WO2018231040A1

WO2018231040A1 - Method for obtaining copper by means of leaching and direct crystallisation

Info

Publication number: WO2018231040A1
Application number: PCT/MX2017/000064
Authority: WO
Inventors: Carlos Rafael BASURTO LÓPEZ
Original assignee: Nul Unu, S.A. De C.V.
Priority date: 2017-06-16
Filing date: 2017-06-16
Publication date: 2018-12-20
Also published as: MX2019015329A

Abstract

The present invention relates to copper leaching, more specifically to a method for leaching copper oxide ore to produce copper precipitates, which method uses a non-polluting leaching agent and comprises the following steps: (a) crushing the ore; (b) leaching the ore; (c) carrying out induced crystallisation; (d) washing and stabilising; (e) conditioning; and (f) drying and packaging.

Description

PROCESS FOR OBTAINING COPPER BY MEANS OF LIXIVIATION AND

DIRECT CRYSTALLIZATION TECHNICAL FIELD OF THE INVENTION

The present invention relates to copper leaching, more specifically to a process for leaching copper minerals (carbonates and oxides) to produce high purity copper crystals using a non-contaminating agent.

BACKGROUND OF THE INVENTION

At present, copper continues to experience a significant demand, which is estimated to remain on the rise not only due to the multiple fields in which as a metal it can be used, but also due to its potential for use in diverse and continuous technological and industrial developments. in areas such as electronics, computer science, communications, pipe manufacturing, solar panels, automotive industry and power energy transfer, among others, making this one of the most required metals. In this way, having efficient processes for the production of copper in terms of: reducing costs, not degrading the environment, providing greater operational safety and optimizing their productive capacity, is essential for the mining industry and, ultimately, For the world economy. In consideration of the aforementioned, some of the processes that, until now, have been used to leach copper ore will be enunciated:

a) Leaching with ammonia

b) Leaching with thiurea

c) Use of sea and salt water

d) Acid leaching

e) Leaching by sulfuric acid with water

Several factors have influenced these processes to not achieve optimum production and efficiency standards, staking, among others, their high implementation costs, rational operational complexity and high environmental impact.

In fact, the leaching process with ammonia, due to its great polluting power and toxicity, has not been successful in the industry.

Leaching with thiurea, a compound developed based on organic substances mixed with sodium cyanide -tampoco has managed to consolidate itself as a mining process as it turns out to be highly degrading to the environment.

The leaching process using seawater and saltpeter, meanwhile, has not been successfully used due to the low purity of the copper liquor obtained manifested by the excessive formation of salt crystals.

In turn, leaching by acids, alone or compounds, for example, hydrochloric acid, nitric acid, or mixed between them, also called royal water, has been used to dissolve noble metates such as gold and silver, being extremely aggressive, toxic and high cost. It is used only at the laboratory level. Finally, sulfuric acid leaching (H2S04) with water (H20) corresponds to the process according to which almost all copper leaching is carried out in mining. This process, which allows copper cathodes to be obtained from the copper oxide ore, begins with the crushing and sorting of the ore from the mine, and then being transferred to leaching pias, after impregnating the crushed and classified ore, batteries that are irrigated with a solution of sulfuric acid, plus water (with a controlled aqueous acidity that is determined depending on the mineralogy characteristic of the deposit and that usually has a pH that varies between 1.5 and 3.0).

The present invention provides a novel and inventive process with which current problems are largely resolved.

DESCRIPTION OF THE INVENTION

BRIEF DESCRIPTION OF THE FIGURES

Figure 1 illustrates in a condensed manner the steps involved in the process of the present invention.

Figure 2 illustrates the steps involved in STEP I of the process of the present invention.

Figure 3 illustrates the steps involved in STEP II of the process of the present invention.

Figure 4 illustrates 80 X optical microscope photographs of the copper obtained with the process of the present invention.

Figure 5 illustrates Photographs with copper scanning electron microscope obtained with the process of the present invention.

