FR2966470A1 - Treating gold ore to extract gold contained in ore, by placing ore having liquid and solid phases and then forming prepared ore from ore, placing etching solution comprising sodium thiosulfate, and mixing prepared ore with etching solution - Google Patents

Abstract

The process comprises placing ore (12) having a liquid phase (12L) and a solid phase and then forming a prepared ore (14) from ore, placing an etching solution (16) comprising sodium thiosulfate, cupri-ethylene-diamine or sodium thiosulfate, copper sulfate and nickel sulfate and polyethylene amine, mixing the prepared ore with the etching solution in an etching container to form an ore pulp (18) so that, during an etching phase, that etching solution dissolves the gold contained in the prepared ore, and capturing solubilized gold during the etching phase by receiving unit. The process comprises placing ore (12) having a liquid phase (12L) and a solid phase and then forming a prepared ore (14) from ore, placing an etching solution (16) comprising sodium thiosulfate, cupri-ethylene-diamine or sodium thiosulfate, copper sulfate and nickel sulfate and polyethylene amine, mixing the prepared ore with the etching solution in an etching container to form an ore pulp (18) so that, during an etching phase, that etching solution dissolves the gold contained in the prepared ore, capturing solubilized gold during the etching phase by receiving unit and constituting a weak solution (28) devoid of gold, retaining a portion to be preserved of the weak solution and reusing the part to be preserved of the weak solution to form the etching solution, and purging a part to be exclude from the weak solution towards a neutralization unit to neutralize the adverse effects of the part to be excluded from the weak solution on the environment. The formation of the prepared ore comprises removing a part of the liquid phase of the ore so that the prepared ore has a liquid phase and a solid phase in predetermined proportions defining a flow of introduction of liquid phase of prepared ore to mix with the etching solution, and removing a portion of the liquid phase of the ore to obtain a rate of introduction of liquid phase of prepared ore in the ore pulp such that the liquid phase of prepared ore is 3-20% of the total weight of the prepared ore. The part to be excluded of the weak solution is purged at a purging rate equivalent to the rate of introduction of the liquid phase of prepared ore to be mixed with the etching solution. The receiving unit fixing the solubilized gold comprises active carbon and ion exchange resins or metal powders. A very low amount of cyanide is used to pass the solubilized gold in the aurothiosulfate form to aurocyanide form before the solubilized gold is captured by the activated carbon. The ore pulp is transformed, during the etching phase, into an etched pulp (20) having a solid phase and a liquid phase also called rich solution in which solubilized gold is present and in which the solubilized gold passes the aurothiosulfate form to the aurocyanide form. During a separation operation, the solid phase of the etched pulp is separated from rich solution to recover the rich solution and the solid phase of the etched pulp weak in gold is isolated to recover the liquid phase of the etched pulp low in gold corresponding to the weak solution. During a phase for transformation into aurocyanide, very small quantity of cyanide of 5-20 mg of cyanide per liter of rich solution is introduced into that rich solution so that the gold dissolved in the rich solution passes from the aurothiosulfate to the aurocyanide form. During a phase of recovery of gold, the activated carbon and the ion exchange resins or metal powders are used to capture the solubilized gold in the aurocyanide form. The prepared ore and the etching solution are mixed with the activated carbon, ion exchange resins and the very low amount of cyanide. The prepared ore is placed on an etching container forming a sealed area, and the etching solution sprays the prepared ore. During the attack phase, the etching solution etches the prepared ore by percolation to obtain a rich solution in which the solubilized gold is present. The prepared ore is placed on an etching container forming a sealed area and the etching solution prepared this mineral waters. The step of removing a portion of the liquid phase of the ore is operated by a module consisting of a drying tube, spin-dryer, centrifuge, pressure belt filter, filter press, horizontal belt filter or forced or natural evaporation module. The part to be preserved of the weak solution is discharged into a storage container of the etching solution. The storage container of the etching solution is connected to a preparation container of a concentrated etching solution. The etching container is connected to the preparation container and is fed in concentrated etching solution. The process further comprises carrying out an electrolysis of the part to excluded of the weak solution so as to recover the copper contained in that part to be excluded of the weak solution and then meeting the standards of copper material discharge in environment. The part to be excluded of the weak solution is neutralized by neutralization agents to recover copper and limit the effects of the part to be excluded of the weak solution on the environment and by total or partial evaporation of its liquid phase then recovery of copper and neutralization of the residual part. An independent claim is included for a system for extraction of gold contained in the ore by the treatment of the gold ore.

Description

Process and processing system for extracting gold contained in a gold ore

The invention relates generally to the field of gold ore processing. More specifically, the invention relates to a method and a processing system for extracting gold contained in a gold ore.

It is known to treat gold ore from attack solutions containing sodium cyanide or potassium, which allows to dissolve effectively and without difficulty the gold contained in the gold ore. The use of cyanide, however, has several disadvantages. First, the dose of cyanide to be used in the attack solution is dangerous to the environment in the event of a spill. Secondly, the cyanidation processes can not be implemented when the gold ore contains native carbons since they absorb solubilized gold in the form of aurocyanide.

Alternative treatment methods, such as that disclosed in WO 1991/11539, utilize ammonium thiosulfate etching solutions. These methods are advantageous because they make it possible to dispense with the use of cyanide while using a reagent, ammonium thiosulfate, considered as non-polluting and inexpensive. However, these processes are not without their drawbacks since it appears that the attack of the gold ore with an attack solution containing ammonium thiosulfate is much more difficult to control than cyanidation and leads to a strong consumption of reagents, including ammonia which is a volatile product and ultimately polluting.

Still other methods are to extract the gold contained in a gold ore by mixing it with an etching solution comprising thiosulfate and an amine. In this way, the etching solution solubilizes the gold contained in the ore pulp and forms a rich solution from which it is possible, on the one hand, to fix the gold on ion exchange resins or to recover it by cementation on metallic powders and, on the other hand, to constitute a poor solution devoid of gold. Such a process is known to the person skilled in the art, in particular by the example given in document No. WO 2007/098603, which describes a method for treating gold ore from an etching solution comprising in particular thiosulphate. sodium and an ethylenediamine. The use of an attack solution based on sodium thiosulfate makes it possible to dispense with ammonia and thus to obtain a less polluting attack solution, at a price that is also competitive. Such an embodiment, however, has disadvantages. First, even if the sodium thiosulfate is not very expensive, it is necessary that the attack solution contains a high concentration which represents a significant part of the operating cost of this process. In addition, the etching solution solubilizes not only the gold but also many other metals contained in the gold ore which, after several cycles of use of the etching solution, leads to an accumulation of residual metals and therefore to a degradation of the efficiency and the kinetics of the attack.

