A thiosulfate method for selective gold extraction

Abstract

The present invention discloses a thiosulfate method for selective gold extraction, comprising the following steps: adding gold ore and anion exchange resin to an aqueous solution of a leaching agent for stirring and leaching to obtain a slurry containing a gold-loaded resin; the leaching agent comprises thiosulfate, a copper salt, and aqueous ammonia; separating the gold-loaded resin from the slurry, desorbing the gold-loaded resin using a desorbent to obtain a gold-rich desorbent; and adding dithionite to the gold-rich desorbent for reduction to obtain an elemental gold product. The process of the present invention simultaneously achieves resin adsorption recovery during gold leaching and avoids co-adsorption of copper. Therefore, the gold-loaded resin can be enriched in one-stage desorption, significantly simplifying the gold extraction process. Furthermore, the process has a high gold leaching rate, a short leaching time, low reagent consumption, and low leaching cost. Furthermore, the resin does not need to be regenerated and can be directly recycled for gold leaching. The reduced barren liquid, supplemented with a small amount of desorbent, can be recycled for desorption of the gold-loaded resin, resulting in low recovery costs.

Description

Technical Field

[0001] The invention belongs to the field of hydrometallurgy, and in particular relates to a thiosulfate method selective gold extraction process. Background Art

[0002] Cyanide extraction has long been the mainstream gold extraction technology due to its simple process, low production costs, and high leaching rates. However, cyanide is highly toxic, and its use poses significant environmental risks. Therefore, the development of clean gold extraction technologies is crucial for the green and sustainable development of the gold industry. Currently, the most widely reported methods include the halogen method, thiourea method, thiocyanate method, lime sulfur method, glycine method, and thiosulfate method. In comparison, the thiosulfate method offers advantages such as a non-toxic and inexpensive leaching agent, gold extraction in an alkaline medium, and excellent leaching performance for ores difficult to treat with cyanide, such as those containing carbon and copper. Therefore, it is widely considered the most promising gold extraction process.

[0003] The thiosulfate gold leaching reaction is shown in formula (1-1). In the absence of a catalyst, the reaction rate is very slow. Usually, Cu(II) and NH3 are introduced to catalyze the leaching. Thus, the thiosulfate method forms a mixture of Cu(II), NH3, S2O3 2– However, S2O3 2– Unstable, the decomposition produces sulfur oxygen impurity ions such as S3O6 2– 、S4O6 2– The ions will be adsorbed or deposited on the gold surface, passivating the gold surface and hindering further dissolution of the gold, making it difficult for the gold leaching rate of this method to reach the level of the cyanide method. This is one of the key factors restricting the industrial application of the thiosulfate method.

[0004] 4Au + 8S2O3 2– + O2+ 2H2O → 4Au(S2O3)2 3– + 4OH – (1-1)

[0005] The complex process and high cost of gold recovery in the leachate are another problem that restricts the promotion and application of the thiosulfate method. Gold can be directly recovered from the solution by methods such as replacement and electrodeposition. However, since the copper concentration in the leachate can be as high as hundreds or even thousands of times that of gold, copper will be replaced / deposited together with gold during recovery, resulting in a large consumption of replacement metal and low current efficiency, resulting in high gold recovery costs, and low gold product grade, which still requires further separation and purification, and a long process flow. Therefore, it is necessary to separate copper and gold in advance and achieve gold enrichment. Methods such as adding activated carbon, resin, etc. to the leachate for adsorption are expected to achieve the above purpose. However, activated carbon has a low affinity for Au(S2O3)2 3– The affinity of the resin is very weak and cannot effectively adsorb gold. Strong alkaline anion resin can effectively adsorb gold. However, a large amount of copper (in the form of Cu(S2O3)35– The copper and gold are also adsorbed simultaneously. Therefore, a complex two-stage desorption process is required to separate and enrich the copper and gold by first desorbing the copper and then the gold. Furthermore, due to the high copper content, a large amount of desorbent is required, resulting in high desorption costs.

[0006] In summary, due to S2O3 2– The passivation effect of sulfur-oxygen impurity ions produced by oxidative decomposition on gold leaching results in a low gold leaching rate. In addition, the copper introduced during leaching seriously interferes with gold recovery, making the gold recovery process complicated and costly, making the promotion and application of thiosulfate method for gold extraction difficult. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to overcome the deficiencies and defects mentioned in the above background technology and provide a thiosulfate method selective gold extraction process with high gold leaching rate, short process and low cost.

[0008] In order to solve the above technical problems, the technical solution proposed by the present invention is:

[0009] A thiosulfate method for selective gold extraction comprises the following steps:

[0010] (1) Adding gold ore and anion exchange resin to an aqueous solution of a leaching agent, stirring and leaching at a pH of 9 to 10 to obtain a slurry containing a gold-loaded resin; the leaching agent comprises thiosulfate, copper salt, and ammonia water; the thiosulfate concentration is 0.05 to 0.1 mol / L, the copper salt concentration is 1.5 to 5 mmol / L, and the ammonia water concentration is 0.1 to 0.5 mol / L;

[0011] (2) separating the gold-loaded resin from the ore pulp, and desorbing the gold-loaded resin with a desorbent to obtain a gold-rich desorption solution; the desorbent is a mixed solution containing chloride salt and sulfite;

[0012] (3) Add dithionite to the gold-rich desorption solution for reduction to obtain elemental gold product.

