Low cyanide gold leach reagent system and heap leach process

Abstract

The application provides a low cyanide gold leaching agent system and a heap leaching process thereof, and belongs to the technical field of hydrometallurgy. The application designs a low cyanide gold leaching agent system to construct a synergistic process of "interface activation, cyanide etching and iron precipitation inhibition". The amino acid leaching aid adsorbed on the surface of gold weakens the lattice energy, so that the etching efficiency of trace cyanide ions is improved; the chelating agent containing mercapto malic acid forms a super stable water-soluble complex with iron ions through specific mercapto groups in the molecule, completely blocks the generation of iron hydroxide precipitation, and regenerates the stable ferrous ion into potassium ferricyanide in situ through dissolved oxygen, so that the accumulation of free cyanide in the solution system is eliminated; at the same time, the chelating agent-iron complex forms a self-buffering pair to accurately control the pH of the heap leaching liquid and prevent the occurrence of secondary precipitation due to local alkalization. Under the synergistic effect of the core chelating agent ensuring the stability of penetration and the leaching aid accelerating the dissolution of gold, the heap leaching period is compressed to 45 days.

Description

Technical Field

[0001] This invention relates to the field of hydrometallurgical technology, specifically to a low-cyanide gold leaching reagent system and its heap leaching process. Background Technology

[0002] Faced with the ban on cyanide in mineral extraction, traditional cyanide heap leaching processes are facing development difficulties due to the risks of high toxicity, high reagent consumption (accounting for 30-50% of the cost) caused by side reactions of impurity ions, and environmental governance.

[0003] While existing low-cyanide reagents reduce the amount of sodium cyanide used, they exhibit shortcomings in heap leaching scenarios: 1. Reagent decomposition and inactivation: Thiosulfate reagents are decomposed by ultraviolet light in open-air heap leaching (half-life < 72 h). Typical industrial practice shows that the effective concentration of the reagent decreases by more than 40% per month, and the leaching rate drops from 92% to 68%; 2. Insufficient adaptability to heap leaching: When gold leaching reagents are left for a long time, they are decomposed by microorganisms, generating ferric hydroxide precipitates that block the pores of the ore heap, causing the permeability to drop sharply by 65%, forcing a longer leaching cycle; 3. The unit consumption of mainstream environmentally friendly gold extraction agents is 10 times that of sodium cyanide. Coupled with decomposition losses and unblocking costs, the cost of processing per ton of ore increases. Summary of the Invention

[0004] In view of the technical problems existing in the background art, this application provides a low-cyanide gold leaching agent system and its heap leaching process, aiming to solve the problems of instability, long leaching cycle and high cost of existing low-cyanide gold leaching agent systems.

[0005] In a first aspect, this 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 thioglutamic acid ester, and the iron ion anti-precipitation chelating agent is mercaptomalic acid.

[0006] In the technical solution of this application embodiment, a low-cyanide gold leaching agent system is designed, using mercaptomalic acid as a chelating agent (as a masking agent for key impurity metals). The specific mercapto groups (-SH) in its molecule form an ultra-highly stable water-soluble complex with iron ions, completely blocking the formation of ferric hydroxide precipitation, solving the problem of ore pile blockage, maintaining the ore pile permeability coefficient, and eliminating the need for unblocking during the heap leaching process. The 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 amount of sodium cyanide used by more than 90% compared to the traditional industrial requirement (500ppm). With the synergistic effect of the chelating agent ensuring permeability stability and the leaching aid accelerating gold dissolution, the heap leaching cycle is compressed to 45 days. At the same time, the chelating agent-iron complex forms a self-buffering pair to prevent secondary precipitation. In addition, the introduced gold leaching aids mercaptomalic acid and glycine comply with the GB 2760 food safety standard. This gold leaching agent system achieves a triple breakthrough in environmental protection, economy, and high efficiency.

[0007] In some embodiments, the mass concentration of the leaching agent 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, by designing the dosage of each component in the pharmaceutical system, better synergistic effects can be achieved.

[0009] Secondly, this application provides a heap leaching process using a low-cyanide gold leaching agent system. The process, employing the aforementioned low-cyanide gold leaching agent system, includes the following steps:

[0010] S1. The gold-bearing mineral material is crushed to obtain a crushed sample, which is then added to a heap leaching column to obtain heap leaching material;

[0011] S2. The leaching aid and the iron ion anti-precipitation chelating agent are added to water in sequence, mixed evenly, and then the pH value is adjusted. Then the main leaching agent is added to obtain a mixed gold leaching solution.

