A method for analyzing gold content in ores

Abstract

This invention relates to the field of gold content analysis technology in ores, and more particularly to a method for analyzing gold content in ores. This method recovers large and fine free gold particles in stages, and achieves quantitative analysis of the total gold content through oxidation desulfurization and a dissolution-complexation reduction system. It also enables efficient refining and recovery of gold, achieving integrated analysis and recovery.

Description

Technical Field

[0001] This invention relates to the field of gold content analysis technology in ores, and specifically to a method for analyzing gold content in ores. Background Technology

[0002] With the development of society and the economy and the improvement of people's living standards, the consumer market is generally demanding higher and higher quality gold. This, in turn, urges the mining industry to develop high-quality ores to meet market demands. The ability to quickly and accurately determine the gold content in ores is of great significance for the rational development and resource utilization of mineral resources, and brings enormous economic value.

[0003] Gold exists in ores in various forms, including free gold, encapsulated gold, and sulfide-bound gold. Traditional fire assays, cyanide assays, or aqua regia dissolution methods have the following drawbacks: For ores containing coarse-grained gold, sample uniformity and poor sample representativeness lead to poor reproducibility of analytical results and may even miss industrially valuable ore bodies. The analysis of low-grade gold ores is equally challenging. Due to their lower gold grade, traditional analytical methods struggle to accurately detect gold content from small samples: incomplete extraction of encapsulated or sulfide-bound gold results in lower values; free gold particles vary in size and are easily lost during grinding; high concentrations of cyanide or aqua regia pose environmental and operational safety risks; and the inability to optimize processes based on sulfide types leads to reagent waste.

[0004] Therefore, a comprehensive analysis method that balances accuracy, environmental friendliness, and economy is needed. Summary of the Invention

[0005] To address the above-mentioned technical problems, this invention provides a method for analyzing the gold content in ores. Firstly, this method optimizes the ore sample pretreatment process, enabling accurate and efficient dissolution of gold from the ore sample while avoiding gold ion loss during sample processing, thus ensuring reliable detection results. Secondly, it recovers large and fine free gold particles in stages, and achieves quantitative analysis of the total gold content through oxidation-desulfurization and a dissolution-complexation reduction system. Furthermore, it enables efficient refining and recovery of gold, achieving integrated "analysis-recovery" processes.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0007] This invention provides a method for analyzing the gold content in ores, comprising the following steps:

[0008] S1. Take ore samples from different mining sites and use mineral liberation analysis (MLA) to analyze the types of sulfides in the ore samples, determine the occurrence state and particle size distribution of gold, and thus determine the analytical method.

[0009] S2. Weigh an ore sample with mass m, dry and crush it to a particle size <2mm, then sieve it to collect free gold particles ≥2mm, and record it as m1; ball mill the first sieve material to <0.5mm, perform a second sieve, collect free gold particles ≥0.5mm, and record it as m2; then ball mill the second sieve material to <-400 mesh to obtain slurry;

[0010] S3. Mix the slurry with peracetic acid, adjust the pH to ≤3, and heat the reaction for at least 6 hours to allow the sulfides to fully decompose and release the encapsulated gold, thus obtaining a mixed solution.

[0011] S4. Then place the mixed solution in a high temperature and high pressure oxygen environment and react for at least 2 hours to completely destroy the sulfide lattice. After solid-liquid separation, a solid is obtained.

[0012] S5. Add the solid to the NaI / I2 solution and microwave heat for at least 2 hours to utilize the I3 formed by NaI and I2. - Oxidizes sulfides and simultaneously dissolves gold (Au oxide) 0 →Au + This process dissolves solid gold to form a stable [AuI4]- complex ion, which is then separated into solid and liquid phases to obtain a product containing [AuI4]. - The target solution;

[0013] S6. The gold content in the target solution was determined by spectrophotometry and recorded as m3.

[0014] S7. Gold content of ore sample = (m1 + m2 + m3) / m * 100%.