In this context, the purpose of the present invention is to propose a method for treating gold ore which is free from at least one of the limitations mentioned above and, in particular, which makes it possible, on the one hand, to reduce the environmental risks associated with it. to the processing of the ore by means of a solution of attack potentially not dangerous for the environment and, on the other hand, to control the use of this solution of attack so as not to have to replace it too frequently and in too large quantities.

To this end, the invention relates to a gold ore processing method for extracting gold contained in an ore, comprising a plurality of stages consisting of, dynamically and cyclically, to: dispose of an ore having a liquid phase and a solid phase and form, from the ore, a prepared ore; having an etching solution comprising sodium thiosulfate and cupriethylenediamine or sodium thiosulfate, copper and / or nickel sulfate and an amine; mixing the prepared ore with the etching solution so that, during an attack phase, this etching solution solubilizes the gold contained in this prepared ore; collecting the solubilized gold during the attack phase via receiving means and constitute a poor solution devoid of gold.

According to the invention the formation of said prepared ore consists of removing a part of the liquid phase of said ore so that the prepared ore has a liquid phase and a solid phase in predetermined proportions defining a flow rate of liquid phase introduction of prepared ore to mix with the attack solution. Moreover, the method comprises an additional step of, on the one hand, retaining a portion to preserve the poor solution and reuse the part to keep the poor solution to form the attack solution and on the other hand , to purge a portion to be excluded from the poor solution to neutralization means for neutralizing the harmful effects of the part to be excluded from the poor solution on the environment. In addition, the portion to be excluded from the lean solution is purged at a purge rate equivalent to the rate of introduction of the liquid phase of ore prepared to mix with the etching solution.

Removing a predetermined percentage of the liquid phase from the ore prior to the formation of the ore pulp avoids the amount of liquid phase within the system from irreversibly increasing during the various cycles of treatment of the ore. gold ore. In addition, the amount of poor solution thus purged makes it possible to maintain an effective etching kinetics for an optimized operating cost.

According to one embodiment, the formation of the prepared ore consists of removing a portion of the liquid phase of the ore so as to obtain a flow rate of liquid phase introduction of ore prepared in the ore pulp such that the liquid phase of prepared ore represents from 3 to 20% (Yo of the total weight of said prepared ore) This percentage corresponding to the necessary purge of the etching solution for a good process efficiency at an optimized operating cost.

In a first case, the receiving means fixing the solubilized gold comprise active carbons; the latter to ensure a good fixation of gold.

In this case, a very small amount of cyanide is used to pass the solubilized gold from the aurothiosulfate form to the aurocyanide form before this solubilized gold is captured by the activated carbons.

According to a first embodiment of the process according to the invention: the prepared ore and the etching solution are mixed in an attack container to form an ore pulp; the ore pulp is transformed, during the attack phase, an attacked pulp having a solid phase and a liquid phase also called rich solution in which the solubilized gold is; during a separation operation, the solid phase of the etched pulp is separated from the rich solution so as to recover this rich solution; during a conversion phase to aurocyanide, the very small amount of cyanide, for example ranging from 5 to 20 mg of cyanide per liter of rich solution, is introduced into this rich solution so that the gold solubilized in said rich solution weakly cyanurea changes from the aurothiosulphate form to the aurocyanic form; and during a gold recovery phase, columnar activated carbons are used to capture solubilized gold in the form of aurocyanide.

Such an embodiment has several advantages. It allows, in the first place, to evacuate without special treatment the solid phase at the end of the attack. It also allows, thanks to the addition of very small amounts of cyanide in the rich solution to capture the gold on activated carbons by using cyanide quantities falling under the simple procedure of declaration in the light of French legislation in this area.

According to a second embodiment of the process according to the invention: the prepared ore and the etching solution are mixed with the active carbons and the very small amount of cyanide in an attack container to form an ore pulp; the ore pulp is transformed, during the attack phase, an attacked pulp having a solid phase and a liquid phase in which the solubilized gold is passed from the aurothiosulfate form to the aurocyanure form; and during a gold recovery phase, activated carbons are used to capture this solubilized gold. In this case, during a separation operation, the solid phase of the gold-poor etched pulp is isolated from in order to recover the liquid phase of the attacked pulp poor in gold corresponding to the poor solution.

According to a third embodiment of the process according to the invention: the ore prepared is placed on a driving container forming a sealed area and the attack solution waters this prepared ore; during the attack phase, the attack solution attacks the ore prepared by percolation so as to obtain a rich solution in which the solubilized gold is found; during a conversion phase to aurocyanide, the very small amount of cyanide, for example ranging from 5 to 20 mg of cyanide per liter of rich solution, is introduced into this rich solution so that the gold solubilized in said rich solution weakly cyanurea changes from the aurothiosulphate form to the aurocyanic form; and during a gold recovery phase, activated carbons are used to capture solubilized gold in the form of aurocyanide.

In a second case, the receiving means fixing the solubilized gold comprise ion exchange resins or metal powders; which ensures the fixation of the gold even when the gold ore contains native carbons.

According to a first embodiment of the process according to the invention: the prepared ore and the etching solution are mixed in an attack container to form an ore pulp; the ore pulp is transformed, during the attack phase, an attacked pulp having a solid phase and a liquid phase also called rich solution in which the solubilized gold is; during a separation operation, the solid phase of the etched pulp is separated from the rich solution so as to recover this rich solution; during a gold recovery phase, ion exchange resins or metal powders are used to capture the solubilized gold.

According to a second embodiment of the process according to the invention: the prepared ore and the etching solution are mixed with the ion exchange resins in an attack container to form an ore pulp; the ore pulp is transformed, during the attack phase, into an attacked pulp having a solid phase and a liquid phase in which the solubilized gold is located; and during a gold recovery phase, the ion exchange resins are used to capture this solubilized gold.

In this case, during a separation operation, the solid phase of the gold-poor etched pulp is isolated so as to recover the liquid phase of the gold-poor attacked pulp corresponding to the poor solution.

According to a third embodiment of the process according to the invention, the ore prepared is placed on an attacking container forming a sealed area and the etching solution waters this prepared ore; during the attack phase, the attack solution attacks the ore prepared by percolation so as to obtain a rich solution in which the solubilized gold is found; and during a gold recovery phase, RE ion exchange resins or metal powders are used to capture the solubilized gold.

According to one embodiment, the step of eliminating part of the liquid phase of the ore is carried out via a module selected from a drying tube, a wringer, a centrifuge, a pressure band filter, a filter press, a horizontal band filter or a module with natural or forced evaporation.