[0012] S3. The mixed gold leaching solution is added from the top of the heap leaching column to leach the heap leaching material from top to bottom. The outflowing leachate is collected and pumped back to the top of the heap leaching column for circulating leaching. After the circulating leaching is completed, gold- and iron-containing precious solution and leaching mineral tailings are obtained.

[0013] In the technical solution of this application embodiment, a synergistic process of "interface activation, cyanide etching, and inhibition of iron precipitation" is constructed: the amino acid leaching aid adsorbs the gold surface, weakening the lattice energy, thereby increasing the etching efficiency of trace cyanide ions by 40-60%, and reducing the amount of cyanide used by more than 90% compared to the traditional industrial requirement (500ppm); the specific thiol group (-SH) in the chelating agent molecule forms an ultra-highly stable water-soluble complex with iron ions, completely blocking the formation of ferric hydroxide precipitation, solving the problem of ore pile blockage, maintaining the ore pile permeability coefficient, eliminating the need for unblocking during the heap leaching process, and the ferrous ions stabilized by the chelating agent are efficiently regenerated into potassium ferricyanide through in-situ oxidation with dissolved oxygen, eliminating the accumulation of free cyanide ions in the solution system (residual free cyanide in the tail liquid <0.5%). (ppm); At the same time, the chelating agent-iron complex forms a self-buffering pair, which precisely controls the pH fluctuation of the heap leaching solution and prevents secondary precipitation caused by local alkalization; With the synergistic effect of the core chelating agent ensuring stable penetration and the leaching aid accelerating gold dissolution, the heap leaching cycle is compressed to 45 days (the overall gold leaching rate is 65%, reaching 94% of the leaching limit, while traditional industrial cyanidation conditions require 120 days); the residual free cyanide in the tail liquid is <0.5 ppm.

[0014] In some embodiments, in step S2, the pH value in the pH adjustment is 10.0~10.6.

[0015] 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.

[0016] In some embodiments, in step S3, the intensity of the cyclic rinsing is 5 L / m. 2 •h; The cyclic rinsing time is 45 days.

[0017] In this embodiment, the leaching reaction is fully carried out through cyclic rinsing.

[0018] In some embodiments, in step S1, the ore particle size in the crushed sample is ≤2.8mm, accounting for ≥99%.

[0019] In this embodiment, the sample is crushed to facilitate the subsequent leaching reaction.

[0020] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description

[0021] To more clearly illustrate the technical solutions of this application, the accompanying drawings used in this application will be briefly described below. Obviously, the drawings described below are merely some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without any creative effort.

[0022] Figure 1 The images show a comparison of leaching systems with and without thiomalic acid in this application. (a) is a comparison image of a 12-hour stirred leaching test. (b) is a photo of a 7-day heap leaching test without thiomalic acid. (c) is a photo of the brown precipitate formed in the test group without thiomalic acid. (d) is a photo of the brown precipitate formed in the test group without thiomalic acid.

[0023] Figure 2 The images show the FTIR and SEM-EDS spectra of the brown precipitate after 12 hours of leaching in the leaching system without the addition of mercaptomalic acid in this application.

[0024] Figure 3 The images show SEM and energy dispersive spectroscopy (EDS) images of gold ore before and after leaching in the leaching system without the addition of mercaptomalic acid in this application. (a) is the backscattering image of the sample before leaching, (b) is the elemental surface distribution map of the sample before leaching, (c) is the elemental EDS image of the sample before leaching, (d) is the backscattering image of the sample after leaching, (e) is the elemental surface distribution map of the sample after leaching, and (f) is the elemental EDS image of the sample after leaching.

[0025] Figure 4 This is a Zeta potential distribution diagram of gold powder, ferrous glycinate, and the gold powder mixture (gold powder adsorbate) in the leaching system without the addition of mercaptomalic acid in this application.

[0026] Figure 5 (a) is a simulation test diagram of heap leaching of single-size ore in this application, and (b) is a physical image of the heavy leaching product of the simulation test of heap leaching of single-size ore in this application. Detailed Implementation

[0027] The embodiments of the technical solution of this application are described in detail below. The following embodiments are only used to illustrate the technical solution of this application more clearly, and are therefore only examples, and should not be used to limit the scope of protection of this application.