Figure 6 illustrates the schematic of the progressive conversion model.

Figure 7 illustrates a schematic of the unreacted core model.

Figure 8 illustrates a cross section of minerals leached with sulfuric acid at different times (A: 2 weeks, 4 weeks, C: 6 weeks).

Figure 9 illustrates a graph of Copper Leaching Kinetics.

Figure 10 illustrates a graph of the kinetics of acid consumption of the mineral.

Figure 11 illustrates a graph of the Reason between acid consumption of the mineral and dissolved copper.

Figure 12 illustrates a graph of the adjustment of the unreacted core model for copper conversion.

DETAILED DESCRIPTION OF THE INVENTION

The stages involved in the process for obtaining copper can be seen condensed in Figure 1, where such a condensed process comprises the following stages:

a) Crushing ore

b) Leaching of ore

c) Induced crystallization

d) Wash and stabilized

e) Conditioning

f) Drying and packaging

And with only these inputs required by the process: Mineral; Reagents; Water and Steel Plate.

This process for leaching copper ores (carbonates and oxides) to produce high purity copper crystals has certain essential technical characteristics at each stage of the process, as (for its best explanation, the process through leaching continues and crystallization We will divide it directly into two main stages:

STAGE I

A) The copper ore (mainly carbon atoms and oxides) extracted from the mine is transported to the beneficiation plant where it is crushed to an adequate size, which it can be -1/4 "(depending on the nature of the ore), to have the copper ores released and stored in a hopper that we will call fine. The stored ore is fed to the continuous leaching reactors through a band Conveyor to a mixer drawer adding NaCI and KCI as solid reagents, these reagents will be based on the preliminary tests carried out, simultaneously a dilute solution of H2S04 is added, which can contain from 5 to 10%.

B) In the reactors the first stage of the main process is carried out, which is the leaching of copper ores, which means the dissolution of copper to form a rich solution of C11SO4, depending on the nature of the mineral the reaction time or of residence will be between 30 to 40 minutes to arrive at the maximum concentration of copper in the solution and ensure optimal conditions for the next stage of nucleation. The outgoing pulp of the reactors is passed, by pipe and preferably by gravity, to a thickener tank to separate the rich solution from the depleted mineral (Jal). The depleted mineral (Jal) is discharged from the thickener tank at the bottom and passed to a filter to extract as much as possible of the rich solution it has, once it leaves the filter with a minimum humidity of 3-4% it is transported by a system of conveyor belts or pumping, adding a lime slurry to neutralize and reduce the acidity being duly harmless and be deposited in a dam dam for confinement. The foregoing, as further illustrated in Figure 2.

It is important to mention that if it is static leaching in the sink, the leaching time is 36 to 48 hours and if it is dynamic leaching with continuous reactors, the leaching time is 26 to 32 minutes.

STAGE II

A) Once the solution is free of solid material it is passed to a flow buffer tank and it is also used for the addition of reagents necessary to give the nucleation conditions that can be H3PO4, H2SO4 or even NaCI and / or KCI; hence the crystallizing tanks are fed in which steel plates (low carbon) with an inclination of 60 ° with respect to the horizontal are arranged inside and for several hours, which depends on concentration conditions, temperature, etc., after the time has elapsed, the already depleted copper solution is discharged and resumed at the beginning of the leaching stage to be reused and regenerated with the addition of depleted reagents such as H2S04 and H3P04, this solution is passed through a bed of phosphoric rock to decrease the content of Fe in solution from the mineral and leaching (also depending on the nature of the mineral) and then through a bed of zeolite in order to filter that solution and Prepare it to be fed to leaching.