In one embodiment, the portion to be kept of the lean solution is poured into a storage container for the etching solution. In one embodiment, the storage container for the etching solution is connected to a preparation container for a concentrated etching solution.

In one embodiment, the etching container is connected to the preparation container and fed with concentrated etching solution.

According to one embodiment, the treatment method comprises an additional step of electrolysis of the part to be excluded from the poor solution so as to recover the copper contained in this part to be excluded from the poor solution and thus comply with the rejection standards. 30 in the copper environment.

According to one embodiment, the part to be excluded from the poor solution is neutralized by neutralization agents making it possible to recover the copper and to limit the effects of the part to be excluded from the poor solution on the environment. According to one embodiment, the part to be excluded from the poor solution is neutralized by total or partial evaporation of its liquid phase, then recovery of the copper and neutralization of the residual part.

In one embodiment, the etching solution comprises sodium thiosulfate and cupriethylenediamine; the latter has the advantage of being neither flammable nor particularly dangerous to handle. In one embodiment, the etching solution comprises an amine of the polyethylene amine family.

In one embodiment, the etching solution comprises a mixture of copper sulphate and nickel sulphate; the latter product improving the stability of the solution.

According to a second aspect, the invention also relates to a system for extracting gold contained in an ore by the implementation of the gold ore processing method, comprising: an ore feed container having a liquid phase and a solid phase; preparation means capable of transforming the ore into prepared ore having a liquid phase and a solid phase; a storage container for a etching solution comprising sodium thiosulfate and cupriethylenediamine or sodium thiosulfate, copper and / or nickel sulfate and an amine; an attack container connected to the preparation means of the prepared ore and the storage container of the etching solution so as to mix said prepared ore with said etching solution and to generate an etching phase in the course of wherein said etching solution solubilizes the gold contained in said prepared ore; receiving means capable of picking up the solubilized gold during the attack phase via receiving means and forming a poor solution devoid of gold;

According to the invention, the preparation means of the prepared ore are able to remove a part of the liquid phase of the ore so that the prepared ore has a liquid phase and a solid phase in predetermined proportions defining a phase introduction rate ore liquid prepared to mix with the attack solution; the device further comprises purge means able, on the one hand, to retain a part to keep the poor solution and reuse the part to keep the poor solution to form the etching solution and, secondly, purging a portion to be excluded from the poor solution whose flow corresponds to an optimum yield of the kinetics of attack and at an optimized operating cost, to neutralization means making it possible to neutralize the harmful effects of the part to be excluded (28EX) the poor solution on the environment; and the purge means are capable of purging the part to be excluded from the lean solution at a purge rate equivalent to the rate of introduction of the liquid phase of ore prepared to be mixed with the etching solution.

Other features and advantages of the invention will emerge clearly from the description which is given below, for information only and in no way limitative, with reference to the appended drawings among which:

FIG. 1 is a schematic flowchart of a first embodiment of the gold ore treatment process according to the invention in which the attack is carried out in an attack container prior to the setting of the gold by activated carbons. ; FIG. 2 is a schematic flow diagram of a second embodiment of the gold ore treatment process according to the invention in which the etching is carried out in an etching container prior to the attachment of the gold by exchange resins. ions; FIG. 3 is a schematic flow diagram of a third embodiment of the gold ore processing method according to the invention in which the etching is carried out in a driving container also comprising active carbons; FIG. 4 is a schematic flow chart of a fourth embodiment of the gold ore processing method according to the invention in which the etching is carried out in an etching container also comprising ion exchange resins; FIG. 5 is a schematic flow diagram of a fifth embodiment of the gold ore processing method according to the invention in which the etching is carried out by percolation in an attacking container forming a sealed area and in which the means for reception include activated carbons; FIG. 6 is a schematic flow diagram of a sixth embodiment of the gold ore processing method according to the invention in which the etching is carried out by percolation in an etching container forming a sealed area and in which the means for reception include ion exchange resins.

In the first place, it should be noted that, by convention, the term "container" refers to any element that can contain, under appropriate conditioning conditions for the treatment of gold ores, a product in liquid, fluid or solid form, and this regardless of the amount of product that can be stored. In this respect, a container may correspond to a tank made of metal or plastic, a pipe of small diameter and of sufficient length, a sealed natural basin that can receive large amounts of a liquid, a sealed area formed from a plastic material for example and for performing a leaching operation, etc.

Figure 1 is now described in detail.

According to this embodiment, the treatment method according to the invention consists first of all in having an ore 12 in a form similar to or similar to that of an ore coming directly from an extraction mine or, conversely in a processed form (by grinding or any other suitable processing operation).

In its natural state, gold ore 12 always has a liquid phase 12L and a solid phase; the proportions of the liquid phase 12L and the solid phase of the gold ore 12 may vary according to its nature. There are in fact in the natural state gold-bearing ores with more or less water.

This ore 12 is placed in a container 12c before its treatment. 2966470 s

According to the invention, the ore 12 is prepared, during a so-called ore preparation step 12, to form a prepared ore 14 also comprising a solid phase 14s and a liquid phase 14L in proportions, this time predetermined. More precisely, during this ore preparation step 12, part of the liquid phase 12L of the ore 12 is extracted so that the prepared ore 14 contains a previously determined proportion of the liquid phase 14L.

The percentage of 14L liquid phase of prepared ore 14 used in the following process then corresponds to a 14L liquid phase introduction rate of prepared ore 14 to be mixed with the etching solution 16. 14L liquid phase introduction of prepared ore 14 is determined so as to obtain good etching kinetics and therefore a good yield for an optimized operating cost.

It has been measured that this result is obtained when the feed rate is such that the 14L liquid phase of prepared ore 14 represents from 3 to 20% of the total weight of the prepared ore 14.

It should be noted that the ore preparation step 12 of extracting a portion of the liquid phase 12L of the ore 12 can be carried out according to different procedures. In particular, this operation can be carried out by introducing the ore 12 into a filter press and applying a pressure high enough to extract a portion of its liquid phase 12L. According to a variant, it is also possible to carry out this ore preparation operation 12 by ensuring the evaporation, by natural or artificial means, of a part of the liquid phase 12L of the ore 12.

These examples of embodiments are cited only by way of example and not limitation.

It should be noted, by way of example, that this ore preparation operation 12 can be carried out via a module chosen from a drying tube, a wringer, a centrifuge, a press belt filter and a horizontal band filter. At the end of this preparation step, the ore 12 is therefore transformed into prepared ore 14 and optionally placed in a specific container 14c.