[0028] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0029] To address the issues of instability, long leaching cycles, and high costs associated with existing low-cyanide gold leaching systems, this application provides a low-cyanide gold leaching system and its heap leaching process. The low-cyanide gold leaching system employs a synergistic process of "interface activation, cyanide etching, and iron precipitation inhibition": an amino acid-based leaching aid adsorbs gold onto the surface, weakening the lattice energy and increasing the etching efficiency of trace cyanide ions by 40-60%, while reducing the amount of cyanide used to over 90% of the traditional industrial requirement (500 ppm); mercapto-containing malic acid is used as a chelating agent (as a masking agent for key impurity metals), whose specific thiol groups (-SH) form highly stable water-soluble complexes with iron ions, completely blocking the formation of iron hydroxide precipitates, solving the problem of ore heap clogging, maintaining the ore heap permeability coefficient, and preventing sludge buildup during the heap leaching process. To meet demand, the ferrous ions stabilized by the chelating agent are efficiently regenerated into potassium ferricyanide through in-situ oxidation with dissolved oxygen, eliminating the accumulation of free cyanide ions in the solution system (free cyanide residue in the tail liquid <0.5ppm). Simultaneously, the chelating agent-iron complex forms a self-buffering pair, precisely controlling pH fluctuations in the heap leaching solution and preventing secondary precipitation caused by localized alkalization. With the synergistic effect of the core chelating agent ensuring stable penetration and the leaching aid accelerating gold dissolution, the heap leaching cycle is reduced to 45 days (overall gold leaching rate of 65%, reaching the leaching limit of 94%, while traditional industrial cyanidation requires 120 days); free cyanide residue in the tail liquid is <0.5ppm. Furthermore, the introduced gold leaching aids, thiomalic 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.

[0030] In a first aspect, this 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 thioglutamic acid ester, and the iron ion anti-precipitation chelating agent is mercaptomalic acid.

[0031] In the technical solution of this application embodiment, a low-cyanide gold leaching agent system is designed, using mercaptomalic acid as a chelating agent (as a masking agent for key impurity metals). The specific mercapto groups (-SH) in its molecule form an ultra-highly stable water-soluble complex with iron ions, completely blocking the formation of ferric hydroxide precipitation, solving the problem of ore pile blockage, maintaining the ore pile permeability coefficient, and eliminating the need for unblocking during the heap leaching process. The 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 amount of sodium cyanide used by more than 90% compared to the traditional industrial requirement (500ppm). With the synergistic effect of the chelating agent ensuring permeability stability and the leaching aid accelerating gold dissolution, the heap leaching cycle is compressed to 45 days. At the same time, the chelating agent-iron complex forms a self-buffering pair to prevent secondary precipitation. In addition, the introduced gold leaching aids mercaptomalic acid and glycine comply with the GB 2760 food safety standard. This gold leaching agent system achieves a triple breakthrough in environmental protection, economy, and high efficiency.

[0032] Furthermore, in some embodiments, the mass concentration of the main leaching agent 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.

[0033] In the technical solution of this application embodiment, better synergistic cooperation can be achieved by designing the dosage of each component in the pharmaceutical system.

[0034] Secondly, this application provides a heap leaching process using a low-cyanide gold leaching agent system. The process, employing the aforementioned low-cyanide gold leaching agent system, includes the following steps:

[0035] S1. The gold-bearing mineral material is crushed to obtain a crushed sample, which is then added to a heap leaching column to obtain heap leaching material;

[0036] S2. The leaching aid and the iron ion anti-precipitation chelating agent are added to water in sequence, mixed evenly, and then the pH value is adjusted. Then the main leaching agent is added to obtain a mixed gold leaching solution.

[0037] S3. The mixed gold leaching solution is added from the top of the heap leaching column to leach the heap leaching material from top to bottom. The outflowing leachate is collected and pumped back to the top of the heap leaching column for circulating leaching. After the circulating leaching is completed, gold- and iron-containing precious solution and leaching mineral tailings are obtained.

[0038] In the technical solution of this application embodiment, a synergistic process of "interface activation, cyanide etching, and inhibition of iron precipitation" is constructed: the amino acid leaching aid 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 by more than 90% compared to the traditional industrial requirement (500ppm); the specific thiol group (-SH) in the chelating agent molecule forms an ultra-highly 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 coefficient, eliminating the need for unblocking during the heap leaching process, and the chelating agent stabilizes the ferrous ions. The gold is efficiently regenerated into potassium ferricyanide through in-situ oxidation with dissolved oxygen, eliminating the accumulation of free cyanide ions in the solution system (free cyanide residue in the tail liquid <0.5ppm). At the same time, the chelating agent-iron complex forms a self-buffering pair, precisely controlling the pH fluctuation of the heap leaching solution and preventing secondary precipitation caused by local alkalization. With the synergistic effect of the core chelating agent ensuring stable penetration and the leaching aid accelerating gold dissolution, the heap leaching cycle is reduced to 45 days (overall gold leaching rate of 65%, reaching 94% of the leaching limit, while traditional industrial cyanidation conditions require 120 days); the free cyanide residue in the tail liquid is <0.5ppm.