B) After discharging the spent solution, by means of a vibration system the copper adhered to the plates is discharged and deposited in a hopper for its next step in the process that is composed of a rinsing stage through the use of sorters of spiral equipped with a water spray system to rinse and neutralize the pH of the metallic copper completely and eliminate the remains of Fe from the nucleacton operation since to produce a kilogram of Copper it is necessary to consume a kilogram of Fe el which manifests as an extremely fine black powder, after this stage the metallic copper passes to another spiral classifier where a diluted solution of H3P04 is added to 0.5% to condition the surface of the crystals thus avoiding natural oxidation. This solution after being in contact with the copper is returned to the preparation tank to be reused continuously for all the copper produced. The above, as further illustrated in Figure 3.

Once the metallic copper is conditioned and depending on the needs of the customer, the product can be transferred to briquetting presses to generate whiskers that are easy to handle or to a drying and packing system in case the product is required in the form of a shot.

More specifically, the present invention provides a hydrometallurgical process for the benefit of copper ores comprising leaching (mainly carbonates and oxides) that can be static or dynamic, with a dilute acid solution followed by a nucleation stage generating copper crystals. of arta purity.

The components and characteristics of the process of the present invention, as illustrated in figures 2 and 3, they are identified as follows:

1 Fresh Mineral Mine

2 Crushing Area

3 fresh ore 1/4 "

4 Rinse water for plant use

5 Hopper of fines

6 Magnetic feeder

7 Integrated Pesometer

8 Mineral

A1 Fresh water replacement

A2 H2S04 replacement concentrate

9 Receiving tank of redoubled crystallization solution

10 Leaching Solution

11 50% continuous pulp leaching reactors and 30-40 minutes of Contact time

12 leached ore

13 Thickener Tank

14 Leached Mining

15 Band type vacuum filter

16 Mineral leached, depleted and neutralized to dam

17 Rich solution

18 Rich solution buffer tank for crystallization

19 Crystallization Reagent 1

20 Crystallization Reagent 2

21st Plates of Faith

21b Continuous Crystallization Plates No 1

21c Plates of Faith

21 d Continuous crystallization plates No 2

23rd Cupuro Crystals

23b Cupuro Crystals

The copper ore previously mixed with NaCI-KCI is reacted with a diluted solution of 5 to 10% H2S04, a minimum amount of H3P04, thereby obtaining CUS04 in solution, NaHS04 also in solution, another amount of Fe8 (P0 « ) 2 and an amount, depending on the nature of the mineral, of free H2S04. After the solution is filtered and its pH is regulated with a diluted solution of NH »OH, a piece of steel (low carbon) is introduced in order to initiate the nucleation and growth of copper crystals.

Reactions 1 and 2 refer to the process of dissolving copper in carbonated and oxidized minerals and in reaction 3 it is the dissolution of sodium chloride which is indicated to reinforce the process of dissolution of copper by hydrochloric acid and formation of sodium acid sulfate as a precursor or initiator of the process of spontaneous formation of copper crystals in the interaction of copper sulfate and the steel part. The addition of phosphoric acid, formula 4 (depending on the nature of the mineral), in this first stage of the process is to mitigate the effects that iron has on dissolution reactions since it is more reactive than copper and would occupy a large part of the solution decreasing the possibility of copper increasing its concentration and thus decreasing the essential process of creating and growing copper crystals.

The nature of minerals such as carbonates and ions oxides makes it possible for the efficiency of these reactions to be increased with the agitation that is carried out in the reactors for dynamic leaching being reflected in the increase of the total recovery to values above 90% of leachable copper.

The mechanism of crystal formation is based on the physicochemical phenomena of nucleation and crystal growth, which are represented in the inverse process of dissolving some salt in aqueous solution, thus:

• Ionic salts are soluble in water and covalent compounds are not.

• That is, nitrates and most halides are soluble in water.

• Sulfides, oxides, silicates and phosphates; except alkalis, which are ionic.

• Sodium chloride and calcium chloride are soluble in water, silver chloride and calcium chloride are not.

• The reason is that, in the case of the second ones; Agci and CaCI, the link between the metal ion and the halide ion is partially ionic and partially co lens. The dissolution of salt in water is the result of two opposite effects:

> The work done on electrostatic forces to maintain the ions in the crystal, this is a function of the energy of the crystalline network.

