Low-cyanide gold leaching agent system and dump leaching process thereof

Abstract

The invention provides a low-cyanide gold leaching agent system and a dump leaching process thereof, and belongs to the technical field of hydrometallurgy. According to the method, a synergistic process of'interface activation, cyanide etching and iron precipitation inhibition 'is constructed by designing a low-cyanide gold leaching agent system. The amino acid auxiliary leaching agent adsorbs the gold surface to weaken lattice energy, so that the etching efficiency of trace cyanide ions is improved; mercapto-containing malic acid is used as a chelating agent, specific mercapto in molecules of the mercapto-containing malic acid and iron ions form an ultrahigh-stability water-soluble complex, generation of ferric hydroxide precipitates is thoroughly blocked, ferrous ions stabilized by the chelating agent are subjected to in-situ oxidation through dissolved oxygen and efficiently regenerated into potassium ferricyanide, and accumulation of free cyanogens in a solution system is eliminated; meanwhile, a chelating agent-iron complex forms a self-buffering pair, the pH of the dump leaching solution is accurately controlled, and secondary precipitation caused by local alkalization is prevented. According to the process, under the synergistic effect that the core chelating agent guarantees permeation stability and the leaching aid accelerates gold dissolution, the heap leaching period is compressed to 45 days.

Description

Technical Field

[0001] The invention relates to the technical field of hydrometallurgy, and in particular to a low-cyanide gold leaching agent system and a heap leaching process thereof. Background Art

[0002] Faced with the ban on cyanide in mineral extraction, the traditional cyanide heap leaching process has fallen into a development dilemma due to the risk of severe toxicity, high reagent consumption caused by side reactions of impurity ions (accounting for 30-50% of the cost), and environmental protection management.

[0003] Although existing low-cyanide agents reduce the use of sodium cyanide, they expose defects in heap leaching scenarios: 1. The agent decomposes and becomes inactivated. Thiosulfate agents are catalytically decomposed by ultraviolet rays in open-air heap leaching (half-life <72 h). Typical industrial practice shows that the effective concentration of the agent decays by more than 40% per month, and the leaching rate drops from 92% to 68%; 2. Heap leaching has insufficient adaptability. When the gold leaching agent is retained for a long time, it is decomposed by microorganisms to generate iron hydroxide precipitates that block the pores of the ore pile, causing the permeability to drop sharply by 65%, forcing the leaching cycle to be extended; 3. The unit consumption of mainstream environmentally friendly gold extraction agents is 10 times that of sodium cyanide. Combined with the decomposition loss and dredging costs, the processing cost per ton of ore increases. Summary of the Invention

[0004] In view of the technical problems existing in the background technology, the present application provides a low-cyanide gold leaching reagent system and a heap leaching process thereof, aiming to solve the problems of instability, long leaching cycle and high cost of the existing low-cyanide gold leaching reagent system.

[0005] In the first aspect, the present application provides a low-cyanide gold leaching agent system, which comprises a leaching agent body, a leaching aid and an iron ion anti-precipitation chelating agent; the leaching agent body is cyanide, the leaching aid is one or more of glycine, glutamic acid, thioglycine ester and thioglutamate ester, and the iron ion anti-precipitation chelating agent is mercaptomalic acid.

[0006] The technical solution of the embodiments of the present application designs a low-cyanide gold leaching reagent system. Mercaptomalic acid serves as a chelating agent (serving as a masking agent for key impurity metals). The specific thiol (-SH) group in its molecule forms an ultra-stable, water-soluble complex with iron ions, completely blocking the formation of iron hydroxide precipitation, solving the problem of ore pile blockage, maintaining the ore pile permeability, and eliminating the need for heap leaching to clear the ore. An amino acid leaching aid adsorbs the gold surface, weakening the lattice energy, increasing the etching efficiency of trace cyanide ions by 40-60%, and reducing the sodium cyanide dosage to over 90% compared to the traditional industrial requirement of 500 ppm. The synergistic effects of the chelating agent ensuring permeation stability and the leaching aid accelerating gold dissolution shorten the heap leaching cycle to 45 days. The chelating agent-iron complex forms a self-buffering pair, preventing secondary precipitation. Furthermore, the introduced gold leaching aids mercaptomalic acid and glycine comply with the GB 2760 food safety standard. This gold leaching reagent system achieves a triple breakthrough in environmental protection, economy, and efficiency.

[0007] In some embodiments, the mass concentration of the leaching agent body is 50 mg / L; the mass concentration of the leaching aid is 5-10 g / L; and the mass concentration of the iron ion anti-precipitation chelating agent is 10-20 g / L.

[0008] In this embodiment, better synergy between the components can be achieved by designing the dosage of the components in the pharmaceutical system.