[0013] As a further improvement, the thiosulfate in step (1) is one or more of sodium thiosulfate, ammonium thiosulfate and calcium thiosulfate.

[0014] As a further improvement, the copper salt in step (1) is copper sulfate.

[0015] As a further improvement, the anion exchange resin in step (1) is a strongly basic chloride-type anion exchange resin.

[0016] As a further improvement, the anion exchange resin concentration in step (1) is 5-20 kg / m 3 .

[0017] As a further improvement, the leaching conditions in step (1) are: temperature of 25-45°C, stirring rate of 400-800 r / min, and time of 4-12 h.

[0018] As a further improvement, the chloride salt in step (2) is sodium chloride, and the sulfite is sodium sulfite.

[0019] As a further improvement, the desorption conditions in step (2) are as follows: sodium chloride concentration is 0.5~1 mol / L, sodium sulfite concentration is 0.01~0.05 mol / L, desorbent dosage is 5~10 times of resin bed volume, and desorbent flow rate is 1~5 resin bed volumes / hour.

[0020] As a further improvement, the dithionite in step (3) is sodium dithionite.

[0021] As a further improvement, the reduction conditions in step (3) are as follows: the amount of sodium dithionite is 1.5 to 2 times the theoretical amount, and the reduction time is 5 to 20 min.

[0022] The purpose of the present invention is to eliminate S2O3 2– The sulfur-oxygen impurity ions produced by oxidative decomposition passivate gold leaching, thereby increasing the leaching rate. This also reduces the negative impact of high concentrations of impure copper on gold recovery, simplifying the recovery process and reducing recycling costs. By addressing these two major issues, the industrial application of the thiosulfate method, a green, non-cyanide gold extraction method, is being promoted.

[0023] The mechanism of the present invention is as follows:

[0024] The copper ammonia catalyzed thiosulfate leaching reaction of gold is shown in equations (1)-(2). Oxidant Cu(NH3)4 2+ Au loses electrons and is oxidized to Au + , Au + With S2O3 2– Coordination to generate Au(S2O3)2 3– , achieving gold leaching. At the same time, Cu(NH3)4 2+ The electrons lost by Au are reduced to Cu(S2O3)3 5– , which is oxidized to Cu(NH3)4 under the oxidation of dissolved oxygen 2+ (will not be adsorbed by anion exchange resin), achieving Cu(NH3)4 2+ During leaching, a strong alkaline chloride anion resin is added to absorb the leached gold (Au(S2O3)2 3– ) and copper in the slurry (Cu(S2O3)3 5– ) are shown in equations (3)-(4).2– S3O6 produced by oxidative decomposition 2− 、S4O6 2− The affinity with resin is significantly stronger than Cu(S2O3)3 5– But weaker than Au(S2O3)2 3− Therefore, the Cu(S2O3)3 adsorbed by the resin in the initial leaching 5– It is easy to be S3O6 2− 、S4O6 2− The gold-loaded resin is desorbed by a mixed solution of sodium chloride and sodium sulfite, and the reaction is shown in equation (7). SO3 2– First, with the adsorbed Au(S2O3)2 3– The reaction generates Cl with a higher affinity to the resin – Weak Au(S2O3)(SO3) 3– Then the complex ion is Cl – Replaced by Au(S2O3)(SO3) 3– Diffusion into the solution, to achieve the desorption of gold on the loaded resin. Sodium dithionite is used to reduce and recover the gold in the desorption solution. The reaction is shown in equation (8). Au(S2O3)(SO3) 3– The gold in the solution is reduced to elemental gold, S2O4 2- Oxidized to SO3 2– Among them, |-NR3 + Cl − The “|” in the column represents the main structure of the chloride-type anion resin, -NR3 + It is a quaternary ammonium group.

[0025]

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] (1) High gold leaching rate, short leaching time, low reagent consumption and low leaching cost. The dissolved gold can be immediately adsorbed by the resin, and the gold concentration in the slurry is extremely low, which improves the leaching kinetics of gold. At the same time, S2O3 2– The sulfur and oxygen impurity ions produced by oxidation and decomposition can also be immediately adsorbed by the resin, eliminating their passivation effect on gold leaching, greatly facilitating gold leaching. Due to the above two reasons, an ideal gold leaching rate can be achieved, and the leaching time is shortened, thereby significantly reducing reagent consumption and gold leaching costs.

[0028] (2) The gold-loaded resin desorption process is simple, requires less reagents, is highly efficient, and is low in cost. Compared to recovery methods such as replacement and electrodeposition, the gold leaching and gold resin adsorption recovery in the present invention are carried out simultaneously, eliminating the steps of solid-liquid separation of the ore pulp, solution clarification, and deoxidation, making the operation simple. Compared to traditional resin adsorption recovery, since the resin in the present invention does not adsorb copper, the gold-loaded resin can be enriched in one-stage desorption, and the desorbent dosage is low, so the desorption process is simple and the cost is low.

