RU2776360C2 - Method for dissolution of primary copper of metallogenic origin obtained from ores and/or chalcopyrite concentrates containing it - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to a method for extraction of copper from primary sulfide minerals and primary and secondary copper concentrates. The method includes following sequential stages: a stage of restorative activation (I), which corresponds to a non-oxidative stage including bringing mineral or mineral concentrate into contact with chloride ions in an acidic medium, which are added in the form of sodium chloride in the range from 25 to 80 kg per ton of material, and with recirculating solutions of the same method, which contain chloride ions, divalent iron and copper ions, always in a medium with a potential of up to 500 mV and the total moisture content of less than 10%, and a stage (II) of autocatalytic dry restorative conversion, including conducting periods of time without irrigation for aeration, providing restoration of mineral or chalcopyrite concentrate to mineralogical components, which are solubilized using acid and chloride with subsequent washing with technological solutions to remove reaction products, while periods of time without irrigation and washing periods are repeated at least once.

EFFECT: increase in the extent of copper extraction from primary sulfide minerals with high content of chalcopyrite and chalcopyrite concentrates is provided.

19 cl, 18 dwg, 16 ex

Description

FIELD OF TECHNOLOGY TO WHICH THE INVENTION RELATES

The present invention relates to a chemical autocatalytic process for the recovery of copper by reductive solubilization of mineral components that exist in nature in the form of primary copper sulfides, consisting mainly of chalcopyrite (CuFeS ₂ ). In addition, the present invention can also be applied to secondary copper minerals, primary and secondary copper sulfide concentrates, and other sulfide-based metals such as nickel, zinc, cobalt, lead, molybdenum, including, regardless of the presence of common sulfide mineral impurities. , as in the case of the presence of arsenic.

BACKGROUND OF THE INVENTION

The present invention is a response to the technical problem caused by the depletion of secondary copper oxide and copper sulfide, which has been extensively exploited in hydrometallurgical processes during the development of the large-scale mining industry in the world.

Chalcopyrite is a primary copper sulfide and is a component of copper ore, which contains more than half of the current copper resources identified worldwide (Wang, 2005). The problem that arises during the solubilization of chalcopyrite is that its surface becomes resistant to any chemical or electrochemical reaction due to the formation of a film or a passivating layer. As a result, the mineral becomes resistant to hydrometallurgical processes, which, along with the gradual depletion of copper reserves in the form of oxides and secondary sulfides, leads to the absence of ongoing leaching, solvent extraction and electrochemical recovery (LX/SX/EW) operations and the presence of spare capacity.

For chemical leaching processes, the passivation effect that occurs on the mineral, mainly due to the presence of elemental sulfur or other insoluble sulfur containing substances and/or insoluble salt complexes, e.g. cuprous chloride containing components, inhibits the interaction between the leaching solution and the mineral, blocking the redox processes necessary to continue copper solubilization (Liu Q., 2017).

In the case of biotechnological processes, such as other chemical processes, this type of passivation is a significant problem, but to a greater extent, since the effect of passivation is enhanced by the appearance of many other passivating agents, such as jarosite, iron oxyhydroxides, polysulfides and elemental sulfur (Hackl R.P.et al., 1995; Stott MB et al., 2000, Ahmadi A. et al., 2010 and Lotfalian M. et al., 2015).

As a result, there is currently no hydrometallurgical technology that can solubilize copper in a cost-effective manner from primary sulfide minerals characterized by a high content of chalcopyrite. With regard to concentrates, their solubilization is achieved if the passivation layer is chemically or mechanically destroyed when it begins to cover the surface of the mineral.

The Chilean Copper Commission published in its 2016 report that concentrate production will increase from 69.2% to 89.9% by 2027, mainly due to the fact that the deposits reach the area of primary sulphides, which are processed mainly through flotation, and then pyrometallurgical methods. On the other hand, concentrate production is not projected to increase with the growth in processed products, so the value of exports is expected to decline. In addition, the negative effects of processing this type of concentrate are reported, which have a number of disadvantages such as the formation of sulfur dioxide, the generation of waste (responsible for environmental pollution) and, among other things, high energy consumption (Cochilco, 2016b).

Accordingly, it would be desirable to provide a copper solubilization process that does not occur or reduces the passivation phenomenon and that in turn is directly applicable to both primary sulfide minerals and their respective concentrates. This is analogous to the sulfide minerals of other base metals such as nickel, zinc, cobalt, etc.

DESCRIPTION OF THE PRIOR ART

In the prior art, this problem is solved by various methods, including methods of chemical and biological leaching. Leaching is defined as the selective dissolution of metals from their containing solids in an aqueous solution (Domic, 2001).

Mineral dissolution, both chemical and biological, is a heterogeneous phenomenon in which the reaction occurs at the solid-liquid interface, and also includes solid-liquid-gas and solid-liquid-gas-bacteria interactions.

In general terms, the dissolution of a mineral is governed by 5 steps: (1) diffusion of reactants, (2) adsorption of reactants, (3) chemical reaction between the solid and reactants, (4) desorption of the product from the solid, and (5) diffusion of the reaction product.

Typically, hydrometallurgical processes for both oxides and sulfides are usually controlled by diffusion steps (Wen C, 1968, Crest, A, 2000, Dixon and Petersen, 2003). On the other hand, heterogeneous reactions involving solid-gas and solid-solid phases at room temperature without the participation of a liquid phase have an extremely low reaction rate (Lefebvre R., 2001, Evans K., 2006).

Publication WO2007134343 (Muller et al., 2007) refers to a hydrometallurgical process comprising two steps: a first non-oxidizing step in an acid environment and a second oxidizing step involving solid-liquid-gas interaction. It is designed to recover copper from primary and secondary minerals and involves leaching the material in an acid solution with chloride in the presence of dissolved oxygen and cuprous ions as oxidizing agents.