[0039] Furthermore, in some embodiments, in step S2, the pH value in the pH adjustment is 10.0~10.6.

[0040] In the technical solution of this application 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.

[0041] Furthermore, in some embodiments, in step S3, the intensity of the cyclic rinsing is 5 L / m. 2 •h; The cyclic rinsing time is 45 days.

[0042] In the technical solution of this application embodiment, the leaching reaction is fully carried out through cyclic rinsing.

[0043] Furthermore, in some embodiments, in step S1, the ore particle size in the crushed sample is ≤2.8mm, accounting for ≥99%.

[0044] In the technical solution of this application embodiment, the sample is crushed to facilitate the subsequent leaching reaction.

[0045] The following are some specific embodiments. It should be noted that the embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0046] Example 1

[0047] Example 1 provides a low-cyanide gold leaching agent system comprising sodium cyanide, glycine, and thiomalic acid.

[0048] The treatment of gold minerals using the above-mentioned gold leaching reagent system specifically includes the following steps:

[0049] (1) The gold-bearing mineral was crushed, and the particle size distribution was as follows. Then, it was added to a heap leaching column with a height of 1.2m and an inner diameter of 10cm, and the mineral accumulation height was 1m;

[0050] (2) Add 50g glycine and 150g mercaptomalic acid to 10L aqueous solution, mix well, add sodium hydroxide to adjust the pH value to 10.3, and then add 0.5g sodium cyanide to obtain a mixed gold immersion solution.

[0051] (3) The above mixed gold leaching solution is added from the top of the heap leaching column to leach the mineral from top to bottom. The leaching intensity is 5 L / m. 2 •h, collect the outflowing leachate and pump it back to the top of the heap leaching column for 45 days of circulating rinsing to obtain gold and iron-containing precious solutions and leaching mineral tailings.

[0052] Table 1 Particle size distribution of gold-bearing minerals after crushing

[0053]

[0054] The gold content in the leaching tailings of each embodiment and comparative example was determined using the fire assay method, and the testing and analysis methods were in accordance with GB / T 7739 "Chemical Analysis Methods for Gold Concentrates". Therefore, the gold leaching rate η was...

[0055]

[0056] Where η represents the gold leaching rate (%), m1 represents the mass of the original gold ore (g), β1 represents the grade of the original gold ore (g / t), m2 represents the mass of the residue after gold ore leaching (g), and β2 represents the grade of the residue after gold ore leaching (g / t).

[0057] The concentrations of gold, iron, and cyanide in the gold- and iron-containing precious solutions in each embodiment and comparative example were then detected by ICP-OES. The gold leaching rate test results of the two methods were compared, and data with a deviation of less than 1% between the test results of the two methods were considered valid. Finally, the gold leaching rate and the concentrations of iron and cyanide in the precious solutions in each embodiment and comparative example were measured.

[0058] Examples 2-6, Comparative Examples 1-4

[0059] Examples 2-6 and Comparative Examples 1-4 respectively provide a heap leaching process for a low cyanide gold leaching agent system. Compared with Example 1, the difference is that the mass concentration and type of leaching aid in the mixed gold leaching solution in step (2) of Examples 2-6 and Comparative Examples 1-3 are different. In Comparative Example 4, glycine was not added in step (2) and the mass concentration of sodium cyanide was the industrial standard concentration, as shown in Table 2. Other steps are roughly the same as in Example 1 and will not be repeated here.

[0060] Table 2 shows the mass concentration and type of leaching aids, gold leaching rate, and iron and cyanide concentrations in the mixed solutions of Examples 1-6 and Comparative Examples 1-4.