> The ionization of ions in the crystal lattice; the ions united with the Water molecules to form hydrated ions due to the polar nature of water molecules.

The following aspects are also involved:

✓ The energy of the solid ion network parameter.

✓ Water polarity.

✓ The solubility of salt.

✓ Temperature effect.

And some others that have influence; as: organic solvents, solubility product (s), common ion and complex and kinetic formation.

Finally, the copper produced is rinsed with water for the elimination of the Fe released in the crystallization process and subsequently conditioned and stabilized with a dilute phosphoric acid solution to give the surface a protection against the natural oxidation of the environment.

Technical advantages:

• Does not use electric current like Traditional Technology by electrolysis.

• Does not use fossil fuels as in the method of obtaining copper through reduction furnaces.

• It is totally friendly with the environment.

• Complies with NOM - 159 - SEMARNAT - 2011 and does not produce waste of any kind, except for coughs that fully comply with the corresponding NOM.

• 100% reuse the leaching solution, once regenerated and reconditioned.

• 100 ¾ ecological.

• For plants of the same production capacity, it requires much lower capital investment costs; As a consequence of the high physicochemical efficiency, it allows smaller and smaller installations than traditional technology.

• Lower process costs than traditional technology.

• Obtaining Shot Copper Copper with purity greater than 99.5%.

• Recovers at least 90.00% of leachable copper in the ore. • Recovers 100% of the copper dissolved in the pregnant solution.

• It does not require any additional purification process to the copper solution, where the shot is obtained.

• Applies at different production scales.

For the product obtained the following test was carried out:

SAMPLE IDENTIFICATION

The previous test shows that our process is highly efficient due to the percentage of copper obtained, which is 99.8649%.

Also, from figures 4 and 5 you can see the microscopic characteristics of the copper obtained.

As described above, it is noted that the best process known to the applicant to implement said invention is the one clarified in the present description.

Cobra Dissolution Kinetics

The leaching kinetics of minerals is the determination of the rates and mechanisms of dissolution or extraction of metals of economic interest. The study of kinetics provides vital information from a practical and conceptual point of view, since on the one hand, kinetic studies provide valuable engineering data for the design and evaluation of mining projects, on the other, they allow determining the conditions of operation and the mechanisms and limiting stages involved, in addition to predicting the rate of copper extraction under various temperature conditions, concentration of leaching and oxidizing agents, etc.

The chemistry that involves the dissolution of copper ores is essentially a simple decomposition in the case of oxidized ores, and an oxide-reduction reaction in the case of sulfur ores, where the products of the reactions are water soluble. . The same happens in the various oxides, silicates, carbonates and sulfates in the bargain that undergo similar reactions to form soluble salts.

Kinetic Leaching Models

There are two models that make it possible to represent the leaching of a mineral, in which a liquid (reagent) comes into contact with a solid (mineral), reacts with it and transforms it into a product [10]. It must be kept in mind that any model or conceptual scheme that represents the evolution in time of a reaction corresponds to a mathematical representation that is, its kinetic equation. Therefore, if a model is chosen, its kinetic equation must be accepted accordingly and vice versa. It can be said, then, that the model that best represents the real behavior of a process, its kinetic expression will predict and describe the kinetics of the real process. Also, if the chosen model does not fit or differs greatly from the actual behavior of the process, then its kinetic equation will prove useless.

In summary, the conditions that a kinetic model should meet are: that it represents in the best possible way the behavior of the real process and that it has a simple and easy to handle mathematical expression. A model could depend on a host of variables that make it better approach what happens in reality, but its use would be complicated from the mathematical point of view and the availability of data required.

Progressive Conversion Model

In this model it is considered that the reagent enters and reacts through the entire solid particle at all times, which causes different reaction rates in the different places of the latter. In this way, the mineralogical species present in the solid react continuously and progressively throughout the particle as shown in Figure 6. Model of the Unreacted Core (N.S.R.)