[0009] In a second aspect, the present application provides a heap leaching process using a low-cyanide gold leaching agent system, wherein the heap leaching process uses the low-cyanide gold leaching agent system to leach gold, comprising the following steps: S1. The gold-containing mineral material is crushed to obtain a crushed sample, which is then added to a heap leaching column to obtain a heap leaching material; S2. The leaching agent and the iron ion anti-precipitation chelating agent are sequentially added to water, mixed evenly, and then the pH value is adjusted, and then the leaching agent body is added to obtain a mixed gold leaching solution; S3. The mixed gold leaching solution is added from the upper part of the heap leaching column to leach the heap leaching ore from top to bottom, the outflowing leachate is collected and pumped to the upper part of the heap leaching column again for circulation leaching. After the circulation leaching is completed, gold-containing and iron-containing precious liquid and leaching mineral tailings are obtained.

[0010] In the technical solution of the embodiment of the present application, a synergistic process of "interface activation, cyanide etching, and inhibition of iron precipitation" is constructed: the amino acid leaching agent adsorbs the gold surface to weaken the lattice energy, thereby increasing the etching efficiency of trace cyanide ions by 40% to 60%, and the amount of cyanide used is reduced to more than 90% compared with the traditional industrial requirement (500ppm); the specific thiol (-SH) in the chelating agent molecule forms an ultra-high stability water-soluble complex with the iron ion, completely blocking the precipitation of iron hydroxide, solving the problem of ore pile blockage, maintaining the permeability coefficient of the ore pile, and eliminating the need for dredging during the heap leaching process. The ferrous ions stabilized by the chelating agent are efficiently regenerated into potassium ferrocyanide through in-situ oxidation with dissolved oxygen, eliminating the accumulation of free cyanide in the solution system (residual free cyanide in the tail liquid is less than 0.5 ppm); at the same time, the chelating agent-iron complex forms a self-buffering pair, precisely controlling pH fluctuations in the heap leachate and preventing secondary precipitation caused by localized alkalinization. With the synergistic effect of the core chelating agent ensuring osmotic stability and the leaching aid accelerating gold dissolution, the heap leaching cycle is compressed to 45 days (with an overall gold leaching rate of 65%, reaching the leaching limit of 94%, compared to 120 days under traditional industrial cyaniding conditions). The residual free cyanide in the tail liquid is less than 0.5 ppm.

[0011] In some embodiments, in step S2, the pH value in the pH adjustment is 10.0-10.6.

[0012] In this embodiment, the pH fluctuation of the heap leachate is precisely controlled within ±0.3 (pH 10.0-10.6) to prevent secondary precipitation caused by local alkalization.

[0013] In some embodiments, in step S3, the intensity of the circulating elution is 5L / m 2 h; the cycle elution time is 45 days.

[0014] In this embodiment, the leaching reaction is fully carried out through the circulating elution.

[0015] In some embodiments, in step S1, the particle size of the ore in the crushed sample is ≤2.8 mm, accounting for ≥99%.

[0016] In this embodiment, the sample is crushed to facilitate the subsequent leaching reaction.

[0017] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] To more clearly illustrate the technical solution of this application, the following is a brief introduction to the drawings used in this application. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be derived from these drawings without inventive effort.

[0019] Figure 1 Comparison diagram of the leaching system with and without the addition of mercaptomalic acid in this application, (a) is a comparison picture of the stirring leaching test for 12 hours, (b) is a photo of the heap leaching test for 7 days without the addition of mercaptomalic acid, (c) is a physical picture of the test group without the addition of mercaptomalic acid, and the generation of brown precipitate, (d) is a physical picture of the collection of brown precipitate generated by the test group without the addition of mercaptomalic acid.

[0020] Figure 2 FTIR and SEM-EDS images of the brown precipitate after leaching for 12 hours in the leaching system without adding mercaptomalic acid in this application; Figure 3 The SEM and energy spectrum images of gold ore before and after leaching in the leaching system without adding mercaptomalic acid in this application, (a) is the backscattered image of the sample before leaching, (b) is the element surface distribution image of the sample before leaching, (c) is the element energy spectrum analysis image of the sample before leaching, (d) is the backscattered image of the sample after leaching, (e) is the element surface distribution image of the sample after leaching, and (f) is the element energy spectrum analysis image of the sample after leaching; Figure 4 This is a Zeta potential distribution diagram of gold powder, ferrous glycinate, and the gold powder mixture after leaching (gold powder adsorbent) in the leaching system without adding mercaptomalic acid in this application; Figure 5 (a) is a diagram of a simulation test of heap leaching of a single particle size ore in this application, and (b) is a physical diagram of the heavy leachate product of the simulation test of heap leaching of a single particle size ore in this application. DETAILED DESCRIPTION

[0021] The following embodiments of the technical solution of the present application are described in detail. The following embodiments are only used to more clearly illustrate the technical solution of the present application and are therefore only used as examples and are not intended to limit the scope of protection of the present application.