At the same time, the process according to the invention consists in disposing, in a storage container 16 Cs, corresponding for example to a tank or a sealed natural basin, an attack solution 16 composed of sodium thiosulphate and cupriethylenediamine.

In one embodiment, the etching solution 16 used to treat an oxidized gold ore comprises 19 kg sodium thiosulfate and 9.5 liters cupriethylenediamine, which provides good etching kinetics. However, according to other variants, the etching solution 16 may also contain sodium thiosulfate accompanied by copper sulfate and ethylenediamine or other amines such as glycine (C2HSO2N) which has the advantage of be one of the simplest amino acids, ethanol amine (C2H7N0), diethylene triamine (C4H13N3) or any other type of polyethylene amine. Cupriethylenediamine (C2H10CuN2O2) has the advantage of not being flammable. In addition, this etching solution 16 may also comprise, instead of copper sulphate alone, a mixture of copper sulphate and nickel sulphate, which advantageously reduces the consumption of sodium thiosulfate during the attack. .

It should be pointed out that the etching solution 16 according to the invention has the great advantage of not containing cyanide and therefore of greatly limiting the risks which could be caused by the accidental spill of the storage tank 16cS containing the solution. attack 16 in the environment.

The prepared ore 14 and the etching solution 16 are then poured into an etching container 18c to form an ore pulp 18. The mixture of this prepared ore 14 and the etching solution 16 then generates a phase. an attack during which the gold contained in the prepared ore 14 is solubilized by the action of the etching solution 16 on the prepared ore 14.

It follows from this etching step that the ore pulp 18 contained in the etching container 18c is converted into an etched pulp 20 - also contained in the etching container 18c - having a solid phase 20s and a liquid phase. also called 20L rich solution in which solubilized gold is found.

Considering the quantities of prepared ore 14 generally subjected to this attack phase, the etching container 18c is exposed to industrial risks. It may happen that this container 18c containing the prepared ore 14 and the attack solution 16 leaks or overflows.

While this situation was very problematic in the implementation of the prior art processes using high cyanide attack solutions, in the process according to the invention the problems generated by this type of leakage or accidental spill are very difficult. much less important since the reactants constituting the attack solution 16 are far less dangerous for the environment.

It should further be emphasized that, in an advantageous embodiment, this etching step may be preceded by a free gold recovery step - i.e. contained in the ore pulp 18 under metal form - gravimetrically. To do this, it is for example possible to pass the ground ore pulp 18 in centrifuges and recover free gold due to its high density. This prior recovery step has, on the one hand, the advantage of easily recovering this free gold and, on the other hand, that of extracting the coarse free gold from the ore pulp 18 which, in any case way, would be difficult to solubilize.5

After this etching phase has been carried out, the method according to the invention comprises a separation operation of the solid 20s and liquid 20L phases of the etched pulp 20 for rejecting the solid phase 20s and to keep only the liquid phase 20L corresponding to the rich solution 20L in which the solubilized gold is.

Preferably, the solid phase 20s of the etched pulp 20 is obtained during this step and washed before discharge, which limits the risk to the environment.

According to one embodiment, this recovery step of the rich solution 20L can for example be carried out using a horizontal vacuum band filter; this makes it possible to wash the solid phase 20s of the impregnated pulp 20 by piston effect; i.e., a wash with a quantity of water corresponding to the amount of rich solution 20L contained in the filter cake.

Advantageously, the recovered 20L rich solution is then enriched with a very low dose of cyanide 22 so that the solubilized gold changes from the aurothiosulfate form to the aurocyanide form.

According to one embodiment, it is for example introduced into the rich solution a quantity of cyanide 22 ranging from 5 to 20 mg per liter of rich solution 20L.

This operation is called transformation into aurocyanure.

The addition of cyanide 22 in a very small amount in the rich solution 20L is less dangerous than in the attack phase since, on the one hand, the rich solution 20L is not mixed with the solid phase and, on the other hand, on the other hand, the amount of cyanide used is small enough not to present a proven risk for the environment; in particular because cyanide is consumed almost entirely during the transition from the aurothiosulphate state to the aurocyanic state.

At the end of the gold transformation step in the form of aurocyanide, the solubilized gold is recovered in the rich solution 20L by the use of activated carbons 20cA. More particularly, the rich solution 20L is poured onto columnar activated carbons 20cA which collect the solubilized gold. At the end of this passage of the 20L rich solution on the activated carbon 20cA they are set aside and then treated to allow the recovery of gold 10 and there remains only a poor solution 28 lacking gold 10.

It should be noted that during the etching phase gold is not the only metal contained in the prepared ore 14 to have solubilized. On the contrary, this prepared ore 14 may contain other metals such as zinc, iron, copper, chromium etc. more or less solubilized by the attack solution 16. It was found, therefore, that the 100% recycling of the poor solution 28 resulting from this attack phase leads to a significant accumulation of the residual metals in the poor solution 28, which inevitably results in a degradation of the efficiency of the attack phase.

As a result, it is realized as part of the treatment method according to the invention a regular purge of the poor solution 28 allowing, on the one hand, to exclude a part to exclude 28EX from the poor solution 28 and, of on the other hand, to keep a part to keep 28co of the poor solution 28 in proportions ensuring good kinetics of attack while providing an optimized production cost.

More particularly, and according to the invention, the proportions of the part to be excluded 28EX from the poor solution 28 define a purge rate equivalent to the rate of introduction of the liquid phase 14L prepared ore 14 to mix with the etching solution 16.

Performing such a purge makes it possible to limit the accumulation of residual metals in the lean solution and to prevent the amount of liquid phase used in the circuit from increasing irremediably during the treatment cycles.

The part to be excluded 28EX from the poor solution 28 is then poured into a neutralization container 30c corresponding, for example, to a tank in order to neutralize the detrimental effects of the 28EX part of the poor solution 28 on the environment. . To do this, it is possible to use neutralization agents 30A capable of acting on the exclude 28EX part of the poor solution 28 in order to limit its effects on the environment. It is also possible alternatively or simultaneously to perform an electrolysis of this exclude portion 28EX of the poor solution 28 so as to recover the copper contained in this solution. In addition, it is possible to neutralize this part exclude 28EX from the poor solution 28 by evaporation, total or partial and natural or artificial, of its liquid phase and recovery of copper and neutralization of the residual part.

On the other hand, the 28cc holding part of the poor solution 28 is poured into the 16cS storage container of the etching solution 16 for reuse in a new gold ore processing cycle.

In one embodiment, the storage container 16cS of the etching solution 16 may also be connected to a preparation container 16cp of a concentrated etch solution 16 'so as to modify the solution concentration as required. attack 16 used in the attack container 18c.

