Heap leaching process for improving gold ore leaching rate

Abstract

The application provides a heap leaching method for improving leaching rate of gold ore, and belongs to the technical field of mineral processing. First, the mineral is separated into oversize and undersize; then the undersize is granulated by mixing sodium carboxymethyl cellulose, bentonite and ferrous sulfate as a binder; and then the undersize granules are mixed with the oversize and subjected to cyanide-free heap leaching. The method solves the problem of poor heap permeability of gold ore due to a large amount of clay minerals through staged granulation and stacking. In the granulation stage, the ferrous hydroxide colloid produced by the hydrolysis of ferrous sulfate in the binder can assist the agglomeration of ore granules and enhance the stability of the granules; in the subsequent cyanide-free heap leaching, in the thiourea gold leaching system, ferrous sulfate can act as an auxiliary reducing agent and a catalyst to promote the oxidation and dissolution of gold; at the same time, the ferrous ions can adjust the redox potential of the system, so that the thiourea gold leaching reaction is in a more favorable potential interval, the oxidation efficiency of thiourea is improved, the invalid decomposition of thiourea is reduced, and thus the dosage of thiourea and reagents is reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of mineral processing, and particularly relates to a heap leaching method for improving gold ore leaching rate. BACKGROUND

[0002] The heap leaching process is based on the basic principle of hydrometallurgy. After the ore is piled up, the leaching agent (such as cyanide solution) is sprayed to make the gold in the ore dissolve into the solution, and then the gold is recovered through subsequent adsorption, elution and electrolysis. This process saves the complex steps of crushing and grinding in traditional beneficiation. The process is widely used in low-grade ore processing after open-pit mining, tailings recovery in beneficiation plant and pretreatment of complex and difficult-to-treat gold ore.

[0003] However, the heap leaching process also faces many technical challenges in the development process. The early heap leaching process has low leaching efficiency, high reagent consumption and high risk of environmental pollution. For example, in traditional cyanide heap leaching, excessive use of cyanide may cause soil and water pollution; the leaching rate of high clay mineral refractory gold ore is often less than 60%.

[0004] Therefore, it is of great practical significance and broad application prospect to develop a cyanide-free leaching and granulation heap leaching process to prevent soil and water pollution, improve ore permeability, reduce the amount of gold leaching agent, and improve the environmental protection and efficiency of the heap leaching process. SUMMARY

[0005] In view of the technical problems in the background art, the present application provides a heap leaching method for improving gold ore leaching rate. The method mixes sodium carboxymethyl cellulose, bentonite and ferrous sulfate in a specific ratio as a binder, and uses the binder to granulate the ore with a particle size less than or equal to 2 mm to obtain undersize particles; then the undersize particles are mixed with oversize particles with a particle size greater than 2 mm and piled up. The method solves the problem of poor permeability of the piled ore due to the presence of clay minerals by classifying and granulating, and then piling up.

[0006] The introduction of the binder in the method not only solves the problem of granulation, but also reduces the amount of reagent for the subsequent gold leaching process. The bentonite in the binder improves the overall strength and water resistance of the particles, the sodium carboxymethyl cellulose optimizes the material flowability, and the ferrous sulfate assists in enhancing the stability and provides support for the gold leaching process. The three work together without adverse mutual interference and do not have harmful effects on thiourea gold leaching.

[0007] The present application provides a heap leaching method for improving gold ore leaching rate, which comprises the following steps:

[0008] S1, crushing and grinding the gold ore raw material to be treated to obtain ore with a particle size of less than 10 mm;

[0009] S2, using a standard sieve with a 2mm aperture to separate the ore obtained in step S1 into oversize material with a particle size greater than 2mm and undersize material with a particle size less than or equal to 2mm;

[0010] S3, mixing sodium carboxymethyl cellulose, bentonite and ferrous sulfate in proportion to form a medicament A; mixing the undersize material obtained in step S2 with medicament A and water, stirring to obtain undersize particles, and drying for standby use;

[0011] S4, mixing the oversize material obtained in step S2 with the dried undersize particles obtained in step S3, and stacking to obtain a mineral heap;

[0012] S5, mixing thiourea and ferric sulfate in a volume ratio of 1:1 to prepare a leaching solution, adjusting the pH value of the leaching solution to 2.0-1.0, and performing cyanide-free heap leaching on the mineral heap.