WO2016179718 (Engdahl et al., 2017) relates to a solid-liquid-gas oxidizing process in a sinter drum and a mineral agglomeration process carried out inside said mineral pretreatment drum, both of which are used mainly in hydrometallurgy. Said drum and method employs a gas recirculation system and step as part of the invention.

Patent application publication WO02070757 (Hunter, 2002) presents an oxidative solid-liquid-gas-bacteria interaction process for leaching primary copper minerals in the form of chalcopyrites. The method consists in inoculating the mineral with a bacterial culture that oxidizes the sulfide, but does not oxidize the ferrous iron to the ferric state. After this stage, the leaching solution is mixed with bacteria that oxidize ferrous ions, thus creating favorable conditions for leaching of chalcopyrite, but not in order to avoid its passivation.

Publication WO2016026062 (Álvarez, 2016) presents an oxidizing process with solid-liquid-gas-bacteria interaction and refers to a process for leaching secondary and primary copper sulfides in a medium containing chloride ions, ferrous ions and ferric iron ions, with iron oxidizing bacteria and archaebacteria adapted to high concentrations of chloride ions. In addition, it involves the introduction of heated air to raise the temperature and increase the rate of mineral dissolution reactions.

US7491372 (Faine, 2005) presents an oxidative solid-liquid-gas interaction process and relates to a calcium chloride method to improve agglomerate quality and hence heap permeability. In addition, the study of the phenomena of this process is based on the promotion of the formation of oxidants (Fe ³⁺ and Cu ²⁺ ) through the action of oxygen and the redox pair of copper and iron, which causes the solubilization of sulfide minerals.

The present invention differs from the prior art in that the solubilization of primary sulfide (chalcopyrite) is carried out by means of a reductive autocatalytic solid-solid interaction process, without the need for addition, facilitated by the addition of salts in their reduced state and under supersaturation conditions, due to the weathering phenomenon , which is defined as the loss of hydration or crystallization water or salts from a mineral when exposed to air. This phenomenon occurs regardless of the presence of common impurities such as arsenic.

BRIEF DESCRIPTION OF THE INVENTION

The present invention relates to a reductive autocatalytic chemical process with solid-solid interaction under supersaturation conditions to solubilize copper from a primary sulfide mineral, in particular chalcopyrite, which contains it. The process includes two steps, referred to as a "reductive activation step" and an "autocatalytic dry reductive conversion" or weathering step. These steps may be repeated as many times as necessary to achieve maximum solubilization of the primary sulfide, either with respect to the mineral or concentrates.

These two sequential and/or parallel steps are governed by different solid-solid reduction chemistry. To this end, a supersaturation condition is used, involving sulfuric acid, iron(II) salts, chloride salts, copper and water, which ensures the solubilization of copper sulfide of primary origin.

The first or reductive activation step corresponds to a non-oxidative agglomeration and curing step under supersaturation conditions that activates the sulphide surface to promote the formation of a reducing environment for the second process step, including contact between sulfuric acid, water, ferrous ion, copper ion, and chloride ion in the medium. with low humidity and low redox potential.

The second or autocatalytic dry reductive conversion step corresponds to a solid-solid reductive dissolution step where the reductive state is enhanced due to the weathering phenomenon for extended periods of time without irrigation. This autocatalytic dry reduction step is completed by first washing the mineral or concentrate to remove the soluble copper formed and to minimize the change in bed reducing conditions. This autocatalytic dry reduction step does not require the introduction of air.

The redox potentials that control both the reductive activation and autocatalytic dry reductive conversion steps that cause autocatalysis are in the range of 250 to 500 mV due to the supersaturation condition of the salts in their reduced state, and due to the fact that the agents involved as reducing agents are double redox pairs; therefore, they can also act as oxidizing agents in the same potential range.

The reactions and mechanisms involved in the previous steps can take place in any sulfide mineral containing iron and copper, even in small quantities, and it is obvious that they will exert their influence on the dissolution of some other base metal in a reduced state, such as metal sulfide. This applies to minerals characterized by a high content of nickel, zinc, cobalt, molybdenum, etc.

BRIEF DESCRIPTION OF GRAPHICS

Figure 1: Cyclic voltammograms of three different primary minerals using only autocatalytic dry reduction conversion.

Figure 2: Cyclic voltammograms of mineral 1 versus temperature using only autocatalytic dry reduction conversion.

Figure 3: Cyclic voltammograms of three different primary minerals obtained with the inclusion of a step of reductive activation and autocatalytic dry reductive conversion.

Figure 4: Cyclic voltammograms of three different primary minerals obtained with the inclusion of a step of reductive activation and autocatalytic dry reductive conversion, using higher concentrations of chloride ions than iron ions.

Figure 5: Revealing the phenomenon of autocatalytic dry reductive transformation by cathodic linear sweep of the primary mineral with change in reductive activation time.

Figure 6: Estimation of the potential at the solid-liquid interface over time by means of a linear potential sweep in the reductive activation stage.

Figure 7: distribution of mineralogical copper-bearing components of the investigated primary mineral.

Figure 8: Comparison of copper extraction from primary sulfide versus degree of reflux between conventional bioleaching and the present invention.

Figure 9: comparison of copper extraction from primary sulfide versus time between conventional bioleaching and the present invention.

Figure 10: Extraction of copper from primary sulphide in the autocatalytic dry reduction conversion step in relation to particle size.

Figure 11: Copper extraction versus weathering time and repetition of autocatalytic dry reduction conversion.

Figure 12: Extraction of copper from primary sulfide versus acid concentration in the reductive activation step.

Figure 13: Extraction of copper in relation to the type of conventional crushing compared to crushing with HPGR.

Figure 14: Extraction of copper from chalcopyrite concentrate versus time using reductive activation and autocatalytic dry reductive conversion steps.

Figure 15: Extraction of copper from primary sulfide using various concentrations of sodium chloride salts in the steps of reductive activation and autocatalytic dry reductive conversion.