As illustrated in Figure 7 of the scheme of the unreacted core model, it is considered that in this model, the reaction is considered to occur first on the outer surface of the particle, forming a surface reaction zone, which moves to the solid inside. Once the reaction progresses, there will be at any time a porous reacted zone of completely converted material (commonly referred to as an ash layer) and an internal zone of unreacted material, which decreases in size as the leaching of the mineral progresses .

Comparison between Models and Actual Operation

It has been found that for minerals that exhibit relatively homogeneous mineralization through the bargain, the model that best quantifies the actual behavior is the unreacted core model. This is reflected in a large number of experimental cases in which when cutting and examining the cross-section of the particles, a layer of unreacted solid material can be observed, surrounded by a layer of ash. Undoubtedly, the contour of the unreacted surface may not be perfectly defined as indicated by the model, but in general for these types of minerals, as often as possible, the unreacted core model fits better than the model of progressive conversion See Figure 8, which shows the cross-section of minerals leached with sulfuric acid at different times (A: 2 weeks, 4 weeks, C: 6 weeks). Leaching of an oxidized mineral The chemical composition of the mineral was analyzed by total dissolution by acid attack followed by atomic absorption. Table 1 shows the chemical analysis of the mineral. The value obtained for the maximum acid consumption of the mineral was 73 [kg acid / ton mineral]. The microscopy analysis identified the oxidized species of malachite and crisocola copper.

Table 1: Chemical ore anisls

Chemical analysis of the concentrated solution

The refining solution (concentrated solution) of leaching was analyzed by atomic absorption to know the concentrations of the most abundant ions present. Table 2 shows the results of the chemical analysis.

Table 2: Chemical analysis of the refining solution

To determine the concentration of acid in the concentrated solution, a potentiometric titration method was applied. The acid concentration in the concentrated solution is 15 [gr / l] and was used with this value in experiment 1. For experiment 2 the acid concentration was increased to 30 [gr / l].

Table 3: Initial conditions in each experiment

The concentration of sulfuric acid in both leaching solutions (diluted and concentrated) must be the same during the course of the experiment. Table 3 summarizes the initial conditions that were applied in each experiment.

Experimental data collection

During the leaching tests, samples of the solutions were taken in the reactors, after each sampling the volume of leaching solution in each reactor was replenished to maintain the volume of leaching solution and initial acidity of each experiment. Therefore, the chemical analyzes of the extracted samples were corrected by volume extracted and initial concentration of the ions present in the leaching solution. RESULTS

Experiments were carried out with different amounts of acid in solution, experiment 1 with 15 [gr / K] of H2S04 and experiment 2 with 30 [gr / H] of H2S04. In addition each experiment consists of a leaching of the mineral with a solution of low ionic load (diluted) and a leaching with high ionic load (concentrated or refining).

The results of copper leaching kinetics with diluted and concentrated leaching solutions are presented in Figure 9. According to Figure 9, at the end of experiment 1 (175 [hr]) the leaching performed with diluted solution the copper recovery reached 76%, while the copper recovery made with concentrated solution was 60%. On the other hand, at the end of experiment 2 (131 [hr]) the copper recovery reached 66% in the diluted leaching solution, while in the concentrated solution the copper recovery was 44%. It can be seen that with an acid concentration of 30 [gr / l] in both leaching solutions (diluted and concentrated) the recovery of copper is very similar to that obtained with an initial acid concentration of 15 [gr / l],

As illustrated in the graph of Figure 9, of the Copper Leaching Kinetics, where the results show that the presence of a high ionic charge results in a reaction rate inhibitory effect. In addition there is no greater recovery of copper to increase the concentration of acid.

Kinetics of mineral acid consumption

Figure 10 shows the results for the consumption of acid accumulated by the mineral during its leaching with diluted and concentrated leaching solutions. The mineral acid consumption at the end of experiment 1 was 34 and 26 [kg of acid / Ton mineral] in the diluted and concentrated leaching solution, respectively, and the accumulated acid consumption of the mineral with an acid concentration of 30 [gr / lt] at the end of the experiment (131 [hr]) was 45 and 33 kilos of acid per ton of ore in the diluted and concentrated solution respectively.