[0013] Further, in medicament A, the weight ratio of sodium carboxymethyl cellulose, bentonite and ferrous sulfate is (0.2-0.1):(5-2):1.

[0014] Further, in step S3, the weight ratio of undersize material, medicament A and water is 100:(1-3):(8-15).

[0015] Further, the water content of the dried undersize particles is 5%-8%.

[0016] Further, when stacking, the radius R of the heap leaching column is 12.5cm, the column height is 0.5-1.5m, and the bulk density is 1.6-1.8g / cm 3 , and the air permeability coefficient of the heap is (1-5)×10 -6 m 2 .

[0017] Further, in the leaching solution, the concentration of thiourea is 0.5%-1.5%, and the concentration of ferric sulfate is 0.2%-0.6%.

[0018] Further, when performing cyanide-free heap leaching, the spraying intensity is 5-12L / (m 2 h), and the leaching time is 40-60d.

[0019] Further, when performing cyanide-free heap leaching, the liquid-solid ratio of the mineral heap to the leaching solution is 1:(2-4).

[0020] Further, the way to adjust the pH value of the leaching solution is to add concentrated sulfuric acid with a volume fraction of 98%.

[0021] Further, in step S4, the weight ratio of oversize material to dried undersize particles is 2:1.

[0022] The beneficial effects of the present application are:

[0023] The present application provides a heap leaching method for improving the leaching rate of gold ore, which improves the leaching rate of gold in the heap leaching process and saves the cost of reagents. The method first classifies and granulates, and then piles up, solving the problem of poor permeability of the piled-up gold ore due to the large amount of clay minerals, and the classification and granulation workload is small and the cost is low. Moreover, the present application mixes sodium carboxymethyl cellulose, bentonite and ferrous sulfate in a specific ratio as a binder, which not only solves the problem of granulation, but also reduces the reagent consumption for subsequent gold leaching process.

[0024] Specifically, bentonite as an inorganic binder, with strong adsorption and colloidal properties, adsorbs ore particles through surface charge, and builds a stable skeleton structure to provide basic support for particle formation. Sodium carboxymethyl cellulose as an organic polymer binder, with the help of molecular chain winding, enhances the bonding force between particles, improves the plasticity of the material, improves the operability in the granulation process, and reduces dust generation. Ferrous sulfate, in the granulation stage, the hydrolysis of ferrous hydroxide colloid has certain adhesion, which can assist the agglomeration of ore particles, although the adhesion effect is weaker than bentonite and sodium carboxymethyl cellulose, but it can synergistically enhance the stability of the particles; in the subsequent cyanide-free heap leaching, in the thiourea gold leaching system, ferrous sulfate can be used as an auxiliary reducing agent and catalyst: in the presence of oxidizing agent (oxygen), ferrous ions (Fe² + ) are oxidized to high iron ions (Fe³ + ), and high iron ions are commonly used oxidizing agents for thiourea gold leaching, which can promote the oxidation and dissolution of gold; at the same time, ferrous ions can adjust the redox potential of the system, so that the thiourea gold leaching reaction is in a more favorable potential interval, improving the oxidation efficiency of thiourea, reducing its ineffective decomposition, thereby reducing the dosage of thiourea and reducing the reagent consumption.

[0025] The above description is only a summary of the technical solutions of the present application, in order to more clearly understand the technical means of the present application, which can be implemented according to the content of the specification, and in order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the following specific embodiments of the present application are described. BRIEF DESCRIPTION OF DRAWINGS

[0026] In order to more clearly illustrate the technical solutions of the present application, the following will briefly introduce the drawings used in the present application. Obviously, the drawings described below are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creating laborious work.

[0027] Fig. 1 The real object diagram when cyanide-free heap leaching is carried out in Comparative Example 1.