[0015] This invention first analyzes the sulfide types in the ore sample to determine the analytical method. Second, through staged grinding and sieving, large-particle free gold, small-particle free gold, and slurry are collected in stages to ensure no loss of free gold, fully dissociate the gold ore, and completely release the gold bound to the sulfides. Finally, a wet method is used to analyze the gold content in the slurry. The slurry is then oxidized with mild and environmentally friendly peracetic acid in an acidic environment to destroy the sulfide encapsulation structure and expose the gold particles. If undissolved minerals remain, the mixed solution is further subjected to high-temperature, high-pressure oxidation in an oxygen atmosphere to oxidize the sulfides (e.g., pyrite, arsenopyrite, etc.) into soluble sulfates (Fe2(SO4)3, H2SO4), and arsenic is converted into arsenic trioxide (FeAsO4·2H2O), fully releasing the encapsulated gold. Finally, the gold is leached using an environmentally friendly, cyanide-free NaI / I2 solution (a non-cyanide gold leaching system) and microwave-assisted dissolution to obtain gold containing soluble [AuI4]. - The target solution of the complex was obtained; finally, the gold content of the target solution was calculated by spectrophotometry at 548 nm.

[0016] The analytical method of this invention, on the one hand, uses mineral dissociation to analyze the type of sulfides in ore samples, determines the analytical method, and optimizes the process steps, solving the problem that traditional methods cannot optimize the process according to the type of sulfides, resulting in reagent waste; on the other hand, it uses mild peracetic acid combined with high-temperature oxidation to remove sulfides and release encapsulated gold, and then uses environmentally friendly and low-toxic NaI / I2 solution for microwave-assisted dissolution of gold, avoiding the operational hazards and environmental pollution problems caused by traditional high-concentration cyanide or aqua regia dissolution of gold.

[0017] In summary, this method is simple to operate, requires no large equipment such as ICP-MS, and has low investment costs. It is a full-process analysis method that balances accuracy, environmental friendliness, and economy.

[0018] Preferably, step S3 is as follows: the slurry is mixed with peracetic acid, and 1-3 mol / L of sulfuric acid or hydrochloric acid is added to precisely adjust the pH to ≤3. The mixture is then reacted at 60-80℃ and 300-500 r / min for 6-12 h. The peracetic acid fully oxidizes the slurry and destroys the sulfide structure to obtain a mixed solution.

[0019] Preferably, the solid-liquid ratio of the slurry to peracetic acid is 1:(3-5);

[0020] The concentration of peracetic acid is 5% v / v - 10% v / v;

[0021] Peracetic acid is added to the slurry in 3-5 batches at a solid-liquid ratio of 1:(3-5) to avoid violent exothermic reactions and reduce reagent consumption.

[0022] Preferably, step S4 is as follows: the mixed solution is placed in an oxygen environment of 200-250℃ and 2-3 MPa for 1-2 hours to ensure that the sulfide is completely converted into soluble sulfate, the solid is separated, and the solid is washed with deionized water until the pH of the washing liquid is 7-8 to remove soluble impurities and avoid residual acid on the solid from affecting subsequent operations; at the same time, copper / arsenic is recovered from the waste liquid.

[0023] Preferably, step S5 specifically involves: adding the solid to a NaI / I2 solution, heating it at pH 7-9 and 40-60℃ using microwave for 1-2 hours, separating the solid and liquid, washing the residue with deionized water to improve the gold recovery rate, and collecting the washing liquid and filtrate to obtain the target solution.

[0024] The principle of gold leaching with NaI / I2 solution in this invention is as follows: Potassium iodide (NaI) and iodine (I2) form an oxidation-coordination system, which oxidizes and dissolves elemental gold, resulting in a stable gold-iodine [AuI4] solution. - The gold dissolves into the solution in ionic form, completing the leaching process: Au + 2I- + I2 → [AuI4]-.

[0025] pH 7-9 can prevent I - Oxidized to IO3 - .

[0026] Microwave heating at 40-60℃ accelerates the dissolution of gold. However, when the temperature exceeds 70℃, it easily leads to the volatilization of I2.

[0027] Preferably, in the NaI / I2 solution, the concentration of NaI solution is (1-3) mol / L, and the mass concentration is (149.9–449.7) g / L, with excess I... - Ensure I3 - It exists stably.

[0028] The concentration of I2 is (1-1.5) mol / L, and the mass concentration is (253.8–380.7) g / L;

[0029] The molar ratio of I2 / NaI is 1:(1-3), with NaI in excess. This avoids excess I2, which could lead to side reactions, and also preserves the solubility of I2 in the NaI system, thus ensuring complete dissolution of gold.