[0061]

[0062] As shown in Table 2, the introduction of glycine, glutamic acid, thioglycine ester, and thioglutamic acid ester is the core mechanism for improving the gold leaching rate (to 65-66%) and significantly reducing the free cyanide in the tailings (<0.5 mg / L): their molecules weaken the metal lattice energy by adsorbing the gold surface, thereby increasing the etching efficiency of trace cyanide (60 ppm) by 40-60%. At the same time, the chelating agent (thiomalic acid) forms a stable complex with iron ions, which not only blocks the precipitation of ferric hydroxide to maintain the permeability of the ore pile, but also promotes the oxidation of ferrous ions to potassium ferricyanide by dissolved oxygen, thus consuming free cyanide in situ and achieving cyanide self-purification. Compared with the group without leaching agent (comparative examples 3-4), the gold leaching rate dropped sharply and the cyanide residue increased dramatically, confirming the necessity of the dual-cycle synergy. In addition, the concentration of the leaching aid needs to reach the threshold (≥5g / L) to be effective (comparative example 1 only 48%), while excessive (15g / L) although maintaining the leaching rate, significantly increases the iron ion concentration (comparative example 2 up to 690mg / L), which will increase the chelating agent load. The economics need to be weighed, so it is not considered.

[0063] The leaching rates of the gold leaching reagent systems in Examples 1-3 and Comparative Examples 1-4 were tested. In Example 1, the gold ore was crushed to a density 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 thiomalic acid. The pH of the solution was then adjusted to 10.3 with sodium hydroxide, and sodium cyanide was added. Leaching was carried out with stirring. The leaching residue was tested at leaching times of 2 h, 4 h, 6 h, 8 h, 10 h, 12 h, 24 h, and 36 h, 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.

[0064] Table 3 shows the gold leaching rates of the gold leaching agents in Examples 1-3 and Comparative Examples 1-4 at different time points.

[0065]

[0066] As shown in Table 3, the data from Examples 1-3 and Comparative Example 3 demonstrate that glycine leaching aid can significantly improve the gold leaching rate in a low-concentration sodium cyanide (50 ppm) system. The data from Examples 1-3 and Comparative Example 4 show that even with low cyanide concentrations, the gold leaching rate is significantly improved compared to the traditional high cyanide concentration (500 ppm) process. Examples 1-3 and Comparative Example 1 show that when the glycine leaching aid content is greater than or equal to 5 g / L, the kinetic advantage is more significant in the early stages. This phenomenon stems from the fact that glycine adsorption weakens the lattice energy of the gold surface, thus doubling the mass transfer efficiency of trace cyanide ions. However, when the concentration is insufficient (4 g / L), although the initial growth rate is significant (37.18% in 4 hours), it weakens in the later stages (65.23% in 12 hours), indicating that the threshold concentration (≥5 g / L) is crucial for maintaining high-speed leaching. It is worth noting that excessive glycine (15 g / L) inhibits the leaching effect in the later stages (the leaching rate drops from 75.64% to 57.69% after 24-36 hours), possibly because an excessively thick adsorption layer hinders cyanide diffusion, highlighting the necessity of precise concentration control. Considering the indicators of the heap leaching process, a glycine concentration of 10 g / L is considered the optimal parameter range.

[0067] The gold leaching process described above conforms to the basic elements of the "contraction core model." During gold leaching, the reaction rate may be dominated by one of three factors: internal diffusion control, chemical reaction control, or mixed control, as expressed below. Where x is the gold leaching rate (%), t is the leaching time (min), k1 is the apparent rate constant under internal diffusion control, k2 is the apparent rate constant under chemical reaction control, and k3 is the apparent rate constant under mixed control.

[0068] 1 + 2(1-x) - 3(1-x) 2 / 3 =k1t 1-(1-x) 1 / 3 =k2t

[0069] 1 / 3ln(1-x)‒1+(1-x) −1 / 3 =k3t

[0070] The dissolution process of gold varies during leaching. The influence of leaching factors on the metal leaching rate differs under different control steps. Since heating was not used in the specific industrial setting, this chapter focuses on the leaching kinetics of gold at 298.15 K.

[0071] Based on preliminary experimental results, samples were taken and analyzed at different reaction times to examine the variation of gold leaching rate with leaching time. Based on the gold leaching rates obtained at different leaching times, and combining three model equations—internal diffusion control, chemical reaction control, and mixed control—the main controlling reactions of a low-cyanide gold leaching agent system in the gold leaching process can be determined. Linear fitting of leaching time and leaching rate was performed according to the equations; the slope of the fitted line represents the respective apparent reaction rate constants k1, k2, and k3, and the correlation coefficient R is used as the basis for further analysis. 2 The applicability of the model is determined by the value. Relevant research results are shown in Tables 4-6.