The embodiment of Figure 2 is now described in detail. The embodiment illustrated in FIG. 2 is similar to the one just described and which is illustrated in FIG. 1. However, it differs in that the receiving means 26 used are not composed of 20cA activated carbons but 26RE ion exchange resins.

Alternatively, these receiving means 26 could alternatively be replaced by metal powders to capture the solubilized gold.

Therefore, unlike the previous embodiment, the rich solution 20L obtained at the end of the attack phase is not mixed with a very low dose of cyanide 22 and, thus, the gold 10 solubilized in this rich solution 20L is stored as aurothiosulphate.

Such an embodiment is advantageous for several reasons. First, the 26RE ion exchange resins can be used for the treatment of ore containing native carbon while 26cA activated carbons can not. In addition, the use of such ion exchange resins 26RE makes it possible to dispense with the use of cyanide 22 so that the risks for the environment are even more limited.

In the same way as above, the 20L-rich solution containing the solubilized gold is poured onto the 26RE ion exchange resins so that the latter capture the solubilized gold. At the end of this operation, the ion exchange resins 26RE are treated in order to allow the recovery of gold 10. For example, in one embodiment it is possible to burn these ion exchange resins 26RE in order to conserve that gold 10.

The other steps of the processing method illustrated in FIG. 2 are in all respects similar to those carried out as part of the treatment method illustrated in FIG.

The embodiment of Figure 3 is now described in detail.

The treatment process illustrated in FIG. 3 consists, as before, in initially disposing of a ore 12 possibly converted by grinding or any other suitable transformation operation.

This ore 12, containing a liquid phase 12L and a solid phase, is placed in a container 12c before its treatment.

According to the invention, the ore 12 is prepared, during a so-called ore preparation step 12, to form a prepared ore 14 also comprising a solid phase 14s and a liquid phase 14L in proportions, this time predetermined. More specifically, during this ore preparation step 12, a part of the liquid phase 12L of the ore 12 is extracted so that the prepared ore 14 contains a previously determined proportion of the liquid phase 14L.

The percentage of liquid phase 14L of prepared ore 14 used in the rest of the treatment process then corresponds to a liquid phase introduction rate 14L of prepared ore 14 intended to be mixed with the etching solution 16. 14L liquid phase introduction of prepared ore 14 is determined so as to obtain good kinetics of attack and therefore a good yield for an optimized operating cost. The liquid phase 14L of prepared ore 14 can thus represent from 3 to 20% of the total weight of the ore prepared 14.

As indicated above, this ore preparation step 12 can be carried out according to different procedures. In particular, this operation can be performed by introducing the ore 12 into a filter press and applying a sufficiently high pressure to extract a portion of its liquid phase 12L. According to a variant, it is also possible to carry out this ore preparation operation 12 by ensuring the evaporation, by natural or artificial means, of a part of the liquid phase 12L of the ore 12.

These examples of embodiments are cited only by way of example and not limitation.

In parallel, the method of FIG. 3 consists in disposing, in a storage container 16 Cs corresponding, for example, to a tank or a sealed natural basin, an attack solution 16 composed of sodium thiosulphate and cupriethylenediamine.

However, according to other variants, the etching solution 16 may also contain sodium thiosulfate accompanied by copper sulphate and any suitable amine such as glycine (C2HSO2N) which has the advantage of being one of the amino acids the simpler, ethanol amine (C2H7N0), diethylene triamine (C4H13N3) or any other type of polyethylene amine.

Cupriethylenediamine (C2H10CuN2O2) has the advantage of not being flammable.

In addition, this etching solution 16 may also comprise, instead of copper sulphate alone, a mixture of copper sulphate and nickel sulphate, which advantageously reduces the consumption of sodium thiosulfate during the attack. .

According to this embodiment, the prepared ore 14 and the etching solution 16 are both poured into the etching container 18c with a low dose of cyanide 22 to form the ore pulp 18. Also added in the pulp are ore 18 the receiving means 26 composed of activated carbons 26cA.

The mixture of this prepared ore 14 with the etching solution 16 then generates an etching phase during which the gold contained in the prepared ore 14 is solubilized by the action of the etching solution 16 on 14. In parallel, the presence of cyanide 22 in the ore pulp 18 makes it possible to pass the solubilized gold from the aurothiosulphate form to the aurocyanic form.

The transformation operation in aurocyanure is therefore carried out directly in the attack container 18c corresponding for example to a watertight basin.

On the other hand, since the etching container 18c also contains the active carbons 26cA, the solubilized gold passed in the form of aurocyanide is directly captured by attachment to these activated carbons 26cA. The attacked pulp 20 is therefore directly free of the solubilized gold which is fixed on the active carbons 26cA.

It is therefore possible, after the attack phase, to put the active carbons 26cA aside and treat them to allow the recovery of gold 10. It then remains in the attack solution 20 that a solid phase 20s and a liquid phase 20L devoid of gold corresponding to a poor solution 28 which has the interesting feature of practically no longer contain cyanide.

It should be noted that - as before - it is possible, according to an advantageous embodiment, that this attack phase can be preceded by a free gold recovery step - that is to say, contained in FIG. ore pulp 18 in the form of metal - by gravimetry. To do this, it is for example possible to pass the ground ore pulp 18 in centrifuges and recover free gold due to its high density. This prior recovery step has, on the one hand, the advantage of easily recovering this free gold and, on the other hand, that of extracting the coarse free gold from the ore pulp 18 which, in any case , would be difficult to solubilize.

The gold-free etched pulp 10 is then subjected to a separation operation of these solid 20s and liquid 20L phases. To do this, it is for example possible to use a vacuum band horizontal filter so as to set aside the solid phase 20s of the etched pulp 20 and wash it by piston effect. At the end of this separation operation, the treatment method according to FIG. 3 provides for keeping only the liquid phase 20L of the gold-free etching solution 10 corresponding to a poor solution 28.

In the same way as above, the prepared ore 14 used in the context of this embodiment does not contain only gold but, on the other hand, contains other metals that can be solubilized during the phase of the process. attack.

As a result, it is also realized, as part of the treatment process illustrated in FIG. 3, a regular purge of the poor solution 28 making it possible, on the one hand, to exclude a part to exclude 28EX from the poor solution 28 and, on the other hand, to retain a portion to maintain 28co of the poor solution 28 in proportions ensuring a good attack kinetics while maintaining an optimized production cost and efficiency.

More particularly, and according to the invention, the proportions of the part to be excluded 28EX from the poor solution 28 define a purge rate equivalent to the rate of introduction of the liquid phase 14L prepared ore 14 to mix with the etching solution 16.