[0029] (3) The lean resin can be directly returned to the leaching stage without regeneration, which is simple to operate and low in cost. While gold is being desorbed from the resin, the counterions on the resin are converted into chloride ions (which will adsorb a small amount of sulfite), and the resin returns to its initial form (see equation (7)). That is, gold desorption and resin regeneration are completed simultaneously. Therefore, the lean resin can be directly returned to the leaching stage for gold extraction again without regeneration, eliminating the resin regeneration step, simplifying the gold extraction process, and effectively reducing the cost of gold extraction. Moreover, when the chloride ions and a small amount of sulfite ions adsorbed on the resin are returned to the leaching stage, they are easily absorbed by Au(S2O3)2 due to the resin's weak affinity for these two ions. 3− 、S3O6 2− 、S4O6 2− After replacement, it will not affect the resin adsorption effect, and a small amount of chloride ions and sulfite ions can also promote gold leaching.

[0030] (4) The reduction and recovery of gold in the desorption solution is effective, the cost is low, and the reduced barren solution is easy to recycle. The gold in the desorption solution is reduced using a strong reducing agent, sodium dithionite, which uses a small amount of reagent, has a short reduction time, a high gold recovery rate, and a low cost. After the gold in the desorption solution is reduced, the dithionite is oxidized to sulfite, which happens to be the main component of the desorbent. Therefore, this process not only does not introduce foreign impurity ions, but also can replenish the sulfite lost due to oxidation during the desorption process, which is conducive to the recycling of the desorption barren solution.

[0031] In summary, the process of the present invention simultaneously achieves resin adsorption and recovery during gold leaching and avoids co-adsorption of copper. Therefore, the gold-loaded resin can be enriched in gold with a single desorption step, significantly simplifying the gold extraction process. Furthermore, this process offers high gold leaching rates, short leaching times, minimal reagent consumption, and low leaching costs. Furthermore, the resin can be directly recycled for gold leaching without regeneration, and the reduced barren solution, supplemented with a small amount of desorbent, can be recycled for desorption of the gold-loaded resin, resulting in low recovery costs.

[0032] The present invention is essentially different from the cyanide gold extraction method in that resin is added during the leaching process, as detailed below:

[0033] The purpose of adding resin in the cyanide gold extraction process is as follows: (1) Compared with filtering the pulp and then adding resin to the leachate to absorb and recover gold, adding resin during the leaching process can achieve leaching and gold adsorption in one step, eliminating the need for solid-liquid separation of the pulp, washing, and solution clarification, thus simplifying the gold extraction process; (2) The cyanide leaching process is slow, usually requiring more than 24 hours, resulting in a long production cycle. Since the resin is added during leaching, the gold is effectively adsorbed by the resin immediately after it is dissolved, and the gold concentration in the pulp is extremely low, which improves the kinetic conditions of gold leaching, promotes the dissolution of gold, shortens the leaching time, and improves production efficiency.

[0034] In contrast, the starting point and ultimate purpose of adding resin to the leaching process in the present invention is not to omit conventional processes such as solid-liquid separation of slurry, washing and solution clarification, and to shorten the leaching time as in the cyanide method (the thiosulfate gold leaching speed itself is much faster than the cyanide method, usually only taking 8-12 hours), but to remove impurities, that is, to completely eliminate the adverse effects of impurity ions on gold leaching and recovery, improve gold extraction effect, reduce production costs, and solve the two major problems that restrict the industrial application of the thiosulfate method, thereby achieving its complete replacement for the cyanide method.

[0035] Specifically, the present invention analyzes the reasons why the gold leaching rate of the thiosulfate method is lower than that of the cyanide method and the ideas for solving this problem are detailed as follows: S2O3 2– It is a metastable substance. In Cu(NH3)4 2+ It is easy to decompose under the conditions of existence to produce S3O6 2− 、S4O6 2− As the leaching progresses, the sulfur and oxygen impurity ions gradually accumulate, and the passivation of the leached gold becomes more serious, resulting in the lack of gold dissolution in the later stage of leaching. Therefore, although the gold leaching rate of this method is faster, the gold leaching rate is difficult to catch up with the cyanide method. To solve this problem, the present invention creatively adopts the method of adding a strong alkaline anion exchange resin in the leaching process. 2− 、S4O6 2− At the moment when sulfur and oxygen impurity ions are generated, the resin has a very strong affinity for them. Therefore, the impurity ions are immediately adsorbed by the resin before they reach the gold surface, so they cannot passivate the gold surface, and the gold immersion rate is greatly improved.

[0036] Specifically, the present invention analyzes the reasons for the adverse effects of the catalyst copper introduced during the leaching process on gold recovery and the ideas for solving this problem are detailed as follows: The gold concentration in the thiosulfate leachate is usually only 1-10 mg / L, while the copper concentration can be as high as 100-2000 mg / L. For leachates with such low gold concentrations and impurity copper concentrations much higher than gold, it is obviously uneconomical to directly recover by electrodeposition / copper powder replacement. Separating gold and copper and enriching them before recovery is the only way, but activated carbon has a great effect on the recovery of Au(S2O3)23– It is not possible to adsorb and it is not feasible to use it to recover gold. When using resin adsorption, copper will be adsorbed together with gold. It is necessary to desorb copper first and then desorb gold in two stages to separate and enrich gold. Moreover, due to the high copper loading, the amount of desorbent is large and the desorption cost is high. In order to solve the above problems, it is necessary to avoid the co-adsorption of copper. To this end, the present invention adopts the method of adding resin during leaching, and the copper at the beginning of leaching is Cu(S2O3)3 5– is adsorbed by the resin and as the leaching proceeds, S2O3 2– Gradually decomposes and continuously produces S3O6 2 − 、S4O6 2− Plasma, the resin has a stronger affinity for these ions than Cu(S2O3)3 5– But weaker than Au(S2O3)2 3− Based on this property difference, the present invention cleverly utilizes S2O3 2– The decomposition products will absorb Cu(S2O3)3 on the resin 5– The gold-loaded resin obtained at the end of leaching contains almost no copper. Therefore, the gold-loaded resin can be separated and enriched in a simple desorption step, which significantly simplifies the recovery process. Moreover, since the copper desorption step is omitted, the desorption cost is greatly reduced.