[0072] Table 4 1+2(1-x)-3(1-x) 2 / 3 Fitting data with leaching time

[0073]

[0074] Table 5 1-(1-x) 1 / 3 Fitting data with leaching time

[0075]

[0076] Table 6. Fitting of 1 / 3ln(1-x)⁻¹+(1-x)⁻¹ / ³ to leaching time

[0077]

[0078] Tables 4-6 show the linear fitting of gold leaching rates at different leaching times under 298.15 K conditions. The results indicate that in Comparative Examples 3-4, the chemical reaction control model using cyanide alone (50 ppm NaCN and 500 ppm NaCN) showed the highest goodness of fit, at 0.989 and 0.990 respectively. This suggests that the optimal kinetic function for cyanide gold leaching within 0-36 h is 1 - (1-x)¹ / ³ = k²t, meaning the leaching process is mainly controlled by the chemical reaction. In the low-cyanide gold leaching reagent system, i.e., Examples 1-3 and Comparative Examples 1-2, the mixed control model showed the highest goodness of fit, at 0.941, 0.943, 0.959, 0.968, and 0.964 respectively. Therefore, the optimal kinetic function for glycine-cyanide gold leaching within 0-36 h is 1 / 3ln(1-x)⁻¹ + (1-x). ‒1 / 3This indicates 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, causing the leaching process to shift from being chemically controlled to being controlled by a diffusion-reaction mixture. This conclusion is consistent with the "contraction core model" theory, which states that when the products are relatively compact and hinder mass transfer, internal diffusion is often the controlling step; when the products are relatively loose and do not affect mass transfer, chemical reaction is often the controlling step, thus demonstrating the necessity of introducing thiomalic acid.

[0079] Examples 7-8 and Comparative Examples 5-10

[0080] Examples 7-8 and Comparative Examples 5-10 respectively provide a heap leaching process for 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) of Examples 7-8 and Comparative Examples 5-7 is different. In Comparative Examples 8-10, mercaptomalic acid is replaced with sodium thioacetate, citric acid and ethylenediamine in step (2) respectively, as shown in Table 7. Other steps are roughly the same as in Example 1, and will not be repeated here.

[0081] Table 7 shows the types and concentrations of ferric ion anti-precipitation chelating agents and the leaching rates of gold, iron, and cyanide in Examples 7-8 and Comparative Examples 5-10.

[0082]

[0083] As shown in Table 7, mercaptomalic acid has a significant concentration threshold (≥10 g / L) as an iron ion chelating agent. It forms an ultra-highly stable complex with iron ions through specific mercapto 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 the aggravation of 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 leads to an imbalance in cyanide consumption. The unique structure of thiomalic acid is key. Compared with other chelating agents (Comparative Examples 8-10), even at the same concentration (15 g / L), sodium thioacetate / citric acid / ethylenediamine only achieves a gold leaching rate of 24-27%, while the iron ion concentration soars to 683-1090 mg / L, and cyanide residue exceeds 5 mg / L. This demonstrates that the anti-decomposition properties of its thiol group and its specificity for iron chelation are irreplaceable. Other conventional iron chelating agents are not suitable for the glycine system. While excess chelating agent (25 g / L, Comparative Example 6) maintains the leaching rate and cyanide purification effect, its economic viability must be considered.

[0084] The experimental processes of adding thiomalic acid as an anti-precipitation chelating agent and not adding thiomalic acid were analyzed. During the heap leaching process, at 12 hours of leaching, the heap leaching effects of adding and not adding thiomalic acid were as follows: Figure 1 As shown, (a) is a comparison image of the stirred leaching test after 12 hours; (b) is a photo of the heap leaching test after 7 days without the addition of thiomalic acid; (c) is a photo of the brown precipitate formed in the test group without the addition of thiomalic acid; and (d) is a photo of the brown precipitate collected in the test group without the addition of thiomalic acid. Heap leaching continued for 7 days, and the brown precipitate formed in the test group without the addition of thiomalic acid was collected. The substances were identified by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS), focusing on the characteristic peaks of Fe-N / O bond vibrations and the elemental surface distribution (stoichiometry of Fe, C, O, and N). The analytical results are as follows: Figure 2 As shown.