[0028] Fig. 2The actual figure after pouring out the slag in Comparative Example 1. DETAILED DESCRIPTION

[0029] The embodiments of the technical scheme of the present application will be described in detail below with reference to the drawings. The following examples are only used to more clearly illustrate the technical scheme of the present application, and therefore only serve as examples, and cannot limit the protection scope of the present application.

[0030] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present application; the terms "include" and "have" and any variations thereof used in the specification and claims of the present application and the above description of the drawings are intended to cover the non-exclusive inclusion.

[0031] The purpose of the present application is to provide a cyanide-free leaching, granulation heap leaching process to prevent soil and water pollution, improve ore permeability, reduce the amount of gold leaching agent, and thus improve the environmental protection and efficiency of the heap leaching process.

[0032] The embodiments of the present application provide a heap leaching method for improving the leaching rate of gold ore, comprising the following steps:

[0033] S1, crushing and grinding the gold ore raw material to be treated to obtain ore with a particle size of less than 10 mm, so that the ore particles are preliminarily refined;

[0034] S2, using a standard sieve with a pore size of 2 mm to separate the ore obtained in step S1 into sieve residue with a particle size greater than 2 mm and sieve underflow with a particle size less than or equal to 2 mm, so as to differentially treat ores of different particle sizes;

[0035] S3, uniformly mixing sodium carboxymethyl cellulose, bentonite and ferrous sulfate in proportion to form a reagent A for standby; mixing the sieve underflow obtained in step S2 with reagent A and water, stirring to obtain sieve underflow particles, and drying for standby;

[0036] Among them, in reagent A, according to the weight ratio, sodium carboxymethyl cellulose: bentonite: ferrous sulfate = (0.2~0.1): (5~2): 1. The bentonite improves the overall strength and water resistance of the particles, the sodium carboxymethyl cellulose optimizes the flowability of the material, and the ferrous sulfate assists in enhancing the stability and provides support for the gold leaching process. The three work together and do not interfere with each other, and will not have a harmful effect on the thiourea gold leaching.

[0037] According to the weight ratio, sieve underflow: reagent A: water = 100: (1 - 3): (8 - 15).

[0038] The three are uniformly stirred in a stirring device, the stirring speed of the stirring device is 200-300 r / min, and the stirring time is 5-10 min, so that the material forms particles with certain strength and porosity. After stirring is completed, the prepared particles are placed in a ventilated and dried place to dry, and the moisture content of the dried particles is 5%-8% to meet the requirements of subsequent heap building on the strength and air permeability of the particles.

[0039] S4, the oversize obtained in step S2 is mixed with the dried undersize particles obtained in step S3, and then heap building is performed to obtain a mineral heap;

[0040] The weight ratio of the oversize to the dried undersize is 2:1. The particles of the two particle sizes are thoroughly mixed, and then heap building is performed according to the heap building process.

[0041] During heap building, the radius R of the heap leaching column is 12.5 cm, the column heap height is 0.5-1.5 m, the heap density is 1.6-1.8 g / cm 3 , and the air permeability coefficient of the heap is (1-5) x 10 -6 m 2 .

[0042] S5, thiourea and ferric sulfate are mixed in a volume ratio of 1:1 to prepare a leaching solution, concentrated sulfuric acid with a volume fraction of 98% is added to adjust the pH value of the leaching solution to 2.0-1.0, and then cyanide-free heap leaching is performed on the mineral heap.

[0043] In the leaching solution, the concentration of thiourea is 0.5%-1.5%, and the concentration of ferric sulfate is 0.2%-0.6%.

[0044] During cyanide-free heap leaching, the liquid-solid ratio of the mineral heap to the leaching solution is 1: (2-4).

[0045] The spraying intensity is 5-12 L / (m 2 h), and the leaching time is 40-60 d.

[0046] Some specific examples are listed below. It should be noted that the examples described below are exemplary and are used to explain the present application, and cannot be understood as limiting the present application. If a specific technology or condition is not specified in the examples, it is performed according to the technology or condition described in the literature in the art or according to the product manual. If the reagent or instrument is not specified by the manufacturer, it is a conventional product that can be obtained by purchase.