[0037] In summary, the purpose of adding resin to the cyanide system is fundamentally different. The present invention solves the adverse effects of impurity ions on the leaching and recovery of gold by adding resin during the leaching process, thereby significantly improving the gold extraction effect, effectively simplifying the gold extraction process, and significantly reducing the gold extraction cost, producing very obvious results. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0039] Figure 1 This is a process flow chart of the selective gold extraction process using the thiosulfate method of the present invention. DETAILED DESCRIPTION

[0040] To facilitate understanding of the present invention, the present invention will be described in more comprehensive and detailed form below in conjunction with the accompanying drawings and preferred embodiments. However, the protection scope of the present invention is not limited to the following specific embodiments.

[0041] Unless otherwise defined, all technical terms used hereinafter have the same meanings as those generally understood by those skilled in the art. The technical terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention.

[0042] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods.

[0043] like Figure 1 As shown, the thiosulfate selective gold extraction process according to some specific embodiments of the present invention comprises the following steps:

[0044] (1) Add gold ore and anion exchange resin to an aqueous solution of a leaching agent and stir to leach to obtain a slurry containing gold-loaded resin. The leaching agent includes thiosulfate, copper salt and ammonia water.

[0045] In some embodiments, the thiosulfate is one or more of sodium thiosulfate, ammonium thiosulfate, and calcium thiosulfate. The copper salt can be copper sulfate, etc.

[0046] In some embodiments, the anion exchange resin is a strongly basic chloride-type anion exchange resin, such as 201×7 resin, Amberlite IRA-400 resin, and the like.

[0047] In some embodiments, the leaching conditions are: thiosulfate concentration is 0.05-0.1 mol / L (preferably 0.07-0.08 mol / L), copper salt concentration is 1.5-5 mmol / L (preferably 1.8-2.5 mmol / L, more preferably 2 mmol / L); ammonia concentration is 0.1-0.5 mol / L (preferably 0.2-0.3 mol / L); anion exchange resin concentration is 5-20 kg / m 3 The gold ore slurry concentration is 20-50wt%, the slurry pH is 9-10, the temperature is 25-45°C, and the leaching time is 4-12 hours. The slurry concentration is defined as the mass of gold ore added divided by the total mass of the leaching system × 100%.

[0048] The realization of the present invention depends on the production of sufficient S3O6 2− 、S4O6 2− , thereby Cu(S2O3)3 5– The higher the concentration of copper salt as oxidant, the greater the consumption of thiosulfate and the production of S3O6 2− 、S4O6 2− The more, the higher the concentration of ammonia water as a copper salt stabilizer, the more stable the copper salt, the lower the thiosulfate consumption, and the S3O6 produced. 2− 、S4O6 2−The less, the above pH also ensures the production of sufficient S3O6 2− 、S4O6 2− If the pH is lower or higher than the above range, it is difficult to produce enough S3O6 2− 、S4O6 2− In the above thiosulfate, ammonia and copper salt concentration range and pH, the initial adsorption of Cu(S2O3)3 by the resin 5– Basically, all of them are S3O6 generated in the system 2− 、S4O6 2− Replaced, the final copper (Cu(S2O3)3 5− ) is hardly adsorbed by the resin. Specifically, under the above copper salt, ammonia concentration and pH, the initial concentration of thiosulfate is 50-100 mmol / L, and the intermediate product S3O6 produced by its decomposition is 2− 、S4O6 2− The total concentration is about 15~30 mmol / L. The initial concentration of copper salt is 1.5~5 mmol / L, about 1 / 3 of which is Cu(S2O3)3 5− exists in the form of 0.5-1.7 mmol / L adsorbed by the resin, 15-30 mmol / L of S3O6 2− 、S4O6 2− Sufficient to absorb 0.5-1.7 mmol / L of Cu(S2O3)3 adsorbed by the resin 5− Replace them all.

[0049] In some embodiments, the stirring rate of the stirring leaching is 400-800 r / min, at which the Cu(S2O3)3 5– Cu(NH3)4 2+ Conversion, Cu(S2O3)3 in solution 5– The concentration decreases, further reducing the adsorption of copper.

[0050] (2) Separate the gold-loaded resin from the ore pulp and use a desorbent to desorb the gold-loaded resin to obtain a gold-rich desorption solution. The desorbent is a mixed solution containing chloride salt and sulfite.

[0051] In some embodiments, the chloride salt can be sodium chloride or the like, and the sulfite salt can be sodium sulfite or the like.

