160 t/year of Fe, 0.1 t/year of As, 6 t/year of Cu, and 272 t/year of Mn). The environmental impact of the Bor mining area is significantly larger than that of the Majdanpek mining area. In addition, on the basis of the distribution of anomalous values in river water, pollution caused by mining activities reaches the Danube River, which is located more than 100 km from the Bor and Majdanpek mining areas. Concentrations of SO42−, Fe, As, Cu, and Mn in the Bela River in the Bor mining area have been greatly decreased after mixing of acidic polluted water of the Bela River with water of the Timok River containing a high bicarbonate concentration. This fact suggests that river water in the Bor and Majdanpek mining areas has sufficient capacity for neutralization. Considering appropriate countermeasures of environmental reclamation, such as artificial neutralization at some important sources of waste water before discharging the waste water from the mining sites, there is a possibility for environmental reclamation in both mining areas because unpolluted river water in the study area has sufficient capacity for neutralization in a natural system.

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The possibility of application of low-cost and easily available materials such as cardboard or sawdust for the heavy metals removal from the acid mine water was investigated. The sawdust was obtained from oak and fir-wood. Those materials were tested on the real acid mine wastewater that contained copper, iron, zinc, nickel, and manganese in the concentrations above the maximal allowed level. The adsorption degrees of those elements were investigated. The results were shown that the iron was mechanically removed. The results of chemical analysis of effluent obtained by the use of sawdust from fir-wood indicate that the values for iron and nickel ions were lower than allowed values by the legislative direction. The highest value for copper adsorption degree of 98.31% was achieved at pH value of 7.94. Content of manganese in the effluent and at the end of process, was near the initial value. Using the sawdust obtained from oak as the adsorption material, zinc and manganese concentration in the effluent was near the start values and copper and iron content was decreased but the values were higher than allowed.Using the cardboard, the copper adsorption degree was up to 95 mass%, iron content was under the limit value for the applied chemical detection method. The content of the manganese was not changed and the content of the zinc was decreased but the concentration was over the maximum allowed value.