[0085] Depend on Figure 1 It can be seen that brown precipitate appeared on the upper part of the ore body without the addition of mercaptomalic acid, while no brown precipitate was produced on the upper part of the ore body with the addition of mercaptomalic acid; Figure 2 It can be seen that the precipitate is ferrous glycine, and some samples also contain a small amount of ferrous hydroxide. This indicates that mercaptomalic acid can form a highly stable water-soluble complex with iron ions in the reagent system, completely blocking the formation of ferric hydroxide precipitate, solving the problem of ore pile blockage, maintaining the ore pile permeability coefficient, and eliminating the need for dredging during the heap leaching process.

[0086] Ferrous glycinate precipitated in the solution phase exists as a flocculent suspension in the leaching system, forming a gel-like state. This leads to electrostatic attraction, potentially encapsulating finely dissociated gold particles in the ore, thus affecting the contact between gold and glycine and ultimately hindering the improvement of gold leaching rate. To verify this hypothesis, the surface morphology and energy dispersive spectroscopy (EDS) spectra of the gold ore before and after leaching were observed using SEM, such as... Figure 3 As shown, ferrous glycine formed a flocculent precipitate and coated the surface of the gold powder.

[0087] The zeta potential distribution method was used to study the gold powder, ferrous glycine, and the post-leaching gold powder mixture (gold powder adsorbate) in the leaching system environment. The results are as follows: Figure 4 As shown, the Zeta potential distribution of gold powder is centered at -10.67 mV, while that of ferrous glycinate powder is centered at -2.80 mV. Under the same leaching conditions, the Zeta potential distribution of the leached gold powder mixture (gold powder adsorbate) is centered at -2.23 mV, with a peak value between the peak values ​​of the two, but overall closer to the Zeta potential distribution of ferrous glycinate. This indicates that ferrous glycinate will coat the surface of the gold powder, a phenomenon consistent with... Figure 3 The SEM images are consistent.

[0088] To verify the formation mechanism of the precipitate and its impact on the gold leaching mechanism.

[0089] A heap leaching simulation test was conducted using ore of a single particle size. The experimental process and leaching product diagrams are shown below. Figure 5 As shown in (a) and (b), 1000g of a single-target particle size ore sample was loaded into a custom-made simple leaching column (8cm in diameter and 20cm in height) and operated at saturated drip intensity. The inflow rate was controlled by a peristaltic pump to ensure that the pores of the column were always in a liquid-saturated state (dynamic balance between inflow and outflow rates, and constant liquid level). The reagent system was the same as Comparative Example 7. The experimental period was 15 days. Inflow and outflow samples were collected simultaneously at preset time points (2 days, 10 days, and 15 days). After rapid filtration through a 0.22μm filter membrane, the instantaneous concentrations of Au and Fe in the solution were immediately determined by ICP-OES.

[0090] In a saturated drip leaching system, the leaching behavior of ores with different particle sizes shows significant differences.

[0091] On the second day, the effluent from the coarse-grained columns of 1.7~2.8mm and 0.85~1.7mm turned reddish-brown, and ICP-OES analysis showed that their iron concentrations were as high as 4638 mg / L and 3242 mg / L, respectively. In contrast, the effluent from the 0.425~0.85mm and <0.425mm particle sizes was colorless and had extremely low iron concentrations (121 mg / L and 37 mg / L, respectively), and no dissolved gold was detected in any of the particle sizes.

[0092] On day 10, the coarse-grained (1.7~2.8mm, 0.85~1.7mm) solution deepened in color to a reddish-brown hue, and the iron concentration further increased to 7600mg / L and 7200mg / L, respectively; the 0.425~0.85mm particle size solution showed a bright yellow color for the first time, and the iron concentration increased to 1155mg / L; the fine-grained (<0.425mm) solution remained colorless (iron concentration 129mg / L), and no dissolved gold was detected in any of the particle sizes.

[0093] On day 15, the coarse-particle-size solution turned dark red with bottom precipitation, and the iron concentration reached 7637 mg / L (1.7~2.8 mm) and 7668 mg / L (0.85~1.7 mm). The 0.425~0.85 mm solution evolved into a clear reddish-brown color, and the iron concentration increased sharply to 7230 mg / L. The fine-particle-size (<0.425 mm) solution turned bright yellow, with an iron concentration of 945 mg / L. In addition, gold was detected in the 0.425~0.85 mm and <0.425 mm particle-size solutions, at 0.226 mg / L and 0.388 mg / L, respectively, with liquid leaching rates of 31.39% and 31.04%, respectively.