[0030] This invention reveals that the NaI / I2 solution system has higher solubility than KI / I2, and can be used to prepare high-concentration I... - This reduces the amount of solution used, and NaI is cheaper than KI, making it suitable for industrial-scale applications. The waste liquid is free of cyanide pollution, and gold can be recovered and I- regenerated using reducing agents (such as Na2S2O3 or ascorbic acid).

[0031] Preferably, in step S6, the gold content in the target solution is tested by spectrophotometry, including: testing the gold standard solution-absorbance standard curve at different concentrations of the gold standard solution at a wavelength of 548 nm, while using deionized water as a blank reference; then testing the absorbance of the target solution, and obtaining the gold content in the target solution by subtracting the absorbance from the gold standard solution-absorbance standard curve.

[0032] This invention utilizes [AuI4] at 548 nm. - It exhibits high molar absorptivity with a linear range of 0.1-5 g / L; after subtracting matrix interference, the RSD is <2%.

[0033] Preferably, in step S6, the method for recovering gold from the target solution includes the following steps:

[0034] (1) Activated carbon adsorption: to [AuI4] - Add 5 g / L of 20-50 mesh activated carbon to the target solution, stir at 200-300 r / min for 4-8 h, and the gold-loaded carbon is ≥5 kg / t. Separate the solid to obtain activated carbon that adsorbs gold. At the same time, reduce the waste liquid with Na2S2O3 with a mass concentration of 5%-10% to precipitate I2.

[0035] (2) Electrolysis-smelting: After washing and desorbing the gold adsorbed by activated carbon 3-5 times with a mixed solution of 1% NaOH and 1% NaI, the gold mud is added to the electrolytic cell of the electrolysis system and reduced by electrolysis to obtain gold mud; the gold mud is then dissolved and cleaned with dilute hydrochloric acid, washed until neutral, dried at 105℃, and smelted at 1200℃ to obtain gold ingots with a purity ≥99.5%.

[0036] Preferably, in step (1), the resulting waste liquid is reduced and precipitated with Na2S2O3 at a mass concentration of 5%-10% to achieve the recycling of I2, and I2 < 5 mg / L, which meets the emission standards. Attached Figure Description

[0037] Figure 1 This is a flowchart of the gold content analysis in the ore according to the present invention;

[0038] Figure 2 This is a graph showing the linear relationship between absorbance and concentration of the gold standard solution of this invention. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0040] The product models cited in this invention specification are for illustrative purposes only and are not affiliated with the rights holder or manufacturer.

[0041] Example 1

[0042] I. Methods for analyzing gold content in ores, including:

[0043] S1. Take mineral samples from different geological sites to increase the representativeness of the samples. Use mineral dissociation method (MLA) to analyze the pyrite-type gold ore and determine the analytical method.

[0044] S2. Weigh 1 kg of pyrite-type gold ore sample, place it in an oven at 105-110℃ and dry it for 2-4 hours to remove moisture; then crush it with a jaw crusher to a particle size <2 mm, sieve it, and collect the free gold with a particle size ≥2 mm, which is recorded as m1 = 0.12 g.

[0045] The material that passed through the first sieve was then ground to 0.5 mm using a ball mill, followed by a second sieve to collect free gold particles with a diameter ≥ 0.5 mm, denoted as m. 2＝ 0.08g; the material that passes through the second sieve is then ground in a ball mill to -400 mesh to obtain a slurry, ensuring that the gold ore is fully liberated;

[0046] S3. Add the slurry and 10% v / v peracetic acid to the reaction vessel at a solid-liquid ratio of 1:5. The peracetic acid is added in three batches to avoid the occurrence of burns caused by the violent exothermic reaction of peracetic acid. Continue to add 3 mol / L dilute sulfuric acid to the reaction vessel to adjust the pH to 1. After stirring at 300 r / min at 80℃ for 6 h, the mixture is stirred to fully oxidize the sulfides on the gold surface, destroy the sulfide structure, and release the exposed gold particles to obtain a mixed solution.

[0047] S4. If undissolved sulfides remain, place the mixed solution in an autoclave and purge at 250°C with oxygen at 3 MPa for 2 hours to further oxidize the sulfides and soluble sulfates (SO42-). 2- Stop the oxygen supply, open the reaction vessel, centrifuge the reaction solution at 10000r / min for 50min to separate the solid and liquid, wash the solid with deionized water until the pH of the washing solution is 7, remove soluble sulfate and other impurities, and avoid residual acid on the solid from affecting subsequent operations.