Performing such a purge makes it possible to limit the accumulation of residual metals in the lean solution and to prevent the amount of liquid phase used in the circuit from increasing irremediably during the treatment cycles.

The part to be excluded 28EX from the poor solution 28 is then poured into a neutralization container 30c corresponding, for example, to a tank in order to neutralize the harmful effects of the part to exclude 28EX from the poor solution 28 on the environment. To do this, it is possible to use neutralization agents 30A capable of acting on the exclude 28EX part of the poor solution 28 in order to limit its effects on the environment. It is also possible alternatively or simultaneously to perform an electrolysis of this exclude portion 28EX of the poor solution 28 so as to recover the copper contained in this solution. In addition, it is possible to neutralize this part exclude 28EX from the poor solution 28 by evaporation, total or partial and natural or artificial, of its liquid phase and recovery of copper and neutralization of the residual part.

Furthermore, according to this embodiment, the portion 28co to retain the poor solution 28 is poured into the storage container 16cS of the etching solution 16 to be reused in a new gold ore processing cycle 12.

In one embodiment, the storage container 16cS of the etching solution 16 may also be connected to a preparation container 16cp of a concentrated etching solution 16 'so as to modify the concentration of the etching solution as required. 16 used in the attack container 18c. The embodiment illustrated in Figure 4 is now described in detail.

The embodiment method illustrated in FIG. 4 is similar to that just described with reference to FIG. 3. It is simply distinguished by the fact that the receiving means 26 used are not composed of activated carbons. 20cA but 26RE ion exchange resins.

Therefore, contrary to the previous embodiment, the prepared ore 14 and the etching solution 16 are mixed in the etching container 18c with ion exchange resins 26RE only - and thus without a dose of cyanide 22 - to form the Ore pulp 18. The mixing of this prepared ore 14 with the etching solution 16 then generates an etching phase during which the gold contained in the prepared ore 14 is solubilized by the action of the etching solution 16 on the prepared ore 14. In parallel, since the etching container 18C also contains the ion exchange resins 26RE, the solubilized gold is directly captured on these ion exchange resins 26RE.

It is therefore possible, after the attack phase, to treat the ion exchange resins 26RE to recover the gold 10.

The other steps of the treatment method illustrated in FIG. 4 are in all respects similar to those carried out as part of the treatment method illustrated in FIG.

The embodiment of FIG. 5 is now described.

The treatment process illustrated in FIG. 5 consists, as the previous embodiments, in having an ore 12 coming directly from an extraction mine or having undergone appropriate transformations (by grinding, crushing or any other transformation operation appropriate).

This ore 12 comprising a solid phase and a liquid phase 12L is placed in or on a container 12c before treatment.

Ore 12 is previously prepared, during the ore preparation step 12, to form a prepared ore 14 having a solid phase 14s and a liquid phase 14L in predetermined proportions. More specifically, during this ore preparation step 12, a part of the liquid phase 12L of the ore 12 is extracted so that the prepared ore 14 contains a previously determined proportion of the liquid phase 14L.

The percentage of liquid phase 14L of prepared ore 14 used in the following treatment process then corresponds to a liquid phase introduction rate 14L prepared ore 14 to be mixed with the attack solution 16, such as the process has good kinetics of attack and therefore a good performance for an optimized operating cost.

This result is obtained when the feed rate is such that the liquid phase 14L of prepared ore 14 represents from 3 to 20% of the total weight of the prepared ore 14.

At the end of this preparation step, the ore 12 is therefore transformed into prepared ore 14 and optionally placed in or on a specific container 14c.

In parallel, the method of FIG. 5 consists in disposing, in a storage container 16 Cs, for example corresponding to a tank, an attack solution 16 composed, by way of non-limiting example, of sodium thiosulfate and cupriethylenediamine. In addition, this etching solution 16 may also comprise sodium thiosulfate, ethylenediamine and copper sulphate, or, instead of copper sulphate alone, a mixture of copper sulphate and nickel sulphate. which advantageously reduces the consumption of sodium thiosulfate during the attack.

It should be pointed out that the etching solution 16 according to the invention has the great advantage of not containing cyanide and therefore of greatly limiting the risks that could be caused by the accidental spillage of the storage tank 16cS containing the solution of 16 attack in the environment.

In contrast to the embodiment of Figures 1, 2, 3 and 4, as part of the treatment process according to Figure 5, the prepared ore 14 and the etching solution 16 are not mixed in a tank.

In contrast, according to this embodiment the prepared ore 14 - which has been previously crushed or crushed - is placed on an attacking container 18c in the form of a sealed area. This attack container 18c is, for example, made of a material of plastic material such as a flexible membrane of PVC or polyethylene. This attack container 18c is also slightly inclined. The prepared ore 14 provided on this sealed-area etching container 18c is then sprayed with the etching solution 16 according to a method well known to those skilled in the art known as heap leaching. In this way, the etching solution 16 passes through the prepared ore 14 crushed and arranged on the sealed area and carries out the attack of this prepared ore 14. During this attack, the gold 10 contained in the ore prepared 14 is solubilized which allows to collect, by percolation and thanks to the inclination of the base of the attack container 18c, a rich solution 20L while the solid phase 20s remained on the attack container 18c can be recovered, washed and neutralized before rejection. It should be noted that, in accordance with the foregoing embodiments, this etching step may be preceded by a free gold recovery step - i.e., contained in ore pulp 18 in the form of metal - by gravimetry. To do this, it is for example possible to pass the prepared ore 14 in centrifuges and recover the free gold due to its high density. This prior recovery step has the particular advantage of easily recovering this free gold.

After this leaching attack phase has been performed, the 20L rich solution is enriched with a very low dose of cyanide 22 so that the solubilized gold changes from the aurothiosulfate form to the aurocyanic form. According to one embodiment, for example, a quantity of cyanide 22 ranging from 5 to 20 mg per liter of rich solution 20L is introduced into the rich solution 20L. This addition of cyanide 22 in a very small quantity is less dangerous than in the attack phase since, on the one hand, the rich solution 20L is generally not found in a natural basin and, on the other hand, the quantities of cyanide 22 used are low enough not to present a proven risk to the environment.

At the end of the gold transformation step in the form of aurocyanide, the solubilized gold is recovered in the rich solution 20L by the use of activated carbons 20cA. More particularly, the rich solution 20L is poured onto columnar activated carbons 20cA which collect the solubilized gold.

At the end of this passage of the 20L rich solution on the activated carbon 20cA they are set aside and then treated to allow the recovery of gold 10 and there remains only a poor solution 28 lacking gold 10.