[0094] The above verification process shows that ore particle size dominates the gold leaching process by controlling iron leaching kinetics. Coarse-grained ore (0.85~2.8 mm) exhibits explosive iron ion leaching due to its high porosity and large oxidation contact area (>3000 mg / L on day 2, >7000 mg / L on day 10). However, the excess iron exceeds the chelating capacity of glycine, leading to iron precipitation (a deep red solution with precipitate on day 15), which clogs pores and completely inhibits gold dissolution. Fine-grained ore (<0.425 mm), with its dense structure, slows oxidation, resulting in slow iron leaching (only 945 mg / L on day 15), and similarly, no gold leaching occurs. Gold leaching requires two conditions: medium-sized ore (0.425~0.85 mm) triggers a synergistic mechanism at the iron concentration threshold (~7000 mg / L)—glycine chelates iron to form an active complex. Therefore, this environment allows cyanide ions to directionally etch gold rather than be consumed by free iron.

[0095] In summary, this application provides a gold leaching reagent system for removing arsenic and a method for treating low-grade gold ore rich in arsenopyrite. By designing a low-cyanide gold leaching reagent system, a synergistic process of "interface activation, cyanide etching, and inhibition of iron precipitation" is constructed: an amino acid leaching aid adsorbs the gold surface, weakening the lattice energy, thus increasing the etching efficiency of trace cyanide ions by 40-60%, and reducing the amount of cyanide used by more than 90% compared to the traditional industrial requirement (500 ppm); mercapto-containing malic acid is used as a chelating agent (as a masking agent for key impurity metals), whose specific thiol groups (-SH) form ultra-highly stable water-soluble complexes with iron ions, completely blocking the formation of ferric hydroxide precipitation, solving the problem of ore pile blockage, maintaining the ore pile permeability coefficient, and preventing sludge buildup during the heap leaching process. To meet demand, the ferrous ions stabilized by the chelating agent are efficiently regenerated into potassium ferricyanide through in-situ oxidation with dissolved oxygen, eliminating the accumulation of free cyanide ions in the solution system (free cyanide residue in the tail liquid <0.5ppm). Simultaneously, the chelating agent-iron complex forms a self-buffering pair, precisely controlling pH fluctuations in the heap leaching solution and preventing secondary precipitation caused by localized alkalization. With the synergistic effect of the core chelating agent ensuring stable penetration and the leaching aid accelerating gold dissolution, the heap leaching cycle is reduced to 45 days (overall gold leaching rate of 65%, reaching the leaching limit of 94%, while traditional industrial cyanidation requires 120 days); free cyanide residue in the tail liquid is <0.5ppm. Furthermore, the introduced gold leaching aids, thiomalic 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.

[0096] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A low-cyanide gold leaching agent 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 thioglutamic acid ester, and the iron ion anti-precipitation chelating agent is mercaptomalic acid. The leaching agent has a mass concentration of 50 mg / L; the leaching aid has a mass concentration of 5-10 g / L; and the iron ion anti-precipitation chelating agent has a mass concentration of 10-20 g / L.

2. A heap leaching process for a low-cyanide gold leaching reagent system, characterized in that, The gold leaching process using the low-cyanide gold leaching reagent system described in claim 1 includes the following steps: S1. The gold-bearing mineral material is crushed to obtain a crushed sample, which is then added to a heap leaching column to obtain heap leaching material; S2. The leaching aid and the iron ion anti-precipitation chelating agent are added to water in sequence, mixed evenly, and then the pH value is adjusted. Then the main leaching agent is added to obtain a mixed gold leaching solution. S3. The mixed gold leaching solution is added from the top of the heap leaching column to leach the heap leaching material from top to bottom. The outflowing leachate is collected and pumped back to the top of the heap leaching column for circulating leaching. After the circulating leaching is completed, gold- and iron-containing precious solution and leaching mineral tailings are obtained.

3. The heap leaching process of the low-cyanide gold leaching agent system according to claim 2, characterized in that, In step S2, the pH value in the pH adjustment is 10.0~10.

6.

4. The heap leaching process of the low-cyanide gold leaching agent system according to claim 2, characterized in that, In step S3, the intensity of the cyclic rinsing is 5 L / m. 2 ·h.

5. The heap leaching process of the low-cyanide gold leaching agent system according to claim 2, characterized in that, In step S3, the cyclic rinsing time is 45 days.

6. The heap leaching process of the low-cyanide gold leaching agent system according to claim 2, characterized in that, In step S1, the ore particle size in the crushed sample is ≤2.8mm, accounting for ≥99%.

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