[0048] S5. Add the washed solid and 2500 ml of NaI / I2 solution (NaI concentration is 3 mol / L, I2 concentration is 1 mol / L, NaI / I2 molar ratio is 1:3, ensuring excess I2 to fully dissolve the gold) to a sealed reaction vessel. Heat to 60°C using a microwave at pH 7 for 2 hours to fully dissolve the gold particles into soluble [AuI4]. - The gold solution is prepared by centrifuging at 10,000 rpm for 30 minutes to separate solids and liquids. The residue is washed five times with deionized water to improve the gold recovery rate. The washing liquid and filtrate are collected to obtain the target solution.

[0049] S6. The gold content in the target solution was determined using spectrophotometry, including: measuring the absorbance of the gold standard solution at 548 nm for 0 g, 0.5 g, 1 g, 1.5 g, 1.7 g, 2.0 g, 2.5 g, 3.0 g, 4.0 g, and 5.0 g to obtain a gold standard solution-absorbance standard curve, with deionized water as a blank reference; then, the absorbance of the target solution was measured to be 0.377, and the result was used to input the absorbance 0.377 into the gold standard solution-absorbance standard curve y = 0.2157x, R... 2 =0.9989, y is absorbance, x is the mass of gold, and the gold content in the target solution is obtained, denoted as m3 = 1.75g.

[0050] S7, Gold content in ore = (0.12 + 0.08 + 1.75) / 1000 × 100% = 0.195%, 6 parallel tests, RSD = 1.8%.

[0051] This invention utilizes [AuI4] at 548 nm. - It exhibits high molar absorptivity with a linear range of 0.1-5.0 g / L; after subtracting matrix interference, the RSD is <2%.

[0052] II. Gold Recovery: Gold is recovered using activated carbon adsorption and electrolysis. The specific method is as follows:

[0053] (1) Activated carbon adsorption

[0054] To [AuI4] - 5 g / L of 20-50 mesh activated carbon was added to the target solution. After stirring at 300 r / min for 4-8 h, solid-liquid separation was performed. The obtained activated carbon particles were washed with a mixed solution of 1% NaOH and 1% NaI. The gold-loaded carbon was ≥5 kg / t. The solid was separated to obtain gold-adsorbed activated carbon, which was then added to the electrolytic cell of the electrolytic system for electrolytic reduction of gold. Simultaneously, the waste liquid was reduced and precipitated with 10% Na2S2O3 to achieve I2 recycling. The electrolytic cell used a stainless steel cathode and a titanium anode. The current density of the cathode area was 1500 A / m2, the electrode spacing was controlled at 20-30 mm, a DC voltage of 3.0 V was applied, and electrolysis was carried out for 12 h. During this period, a loose gold mud layer gradually formed on the cathode surface. The gold concentration of the electrolyte must be controlled at <1.0 g / m3; otherwise, it must be returned to the desorption system. After electrolysis, the power was turned off, the cathode plate was removed, and the gold mud was rinsed off with a high-pressure water gun.

[0055] (2) Electrolysis-melting

[0056] The gold mud was placed in an acid-resistant container and soaked in 10% dilute HCl for 1 hour to dissolve any impurities such as iron and copper. It was then washed with deionized water until neutral. The washed gold mud was dried at 105℃ for 2 hours and then smelted at 1200℃ to obtain gold ingots with a purity ≥99.4%, weighing 1.74g each. That is, 1 kg of ore corresponds to 1.75g ​​of gold in the target solution, and cyanidation-carbon-in-pulp-electrolysis yields 1.74g of gold ingots with a purity of 99.4%.

[0057] This invention achieves quantitative analysis of total gold content and efficient refining and recovery of gold through a closed-loop process of "staged recovery of free gold - gentle oxidation of sulfides - efficient complexation leaching of gold - spectrophotometric detection of gold content - green recycling," realizing integrated "analysis-recovery." The total gold recovery rate is ≥99%, avoiding the operational hazards and environmental pollution associated with traditional methods of dissolving gold using high-concentration cyanide or aqua regia.