Figure 16: Extraction of copper from primary sulfide using various concentrations of ferrous sulfate in the steps of reductive activation and autocatalytic dry reductive conversion.

Figure 17: Extraction of copper from primary sulfide using various percentages of moisture in the autocatalytic dry reduction step.

Figure 18: percentage of mineralogical components from the base mineral compared to mineralogical components from intermediate waste that was subjected to autocatalytic dry reduction conversion.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to an autocatalytic solid-solid reduction chemistry process that solubilizes copper from a primary sulfide mineral or concentrate containing it. In particular, it relates to a dissolution process comprising two sequential and/or parallel steps, which in the new process includes two reduction steps; the first, called reductive activation, provides environmental and ore surface conditioning, promoting copper solubilization during the second stage of autocatalytic dry reduction conversion through the use of salts in their reduced state, low redox potential and weathering phenomena, which contribute to the state of supersaturation.

The method includes the following steps, detailed below.

I. Restorative activation

This step begins by subjecting the crushed mineral to a solidification and agglomeration process using conventional methods and procedures, which include the addition of circulating process solutions and/or water, sulfuric acid, and varying levels of ferrous, chloride, and copper from a source solution or from a recirculation process so that to form a mass of homogeneous and agglomerated mineral. During this addition of reagents, some ferrous iron is added so that the amounts of circulating iron, together with the newly added iron, reach values in the range from 0 to 80 kg of ferrous sulfate per tonne of mineral. The newly added iron may be added in the form of sulfate and/or some other soluble ferrous ion salt whose anion does not adversely interfere with the process, such as iron hydroxide.

A moderate but variable amount of sodium chloride is also added, amounting to no more than 80 kg / t of mineral, depending on the content of the chloride ion circulating in the process solutions.

The amount of fresh and/or circulating sulfuric acid added is between 10 and 50 kg/t of ore, and the final moisture content of the agglomerated mineral is between 4 and 15%, depending on the hygroscopicity and particle size distribution of the mineral.

The additions at this stage can also only be made in the presence of sulfuric acid and some salt providing the chloride ion. This is because the recirculation of solutions from the plant or the initial dissolution of the mineral can provide the necessary ferrous ions to achieve the effects and benefits of the next stage of autocatalytic dry reduction conversion and achieve the autocatalysis and weathering phenomenon.

This mixture of mineral, circulating process solutions, water, acid and chloride, iron and copper ions is left in a state without reflux for a variable period of time, depending on the sulfide content of the mineral, its hygroscopicity, particle size distribution and weathering in such a way as to provide activation its surface in the presence of low humidity, until it becomes suitable and conducive to the next stage of autocatalytic dry reduction conversion. The activation time can vary from 5 to 90 days or more depending on the surface reactivity of each mineral or concentrate and its previous conditioning.

II. Autocatalytic dry reduction conversion via weathering

This second step requires reducing conditions with solid-solid interaction, saturation and supersaturation on the chalcopyrite and/or other sulfides present due to the high concentration of circulating ferrous salts, chlorides and copper promoting autocatalytic reactions, and a condition that is exacerbated by the phenomenon weathering associated with long periods without irrigation.

This dry reduction conversion step is completed by washing the mineral through continuous or intermittent irrigation with variable duration using a solution containing chloride ions, ferrous ions and copper ions. After that, a new period without irrigation begins with a variable duration until the restoration transformation is completed.

Then a new flush is carried out, either continuous or intermittent, again using a solution of chloride ions, copper and iron ions, conditioned according to needs, with the addition of chloride and ferrous salts, depending on the amount that is lost during successive irrigations, and available surface features, which will vary as follows.

a) Chloride concentrations are between 10 and 150 g/l.

b) Iron concentrations range from 1 to 50 g/l.

c) The total irrigation flow rate is between 4 and 10 l/h/m ² .

d) Weathering time is 5 to 90 days or more depending on the surface reactivity of the mineral or concentrate.

The reductive activation and autocatalytic dry reduction steps may be repeated as many times as necessary to re-ensure weathering to achieve maximum solubilization of the copper contained in the mineral or concentrates.

In a preferred embodiment, the present invention relates to a process for the solubilization of metals from minerals and/or primary concentrates of metallogenic origin from sulfide minerals containing them, which comprises the following steps in series and/or in parallel:

I) a reductive activation step, which corresponds to a non-oxidative step, involving bringing the mineral or mineral concentrate into contact with chloride ions in an acidic environment and with recycle solutions from the same process that contain or may contain chloride ions, ferrous and copper ions, always in an environment with low potential and minimum total humidity; and

II) an autocatalytic solid-solid reduction dry reduction step where the reducing conditions are improved by a weathering phenomenon that promotes supersaturation of the medium with chloride, ferrous and copper ions, allowing the mineral or chalcopyrite concentrate to be reduced to mineralogical components that are solubilized with acid and chloride, while this stage ends with washing with process solutions, which ensures the removal of reaction products.

In one embodiment of the present invention, in step I, ferrous iron is added in such a way as to provide an amount of 10 to 50 kg of ferrous ion per ton of material.

In another preferred embodiment of the present invention, in step I, the ferrous ion can be added in the form of sulfate and/or some other soluble salt whose anion does not adversely interfere with the process, such as ferrous hydroxide, and/or by containing the ferrous ion iron in technological recirculation solutions.

In one embodiment of the present invention, in step I, chloride is added in the form of sodium chloride or chloride ion to the curing and agglomerating solution.

In a preferred embodiment of the present invention, in step I, the amount of sodium chloride added is in the range of 25 to 80 kg per ton of material.

In one embodiment of the present invention, in stage I, the amount of sulfuric acid added is in the range of 5 to 50 kg per ton of material.

In one embodiment of the present invention, in step I, the final moisture content of the agglomerated mineral should be less than 10%.

In a preferred embodiment of the present invention, in step I, the final moisture content of the agglomerated mineral should be between 4 and 8%.

