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With increasing use of oxygen enrichment and advances in smelting technology, SO> concentrations in smelter off-gases are increasing, which necessitates larger acid plant equipment and increases in capital and operating. To counteract the shortcomings in conventional acid plants, Chemetics provides two unique solutions: The Chemetics High Strength...
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... Currently, 19.7 million tons of copper are produced worldwide [2], 75 % of which are processed by pyrometallurgical processes, while the rest is processed by hydrometallurgical routes [3][4][5]. Pyrometallurgical processes generate large environmental liabilities, such as tailings dams [6][7][8] produced by flotation processes, which can affect acid rains and increase local pollution [9,10]. Hydrometallurgical processes, together with copper bioleaching processes [11][12][13], have proven to be more environmentally friendly. ...
In multivariate analysis, a predictive model is a mathematical/statistical model that relates a set of independent variables to dependent or response variable(s). This work presents a descriptive model that explains copper recovery from secondary sulfide minerals (chalcocite) taking into account the effects of time, heap height, superficial velocity of leaching flow, chloride concentration, particle size, porosity, and effective diffusivity of the solute within particle pores. Copper recovery is then modelled by a system of first-order differential equations. The results indicated that the heap height and superficial velocity of leaching flow are the most critical independent variables while the others are less influential under operational conditions applied. In the present study representative adjustment parameters are obtained, so that the model could be used to explore copper recovery in chloride media as a part of the extended value chain of the copper sulfides processing.
... Copper is recovered from these minerals mainly through flotation, followed by pyrometallurgical processing, representing 80-85% of world's copper production [8,9]. However, pyrometallurgical treatment is difficult and expensive for low-grade copper ores producing high emissions of sulfur dioxide (SO 2 ), NOx, and CO 2 , which cause problems, such as acid rain and increased local pollution [10][11][12]. ...
... Metals 2021,11, 1539 ...
Heap leaching is a firm extractive metallurgical technology facilitating the economical processing of different kinds of low-grade ores that are otherwise not exploited. Nevertheless, regardless of much development since it was first used, the process advantages are restricted by low recoveries and long extraction times. It is becoming progressively clear that the selection of heap leaching as an appropriate technology to process a specific mineral resource that is both environmentally sound and economically feasible very much relies on having an ample understanding of the essential underlying mechanisms of the processes and how they interrelate with the specific mineralogy of the ore body under concern. This paper provides a critical overview of the role of gangues and clays minerals as rate-limiting factors in copper heap leaching operations. We aim to assess and deliver detailed descriptions and discussions on the relations between different gangues and clays minerals and their impacts on the operational parameters and chemical dynamics in the copper heap leaching processes.
... However, pyrometallurgical processes generate more pollution to the environment because flotation processes generate the tailings dams [5], where acid drainage is generated by oxidation of minerals with high pyrite contents. And, along with large emissions of sulfur dioxide, NOx and CO2 are generated in the smelting plants [6,7]. Furthermore, it should be mentioned that hydrometallurgical methods have lower operating, energy, and water consumption costs [8][9][10]. ...
Currently, there is a large amount of mineral resources not being exploited in large copper mining, a clear example is black copper minerals. These resources are generally not incorporated into the extraction circuits or are not treated, either in stocks, leach pads, or debris. These exotic minerals have considerable amounts of Cu and Mn, which represent a commercial attraction. They are refractory to conventional leaching processes, therefore, for their treatment, the use of reducing agents is necessary to be able to dissolve the MnO2 present in them, which in turn allows Cu extraction. In this research, a comparative study is presented between two iron reducing agents (Fe2+ y Fe0) for the dissolution of Cu and Mn from a black copper mineral in an acidic medium, in addition, a previous pre-treatment process will be carried out (agglomerate and cure) adding NaCl to favour the reduction of MnO2. Finally, it was discovered that there is a higher kinetics of dissolution of Cu and Mn when working with Fe0 in short periods of time, although similar extractions of both elements are obtained in prolonged times. While carrying out a pre-treatment process adding NaCl, it allows to increase Cu and Mn extractions, allowing to obtain high solutions in short periods of time (30 min).
... Sulfurized copper ores are generally treated by flotation-smelting-refining [5][6][7]. Although they have reported economic [8] and metallurgical viability, there are environmental problems associated with the emission of sulfur dioxide and arsenic [9][10][11][12][13]. Arsenic, which has continuously increased in recent decades with the increasing extraction of copper sulfide [14], presents a risk to human health associated with a higher incidence of cancer and cardiovascular and respiratory diseases [15]. ...
Covellite is a secondary copper sulfide, and it is not abundant. There are few investigations on this mineral in spite of it being formed during the leaching of chalcocite or digenite; the other investigations on covellite are with the use of mineraloids, copper concentrates, and synthetic covellite. The present investigation applied the surface optimization methodology using a central composite face design to evaluate the effect of leaching time, chloride concentration, and sulfuric acid concentration on the level of copper extraction from covellite (84.3% of purity). Copper is dissolved from a sample of pure covellite without the application of temperature or pressure; the importance of its purity is that the behavior of the parameters is analyzed, isolating the impurities that affect leaching. The chloride came from NaCl, and it was effectuated in a size range from –150 to +106 μm. An ANOVA indicated that the leaching time and chloride concentration have the most significant influence, while the copper extraction was independent of sulfuric acid concentration. The experimental data were described by a highly representative quadratic model obtained by linear regression (R² = 0.99).
... This sulfide is one of the most common and abundant minerals in the world and is associated with hydrothermal mineralization [6]. On the other hand, foundries produce large emissions of sulfur dioxide (SO 2 ), which together, with NO x and CO 2 , can cause large problems; such as acid rain and increasing local pollution, therefore, the abatement of waste gases is an important task for the protection of the environment [7][8][9]. As a result, new hydrometallurgical alternatives are being developed in the mining industry, because they are more ecological and economic processes to recover copper [10,11]. ...
Chalcocite is the most important and abundant secondary copper ore in the world with a rapid dissolution of copper in an acid-chloride environment. In this investigation, the methodology of surface optimization will be applied to evaluate the effect of three independent variables (time, concentration of sulfuric acid and chloride concentration) in the leaching of pure chalcocite to extract the copper with the objective of obtaining a quadratic model that allows us to predict the extraction of copper. The kinetics of copper dissolution in regard to the function of temperature is also analyzed. An ANOVA indicates that the linear variables with the greatest influence are time and the chloride concentration. Also, the concentration of chloride-time exerts a significant synergic effect in the quadratic model. The ANOVA indicates that the quadratic model is representative and the R² value of 0.92 is valid. The highest copper extraction (67.75%) was obtained at 48 h leaching under conditions of 2 mol/L H2SO4 and 100 g/L chloride. The XRD analysis shows the formation of a stable and non-polluting residue; such as elemental sulfur (S⁰). This residue was obtained in a leaching time of 4 h at room temperature under conditions of 0.5 mol/L H2SO4 and 50 g/L Cl⁻.
Sulfur is evolved by most copper extraction processes. The most common form of evolved sulfur is sulfur dioxide (SO2) gas from smelting and converting. It must be prevented from reaching the environment. Most smelters capture a large fraction of their SO2. It is almost always made into sulfuric acid, occasionally liquid SO2 or gypsum. This chapter describes off-gases from smelting and converting, manufacture of sulfuric acid from smelter gases, and recent and future developments in sulfur capture.