As illustrated in the graph of Figure 10, from the Kinetics of acid consumption of the mineral, it follows that by leaching an oxidized copper mineral with a solution that has a high ionic charge, the rate of acid consumption that experience The mineral is reduced compared to that obtained with the diluted solution. In addition, the acid consumption of the leached ore was higher when the concentration of the leaching agent was 30 [gr / it] compared to the acid consumption reached by the mineral with a concentration of 15 [gr / lt].

Reason between acid consumption of the mineral and dissolved copper

Figure 11 shows the ratio between the acid consumed accumulated and the amount of dissolved copper accumulated over time, where it is observed that when using an acid concentration of 15 [gr / l] the acid consumption of the mineral per kg of copper produced is 4.4 kg of acid per kg of copper for the diluted solution and 3.8 kg of acid per kg of copper for the concentrated solution, while using 30 [gr / R] of acid, the consumption is 7.2 kg of acid per kg of copper for diluted and concentrated solutions. Analyzing the trend, it follows that the higher the concentration of acid, the higher the consumption of acid for diluted and concentrated solutions, so there should be an acid concentration that minimizes the consumption of acid per copper produced without affecting its kinetics.

ANALYSIS AND DEVELOPMENT OF MODELS

The dissolution kinetics of particulate material has been studied using the unreacted core model for diffusion control and chemical reaction control (Levensplel 1962). This model has been used to study the leaching of oxidized copper ores, finding that the reaction rate in oxidized copper ores is much faster than the diffusion rate of reactants and products (Barttett 1992, Shafel 1979). The unreacted core model was used for diffusion control of reactant for the adjustment of the results of the copper dissolution, finding that in the case of diluted solutions the model was not able to reproduce the results. This is because there is no constant estequiornétrk »coefficient that relates the kinetics of copper dissolution and the kinetics of acid consumption. This fact is confirmed in Figure 11, since for the diluted solution the ratio between the acid consumption of the mineral and the dissolved copper is not constant but increasing over time. Due to the above it was necessary to modify the unreacted core model for diffusion control considering the concentration of copper in solution. Diffusion of products through the ash layer as a controlling stage When the reaction rate is controlled by the diffusion of the products from the reaction surface to the solution through the reacted ash layer, the expression that relates the conversion to The time and concentration in solution is:

Where X is the conversion or leached fraction of the mineral, C0 concentration of the product on the surface of the mineral [gr / lt], Csol concentration of the product within the

solution [gr / lt] and P D t is the total conversion time for a difference in concentration between the reaction surface and the sine of the solution of 1 [gr / lt], defined as:

Where pO is the concentration of the product in the solid and Defes the effective diffusion coefficient of the product.

Equation 1 describes the behavior of the fraction of material that has already reacted for a given time and concentration in solution

In Figure 12, which is a graph of the Adjustment of the unreacted core model for copper conversion, the adjustment of the unreacted core model for the diffusion of products (copper) for copper conversion in experiments is observed 1 and 2 using equation 2.0

When adjusting the model to the experimental results, it was determined that C0 has a value of 7 gr / l of copper, which corresponds to the maximum concentration that can be obtained in the solution given the operating conditions.

Table 4: Summary of adjustment values

Table 4 summarizes the values obtained for

The correlation obtained. The correlation of iacytes to the proposed model is adequate, so the model with diffusion control represents well the process that is happening.

X »

Table 5 shows the results of the ratio of the

obtained for diluted and concentrated solutions in order to determine the variation that occurs on the diffusion coefficient of copper by varying the ionic charge of the system.

Table 5: Reason between

of diluted and concentrated solution

Since the copper leaching rate does not depend on the concentration of acid, it follows that the kinetics is not controlled by diffusion of protons into the particle, but rather by the diffusion of copper ions from within the particle.