In one embodiment of the present invention in stage II, the final moisture content of the agglomerated mineral should be less than 10%.

In a preferred embodiment of the present invention in stage II, the final moisture content of the agglomerated mineral should be between 4 and 8%.

In another embodiment of the present invention, the redox potentials controlling both reductive activation and autocatalytic dry reductive conversion steps that cause autocatalysis are in the range of 250 to 500 mV.

In another embodiment of the present invention, after the addition of water, acid and salts in stage I, the resulting mixture is left in a non-irrigated state to activate the surface of the mineral for a period of 5 to 90 days, contributing to the second stage of autocatalytic dry reduction conversion due to the phenomenon of weathering and low redox potential.

In another embodiment of the present invention, after stage II, the mineral is washed by continuous or intermittent irrigation with a solution containing chloride ions, ferrous ions and copper ions.

In one embodiment of the present invention, steps I and II may be repeated one or more times in a row, depending on the presence of metal ions of interest to be solubilized.

In one embodiment of the present invention, after stage II, the wash solutions are drained to allow a new stage of autocatalytic dry reductive conversion to continue in a reducing environment with a minimum total humidity.

In another embodiment of the present invention, the metals to be solubilized are selected from the group which includes, among others, copper, zinc, nickel, molybdenum, cobalt, lead.

In a preferred embodiment of the present invention, the metal to be solubilized is copper.

In one embodiment of the present invention, copper solubilization can also occur from sulfide ores containing arsenic and/or concentrates of sulfide ores containing arsenic.

In one embodiment of the present invention, prior to step I, the mineral is ground to provide maximum surface area available for contact between the component of value and the reagents involved in the process, and thus facilitating diffusion of the latter into the particles.

In one embodiment of the present invention, steps I of reductive activation and II of autocatalytic dry reductive conversion may be applied to copper concentrates.

In the procedure described both generally and in the preferred methods, the ferrous ion acts as a redox potential regulator, creating the reducing environment necessary for the autocatalytic dry reduction step.

Similarly, chloride ions and ferrous ions can be incorporated into the process as sodium chloride and ferrous salts or through the use of process recycle solutions containing chloride ions, ferrous ions and copper.

DEMO EXAMPLES

Example 1 Obtaining Cyclic Voltammograms of Three Different Primary Minerals Using Only Autocatalytic Dry Reductive Conversion

Cyclic voltammetry was used to visualize the redox phenomena that occurred in the autocatalytic dry reduction step (Stage II). This electrochemical technique consists of applying a cycle of voltages (millivolts) for a time at which the potentiostat measures current per unit area (mA/cm ² ). During this cycle, it presents a voltammetric curve that shows the interaction between the mineral (at the DropSens electrode) and the supersaturated leaching solution (electrolyte) through the various redox processes that occur. To do this, three DropSens electrodes were prepared from carbon paste with various chalcopyrite concentrates (mineral 1, mineral 2 and mineral 3) and mixed with graphite as a conductive medium. In addition, a solution of 9 g/l heptahydrate ferrous sulfate salts (FeSO ₄ x7H ₂ O), 10 g/l sodium chloride (NaCl) and a 2 M concentration of sulfuric acid (H ₂ SO ₄ ) was prepared.

For the tests performed, a potential sweep was applied from -0.9 V to +0.9 V at a sweep rate of 20 mV/s for 5 minutes at 20°C.

The results are shown in figure 1, which leads to the conclusion that the oxidation peaks have a similar behavior for 3 minerals and the same cathodic behavior with two reduction peaks for all measured chalcopyrite, which has been described as a phenomenon of reduction of chalcopyrite to less stable components (Weimin Z. et al ., 2013). Despite the lack of stimulation, the second step is present in its original form through a known expansion of each new voltammetric cycle, thus reflecting the autocatalytic nature of the reactions of this second step.

Example 2 Cyclic Voltammograms of Mineral 1 vs. Temperature Using Autocatalytic Dry Reduction Conversion Only

To obtain the results shown in figure 2, the same conditions and parameters were used as in the cyclic voltammograms in figure 1, with the difference that only mineral 1 was used, which was exposed to three different temperatures of 20, 32 and 40°C.

Figure 2 shows how increasing the temperature of the same mineral has less of an effect on the peaks generated at the anode and cathode, especially for temperatures of 32 and 40ºC. This small difference achieved by increasing the temperature may be due to the fact that the proposed technology is subject to a reduction process that is not completely dependent on temperature.

Example 3 Obtaining Cyclic Voltammograms of Three Different Primary Minerals Prepared Including Reductive Activation and Autocatalytic Dry Reductive Transformation

In order to obtain the results shown in figure 3, the same conditions and parameters were used as for the autocatalytic dry reductive converter shown in figure 1, with the difference that the reductive activation step was applied to this test for 7 days using a saturated solution 50 g/l sodium chloride, 25 g/l ferrous sulfate and 2 M concentration of sulfuric acid. After 7 days of activation, cyclic voltammetry was performed under autocatalytic dry reductive conditions.

The results obtained, shown in Figure 3, demonstrate how the reductive activation step for the three minerals has an activating effect, enhancing the phenomena at the anode and cathode zones, but mainly the chalcopyrite reduction process, while significantly increasing the current per unit area.

The difference between the cathodic peaks of voltammograms that include the activation step compared to the peaks obtained without activation is almost 35 times, which is a clear demonstration that the reductive activation step causes destabilization and ideal conditions on the chalcopyrite surface, which promotes autocatalytic dry reductive transformation .

Example 4 Obtaining Cyclic Voltammograms of Three Different Primary Minerals Obtained Including Reductive Activation and Reductive Transformation

To obtain the results shown in figure 4, the same conditions and parameters were used as in the cyclic voltammograms in figures 1 and 3, with the difference that for this test the stage of reductive activation was used for 7 days, increasing the concentration of sodium chloride salts to 100 g/l, ferrous sulfate up to 50 g/l and 2 M concentration of sulfuric acid.

