Abstract
The flotation tailings obtained from Bor Copper Mine contain pyrite (FeS2) and chalcopyrite (CuFeS2), these sulfide minerals are known to promote acid mine drainage (AMD) which poses a serious threat to the environment and human health. This study focuses on the treatment of mine tailings to convert the AMD supporting minerals to more stable forms, while simultaneously valorizing the mine tailings. A combination of hydrometallurgical processes of high-pressure oxidative leaching (HPOL), solvent extraction (SX), and electrowinning (EW) were utilized to recover copper from mine tailings which contain about 0.3% Cu content. The HPOL process yielded a high copper leaching rate of 94.4% when water was used as a leaching medium. The copper leaching kinetics were promoted by the generation of sulfuric acid due to pyrite oxidation. It was also confirmed that a low iron concentration (1.4 g/L) and a high copper concentration (44.8 g/L) obtained in the stripped solution resulted in an improved copper electrodeposition current efficiency during copper electrowinning. Moreover, pyrite, which is primarily in the mine tailings, was converted into hematite after HPOL. A stability evaluation of the solid residue confirmed almost no elution of metal ions, confirming the reduced environmental loading of mine tailings through re-processing.
Highlights
Mine tailings are waste material generated from the flotation process and there are billions of tons of already existing tailings all over the world
This study evaluates the high-pressure oxidative leaching (HPOL) method as an effective way to recover copper and reduce the environmental loading from the mine tailings obtained from Bor Copper Mine, Serbia
The sulfuric acid generated by pyrite oxidation promoted the leaching of chalcopyrite via reaction 5
Summary
Mine tailings are waste material generated from the flotation process and there are billions of tons of already existing tailings all over the world. Several billion tons of additional mine tailings will inevitably be produced, as lower-grade and complex ores are being mined to sustain the world’s growing demand for mineral resources [1,2]. Schlesinger et al [3] (p.68) estimated that flotation tailings account for 98% of the ore fed in to concentrators, which are stored in large tailings dams near their mines. The failure of mine tailings storage facilities can result in catastrophic ramifications and environmental pollution, such as the well-known Brumadinho and Mariana tailings dam disasters in Brazil. The most serious environmental impact resulting from mine tailings is the generation of acid mine drainage (AMD). Pyrite is a gangue mineral that is commonly found in mine tailings, when exposed to an environment with oxygen and water, oxidation of pyrite is promoted via reaction 1, which results in low pH conditions of less than 3 [5,7,8,9]
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