[0022] References herein to "embodiments" mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0023] In order to solve the problems of instability, long leaching cycle and high cost of the existing low-cyanide gold leaching agent system, the present application provides a low-cyanide gold leaching agent system and its heap leaching process. By designing a low-cyanide gold leaching agent system, a synergistic process of "interface activation, cyanide etching, and inhibition of iron precipitation" is constructed: the amino acid leaching agent adsorbs the gold surface to weaken the lattice energy, thereby increasing the etching efficiency of trace cyanide ions by 40~60%, and the amount of cyanide used is reduced to more than 90% compared with the traditional industrial requirement (500ppm); mercaptomalic acid is used as a chelating agent (as a key impurity metal masking agent), and the specific thiol (-SH) in its molecule forms an ultra-high stability water-soluble complex with iron ions, which completely blocks the formation of iron hydroxide precipitation, solves the problem of ore pile blockage, maintains the permeability coefficient of the ore pile, and eliminates the dredging process during heap leaching. To meet customer needs, chelating agent-stabilized ferrous ions are efficiently regenerated into potassium ferrocyanide through in-situ oxidation with dissolved oxygen, eliminating the accumulation of free cyanide in the solution (residual free cyanide in the tail liquor is less than 0.5 ppm). Furthermore, the chelating agent-iron complex forms a self-buffering pair, precisely controlling pH fluctuations in the heap leachate and preventing secondary precipitation caused by localized alkalinization. This process, with the core chelating agent ensuring osmotic stability and the leaching aid accelerating gold dissolution, shortens the heap leaching cycle to 45 days (with an overall gold leaching rate of 65%, reaching the leaching limit of 94%, compared to 120 days under conventional industrial cyanidation conditions). Residual free cyanide in the tail liquor is less than 0.5 ppm. Furthermore, the introduced gold leaching aids, mercaptomalic acid and glycine, comply with the GB 2760 food safety standard. This gold leaching agent system achieves breakthroughs in environmental protection, cost-effectiveness, and efficiency.

[0024] In the first aspect, the present application provides a low-cyanide gold leaching agent system, which comprises a leaching agent body, a leaching aid and an iron ion anti-precipitation chelating agent; the leaching agent body is cyanide, the leaching aid is one or more of glycine, glutamic acid, thioglycine ester and thioglutamate ester, and the iron ion anti-precipitation chelating agent is mercaptomalic acid.

[0025] The technical solution of the embodiments of the present application designs a low-cyanide gold leaching reagent system. Mercaptomalic acid serves as a chelating agent (serving as a masking agent for key impurity metals). The specific thiol (-SH) group in its molecule forms an ultra-stable, water-soluble complex with iron ions, completely blocking the formation of iron hydroxide precipitation, solving the problem of ore pile blockage, maintaining the ore pile permeability, and eliminating the need for heap leaching to clear the ore. An amino acid leaching aid adsorbs the gold surface, weakening the lattice energy, increasing the etching efficiency of trace cyanide ions by 40-60%, and reducing the sodium cyanide dosage to over 90% compared to the traditional industrial requirement of 500 ppm. The synergistic effects of the chelating agent ensuring permeation stability and the leaching aid accelerating gold dissolution shorten the heap leaching cycle to 45 days. The chelating agent-iron complex forms a self-buffering pair, preventing secondary precipitation. Furthermore, the introduced gold leaching aids mercaptomalic acid and glycine comply with the GB 2760 food safety standard. This gold leaching reagent system achieves a triple breakthrough in environmental protection, economy, and efficiency.

[0026] Furthermore, in some embodiments, the mass concentration of the leaching agent body is 50 mg / L; the mass concentration of the leaching aid is 5-10 g / L; and the mass concentration of the iron ion anti-precipitation chelating agent is 10-20 g / L.

[0027] In the technical solution of the embodiment of the present application, better coordination and cooperation between the components can be achieved through the dosage design of the components in the pharmaceutical system.

[0028] In a second aspect, the present application provides a heap leaching process using a low-cyanide gold leaching agent system, wherein the heap leaching process uses the low-cyanide gold leaching agent system to leach gold, comprising the following steps: S1. The gold-containing mineral material is crushed to obtain a crushed sample, which is then added to a heap leaching column to obtain a heap leaching material; S2. The leaching agent and the iron ion anti-precipitation chelating agent are sequentially added to water, mixed evenly, and then the pH value is adjusted, and then the leaching agent body is added to obtain a mixed gold leaching solution; S3. The mixed gold leaching solution is added from the upper part of the heap leaching column to leach the heap leaching ore from top to bottom, the outflowing leachate is collected and pumped to the upper part of the heap leaching column again for circulation leaching. After the circulation leaching is completed, gold-containing and iron-containing precious liquid and leaching mineral tailings are obtained.