Figure 4 shows cyclic voltammograms for three chalcopyrite minerals and it can be seen that increasing the salt concentration in the reductive activation step promotes the cathodic autocatalytic dry reductive transformation event.

Example 5. Identification of the phenomenon of autocatalytic dry reduction conversion by cathodic linear sweep of the primary mineral with a change in the time of reductive activation

To visualize and quantify the reducing effect of a saturated solution on the mineral (chalcopyrite) at the cathode, a linear sweep technique is used. It is an electrochemical technique that expresses the phenomena that have occurred at the cathode in units of current per unit area (I: mA/cm ² ).

The method includes cathodic transmission of a potential sweep of 20 mV/s for 2 minutes in the potential range from 0 to 1 V using a leaching solution as a conductive medium that interacts with the surface of the mineral.

In order to obtain the results shown in Figure 5, the same electrode preparation conditions were used as in Figure 1. The reactivation time period was 1, 7, and 14 days, using two salt conditions: a) 25 g/l ferrous iron and 25 g/l chloride; b) 50 g/l ferrous iron and 100 g/l chloride, and c) 20 g/l ferrous ion without the addition of chloride ion. Under all conditions, 2 M sulfuric acid was used.

The solution used for the line sweep was 9 g/L ferrous sulfate, 10 g/L sodium chloride, and 2 M sulfuric acid.

The results of the linear sweep in Figure 5 show that after 14 days of reductive activation under [Cl ^- ] > [Fe ²⁺ ] conditions, more autocatalytic dry reductive conversion is achieved, confirming the reduction phenomenon as the chalcopyrite dissolution mechanism.

Example 6 Evaluation of the Potential at the Solid-Liquid Interface Over Time Using a Linear Potential Sweep During the Reductive Activation Step

Linear potential sweep is an electrochemical technique that evaluates the redox potential generated at a solid-liquid interface (mineral electrode and solution for reductive activation and autocatalytic dry reduction conversion) over time.

In order to obtain the results shown in figure 6, the same conditions were applied as for obtaining the results in figure 5, with the difference that for this test, the reactivation stage was applied for 1, 2 and 14 days in addition to applying different conditions containing three salts: a) 25 g/l ferrous iron and 25 g/l chloride; b) 50 g/l ferrous ion, 100 g/l chloride and 0.1 g/l ferric ion and c) 20 g/l ferrous ion without added chloride. Under all conditions, 2 M sulfuric acid was used.

After the end of the recovery activation period, a linear potential sweep was performed with the activated electrode and the electrode that was not subjected to activation as a control. The electrodes were moistened with a solution containing 9 g/l ferrous sulfate, 10 g/l sodium chloride and 2 M concentration of sulfuric acid.

The potential sweep in FIG. 6 shows that the potential at the solid-liquid interface decreases for all cases, both for a) and b). However, the greatest reduction in the surface potential of the mineral was obtained under condition c), where only ferrous ion was used, confirming that this condition plays a major role in maintaining sufficient potential for the autocatalytic dry reduction step.

Example 7 Extraction of Copper from Chalcopyrite-High Primary Sulfide with respect to Time

Results were obtained using a low grade (0.24%) primary copper sulfide mineral that was subjected to a conventional crushing process to provide 100% sub-½ inch particles.

Mineralogical analysis (see figure 7) showed that copper in this mineral is contained in the following mineralogical components:

- 99.7% of copper is in the form of chalcopyrite;

- 0.3% copper is in the form of bornite.

The test conditions shown in Figures 8 and 9 were as follows:

a) adding 80 kg/t sodium chloride during curing;

b) adding 40 kg/t of ferrous sulfate during curing;

c) addition of 42 kg/t sulfuric acid during curing;

d) weathering time 90 and 150 days;

e) 100% particle size distribution is less than half an inch and

f) 7% moisture content.

The applied temperature is in the range of 15 to 35°C, depending on the acid concentration characteristic of the gangue and the moisture content of the reductive activation stage. This condition was valid for all tests carried out with crushed minerals and concentrates.

In both Figures 8 and 9, the test is compared to a conventional bioleach run in parallel with the same primary mineral under the following conditions:

a) addition of 14 kg/t sulfuric acid during curing;

b) initial rest time 15 days;

c) 100% particle size distribution is less than half an inch;

d) concentration 1x10 ⁸ cells per ml;

e) intermittent irrigation 12 x 12 hours during the test.

By applying the best reductive activation conditions [Cl ^- ]> [Fe ²⁺ ] in a low grade primary mineral, where more than 99% of the copper is in the form of chalcopyrite, extremely high solubilization of copper can be achieved in two stages of the proposed method of reductive activation and autocatalytic dry reduction conversion. contained in the form of chalcopyrite. In contrast, for conventional bioleaching, only a very low level of extraction was achieved. These experimental results can be seen in figures 8 and 9.

With reference to figure 8, it can also be concluded that an appropriate regulation of the irrigation flow rate used in the proposed method will significantly reduce the volumes of water involved in the process, which will advantageously result in lower operating costs and in the formation of low streams of solutions with a higher copper content. intended for the later stages of the SX/EW.

Example 8 Extraction of Copper from Chalcopyrite-High Primary Sulfide During Autocatalytic Dry Reductive Reduction in Relation to Particle Size

The mineral containing primary copper sulfide in the form of chalcopyrite was crushed to provide 100% -½ inch particles and the -½ inch/+¼ inch, -¼/+#10 and -#10 size fractions were quantified and recorded. The mineral thus obtained was subjected to solidification and agglomeration under the following conditions:

a) adding 60 kg/t of sodium chloride;

b) adding 20 kg/t of ferrous sulfate;

c) addition of 28 kg/t sulfuric acid and

d) 10% moisture content.

Then the mineral was loaded and subjected to weathering for 90 days, after which it was subjected to a 12-hour irrigation with acidified water with pH 1 at a rate of 5 l/h.*m ² . The spent solution was recovered and analyzed for its copper content.