[0047] Example 1

[0048] S1, sample preparation: select the gold ore raw material to be treated, use the jaw crusher to crush it, so that the particle size range is 20-30mm, and then use the high-pressure roller mill to grind the ore to a particle size of less than 10mm, so that the ore particles are preliminarily refined.

[0049] A small part of the ore is uniformly ground to 200 mesh content of more than 80%, and the gold grade of the test sample is tested. It can be seen that the gold grade Au=1.05g / t.

[0050] S2, sample screening: the ore sample obtained in step S1 is screened by using a standard sieve with a pore size of 2mm. Through the screening operation, the ore sample is separated into oversize material with a particle size greater than 2mm and undersize material with a particle size less than or equal to 2mm, so as to differentially treat ores of different particle sizes.

[0051] S3, binder preparation: uniformly mix sodium carboxymethyl cellulose, bentonite and ferrous sulfate in proportion to form a reagent A for later use. Among them, according to the weight ratio, sodium carboxymethyl cellulose:bentonite:ferrous sulfate=0.1:2:1.

[0052] Classification granulation: the undersize material obtained by screening is uniformly mixed, and then an appropriate amount of reagent A and water is added; wherein, according to the weight ratio, undersize material: reagent A: water=100:2:10. Then, uniform stirring is carried out in a stirring device, the stirring speed of the stirring device is 300r / min, and the stirring time is 10min, so that the material forms particles with certain strength and porosity.

[0053] After stirring is completed, the prepared particles are placed in a well-ventilated and dry place to dry, and the water content of the dried particles is controlled to be 7% to meet the requirements of the subsequent heap on the strength and air permeability of the particles.

[0054] S4, ore column heap: the oversize material obtained in step S2 and the dried undersize material particles obtained in step S4 are mixed in a weight ratio of 2:1, and then the heap is built.

[0055] Among them, the radius R of the heap leaching column is 12.5cm, the column height is 1.5m, and the bulk density is 1.7g / cm 3 , the air permeability coefficient of the heap body is 3x10 -6 m 2 .

[0056] S5, cyanide-free heap leaching: the concentration of thiourea is 1.0%, the concentration of ferric sulfate is 0.4%, and the two are mixed in a volume ratio of 1:1 to prepare the leaching solution. When preparing, use deionized water to dissolve, the stirring rate is 300r / min, and the dissolution time is 10 minutes, so as to ensure that the reagent is completely dissolved without precipitation.

[0057] The pH value of the leaching solution was adjusted to 1.5 by adding concentrated sulfuric acid with a volume fraction of 98%, and the spray intensity was set to 10 L / (m 2 h), the leaching time was 50 d, and the liquid-solid ratio of the mineral heap to the leaching solution was 1:3.

[0058] Subsequently, the column was unloaded, the sample was mixed and ground, and the sample was sent for testing. It was found that the gold grade Au1=0.17 g / t.

[0059] Calculation showed that the gold leaching rate = 1-0.17 / 1.05 = 83.81%.

[0060] Comparative Example 1

[0061] The main difference between Comparative Example 1 and Example 1 is that steps S2 and S3 are not performed, and the sample prepared in step S1 is directly subjected to ore column stacking and cyanide-free heap leaching. Other experimental parameters and conditions are basically the same as those in Example 1 and will not be described here.

[0062] It was found that the heap leaching column circulating liquid could not penetrate, and the leaching residue was dense when poured out, as shown in Figs. 1-2 .

[0063] Examples 2-3 and Comparative Examples 2-4

[0064] Examples 2-3 and Comparative Examples 2-4 provide a heap leaching method for improving the leaching rate of gold ore. Compared with Example 1, the difference lies in the different amounts of sodium carboxymethyl cellulose, bentonite, and ferrous sulfate in the reagent A, as shown in Table 1. Other experimental parameters and conditions are basically the same as those in Example 1 and will not be described here.