[0029] In the technical solution of the embodiment of the present application, a synergistic process of "interface activation, cyanide etching, and inhibition of iron precipitation" is constructed: the amino acid leaching agent adsorbs the gold surface to weaken the lattice energy, thereby increasing the etching efficiency of trace cyanide ions by 40% to 60%, and the amount of cyanide used is reduced to more than 90% compared with the traditional industrial requirement (500ppm); the specific thiol (-SH) in the chelating agent molecule forms an ultra-high stability water-soluble complex with the iron ion, completely blocking the formation of iron hydroxide precipitation, solving the problem of ore pile blockage, maintaining the permeability coefficient of the ore pile, and eliminating the need for dredging during the heap leaching process. The chelating agent stabilizes the ferrous ion The ferrocyanide is efficiently regenerated into potassium ferrocyanide through in-situ oxidation with dissolved oxygen, eliminating the accumulation of free cyanide in the solution system (residual free cyanide in the tail liquid is less than 0.5ppm); at the same time, the chelating agent-iron complex forms a self-buffering pair, which accurately controls the pH fluctuation of the heap leach liquid and prevents secondary precipitation caused by local alkalization; with the synergistic effect of the core chelating agent to ensure penetration stability and the leaching aid to accelerate gold dissolution, the heap leaching cycle is compressed to 45 days (the overall gold leaching rate is 65%, reaching the leaching limit of 94%, which requires 120 days under traditional industrial cyaniding conditions); the residual free cyanide in the tail liquid is less than 0.5ppm.

[0030] Furthermore, in some embodiments, in step S2, the pH value in the pH adjustment is 10.0-10.6.

[0031] In the technical solution of the embodiment of the present application, the pH fluctuation of the heap leachate is precisely controlled to be within ±0.3 (pH 10.0~10.6) to prevent secondary precipitation caused by local alkalization.

[0032] Furthermore, in some embodiments, in step S3, the intensity of the circulating elution is 5 L / m 2 h; the cycle elution time is 45 days.

[0033] In the technical solution of the embodiment of the present application, the leaching reaction is fully carried out through circulating elution.

[0034] Furthermore, in some embodiments, in step S1, the particle size of the ore in the crushed sample is ≤2.8 mm, accounting for ≥99%.

[0035] In the technical solution of the embodiment of the present application, the sample is crushed to facilitate the subsequent leaching reaction.

[0036] Some specific examples are listed below. It should be noted that the examples described below are exemplary and are only used to explain the present application, and should not be construed as limiting the present application. Where specific techniques or conditions are not specified in the examples, the techniques or conditions described in the literature in this area or the product specifications are used. Reagents or instruments used without manufacturer's indication are all commercially available conventional products.

[0037] Example 1 Example 1 provides a low-cyanide gold leaching reagent system comprising sodium cyanide, glycine, and mercaptomalic acid.

[0038] The gold leaching agent system is used to treat gold minerals, specifically comprising the following steps: (1) The gold-bearing mineral material was crushed to the following particle size distribution. It was then added to a heap leaching column with a height of 1.2 m and an inner diameter of 10 cm, with a mineral accumulation height of 1 m; (2) Add 50 g of glycine and 150 g of mercaptomalic acid to 10 L of aqueous solution, mix well, add sodium hydroxide to adjust the pH to 10.3, and then add 0.5 g of sodium cyanide to obtain a mixed gold leaching solution; (3) Add the above mixed gold leaching solution from the top of the heap leaching column and leach the minerals from top to bottom at an intensity of 5L / m 2 h, collect the outflowing leachate and pump it to the upper part of the heap leaching column again for 45 days of circulation leaching to obtain gold and iron-containing precious liquid and leaching mineral tailings.

[0039] Table 1 Particle size distribution of gold-bearing mineral materials after crushing The gold content in the leaching tailings of each embodiment and comparative example was detected by fire assay. The test and analysis method was based on GB / T 7739 "Chemical Analysis Methods for Gold Concentrates". The gold leaching rate η is Among them, η represents the gold leaching rate, unit is %; m1 represents the mass of the original gold ore, unit is g; β1 represents the grade of the original gold ore, unit is g / t; m2 represents the mass of the residue after gold leaching, unit is g; β2 represents the grade of the residue after gold leaching, unit is g / t.

[0040] The concentrations of gold, iron, and cyanide in the gold- and iron-containing precious liquors in each example and comparative example were then tested using ICP-OES. The gold leaching rate test results of the two methods were compared, and valid data were considered when the deviation between the two test results was less than 1%. Finally, the gold leaching rate and the iron and cyanide concentrations in the precious liquors in each example and comparative example were measured.

[0041] Examples 2 to 6 Comparative Examples 1 to 4 Examples 2 to 6 and Comparative Examples 1 to 4 respectively provide a heap leaching process of a low cyanide gold leaching agent system. Compared with Example 1, the difference is that the mass concentration and type of the leaching aid in the mixed gold leaching solution in step (2) in Examples 2 to 6 and Comparative Examples 1 to 3 are different, and in Comparative Example 4, no glycine is added in step (2) and the mass concentration of sodium cyanide is the industrial standard concentration, as shown in Table 2. The other steps are substantially the same as in Example 1 and are not repeated here.