[0052] In some embodiments, the resin and the slurry are separated by a sieve. The gold-loaded resin desorption conditions are: sodium chloride concentration of 0.5-1 mol / L, sodium sulfite concentration of 0.01-0.05 mol / L, desorbent dosage of 5-10 times the resin bed volume, and desorbent flow rate of 1-5 resin bed volumes / hour.

[0053] Since the gold-loaded resin obtained at the end of leaching contains almost no copper (mainly (|-NR3)3Au(S2O3)2 3– 、(|-NR3)2 + S3O6 2− 、(|-NR3)2 + S4O6 2− ), so the gold-rich desorption solution is basically gold (Au(S2O3)(SO3) 3– ).

[0054] The lean resin after desorption can be directly returned to leaching without regeneration.

[0055] The separated slurry is filtered to obtain leaching residue and leaching liquid, and the leaching liquid can be returned to the gold leaching in step (1).

[0056] (3) Add dithionite to the gold-rich desorption solution for reduction to obtain elemental gold product.

[0057] In some embodiments, the dithionite can be sodium dithionite or the like.

[0058] In some embodiments, the conditions for gold recovery by reduction are: the amount of sodium dithionite used is 1.5 to 2 times the theoretical amount, and the reduction time is 5 to 20 minutes.

[0059] The reduced barren liquid after reduction can be supplemented with a small amount of desorbent and recycled for desorption of the gold-loaded resin.

[0060] The chemical composition of a gold-containing oxide ore is shown in Table 1. The gold leaching experiments in the following examples and comparative examples were all conducted using this gold ore.

[0061] Table 1 Chemical element analysis of gold-bearing oxide ore

[0062]

[0063] Note: The unit of Au is g / t, and the units of other elements are wt%.

[0064] Comparative Example 1

[0065] First, water was added to the reactor, followed by the leaching agents (sodium thiosulfate, copper sulfate, and aqueous ammonia). Finally, gold ore (81.5% of the ground ore was minus 200 mesh) was added. The slurry pH was adjusted to the set value using sodium hydroxide and sulfuric acid, and then stirred for leaching at a stirring rate of 500 r / min. The specific leaching conditions were: sodium thiosulfate concentration of 0.075 mol / L, copper sulfate concentration of 2 mmol / L, ammonia concentration of 0.3 mol / L, slurry concentration of 33%, temperature of 25°C, slurry pH of 10, and leaching time of 12 hours. The gold leaching yield and sodium thiosulfate consumption at different leaching times are shown in Table 2.

[0066] As shown in Table 2, after leaching for 1 h, the gold leaching rate was only 34.5%, and the sodium thiosulfate consumption was 12.3 kg / t. -矿 As the leaching time increases, the gold content gradually increases. After leaching for 4 hours, the gold content reaches 76.2%, and the sodium thiosulfate consumption increases to 20.3 kg / t. -矿 When the leaching time continues to increase, the gold leaching rate basically stops increasing, that is, the dissolution of gold is hindered, while the consumption of sodium thiosulfate continues to increase. This is because the S3O6 produced by the consumption of sodium thiosulfate 2− 、S4O6 2− The gold surface is passivated, making it difficult for the gold to dissolve further.

[0067] Table 2 Gold leaching rate and sodium thiosulfate consumption at different leaching times

[0068]

[0069] The slurry was filtered to obtain leachate and leach residue. Amberlite IRA-400 resin was added to the leachate for adsorption at a resin concentration of 10 kg / m 3 The changes in the concentrations of gold and copper in the leachate and their adsorption rates over time are shown in Table 3.

[0070] Table 3 Changes in gold and copper concentrations and adsorption rates in the leachate over time

[0071]

[0072] As shown in Table 3, when no adsorption was performed, the gold and copper concentrations in the leachate were 0.96 mg / L and 63.5 mg / L, respectively. The copper concentration was lower than the initial value of 127 mg / L because part of the copper precipitated into the slag during the leaching process. After 10 minutes of adsorption, the gold and copper concentrations dropped to 0.62 mg / L and 52.2 mg / L, respectively, with adsorption rates of 35.4% and 17.8%, respectively. As the adsorption time increased, the gold and copper concentrations gradually decreased. After 120 minutes of adsorption, the gold and copper adsorption rates reached 88.5% and 39.2%, respectively. The main reason for the low copper adsorption rate is that a considerable portion of the copper in the leachate is in the form of Cu(NH3)4 2+ It exists in the form of cations and will not be adsorbed by strong alkaline anion exchange resins. It only exists in the form of Cu(S2O3)3 5– Only copper in the form of copper can be adsorbed by the strong alkaline anion exchange resin.

[0073] The gold-loaded resin obtained after 120 minutes of adsorption in Table 3 was loaded onto a column and subjected to a two-stage desorption process to separate and enrich copper from gold. First, copper was desorbed using 1 M NH₃•H₂O + 0.75 M (NH₄)₂SO₄, followed by gold desorption using 1 M NaCl + 0.05 M Na₂SO₃. The desorbent dosage for both reactions was 10 resin bed volumes, and the desorbent flow rate was 2 resin bed volumes / hour. No gold was lost during the copper desorption process. The desorption rates of copper and gold as a function of desorbent dosage are shown in Table 4.