[0065] Table 1.

[0066]

[0067] As can be seen from the above table, the weight ratio of sodium carboxymethyl cellulose, bentonite, and ferrous sulfate directly determines the final gold leaching effect. The weight ratio of sodium carboxymethyl cellulose, bentonite, and ferrous sulfate needs to be controlled within the range of (0.2-0.1):(5-2):1. When the weight ratio of the amount of ferrous sulfate is fixed at 1, the amount of sodium carboxymethyl cellulose needs to be controlled within the range of 0.1-0.2. Too low an amount will significantly weaken the gold leaching effect, and an appropriate increase (0.1→0.2) has less negative impact on the leaching rate. The amount of bentonite is one of the key factors affecting the gold leaching rate. Too low an amount will cause a significant decrease in the leaching rate, and too high an amount will cause a slight decrease in the leaching rate.

[0068] Note that the present application is not limited to the above-described embodiments. The above-described embodiments are merely examples, and embodiments having substantially the same configuration, function, and effect as the technical idea of the present application are included in the technical scope of the present application. Furthermore, other modes constructed by applying various modifications to the embodiments, or by combining part of the configurations of the embodiments, which can be conceived by those skilled in the art, without departing from the spirit of the present application, are also included in the scope of the present application.

Claims

1. A heap leaching process for improving the leachability of gold ores, characterised in that, The method comprises the following steps: S1, crushing and grinding the gold ore raw material to be treated to obtain ore with particle size less than 10 mm; S2, using a standard sieve with a pore size of 2 mm to separate the ore obtained in step S1 into oversize material with particle size greater than 2 mm and undersize material with particle size less than or equal to 2 mm; S3, uniformly mixing sodium carboxymethyl cellulose, bentonite and ferrous sulfate in a certain proportion to obtain a reagent A; mixing the undersize material obtained in step S2 with the reagent A and water, stirring to obtain undersize particles, and drying for standby; in the reagent A, the weight ratio of sodium carboxymethyl cellulose, bentonite and ferrous sulfate is (0.2-0.1):(5-2):1; S4, mixing the oversize material obtained in step S2 with the dried undersize particles obtained in step S3, and then stacking to obtain a mineral heap; S5, mixing thiourea and ferric sulfate in a volume ratio of 1:1 to prepare a leaching solution, adjusting the pH value of the leaching solution to 2.0-1.0, and cyanide-free heap leaching the mineral heap.

2. The heap leaching method for improving gold ore leaching rate according to claim 1, characterized in that, In step S3, the weight ratio of undersize material, reagent A and water is 100:(1-3):(8-15).

3. The heap leaching method for improving gold ore leaching rate according to claim 1, characterized in that, The water content of the dried undersize particles is 5%-8%.

4. The heap leaching method for improving gold ore leaching rate according to claim 1, characterized in that, The heap leaching column radius R is 12.5 cm, the column heap height is 0.5-1.5 m, the heap density is 1.6-1.8 g / cm 3 , and the heap air permeability coefficient is (1-5) x 10 -6 m 2 .

5. The heap leaching method for improving gold ore leaching rate according to claim 1, characterized in that, In the leaching solution, the concentration of thiourea is 0.5%-1.5%, and the concentration of ferric sulfate is 0.2%-0.6%.

6. The heap leaching method for improving gold ore leaching rate according to claim 1, characterized in that, When cyanide-free heap leaching, the spraying intensity is 5-12 L / (m 2 h), and the leaching time is 40-60 d.

7. The heap leaching method for improving gold ore leaching rate according to claim 1, characterized in that, When cyanide-free heap leaching, the liquid-solid ratio of the amount of mineral heap to leaching solution is 1:(2-4).

8. The heap leaching method for improving gold ore leaching rate according to claim 1, characterized in that, The way to adjust the pH value of the leaching solution is to add concentrated sulfuric acid with a volume fraction of 98%.

9. The heap leaching method for improving gold ore leaching rate according to claim 1, characterized in that, In step S4, the weight ratio of oversize material to dried undersize particles is 2:1.

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