[0042] Table 2 Mass concentration and type of leaching aid in the mixed solution, gold leaching rate, iron and cyanide concentrations in Examples 1 to 6 and Comparative Examples 1 to 4 As can be seen from Table 2, the introduction of glycine, glutamic acid, thioglycine ester, and thioglutamate ester is the core mechanism for improving the gold leaching rate (up to 65-66%) and significantly reducing the free cyanide in the tail liquid (<0.5 mg / L): these molecules weaken the metal lattice energy by adsorbing on the gold surface, thereby increasing the etching efficiency of trace cyanide (60 ppm) by 40-60%. At the same time, the chelating agent (mercaptomalic acid) forms a stable complex with iron ions, which not only blocks the precipitation of iron hydroxide to maintain the permeability of the ore pile, but also promotes the oxidation of ferrous ions to potassium ferrocyanide by dissolved oxygen, consuming free cyanide in situ and achieving cyanide self-purification. Compared with the group without leaching aids (Comparative Examples 3-4), the gold leaching rate dropped sharply and the cyanide residual increased sharply, confirming the necessity of the dual-circulation synergy. In addition, the concentration of the leaching aid must reach a threshold value (≥5g / L) to be effective (only 48% in Comparative Example 1), while excessive amounts (15g / L) maintain the leaching rate but significantly increase the iron ion concentration (up to 690mg / L in Comparative Example 2), which will increase the chelating agent load and require economic considerations, so it is not considered.

[0043] The gold leaching rates of the gold leaching reagent systems in Examples 1-3 and Comparative Examples 1-4 were tested. The gold ore in Example 1 was crushed to a particle size of -0.074 mm (greater than 95%). 100 g of the ore was added to 0.5 L of water, followed by the addition of glycine and mercaptomalic acid. The pH of the solution was then adjusted to 10.3 with sodium hydroxide, followed by the addition of sodium cyanide. Leaching was carried out with stirring. The grade of the leached residue was measured at leaching times of 2, 4, 6, 8, 10, 12, 24, and 36 hours, and the gold leaching rate was calculated. The results are shown in Table 3. The mass concentration of the gold leaching reagent was the same as in Examples 1-3 and Comparative Examples 1-4.

[0044] Table 3 Gold leaching rate of gold leaching agent at different time points in Examples 1 to 3 and Comparative Examples 1 to 4 As can be seen from Table 3, the data in Examples 1 to 3 and Comparative Example 3 show that the glycine leaching aid can significantly increase the gold leaching rate in a low sodium cyanide concentration (50 ppm) system. The data in Examples 1 to 3 and Comparative Example 4 show that even in the case of low cyanide concentration, the gold leaching rate is significantly improved compared to the traditional high cyanide concentration (500 ppm) process. As can be seen from Examples 1 to 3 and Comparative Example 1, when the content of the glycine leaching aid is greater than or equal to 5 g / L, the kinetic advantage is more significant in the early stage. This phenomenon is due to the weakening of the gold surface lattice energy by glycine adsorption, which doubles the mass transfer efficiency of trace cyanide. When the concentration is less than 4 g / L, although the initial growth rate is significant (37.18% in 4 hours), it is weak in the later stage (65.23% in 12 hours), indicating that the threshold concentration (≥5 g / L) is the key to maintaining high-speed leaching. It's worth noting that excessive glycine (15 g / L) inhibited late-stage leaching (leaching efficiency dropped from 75.64% to 57.69% over 24-36 hours). This may be due to a thick adsorption layer that hinders cyanide diffusion, highlighting the need for precise concentration control. Considering the heap leaching process specifications, a glycine concentration of 10 g / L was selected as the optimal parameter range.

[0045] The gold leaching process described above conforms to the basic elements of the "shrinking core model." During the gold leaching process, the reaction rate may be dominated by internal diffusion control, chemical reaction control, or mixed control, as expressed below. Where x is the gold leaching rate during the leaching process (%); t is the leaching time (min); k1 is the apparent rate constant for internal diffusion control; k2 is the apparent rate constant for chemical reaction control; and k3 is the apparent rate constant for mixed control.

[0046] 1+2(1-x)-3(1-x) 2 / 3 =k1t1-(1-x) 1 / 3 =k2t 1 / 3ln(1-x)‒1+(1-x) −1 / 3 =k3t During the leaching process, gold dissolution varies. The influence of leaching factors on metal leaching rates varies under different control steps. Due to the specific industrial site, elevated temperatures were not used. This section focuses on the gold leaching kinetics at 298.15K.

[0047] According to the results of the previous test, samples were taken for analysis at different reaction times to examine the variation of the gold leaching rate with the leaching time. Based on the gold leaching rate obtained at different leaching times, combined with the three model equations of internal diffusion control, chemical reaction control or mixed control, the main controlling reaction of a low-cyanide gold leaching agent system in the gold leaching process can be determined. According to the equation, a linear fit is performed on the leaching time and leaching rate. The slope of the fitting line represents the respective apparent reaction rate constants k1, k2, and k3, and the fitting correlation coefficient R is used to calculate the reaction rate constants k1, k2, and k3. 2 The relevant research results are shown in Tables 4 to 6.