[0074] Table 4 Changes of copper and gold desorption rates with desorbent dosage

[0075]

[0076] As shown in Table 4, when the desorbent dosage was 1 resin bed volume, the copper desorption rate was only 5.2%. As the desorbent dosage increased, the copper desorption rate gradually increased. When the desorbent dosage was 10 resin bed volumes, the copper desorption rate reached 92.5%, with a small amount of copper remaining undesorbed. When the desorbent dosage was 1 resin bed volume, the gold desorption rate was only 11.6%. As the desorbent dosage increased, the gold desorption rate gradually increased. When the desorbent dosage was 10 resin bed volumes, the gold desorption rate reached 96.7%, but a small amount of gold still remained undesorbed, indicating the need to increase the desorbent dosage.

[0077] Example 1

[0078] First, water was added to the reactor, followed by the leaching agents (sodium thiosulfate, copper sulfate, and ammonia). Finally, gold ore (grinded particle size -200 mesh, accounting for 81.5%) and resin (Amberlite IRA-400) were added. The slurry pH was then adjusted to the set value using sodium hydroxide and sulfuric acid before stirring and leaching (at a stirring rate of 500 r / min). The specific leaching conditions were: sodium thiosulfate concentration of 0.075 mol / L, copper sulfate concentration of 2 mmol / L, ammonia concentration of 0.3 mol / L, slurry concentration of 33%, and resin concentration of 10 kg / m 3 The leaching time was 12 h, the temperature was 25 °C, the slurry pH was 10, and the leaching time was 12 h. The changes in gold and copper concentrations, gold leaching rate, and sodium thiosulfate consumption at different leaching times are shown in Table 5.

[0079] As shown in Table 5, after 1 hour of leaching, the gold and copper concentrations in the leachate were 0.004 mg / L and 24.8 mg / L, respectively. Therefore, the dissolved gold was completely adsorbed by the resin, and a large amount of copper was also adsorbed by the resin. At this time, the gold leaching rate was only 61.2%, and the sodium thiosulfate consumption was only 11.5 kg / t. -矿As the leaching time increases, the gold concentration in the leaching solution is very low while the copper concentration gradually increases. This means that the dissolved gold is immediately adsorbed by the resin, while the copper adsorbed by the resin is gradually replaced and enters the solution. This is because S2O3 2– Produced S3O6 2− 、S4O6 2− The affinity between plasma and resin is stronger than Cu(S2O3)3 5– and weaker than Au(S2O3)2 3− Therefore, it can gradually replace the copper on the resin while the gold remains on the resin, thus achieving the selective adsorption of gold. Moreover, since the resin effectively adsorbs S3O6 2− 、S4O6 2− The addition of resin effectively eliminated the passivation effect of sulfur and oxygen impurities on the gold leaching process, resulting in a gold leaching rate of 87.6% after 4 hours of leaching, which was higher than the 78.6% gold leaching rate after 12 hours of leaching without resin (see Table 2). At the same time, the copper concentration in the leachate after 4 hours of reaction was 61.6 mg / L, which was comparable to the copper concentration of 63.5 mg / L in the leachate obtained after 12 hours of leaching without resin in the comparative example (see Table 3). Therefore, the adsorbed copper was essentially completely replaced, and the resin essentially did not adsorb copper. Moreover, the gold leaching rate continued to increase even after 12 hours of leaching, further confirming that the addition of resin during leaching has a significant effect on eliminating the adverse effects of sulfur and oxygen impurities on gold leaching.

[0080] Table 5 Gold and copper concentrations in the leachate at different leaching times, gold leaching rates, and sodium thiosulfate consumption

[0081]

[0082] The resin-containing slurry from Table 5, which had been leached for 4 hours, was separated using a sieve to obtain loaded resin and slurry. The loaded resin was then loaded onto a column. To further verify copper adsorption by the resin, copper was desorbed using 1 M NH₃•H₂O + 0.75 M (NH₄)₂SO₄. The desorbent dosage was 10 resin bed volumes, and the desorbent flow rate was 2 resin bed volumes / hour. Table 6 shows how the copper concentration in the desorbate changes with desorbent dosage. As shown in the table, when the desorbent dosage was 1 resin bed volume, the copper concentration in the desorbate was only 0.05 mg / L. As the desorbent dosage increased, the copper concentration in the desorbate initially increased and then decreased. However, the copper concentration remained below 0.4 mg / L, indicating that copper was barely adsorbed by the resin during the leaching process.

[0083] Table 6 Changes of copper concentration in desorption solution with desorbent dosage

[0084]

[0085] Since the resin contains virtually no copper, 1 M NaCl + 0.05 M Na₂SO₃ was used to directly desorb gold from the resin. The desorbent dosage was 10 resin bed volumes. The variation of gold desorption rate with desorbent dosage is shown in Table 7. As shown in the table, when the desorbent dosage was 1 resin bed volume, the gold concentration in the desorbent was 8.33 mg / L, and the gold desorption rate was 22.1%. With increasing desorbent dosage, the gold concentration and gold desorption rate gradually increased. At 3 resin bed volumes, the gold concentration in the desorbent reached a maximum of 13.04 mg / L and then began to decline. At 5 resin bed volumes, the gold desorption rate exceeded 90%. As the desorbent dosage increased further, the rate of increase in the gold desorption rate slowed. At 10 resin bed volumes, the gold desorption rate reached 99.8%, indicating very complete gold desorption. Compared with Table 4, under the same desorbent dosage conditions, the gold desorption rate in Table 7 is significantly higher, thus making gold desorption easier. Consequently, the desorbent dosage is reduced, lowering desorption costs. Compared with Table 7, the gold concentration in the desorbate obtained for each resin bed volume of desorbent flowing through the resin bed is significantly higher than that of copper, indicating that copper is barely adsorbed by the resin. Therefore, this process achieves selective adsorption recovery of gold.