The test leached ores were dumped, dried, and separated into each of the particle size fractions mentioned above, thus allowing comparison of the copper content of the base mineral with the leached ores of each fraction, which made it possible to plot Figure 10.

In view of figure 10, it can be concluded that the smaller the particle size, the higher the extraction of copper, although for a denser mineral, most of the copper is obtained even in the form of chalcopyrite.

Example 9 Copper Extraction vs Weathering Time in the Autocatalytic Dry Reduction Step and Repeat

The mineral containing primary copper sulfide in the form of chalcopyrite was crushed to provide 100% less than ½ inch ore. With this mineral, 6 samples were agglomerated and cured under the following conditions:

a) adding 80 kg/t of sodium chloride;

b) adding 10 kg/t of ferrous sulfate;

c) addition of 14 kg/t of sulfuric acid;

d) moisture content 8%.

Then the columns were loaded and subjected to the first and second periods of weathering with washings at the end of each of these periods with a flow rate of 10 l/h.*m ² within 24 hours. The weathering time variables for each test were as follows:

a) time of the first weathering period: 3, 7, 14, 32, 46 and 61 days.

b) time of the second weathering period: 32, 32, 28, 10, 30 and 30 days.

The results of this test are shown in Figure 11, which leads to the conclusion that the weathering time contributes to the solubilization of primary sulfide due to autocatalytic dry reduction conversion. In addition, as the formation of reduction reaction products increases, the level of copper extraction increases, which allows us to conclude that the process is autocatalyzed. On the other hand, if a second weathering period is used, it can be concluded that the autocatalytic dry reductive conversion step can be applied as many times as necessary to successively solubilize the primary sulfide present in the form of chalcopyrite.

Example 10 Extraction of Copper from Chalcopyrite-High Primary Sulfide in Relation to Acid Concentration During Reductive Activation

The mineral was crushed to provide 100% particles less than ½ inch in size. Three samples were cured and agglomerated under the following conditions:

a) adding 25 kg/t of sodium chloride;

b) adding 10 kg/t of ferrous sulfate;

c) adding a variable dose for each test of 14, 28 and 42 kg/t sulfuric acid and

d) moisture content 6%.

The samples were then loaded onto the columns and held for a weathering time of 45 days. Subsequently, the columns were irrigated with an acidified pH 1 solution for 12 hours at a flow rate of 5 l/h*m ² and the spent solutions were analyzed for the presence of copper, which made it possible to compare the results of tests with exposure to different doses of sulfuric acid during curing.

The results obtained are shown in figure 12, which allows us to conclude that increasing the acid concentration during the curing stage has a positive effect on copper extraction.

Example 11 Copper Extraction vs. Conventional Crushing vs. HPGR Crushing

Four composite materials were formed from 150 kg of primary mineral, which had the mineralogical characteristics indicated in the graph in figure 7. Three of these composites were obtained mechanically using a high pressure roll crusher, known in the industry as HPGR (high pressure grinding rolls). The pressure values used in each test were 40, 60 and 80 kg/cm ² .

The fourth composite was subjected to conventional crushing, and therefore, the specified connection was used as a comparative test of compounds obtained with a mineral obtained using an HPGR crusher.

The conditions of the four tests were as follows:

a) adding 60 kg/t of sodium chloride;

b) adding 80 kg/t of ferrous sulfate;

c) adding 42 kg/t sulfuric acid and

d) moisture content 7%.

The weathering period was 45 days, after which irrigation with an acidified solution of pH 1 was applied for 12 hours at a flow rate of 5 l/h.*m ² and the spent solutions were evaluated for copper content, thus allowing comparison of the results of tests of minerals obtained under different conditions crushing.

The results obtained by comparing the two types of crushing are shown in Figure 13, where it can be seen that the mineral that was crushed with HPGR under different pressure conditions has a higher level of copper extraction than the mineral that was treated only with conventional crushing. This is due to the higher level of fineness that HPGR provides for the mineral, which allows salts and acid to reach the chalcopyrite particles, initially isolated from the environment, to solubilize them.

Example 12 Extraction of Copper from Chalcopyrite Concentrate vs. Time Using Reductive Activation and Autocatalytic Dry Reductive Conversion

The results of tests with a coarser concentrate were obtained from tests carried out using 100 g of copper concentrate, with a total copper content of 12.4% and 96% copper as chalcopyrite. This concentrate was subjected to reductive activation through a treatment that included the addition of:

a) 60 kg/t of sulfuric acid;

b) 60 kg/t sodium chloride and

c) 5 kg/t of ferrous sulfate.

d) The moisture content is less than 10%.

After reductive activation, dry reductive transformation was carried out by weathering phenomenon for 30 days. After completion of the autocatalytic dry reduction conversion, the concentrate was washed for 5 minutes with a 500 ml wash solution containing 15 g/l sulfuric acid, 120 g/l sodium chloride, 20 g/l ferrous sulfate and 1 g/l copper. The extraction of copper obtained through reductive activation and autocatalytic dry reductive conversion can be seen in Figure 14.

Example 13 Extraction of Copper from Primary Sulfide Using Different Concentrations of Sodium Chloride Salts in Reductive Activation and Autocatalytic Dry Reductive Conversion

The mineral containing primary copper sulfide in the form of chalcopyrite was crushed to provide 100% particles less than ½ inch in size. With this mineral, 4 samples were agglomerated and cured under the following conditions:

a) adding 0, 25, 50 and 80 kg/t sodium chloride;

b) adding 10 kg/t of ferrous sulfate;

c) adding 42 kg/t of sulfuric acid;

d) 10% moisture content.

Then the samples were subjected to weathering for 45 days, after which they were irrigated with an acidified solution with pH 1 for 12 hours at a flow rate of 5 l / h.*m ² , and the spent solutions were evaluated for copper content, which makes it possible to compare test results with different doses of chloride sodium at the curing stage.