[0048] Table 4 1+2(1-x)-3(1-x) 2 / 3 Fitting data with leaching time Table 5 1-(1-x) 1 / 3 Fitting data with leaching time Table 6 Fitting of 1 / 3ln(1-x)-1+(1-x)-1 / 3 and leaching time As can be seen from Tables 4 to 6, the gold leaching rates at different leaching times under 298.15K conditions were linearly fitted. The results show that in Comparative Examples 3 to 4, the chemical reaction control model using cyanide (50ppm NaCN and 500ppm NaCN) alone has the highest fitting degree, which is 0.989 and 0.990, respectively. It can be seen that in the cyanide gold leaching process, the optimal kinetic function within 0 to 36 hours is 1-(1-x)1 / 3=k2t, that is, the leaching process is mainly controlled by chemical reaction. In the low cyanide gold leaching reagent system, that is, in Examples 1 to 3 and Comparative Examples 1 to 2, the mixed control model has the highest fitting degree, which is 0.941, 0.943, 0.959, 0.968, and 0.964, respectively. It can be seen that in the glycine-cyanide gold leaching process, the optimal kinetic function within 0 to 36 hours is 1 / 3ln(1-x)-1+(1-x) ‒1 / 3 , indicating that the leaching process is primarily controlled by a mixed model. Glycine preferentially reacts with impurity metals such as copper and iron in the ore, and the resulting byproducts form a passivation layer, shifting the leaching process from chemical reaction control to diffusion-reaction mixed control. This conclusion is consistent with the "shrinking core model" theory, which states that when the product is densely packed and hinders mass transfer, internal diffusion is often the controlling step; when the product is loose and does not affect mass transfer, chemical reaction is often the controlling step, demonstrating the necessity of introducing mercaptomalic acid.

[0049] Examples 7-8 and Comparative Examples 5-10 Examples 7 to 8 and Comparative Examples 5 to 10 respectively provide a heap leaching process of a low cyanide gold leaching agent system. Compared with Example 1, the difference is that the mass concentration of mercaptomalic acid in the mixed gold leaching solution in step (2) in Examples 7 to 8 and Comparative Examples 5 to 7 is different, and in step (2) in Comparative Examples 8 to 10, mercaptomalic acid is replaced by sodium thioglycolate, citric acid and ethylenediamine, respectively, as shown in Table 7. The other steps are substantially the same as in Example 1 and are not repeated here.

[0050] Table 7 Type and concentration of iron ion anti-precipitation chelating agent and gold leaching rate, iron and cyanide concentration in Examples 7-8 and Comparative Examples 5-10 As can be seen from Table 7, there is a significant concentration threshold (≥10 g / L) for mercaptomalic acid as an iron ion chelating agent. It forms an ultra-high stability complex with iron ions through specific thiol groups, completely blocking the precipitation of iron hydroxide, ensuring the permeability of the ore pile, and making the gold leaching rate stable at 63~66%. When the concentration is insufficient (8 g / L, Comparative Example 5), the insufficient chelating ability leads to aggravated iron precipitation (iron ion 418 mg / L), the gold leaching rate plummets to 52%, and the free cyanide residue surges to 4.02 mg / L, confirming that the failure of chelation causes an imbalance in cyanide consumption. The structural uniqueness of mercaptomalic acid is crucial. Compared to other chelating agents (Comparative Examples 8-10), even at the same concentration (15 g / L), the gold leaching rate of sodium thioglycolate / citric acid / ethylenediamine is only 24-27%, while iron ion concentrations soar to 683-1090 mg / L and residual cyanide exceeds 5 mg / L. This demonstrates the irreplaceable resistance of the thiol group to decomposition and its iron chelation specificity. Other conventional iron chelating agents are unsuitable for the glycine system. While an excess of chelating agent (25 g / L, Comparative Example 6) maintains both leaching rate and cyanide removal effectiveness, economic considerations must be taken into account.

[0051] The experimental process of adding mercaptomalic acid as an anti-precipitation chelating agent for iron ions and not adding mercaptomalic acid as an anti-precipitation chelating agent for iron ions was analyzed. During the heap leaching process, after 12 hours of leaching, the heap leaching effects of adding mercaptomalic acid and not adding mercaptomalic acid were as follows: Figure 1 As shown, (a) is a comparison picture of the stirring leaching test for 12 hours, (b) is a photo of the heap leaching test for 7 days without the addition of mercaptomalic acid, (c) is a physical picture of the brown precipitate generated in the test group without the addition of mercaptomalic acid, and (d) is a physical picture of the brown precipitate generated in the test group without the addition of mercaptomalic acid. The heap leaching was continued for 7 days, and the brown precipitate produced in the group without the addition of mercaptomalic acid was collected. The substance was identified by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS), focusing on the analysis of the characteristic peaks of the Fe-N / O bond vibration and the element surface distribution (the stoichiometric ratio of Fe, C, O, and N). The analysis results are shown in Figure 2. Figure 2 shown.