[0086]

[0087] Example 2

[0088] First, water was added to the reactor, followed by the leaching agents (sodium thiosulfate, copper sulfate, and ammonia). Finally, gold ore (grinded particle size -200 mesh, accounting for 81.5%) and resin (Amberlite IRA-400) were added. The slurry pH was then adjusted to the set value using sodium hydroxide and sulfuric acid before stirring and leaching (at a stirring rate of 500 r / min). The specific leaching conditions were: sodium thiosulfate concentration of 0.075 mol / L, copper sulfate concentration of 2 mmol / L, ammonia concentration of 0.3 mol / L, slurry concentration of 33%, and resin concentration of 10 kg / m 3 , temperature 25 ℃, time 12 h. The changes in gold and copper concentrations, gold leaching rate, and sodium thiosulfate consumption at different pulp pH values ​​with leaching time are shown in Table 8.

[0089] As shown in the table, when the pH is 8, the gold leaching rate is 72.5%, and the copper concentration in the leachate is as low as 35.6 mg / L. This is due to the low consumption of sodium thiosulfate (12.2 kg / t -矿 )), decomposition produces S3O6 2− 、S4O6 2−As the pH increased to 9 and 10, the gold leaching rate and sodium thiosulfate consumption increased significantly, and the copper concentration in the leachate increased to more than 60 mg / L. However, when the pH increased to 11, although the sodium thiosulfate consumption increased further, the S3O6 produced by decomposition 2− 、S4O6 2− Under this condition, it is unstable and difficult to replace the copper adsorbed on the resin. Therefore, the copper concentration in the leachate decreases, and its catalytic gold leaching effect decreases, so the gold leaching rate decreases. When the pH increases to 12, part of the copper will precipitate in the form of hydroxide, passivating the dissolution of gold, so the gold leaching rate further decreases. At the same time, due to the high pH, ​​S3O6 2− 、S4O6 2− It is unstable and decomposes, so it is difficult to replace the copper adsorbed on the resin, so the copper content in the leachate is very low.

[0090]

[0091] Example 3

[0092] First, water was added to the reactor, followed by the leaching agents (sodium thiosulfate, copper sulfate, and aqueous ammonia). Finally, gold ore (81.5% of the ground ore was -200 mesh) and resin (Amberlite IRA-400) were added. The slurry pH was then adjusted to the desired value using sodium hydroxide and sulfuric acid, followed by agitation leaching at a rate of 500 rpm. The specific leaching conditions were: sodium thiosulfate concentration of 0.075 mol / L, copper sulfate concentration of 2 mmol / L, ammonia concentration of 0.3 mol / L, slurry concentration of 33%, temperature of 25°C, slurry pH of 10, and leaching time of 12 hours. The gold leaching yield and sodium thiosulfate consumption at different resin concentrations are shown in Table 9.

[0093] It can be seen from the table that when the resin concentration is 5 kg / m 3 When the gold leaching rate reaches 90.8%, the sodium thiosulfate consumption is 22.1 kg / t -矿 With the increase of resin concentration, the gold leaching rate gradually increased and the sodium thiosulfate consumption gradually decreased. 3 When the gold leaching rate reaches 95.1%, the sodium thiosulfate consumption is 18.8 kg / t -矿 Therefore, the increase of resin concentration is beneficial to improving the gold leaching rate and reducing the consumption of sodium thiosulfate.

[0094] Table 9 Gold leaching rate and sodium thiosulfate consumption at different resin concentrations

[0095]

[0096] Example 4

[0097] First, water was added to the reactor, followed by the leaching agents (sodium thiosulfate, copper sulfate, and ammonia). Finally, gold ore (grinded particle size -200 mesh, accounting for 81.5%) and resin (Amberlite IRA-400) were added. The slurry pH was then adjusted to the set value using sodium hydroxide and sulfuric acid before stirring and leaching (at a stirring rate of 500 r / min). The specific leaching conditions were: sodium thiosulfate concentration of 0.075 mol / L, copper sulfate concentration of 2 mmol / L, ammonia concentration of 0.3 mol / L, slurry concentration of 33%, and resin concentration of 10 kg / m 3 The leaching process was carried out at a temperature of 25°C, a slurry pH of 10, and a duration of 12 hours. After leaching, the resin was separated from the slurry, and the resulting loaded resin was loaded onto a column. The resin was desorbed using 10 resin bed volumes of a mixed solution consisting of 1 M NaCl and 0.05 M Na₂SO₃ at a desorbent flow rate of 2 resin bed volumes / hour. After desorption, sodium dithionite was added to the resulting gold-rich desorption solution for 10 minutes to recover gold. The gold reduction rates at different sodium dithionite dosages are shown in Table 10.