[0058] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions or improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for analyzing the gold content in ores, characterized in that, Includes the following steps: S1. Take ore samples from different mining sites, analyze the types of sulfides in the ore samples using the mineral dissociation method, and determine the analytical method. S2. Weigh out a mass m of the ore sample, dry and crush it to a particle size <2mm, then sieve it to collect free gold particles ≥2mm, and record it as m1; ball mill the first sieve material to <0.5mm, perform a second sieve, collect free gold particles ≥0.5mm, and record it as m2; then ball mill the second sieve material to <-400 mesh to obtain a slurry; S3. Mix the slurry with peracetic acid, adjust the pH to ≤3, and heat the reaction for at least 6 hours to obtain a mixed solution; S4. Place the mixed solution in a high-temperature, high-pressure oxygen environment and react for at least 1 hour to obtain a solid. S5. Add the solid to a NaI / I2 solution and microwave heat for at least 2 hours to separate the solid and liquid, thus obtaining the target solution. S6. The gold content in the target solution was determined by spectrophotometry and recorded as m3. S7. The gold content of the ore sample = (m1 + m2 + m3) / m * 100%.

2. The method for analyzing gold content in ore as described in claim 1, characterized in that, The specific steps of step S3 are as follows: The slurry is mixed with peracetic acid, and 1-3 mol / L sulfuric acid or hydrochloric acid is added to adjust the pH to ≤3. The mixture is then reacted at 60-80℃ and 300-500 r / min for 6-12 h to obtain a mixed solution.

3. The method for analyzing gold content in ore as described in claim 2, characterized in that, The solid-liquid ratio of the slurry to peracetic acid is 1:(3-5); and / or The concentration of the peracetic acid is 5% v / v to 10% v / v; and / or The peracetic acid is added to the slurry in batches at a solid-liquid ratio of 1:(3-5).

4. The method for analyzing gold content in ore as described in claim 1, characterized in that, The specific steps of step S4 are as follows: The mixed solution was placed in an oxygen environment at 200-250℃ and 2-3 MPa for 1-2 hours to separate the solid and liquid. The solid was then washed with deionized water until the pH of the washing solution was 7-8.

5. The method for analyzing gold content in ore as described in claim 1, characterized in that, Step S5 is as follows: The solid was added to a NaI / I2 solution, heated at pH 7–9 and 40–60℃ for 2–4 hours using microwave, and then the solid and liquid were separated. The residue was washed with deionized water, and the washing liquid and filtrate were collected to obtain the target solution.

6. The method for analyzing gold content in ore as described in claim 5, characterized in that, In the NaI / I2 solution, the concentration of NaI solution is (1-3) mol / L, the concentration of I2 is (1-1.5) mol / L, and the molar ratio of NaI / I2 is 1:(1-3).

7. The method for analyzing gold content in ore as described in any one of claims 1-5, characterized in that, The solid-liquid separation is performed by centrifugation and filtration at 8000-10000 r / min for 30-50 min.

8. The method for analyzing gold content in ore as described in claim 5, characterized in that, In step S6, the gold content in the target solution is tested by spectrophotometry, including: at a wavelength of 548 nm, the gold standard solution at different concentrations is tested to obtain the gold standard solution-absorbance standard curve, while deionized water is used as a blank reference. Next, the absorbance of the target solution was tested. By subtracting the absorbance from the gold standard solution-absorbance standard curve, the gold content in the target solution was obtained.

9. The method for analyzing gold content in ore as described in claim 1, characterized in that, Also includes: The method for recovering gold from the target solution includes the following steps: (1) Add 5 g / L of 20-50 mesh activated carbon to the target solution, stir at 200-300 r / min for 4-8 h, and then separate the solid to obtain activated carbon that adsorbs gold. (2) After washing the gold-adsorbed activated carbon 3-5 times with a mixed solution of 1% NaOH and 1% NaI, it is added to the electrolytic cell of the electrolysis system and gold mud is obtained by electrolytic reduction. The gold mud is then dissolved and purified with dilute hydrochloric acid, washed until neutral, dried at 105°C, and then smelted at 1200°C to obtain gold ingots with a purity of ≥99.5%.

10. The method for analyzing gold content in ore as described in claim 9, characterized in that, In step (1), the resulting waste liquid is reduced and precipitated with Na2S2O3 at a mass concentration of 5%-10%.

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