[0052] Depend on Figure 1 It can be seen that brown precipitates appear on the upper part of the ore body without the addition of mercaptomalic acid, while no brown precipitates appear on the upper part of the ore body with the addition of mercaptomalic acid. Figure 2 It can be seen that the precipitated substance is ferrous glycinate, and some tested samples also contain a small amount of ferrous hydroxide. This shows that mercaptomalic acid can form an ultra-highly stable water-soluble complex with iron ions in the reagent system, completely blocking the formation of iron hydroxide precipitation, solving the problem of ore pile blockage, maintaining the ore pile permeability, and eliminating the need for dredging during the heap leaching process.

[0053] The ferrous glycinate precipitated in the solution phase exists in the form of a flocculent suspension in the leaching system, forming a state similar to "gel", which leads to mutual attraction between charges and may wrap the fine gold particles dissociated in the ore, thereby affecting the contact between gold and glycine, and ultimately making it difficult to improve the gold leaching rate. In order to prove the above speculation, the surface morphology and energy spectrum of the gold ore before and after leaching were observed by SEM, as shown in the figure below. Figure 3 As shown, it can be found that ferrous glycinate forms a flocculent precipitate and wraps around the surface of the gold powder.

[0054] The Zeta potential distribution method was used to study the gold powder, ferrous glycine and the gold powder mixture after leaching (gold powder adsorbent) in the leaching system environment. The results are as follows Figure 4 As shown. It can be found that the Zeta potential distribution of gold powder is centered at -10.67mV, and the Zeta potential distribution of ferrous glycine powder is centered at -2.80mV. Under the same leaching conditions, the Zeta potential distribution of the gold powder mixture (gold powder adsorbent) after leaching is centered at -2.23mV, with a peak value between the peak values ​​of the above two, but overall closer to the Zeta potential distribution of ferrous glycine. It can be seen that ferrous glycine will be wrapped on the surface of the gold powder, and this phenomenon is similar to Figure 3 The SEM images are consistent with those in .

[0055] Verify the formation mechanism of precipitates and their influence on the gold leaching mechanism.

[0056] A single particle size ore heap leaching simulation test was conducted. The experimental process and the leaching liquid product diagrams are shown in the following figure. Figure 5As shown in (a) and (b), a 1000g sample of a single target size ore was loaded into a custom-made simple leaching column (8cm diameter, 20cm height) and operated at a saturated dripping intensity. A peristaltic pump controlled the inflow rate to ensure that the column pores were always saturated with liquid (dynamic equilibrium between inflow and outflow rates, constant liquid level). The reagent system used was that of Comparative Example 7. The test lasted 15 days, with inflow and outflow samples collected simultaneously at pre-set time points (days 2, 10, and 15). After rapid filtration through a 0.22μm filter membrane, the instantaneous concentrations of Au and Fe in the solution were determined using ICP-OES.

[0057] In the saturated drip system, the leaching behavior of ores with different particle sizes showed significant differences.

[0058] On the second day, the effluent from the 1.7-2.8 mm and 0.85-1.7 mm coarse particle size columns turned reddish-brown, and ICP-OES detected iron concentrations as high as 4638 mg / L and 3242 mg / L, respectively. However, the effluent from the 0.425-0.85 mm and <0.425 mm particle size columns was colorless and had extremely low iron concentrations (121 mg / L and 37 mg / L). No dissolved gold was detected in any particle size range.

[0059] On the 10th day, the reddish-brown color of the coarse-grained solution (1.7-2.8 mm, 0.85-1.7 mm) deepened, and the iron concentration further increased to 7600 mg / L and 7200 mg / L; the 0.425-0.85 mm particle size solution turned bright yellow for the first time, and the iron concentration increased to 1155 mg / L; the fine-grained solution (<0.425 mm) remained colorless (iron concentration 129 mg / L), and no dissolved gold was detected in any particle size.

[0060] On day 15, the coarse fraction solution turned deep red with precipitation at the bottom, with iron concentrations reaching 7637 mg / L (1.7-2.8 mm) and 7668 mg / L (0.85-1.7 mm). The 0.425-0.85 mm fraction solution evolved into a clear reddish-brown color, with the iron concentration rising sharply to 7230 mg / L. The fine fraction solution (<0.425 mm) turned bright yellow with an iron concentration of 945 mg / L. Furthermore, gold was detected in the 0.425-0.85 mm and <0.425 mm fraction solutions at 0.226 mg / L and 0.388 mg / L, respectively, with liquid-to-liquid leaching rates of 31.39% and 31.04%, respectively.