[0098] As shown in the table, when the sodium dithionite dosage is 0.5 times the theoretical dosage, the gold reduction rate is 72.2%, and the purity of the resulting elemental gold product is 98.2%. As the sodium dithionite dosage increases, the gold reduction rate and the purity of the gold product gradually improve. When the sodium dithionite dosage is 1.5 times the theoretical dosage, the gold reduction rate reaches 98.6%, and the gold product purity is 99.6%. When the sodium dithionite dosage is further increased to 2 times the theoretical dosage, the gold reduction rate increases to 99.9%, the gold in the desorption solution is completely reduced, and the purity of the gold product also increases to 99.9%. Therefore, using sodium dithionite to reduce the gold-rich desorption solution can produce a high-purity gold product.

[0099] Table 10 Gold reduction rate under different dosages of sodium dithionite

[0100]

[0101] Example 5

[0102] First, water was added to the reactor, followed by the leaching agents (sodium thiosulfate, copper sulfate, and ammonia). Finally, gold ore (grinded particle size -200 mesh, accounting for 81.5%) and resin (Amberlite IRA-400) were added. The slurry pH was then adjusted to the set value using sodium hydroxide and sulfuric acid before stirring and leaching (at a stirring rate of 500 r / min). The specific leaching conditions were: sodium thiosulfate concentration of 0.075 mol / L, copper sulfate concentration of 2 mmol / L, ammonia concentration of 0.3 mol / L, slurry concentration of 33%, and resin concentration of 10 kg / m 3The leaching process was carried out at a temperature of 25°C, a slurry pH of 10, and a time of 12 hours. After leaching, the resin was separated from the slurry, and the resulting loaded resin was loaded onto a column. Ten resin bed volumes of a mixed solution consisting of 1 M NaCl and 0.05 M Na₂SO₃ were used to desorb the resin. After desorption, sodium dithionite was added to the resulting gold-rich desorption solution for gold recovery. The amount of sodium dithionite used was 1.5 times the theoretical amount. Table 11 shows the gold reduction rates for different reduction times and sodium dithionite dosages.

[0103] As shown in the table, at a reduction time of 5 minutes, the gold reduction rate reached a high of 98.2%, and the gold purity of the resulting elemental gold product reached 99.6%. Therefore, sodium dithionite is highly efficient in recovering gold from the above desorption solution. The gold reduction rate slightly increases with increasing reduction time. At a reduction time of 20 minutes, the gold reduction rate reached 99.8%, and the gold product purity increased to 99.9%. Therefore, sodium dithionite is highly effective in recovering gold from the gold-rich desorption solution.

[0104]

[0105] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any form. Therefore, any simple modifications, equivalent variations, and modifications to the above embodiments that do not depart from the technical solution of the present invention and are based on the technical essence of the present invention shall fall within the scope of protection of the technical solution of the present invention.

Claims

1. A thiosulfate selective gold extraction process, characterized in that: The following steps are included: (1) Adding gold ore and anion exchange resin to an aqueous solution of a leaching agent, stirring and leaching at a pH of 9 to 10 to obtain a slurry containing a gold-loaded resin; the leaching agent comprises thiosulfate, copper salt, and ammonia water; the thiosulfate concentration is 0.05 to 0.1 mol / L, the copper salt concentration is 1.5 to 5 mmol / L, and the ammonia water concentration is 0.1 to 0.5 mol / L; (2) separating the gold-loaded resin from the ore pulp, and desorbing the gold-loaded resin with a desorbent to obtain a gold-rich desorption solution; the desorbent is a mixed solution containing chloride salt and sulfite; (3) Add dithionite to the gold-rich desorption solution for reduction to obtain elemental gold product.

2. The thiosulfate selective gold extraction process according to claim 1, wherein: The thiosulfate in step (1) is one or more of sodium thiosulfate, ammonium thiosulfate and calcium thiosulfate.

3. The thiosulfate selective gold extraction process according to claim 1 or 2, wherein: The copper salt in step (1) is copper sulfate.

4. The thiosulfate selective gold extraction process according to claim 1, wherein: The anion exchange resin in step (1) is a strongly basic chloride-type anion exchange resin.

5. The thiosulfate selective gold extraction process according to claim 1 or 4, characterized in that: The concentration of the anion exchange resin in step (1) is 5-20 kg / m 3 .

6. The thiosulfate selective gold extraction process according to claim 5, characterized in that: The leaching conditions of step (1) are: gold ore slurry concentration of 20~50wt%, temperature of 25~45℃, stirring rate of 400~800 r / min, and time of 4~12 h.

7. The thiosulfate selective gold extraction process according to claim 1, characterized in that: In step (2), the chloride salt is sodium chloride, and the sulfite is sodium sulfite.

8. The thiosulfate selective gold extraction process according to claim 7, characterized in that: The desorption conditions of step (2) are as follows: sodium chloride concentration is 0.5-1 mol / L, sodium sulfite concentration is 0.01-0.05 mol / L, desorbent dosage is 5-10 times of resin bed volume, and desorbent flow rate is 1-5 resin bed volumes / hour.

9. The thiosulfate selective gold extraction process according to claim 1, characterized in that: The dithionite in step (3) is sodium dithionite.

10. The thiosulfate selective gold extraction process according to claim 9, characterized in that: The reduction conditions in step (3) are as follows: the amount of sodium dithionite is 1.5 to 2 times the theoretical amount, and the reduction time is 5 to 20 min.

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