This was confirmed based on electrochemical measurements of copper diffusion coefficients, in which it was found that the ratio of the diffusion coefficient values in diluted and concentrated solutions is equal to that observed in the ratio of the ° in both solutions.

CONCLUSIONS

The rate of dissolution of copper is limited by diffusion of the cupric ion through the leach residue layer from the reaction zone to the solution, both for diluted and concentrated solutions. The dissolution rate of copper is higher in dilute solutions than in concentrated solutions since the coefficient of Cupric ion diffusion decreases by 60% when using concentrated solutions.

The rate of dissolution of copper is independent of the concentration of sulfuric acid in the range of 15 to 30 [gr / ft].

The consumption of acid per copper produced increases as the concentration of acid in solution increases without increasing the dissolution rate of copper or its recovery. Based on this result, there should be an acid concentration of less than 15 [gr / tt] that maintains the copper dissolution rate while minimizing acid consumption. Due to the above, it is necessary to perform additional leaching tests with a lower amount of acid in order to find the optimum acid consumption per copper produced.

PH and potential variation

The concentrations of

in solution, they have, as a result, very small amounts that are uncomfortable to handle, so the fastest and most practical way to measure the acidity and basicity of a solution is used, that is, using the concept of pH.

By definition, the pH of a solution is the log negative rhythm of a numerical expression of the motor concentration of Ions

Thus, an aqueous solution is worth:

The result of the pH calculation is an adimenstonal quantity without units.

Strong acids and bases are almost completely ionized, in dilute aqueous solutions, so the concentrations of ions [H30 * +] and [OH * -] can be calculated, so the pH also directly to from the concentrations of the acid or base in question.

The knowledge of the pH of the solutions is very important to be able to interpret the behavior of the different substances in chemical reactions, whether in inorganic systems, as in biological systems.

In laboratories, the measurement of the pH of the solutions is carried out by means of devices known as pehachimeters. These work by means of electrodes that are introduced into the solution to be treated, being able to quickly read the pH value scale in said machine. In the same way as pH, pOH is defined as:

The pH and the pOH, maintain a relationship when they are of the same aqueous solution, being quite easily deduced, through the expression of the ionic product of the water (Kw):

If in the previous expression, we take decimal logarithms in both members, we get the following:

Multiplying this expression by -1, you get:

So, finally, and following the definitions of pH and pOH, we have to:

In the case at hand, the pH variations are subject to the nature of each mineral with its consequent operating parameter regulations that, even for the same mine, must be continuously adjusted

In the leaching stage we can have values ranging from 1.5 to 5.0, decreasing the acidity in the crystal nucleation stage to bequeath even 6.0. This forces us to have pH monitoring systems during the stages as it gives us a very clear idea of the kinetics of the chemical reactions present in the process.

An example of this we can name leaching in its simplest form since in these systems we have the influence of copper minerals but also those of iron which, as we saw in the kinetic part, have a weight influence in the process of dissolution contributing to the increase of this phenomenon for the benefit of the whole group and therefore a variation in the pH that can indicate it.

In the case of the Potential this concept, we will say that it is based on the cementation, or as we have been naming here the nucleation, which is the precipitation or formation of crystals of a metal of a certain reduction potential from the solutions of its salts, for another base metal that in this case is the steel of low carbon

In our case, the copper cementation reaction is:

If we apply it, we see that both F and Eo and n are positive, so "6 will give us less than zero. This indicates that the reaction is spontaneous.

Taking advantage of this spontaneous phenomenon, the reason for this patent is precisely this improvement to the process in which copper is being produced with a purity of at least 99.5% of copper without making use of electrical energy for the production of the crystals and consequently of the copper produced.