The results obtained in this test are shown in figure 15, which leads to the conclusion that the addition of sodium chloride during the curing step has a beneficial effect on the dissolution of the primary sulfide in the form of chalcopyrite. However, it can be seen that in the case of this sample, the addition of 50 kg/t allows you to get the maximum level of copper extraction.

Example 14 Extraction of Copper from Primary Sulfide Using Different Concentrations of Ferrous Sulfate During Reductive Activation and Autocatalytic Dry Reductive Conversion

The mineral containing primary copper sulfide in the form of chalcopyrite was crushed to provide 100% particles less than ½ inch in size. With this mineral, 4 samples were agglomerated and cured under the following conditions:

a) adding 25 kg/t of sodium chloride;

b) adding 0, 40, 60 and 80 kg/t ferrous sulfate;

c) adding 42 kg/t of sulfuric acid;

d) moisture content 6%.

Then the samples were subjected to weathering for 45 days, after which they were irrigated with an acidified solution with pH 1 for 12 hours at a flow rate of 5 l / h.*m ² , and the spent solutions were evaluated for copper content, which allows comparison of test results with different doses of sulfate ferrous iron at the curing stage.

The results obtained in this test are shown in Figure 16, which leads to the conclusion that the concentration of iron sulfate has a positive effect on the dissolution of primary sulfide, especially if the addition at the stage of curing reaches 40 kg/t. It can be seen that without the presence of ferrous sulfate, a lower level of copper extraction is achieved, despite the fact that the dissolution of chalcopyrite and gangue provides ferrous ions to the reaction. This condition will always occur due to the recycling of solutions in an industrial process.

Therefore, in the reductive activation step, with the addition of only sodium chloride, the same positive effect can be obtained if the moisture content required for the process can be achieved using only recirculating solutions with a high content of ferrous ions.

Example 15 Extraction of Copper from Primary Sulfide Using Different Moisture Percentages in an Autocatalytic Dry Reduction Conversion

The mineral containing primary copper sulfide in the form of chalcopyrite was crushed to provide 100% particles less than ½ inch in size. With this mineral, 5 samples were agglomerated and cured under the following conditions:

a) adding 50 kg/t of sodium chloride;

b) adding 40 kg/t of ferrous sulfate;

c) adding 42 kg/t of sulfuric acid;

d) moisture content 4, 7, 10, 12 and 15%.

Then the samples were subjected to weathering for 45 days, after which they were irrigated with an acidified solution with pH 1 for 12 hours at a flow rate of 5 l / h.*m ² , and the spent solutions were evaluated for copper content, which allows comparing the results of tests with different levels of content moisture during curing.

The results obtained in these tests are shown in Figure 17, which leads to the conclusion that the use of a low total moisture content in the mineral has an excellent and positive effect on the dissolution of copper contained in the primary sulfide. On the contrary, if a moisture content above 10% was used, which usually occurs in hydrometallurgical operations, the level of copper extraction is significantly reduced. This low moisture state, i.e. less than 10% moisture content, causes an increase in salt concentration due to water loss, improving conditions for reduction and supersaturation, which greatly promotes copper extraction.

Example 16 Mineralogical Components in a Base Mineral and Mineralogical Components in Leached Ores in Different Periods of an Autocatalytic Dry Reduction Conversion

The results were obtained from tests carried out using a low grade (0.24%) primary copper sulfide mineral, which was subjected to a conventional crushing method to provide 100% of particles less than ½ inch in size. With this mineral, 2 samples were agglomerated and cured under the following conditions:

a) adding 80 kg/t of sodium chloride;

b) adding 40 kg/t of ferrous sulfate;

c) adding 42 kg/t of sulfuric acid;

d)) moisture content 7%.

Then 2 samples were subjected to chemical activation and autocatalytic dry reduction conversion for 30 days in one case and 65 days in the other. After this time, in both cases irrigation was applied using an acidified solution with pH 1 for 12 hours at a flow rate of 5 l/h. ^* m and 65 days, respectively.

The mineralogical analysis of the studied basic mineral showed that copper is contained in the form of the following mineralogical components:

- 99.7% copper in the form of chalcopyrite and

- 0.3% copper in the form of bornite.

In the case of leached ores, on the other hand, an optical mineralogical analysis was carried out, similar to that carried out for the main mineral, which made it possible to establish how residual copper was previously present, through chemical analysis of the same leached ores.

The results of the mineralogical analysis are shown in Figure 18, where the first column can be seen indicating the mineralogical composition of the base mineral, which is characterized by the percentage of chalcopyrite (99.7%) and bornite (0.3%), as indicated above.

The second column shows the mineralogical composition of the leached ore associated with a 30-day weathering test with partial chemical activation and autocatalytic dry reduction transformation, where it can be seen that chalcopyrite is partially reduced to the mineralogical components of bornite, chalcocite and covellite. In contrast, for the third column, which illustrates 65 days of weathering and a full period of chemical activation and autocatalytic dry reduction transformation, the presence of bornite, chalcocite, and covellite is not observed, indicating that during stages I and II, chalcopyrite is reduced to less stable components. , and that it dissolves in the same period, indicating that the process is autocatalytic. This phenomenon can be explained by the fact that in the redox process, the reducing agents formed during reductive activation and autocatalytic dry reduction transformation can also participate as oxidizing agents, since they are redox pairs, providing, due to the reduction of dissolution during the transformation of the primary sulfide, the formation less stable components that dissolve at the same stage.

CONCLUSION ON THE EXPERIMENTAL WORK

The main technical advantages of the present invention are based on the step of reductive activation and autocatalytic dry reductive conversion under supersaturation conditions, which help to create a favorable environment for the conversion of primary copper-containing components into soluble components and less stable sulfides, which are known and relatively easier to solubilize.