As before, gold is not the only metal contained in prepared ore 14 to be solubilized in the leaching attack phase. On the contrary, this prepared ore 14 may contain other metals such as zinc, iron, copper, chromium etc. more or less solubilized by the attack solution 16. It was found, therefore, that the 100% recycling of the poor solution 28 resulting from this attack phase leads to a significant accumulation of the residual metals in the poor solution 28, which inevitably results in a degradation of the efficiency of the attack phase.

As a result, it is realized as part of the treatment method according to the invention a regular purge of the poor solution 28 allowing, on the one hand, to exclude a part to exclude 28EX from the poor solution 28 and, of on the other hand, to keep a portion to keep 28co of the poor solution 28 in proportions ensuring good kinetics of attack while maintaining an optimized production cost.

More particularly, and according to the invention, the proportions of the part to be excluded 28EX from the poor solution 28 define a purge rate equivalent to the rate of introduction of the liquid phase 14L prepared ore 14 to mix with the etching solution 16.

Performing such a purge makes it possible to limit the accumulation of residual metals in the lean solution and to prevent the amount of liquid phase used in the circuit from increasing irremediably during the treatment cycles.

The part to be excluded 28EX from the poor solution 28 is then poured into a neutralization container 30c corresponding, for example, to a tank in order to neutralize the harmful effects of the part to exclude 28EX from the poor solution 28 on the environment. To do this, it is possible to use neutralization agents 30A capable of acting on the exclude 28EX part of the poor solution 28 in order to limit its effects on the environment. It is also possible alternatively or simultaneously to perform an electrolysis of this exclude portion 28EX of the poor solution 28 so as to recover the copper contained in this solution. In addition, it is possible to neutralize this part exclude 28EX from the poor solution 28 by evaporation, total or partial and natural or artificial, of its liquid phase and recovery of copper and neutralization of the residual part. On the other hand, the portion to keep 28co of the poor solution 28 is poured into the storage container 16cS of the etching solution 16 in order to be reused during a new gold ore treatment cycle 12. According to one embodiment, the storage container 16cS of the etching solution 16 can also be connected to a preparation container 16cp of a concentrated etching solution 16 'so as to modify the concentration of etching solution as required. 16 used in the attack container 18c. The embodiment shown in Figure 6 now described in detail.

This embodiment is similar to that described in support of FIG. 5. It differs only in that the rich solution 20L obtained after the leaching attack phase is not enriched with a low dose. of cyanide 22.

In contrast, the 20L rich solution is directly contacted with 26RE ion exchange resins or metal particles to capture solubilized gold in this 20L rich solution.

The other steps of this embodiment of the process according to the invention are in all respects similar to those of the process of FIG. 5.

The invention is not limited to the embodiments described and shown above, but on the contrary extends to any other development likely to be performed by the skilled person. 30

Claims (10)