Claims

1. Process for obtaining copper through leaching and direct crystallization, this process includes the following stages:

a) The crushing of copper ore (mainly carbonates and oxides) extracted from the mine is carried to the beneficiation plant where it is crushed to an appropriate size, which can be up to -1/4 "(depending on the nature of the ore ), for the release of copper ore.

b) once crushed and stored, the ore is fed to a pre-mixed drawer in which solid NaCI and KCI reagents are added prior to leaching, the ore is fed by conveyor belts to the leaching reactors, simultaneously a solution is added diluted H2S04, which may contain 5 to 10%, for leaching copper ores and forming a rich solution of CuS04, with a residence time of 26 to 40 minutes, preferably 26 to 32 minutes when leaching is dynamics in continuous reactors and 36 to 48 hours in static leaching machines. The outgoing pulp of the reactors is passed, by pipeline and preferably by gravity, to a tank that is weighed to separate the rich solution from the spent ore, where the sludge is discharged from the thickener tank through the bottom and passed to a filter to extract Remains of rich solution of CuS04 and are transported with a minimum humidity of 3-4% is transported by a system of conveyor belts or pumping, prior neutralization with a slurry of lime to the dam of jales for confinement.

c) The udder concentrated solution of solid material is passed to a flow buffer tank and is also used for the addition of reagents necessary to give the crystallization conditions among which are H3P04, H2S04, Fe pulverized and even NaCI and / or KCI and a dilute solution of NH40H to regulate the pH; once the reagents have been added, the solution is fed to the crystallizing tanks in which steel plates (ASTM 1010) are arranged inside with an inclination of 60 * with respect to the horizontal, for several hours for the deposit of crystals of copper; the solution is then discharged and depleted of copper at the beginning of the leaching stage to be reused after regeneration with H2S04 and H3P04; this solution is passed through a bed of phosphoric rock to decrease the content of Fe in solution from ore and leaching and finally a filtrate in a zeolite roof. d) once the depleted solution has been discharged, the copper is discharged from the steel plates by means of a vibration system and deposited in a hopper; in said hopper it is rinsed by means of the use of spiral classifiers provided with a water spray system to rinse and completely neutralize the pH of the metallic copper and eliminate the remains of Fe from the crystallization operation.

e) after this stage the metallic copper passes to another spiral classifier where a 0.5% diluted solution of H3P04 is added to condition the surface of the crystals thus avoiding natural oxidation; The residues of this solution are retaken preparation tank to be reused continuously for all the copper produced.

f) Finally, the metallic copper is dried, briquetted and packed in the form of ingot or shot.

2. Process for obtaining copper by means of leaching and direct crystallization according to claim 1 characterized in that the copper ores are mainly carbonates and oxides.

3. Process for obtaining copper by means of leaching and direct crystallization according to claim 1 characterized in that, in step c) the addition of powdered Fe consumed is equal to the amount of copper produced.

4. Process for obtaining copper by means of direct leaching and crystallization according to claim 1, characterized in that, in step b) in dynamic leaching, the total recovery is above 90% of the Ibdviable copper.

5. Process for obtaining copper by means of leaching and direct crystallization according to claim 1 characterized in that, in step f) of obtaining the metallic copper in a shot, a purity greater than 99.5% is obtained.

6. Process for obtaining copper by means of leaching and direct crystallization according to claim 1, characterized in that, in step c) once the deposition of copper crystals on the steel plates is made, the copper recovery is 100% of the copper dissolved in the pregnant solution.

7. A non-polluting leaching composition for copper recovery of minerals that contain it mainly oxides and carbonates comprising: a diluted solution of 5 to 10% H2S04, 0.5% H3P04, an amount of NaHS04 also in solution, another amount of Fe3 (P04) 2 and an amount, depending on the nature of the mineral, free H2S04 and NH40H as a pH regulator.

8. The use of the non-polluting leaching composition for the recovery of copper from minerals that contain mainly oxides and carbonates where the diluted solution of 5 to 10% H2S04, 0.5% H3P04, an amount of NaHS04 also in solution, another amount of Fe3 (P04) 2 and an amount, depending on the nature of the mineral, free H2S04 and NH40H as a pH regulator, achieves copper recovery to a purity greater than 99.5%.