On the other hand, the use of ions in their reduced state as reducing agents and ions in their oxidized state as oxidizing agents allows, in the low potential range, reduction and oxidation processes to take place in the same step and in a synergistic or autocatalytic manner, since the applied ions are redox couples.

Another advantage is that, for ease of operation, more copper can be extracted in a shorter time, with minimal moisture content, with low irrigation costs, lower operating costs, and less water in solution compared to currently known conventional hydrometallurgical methods. , which represent an effective additional flexibility with the greatest technical, economic and environmental benefits.

The results obtained differ from current knowledge, in which primary copper sulfide-containing components are generally sought to be dissolved by solid-liquid-gas or solid-liquid-gas-bacteria oxidative processes and in aqueous systems.

In this case, another role is proposed for the reductive activation of the mineral, in addition to the phenomenon of dry reductive transformation with solid-solid interaction. As a result of the proposed method, a larger amount of copper is extracted than with traditional methods. Moreover, by means of the proposed method, a lower water consumption can be achieved.

The method described in the invention claimed in this document solves the problems resulting from the passivation of primary sulfide minerals containing copper, mainly in the first stage or stage of reductive activation, which allows the mineral to be conditioned and cause destabilization of the surface of the primary sulfide, releasing copper ions, required for the dry reduction conversion step.

The advantages of reductive activation are important to the efficient performance of the dry reductive conversion step, which converts chalcopyrite with solid-solid interaction under supersaturation and low moisture conditions to convert primary sulfide to highly soluble components and non-stoichiometric sulfides less resistant to leaching. The effect of passivation is minimized because the products formed in the dry reduction step are mostly non-sulfur, but also acid-soluble sulfides and oxidizers.

The foregoing description is provided for illustrative purposes only and is not intended to describe all possible aspects of the present invention. Although the present invention has been shown herein and has been described in detail with respect to several illustrative embodiments, those skilled in the art will appreciate that minor changes to the description and various other modifications, omissions and additions do not deviate from its spirit and scope. .

Claims (21)

1. A method for extracting copper from primary sulfide minerals and primary and secondary copper concentrates, characterized in that it includes the following successive stages: (I) a reductive activation step, which corresponds to a non-oxidative step, which involves bringing the mineral or mineral concentrate into contact with chloride ions in an acidic environment, which are added in the form of sodium chloride in the range of 25 to 80 kg per tonne of material, and with recycle solutions from the same method, which contain chloride ions, ferrous ions and copper ions, always in an environment with a potential of up to 500 mV and a total moisture content of less than 10%; and (II) an autocatalytic dry reduction solid-solid reaction step where the reducing conditions are improved by weathering phenomena through periods of time without irrigation, which tends to supersaturate the medium with chloride ions, ferrous ions and copper ions, allowing the reduction of the mineral or chalcopyrite concentrate to mineralogical components, which are solubilized with acid and chloride, this stage being completed by washing with process solutions, which ensures the removal of reaction products, while periods of time without irrigation and periods of washing are repeated at least once. 2. The method according to claim 1, characterized in that in step I the ferrous iron is added in such a way as to provide an amount of 10 to 50 kg of ferrous ion per ton of material. 3. The method according to claim 2, characterized in that in step I, the ferrous ion can be added in the form of sulfate and/or some other soluble salt, the anion of which does not adversely interfere with the process, such as ferrous hydroxide, and/ or through the content of ferrous ion in technological recirculation solutions. 4. The method according to claim 1, characterized in that in stage I the amount of added sulfuric acid is in the range from 5 to 50 kg per ton of material. 5. Method according to claim 1, characterized in that in step I the final moisture content of the agglomerated mineral should be between 4 and 8%. 6. Method according to claim 1, characterized in that in step II the final moisture content of the agglomerated mineral must be less than 10%. 7. The method according to claim 6, characterized in that in stage II the final moisture content of the agglomerated mineral should be between 4 and 8%. 8. The method according to claim 1, characterized in that the redox potentials controlling both stages of reductive activation and autocatalytic dry reductive transformation, which cause autocatalysis, are in the range from 250 to 500 mV. 9. The method according to any of the preceding claims, characterized in that after the addition of water, acid and salts in stage I, the resulting mixture is left in a non-irrigated state to activate the surface of the mineral for a period of 5 to 90 days, contributing to the second stage of autocatalytic dry reduction conversion due to weathering phenomena. 10. The method according to claim 1, characterized in that after stage II, the mineral is washed by means of continuous or intermittent irrigation with a solution containing chloride ions, ferrous ions and copper ions. 11. The method according to claim 1, wherein steps I and II may be repeated one or more times in succession depending on the presence of the metal ions of interest to be solubilized. 12. The method according to claim 11, characterized in that, after stage II, the washing solutions are drained to allow the continuation of a new stage of autocatalytic dry reductive conversion in a reducing environment with a minimum total moisture content. 13. The method according to claim 1, characterized in that the metals to be solubilized are selected from the group including, among others, copper, zinc, nickel, molybdenum, cobalt, lead. 14. The method according to claim 13, characterized in that the metal to be solubilized is copper. 15. Process according to any of the preceding claims, characterized in that the solubilization of copper can also occur from sulfide minerals containing arsenic and/or from concentrates of sulfide minerals containing arsenic. 16. The method according to any of the preceding claims, characterized in that before stage I, the mineral is crushed in order to provide the maximum surface area available for contact between the valuable component and the reagents involved in the method, thus facilitating the diffusion of the latter into the particles. 17. A process according to any one of the preceding claims, wherein the reductive activation step I and the autocatalytic dry reductive conversion step II can be applied to copper concentrates. 18. The method according to any one of the preceding claims, wherein the ferrous ion acts as a redox potential regulator, creating the reducing environment necessary for the autocatalytic dry reduction step. 19. The method according to any one of the preceding claims, characterized in that chloride ions and ferrous ions can be included in the process in the form of sodium chloride and ferrous salts or by using process recirculation solutions containing chloride ions, ferrous ions and copper .

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