[0061] The above verification process shows that ore particle size dominates the gold leaching process by controlling the kinetics of iron dissolution. Coarse particles (0.85-2.8 mm) exhibit a burst of iron ion dissolution (>3000 mg / L on day 2 and >7000 mg / L on day 10) due to their high porosity and large oxidative contact area. However, the excess iron exceeds the chelation capacity of glycine, triggering iron precipitation (deep red solution with precipitate on day 15), which blocks pores and completely inhibits gold dissolution. Fine particles (<0.425 mm) exhibit slow iron dissolution (only 945 mg / L on day 15) due to their dense structure, which retards oxidation and similarly results in no gold leaching. For gold leaching to occur, two conditions must be met: Medium particles (0.425-0.85 mm) trigger a synergistic mechanism at a threshold iron concentration (~7000 mg / L)—glycine chelates iron to form an active complex, thereby enabling cyanide to target gold rather than be consumed by free iron.

[0062] In summary, the present application provides a gold leaching agent system for removing arsenic elements and a method for treating low-grade gold ores rich in arsenopyrite. By designing a low-cyanide gold leaching agent system, a synergistic process of "interface activation, cyanide etching, and inhibition of iron precipitation" is constructed: the amino acid leaching agent adsorbs the gold surface to weaken the lattice energy, thereby increasing the etching efficiency of trace cyanide ions by 40-60%, and reducing the amount of cyanide used to more than 90% compared with traditional industrial requirements (500ppm); using mercaptomalic acid as a chelating agent (as a key impurity metal masking agent), the specific thiol (-SH) in its molecule forms an ultra-high stability water-soluble complex with iron ions, completely blocking the formation of iron hydroxide precipitation, solving the problem of ore pile blockage, maintaining the permeability coefficient of the ore pile, and eliminating the dredging process during heap leaching. To meet customer needs, chelating agent-stabilized ferrous ions are efficiently regenerated into potassium ferrocyanide through in-situ oxidation with dissolved oxygen, eliminating the accumulation of free cyanide in the solution (residual free cyanide in the tail liquor is less than 0.5 ppm). Furthermore, the chelating agent-iron complex forms a self-buffering pair, precisely controlling pH fluctuations in the heap leachate and preventing secondary precipitation caused by localized alkalinization. This process, with the core chelating agent ensuring osmotic stability and the leaching aid accelerating gold dissolution, shortens the heap leaching cycle to 45 days (with an overall gold leaching rate of 65%, reaching the leaching limit of 94%, compared to 120 days under conventional industrial cyanidation conditions). Residual free cyanide in the tail liquor is less than 0.5 ppm. Furthermore, the introduced gold leaching aids, mercaptomalic acid and glycine, comply with the GB 2760 food safety standard. This gold leaching agent system achieves breakthroughs in environmental protection, cost-effectiveness, and efficiency.

[0063] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and any embodiments having substantially the same structure and effect as the technical concept within the scope of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the present application, any other embodiments that can be conceived by those skilled in the art and that combine some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A low cyanide gold leaching reagent system, characterized in that: The low-cyanide gold leaching agent system comprises a leaching agent body, a leaching aid and an iron ion anti-precipitation chelating agent; the leaching agent body is cyanide, the leaching aid is one or more of glycine, glutamic acid, thioglycine ester and thioglutamate ester, and the iron ion anti-precipitation chelating agent is mercaptomalic acid.

2. The low cyanide gold leaching agent system according to claim 1, characterized in that: The mass concentration of the leaching agent body is 50 mg / L.

3. The low cyanide gold leaching reagent system according to claim 2, characterized in that: The mass concentration of the soaking aid is 5-10 g / L.

4. The low cyanide gold leaching reagent system according to claim 3, characterized in that: The mass concentration of the iron ion anti-precipitation chelating agent is 10-20 g / L.

5. A heap leaching process using a low-cyanide gold leaching reagent system, characterized in that: Gold leaching using the low cyanide gold leaching agent system according to any one of claims 1 to 4 comprises the following steps: S1. The gold-containing mineral material is crushed to obtain a crushed sample, which is then added to a heap leaching column to obtain a heap leaching material; S2. The leaching agent and the iron ion anti-precipitation chelating agent are sequentially added to water, mixed evenly, and then the pH value is adjusted, and then the leaching agent body is added to obtain a mixed gold leaching solution; S3. The mixed gold leaching solution is added from the upper part of the heap leaching column to leach the heap leaching ore from top to bottom, the outflowing leachate is collected and pumped to the upper part of the heap leaching column again for circulation leaching. After the circulation leaching is completed, gold-containing and iron-containing precious liquid and leaching mineral tailings are obtained.

6. The heap leaching process of the low cyanide gold leaching reagent system according to claim 5, characterized in that: In step S2, the pH value in the pH adjustment is 10.0-10.

6.

7. The heap leaching process of the low cyanide gold leaching reagent system according to claim 5, characterized in that: In step S3, the intensity of the circulating elution is 5L / m 2 ·h.

8. The heap leaching process of the low cyanide gold leaching reagent system according to claim 5, characterized in that: In step S3, the cycle elution time is 45 days.

9. The heap leaching process of the low cyanide gold leaching reagent system according to claim 5, characterized in that: In step S1, the ore particle size in the crushed sample is ≤2.8 mm, accounting for ≥99%.

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