REVENDICATIONS1. A method of processing gold ore for extracting gold (10) contained in an ore (12), comprising a plurality of steps of dynamically and cyclically providing: ore (12) having an ore a liquid phase (12L) and a solid phase and forming, from the ore (12), a prepared ore (14); have an etching solution (16) comprising sodium thiosulfate and cupriethylenediamine or sodium thiosulfate, copper and / or nickel sulphate and an amine: mixing the prepared ore (14) with the solution etching device (16) so that, during an attack phase, this etching solution (16) solubilizes the gold (10) contained in this prepared ore (14); sensing solubilized gold (10) during the etching phase through receiving means (26) and forming a gold-free lean solution (10) (10); characterized in that forming said prepared ore (14) comprises removing a portion of the liquid phase (12L) from said ore (12) so that the prepared ore (14) has a liquid phase (14L) and a solid phase ( 14s) in predetermined proportions defining a liquid phase introduction rate (14L) of prepared ore (14) to be mixed with the etching solution (16); in that the method comprises an additional step of, on the one hand, retaining a holding portion (28co) of the lean solution (28) and reusing the retention portion (28co) of the lean solution (28) to forming the etching solution (16) and, on the other hand, purging a portion to be excluded (28Ex) from the poor solution (28) to neutralization means (30) for neutralizing the adverse effects of the excluding (28Ex) from the poor solution (28) on the environment; and in that the portion to be excluded (28Ex) from the lean solution (28) is purged at a purge rate equivalent to the feed rate of the liquid phase (14L) of prepared ore (14) to be mixed with the solution of attack (16). A gold ore treating method according to claim 1, wherein forming the prepared ore (14) comprises removing a portion of the liquid phase (12L) from the ore (12) so as to obtain a feed rate of liquid phase (14L) of prepared ore (14) in the ore pulp (18) such that the liquid phase (14L) of prepared ore (14) represents from 3 to 20% of the total weight of said prepared ore (14). The gold ore processing method according to one of claims 1 or 2, wherein the solubilized gold-fixing means (26) comprise active carbons (26cA). A gold ore treating method according to claim 3, wherein a very small amount of cyanide (22) is used to pass solubilized gold (10) from the aurothiosulfate form to the aurocyanide form before that gold (10) is removed. ) solubilized is captured by activated carbons (26cA). A gold ore treating method according to claim 4, wherein: the prepared ore (14) and the etching solution (16) are mixed in an etching container (18c) to form an ore pulp (18). ); the ore pulp (18) is transformed, during the attack phase, into an attacked pulp (20) having a solid phase (20s) and a liquid phase (20L) also called rich solution (20L) in which is located solubilized gold (10); during a separation operation, the solid phase (20s) of the etched pulp (20) is separated from the rich solution (20L) so as to recover this rich solution (20L); during a conversion phase to aurocyanide, the very small amount of cyanide (22), for example ranging from 5 to 20 mg of cyanide (22) per liter of rich solution (20L), is introduced into this rich solution (20L). ) so that the gold (10) solubilized in said low cyanide rich solution (20L) changes from the aurothiosulfate form to the aurocyanide form; and during a gold recovery phase (10), the activated carbons (20cA) in columns are used to capture gold (10) solubilized in the form of aurocyanide. The gold ore treating method according to claim 4, wherein: the prepared ore (14) and the etching solution (16) are mixed with the activated carbons (26cA) and the very small amount of cyanide (22). in an attack container (18c) to form an ore pulp (18); the ore pulp (18) is transformed, during the attack phase, into an etched pulp (20) having a solid phase (20s) and a liquid phase (20L) in which the solubilized gold (10) is located passes from the form aurothiosulfate to the form aurocyanure; and during a gold recovery phase (10), activated carbons (20cA) are used to capture this solubilized gold (10). The gold ore processing method according to claim 6, wherein during a separation operation, the solid phase (20s) of the gold-depleted etched pulp (20) is isolated so as to recover the liquid phase ( 20L) of the attacked pulp (20) poor in gold corresponding to the poor solution (28). The gold ore treating method according to claim 4, wherein: the prepared ore (14) is placed on an etching container (18c) forming a sealed area and the etching solution (16) waters this prepared ore. (14); during the etching step, the etching solution (16) percolates the prepared ore (14) so as to obtain a rich solution (20L) in which the solubilized gold (10) is located; during a conversion phase to aurocyanide, the very small amount of cyanide (22), for example ranging from 5 to 20 mg of cyanide (22) per liter of rich solution (200, is introduced into this rich solution (20L) so that the gold (10) solubilized in said low cyanide rich solution (20L) changes from the aurothiosulfate form to the aurocyanure form, and during a gold recovery phase (10), the activated carbons ( 20cA) are used to capture gold (10) solubilized in the form of aurocyanide. The gold ore treating method according to claim 1 or 2, wherein the solubilized gold (10) fixing receiving means (26) comprise ion exchange resins (26RE) or metal powders. The gold ore treating method according to claim 9, wherein: the prepared ore (14) and the etching solution (16) are mixed in an etching container (18c) to form an ore pulp (18). ); the ore pulp (18) is transformed, during the attack phase, into an attacked pulp (20) having a solid phase (20s) and a liquid phase (20L) also called rich solution (20L) in which is located solubilized gold (10); in a separation operation, the solid phase (20s) of the etched pulp (20) is separated from the rich solution (20L) so as to recover this rich solution (20L); In a gold recovery phase (10), ion exchange resins (26RE) or metal powders are used to capture solubilized gold (10). The gold ore processing method according to claim 9, wherein: the prepared ore (14) and the etching solution (16) are mixed with the ion exchange resins (26RE) in a stripping container ( 18c) for forming an ore pulp (18); the ore pulp (18) is transformed, during the attack phase, into an etched pulp (20) having a solid phase (20s) and a liquid phase (20L) in which the solubilized gold (10) is located ; and in a gold recovery phase (10), the ion exchange resins (26RE) are used to capture this solubilized gold (10). The gold ore processing method according to claim 11, wherein: during a separation operation, the solid phase (20s) of the gold-depleted etched pulp (20) is isolated so as to recover the liquid phase. (20L) of the attacked pulp (20) poor in gold corresponding to the poor solution (28). The gold ore treating method according to claim 9, wherein: the prepared ore (14) is placed on an etching container (18c) forming a sealed area and the etching solution (16) waters the ore prepared (14); in the etching step, the etching solution (16) percolates the prepared ore (14) so as to obtain a rich solution (20L) in which the solubilized gold (10) is located; and in a gold recovery phase (10), ion exchange resins (26RE) or metal powders are used to capture solubilized gold (10). A gold ore processing method according to any one of claims 1 to 13, wherein the step of removing a portion of the liquid phase (12L) from the ore (12) is effected through a selected module among a drying tube, a wringer, a centrifuge, a press belt filter, a filter press, a horizontal band filter or a module with natural or forced evaporation. A gold ore processing method according to any one of claims 1 to 14, wherein the portion to be stored (28co) of the lean solution (22) is poured into a storage container (16cS) of the solution of attack (16). The gold ore processing method according to claim 15, wherein the storage container (16cS) of the etching solution (16) is connected to a preparation container (16cp) of a concentrated etching solution ( 16 '). A gold ore processing method according to any one of claims 1 to 16, wherein the etching container (18c) is connected to the preparation container (16cp) and fed with concentrated etching solution (16 '). ). 18. A gold ore processing method according to any one of claims 1 to 17, comprising a further step of electrolyzing the part (28Ex) to be excluded from the lean solution (28) so as to recover the copper in this part (28Ex) of the impoverished solution (22) and meet the environmental discharge standards for copper. 19. A gold ore processing method according to any one of claims 1 to 18, wherein the portion to be excluded (28Ex) from the lean solution (28) is neutralized by neutralizing agents (30a) to recover the copper and limit the effects of the part (28Ex) to be excluded from the poor solution (28) on the environment. 20. A gold ore processing method according to any one of claims 1 to 19, wherein the portion to be excluded (28Ex) from the lean solution (28) is neutralized by total or partial evaporation of its liquid phase and recovery copper and neutralization of the residual part. 21. A gold ore processing method according to any one of claims 1 to 20, wherein the etching solution (16) comprises an amine of the family of polyethylene amines. 22. A gold ore processing method according to any one of claims 1 to 21, wherein the etching solution (16) comprises a mixture of copper sulphate and nickel sulphate. 23. A system for extracting gold (10) contained in an ore (12) by the gold ore processing process, comprising: an ore feed container (12c) (12) having a liquid phase (12L) and a solid phase; preparation means capable of converting the ore (12) into prepared ore (14) having a liquid phase (14L) and a solid phase (14s); a storage container (16c) of an etching solution (16) comprising sodium thiosulfate and cupriethylenediamine or sodium thiosulfate, copper and / or nickel sulfate and an amine; an attack container (18c) connected to the prepared ore preparation means (14) and the storage container (16c) of the etching solution (16) so as to allow said prepared ore (14) to be mixed with this etching solution (16) and generating an etching step in which said etching solution (16) solubilizes the gold (10) contained in said prepared ore (14); receiving means (26) capable of picking up the solubilized gold (10) during the attacking phase via receiving means (26) and forming a gold-free lean solution (28) (10); ); characterized in that the means for preparing the prepared ore (14) are adapted to remove a portion of the liquid phase (12L) from the ore (12) so that the prepared ore (14) has a liquid phase (14L) and a solid phase (14s) in predetermined proportions defining a liquid phase introduction rate (14L) of prepared ore (14) to be mixed with the etching solution (16); in that the device further comprises purge means capable, on the one hand, of retaining a part to be kept (28co) of the poor solution (28) and reusing the part to be preserved (28co) of the poor solution (28); ) to form the etching solution (16) and, on the other hand, to purge a portion to be excluded (28Ex) from the poor solution (28) whose flow corresponds to an optimum yield of the etching kinetics and to an optimized operating cost, to neutralization means (30) for neutralizing the adverse effects of the part (28Ex) to be excluded from the poor solution (28) on the environment; and in that the purge means are capable of purging the part to be excluded (28Ex) from the lean solution (28) at a purge rate equivalent to the rate of introduction of the liquid phase (14L) of prepared ore (14). to be mixed with the etching solution (16).