Method for analyzing content of gold in ore

Abstract

The invention relates to the technical field of analysis of gold content in ore, in particular to a method for analyzing the gold content in the ore. According to the method, large-particle free gold and fine-particle free gold are recovered in stages, quantitative analysis of the total gold content is achieved through oxidation desulfurization and a dissolution-complexation reduction system, efficient refining recovery of gold can be achieved, and analysis-recovery integration is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of gold content analysis in ores, and in particular to a method for analyzing gold content in ores. Background Art

[0002] With the development of society and the improvement of people's living standards, the consumer market generally places higher and higher demands on gold quality, which 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 ore is of great significance to the rational development and utilization of mineral resources, and brings great economic value.

[0003] Gold often 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 shortcomings: for ores containing coarse-grained gold, sample collection is uneven and the sample itself is poorly representative. Using traditional analytical methods will result in poor reproducibility of analytical results and may even miss ore bodies of industrial value. The analysis of low-grade gold ores is equally challenging. Their gold grade is low, and using traditional analytical methods, it is difficult to accurately determine the gold content in the mineral from a small sample. Incomplete extraction of encapsulated or sulfide-bound gold leads to low results. Free gold particles vary in size and are easily lost during the grinding process. High concentrations of cyanide or aqua regia create environmental and operational safety pressures. The process cannot be optimized based on the type of sulfide, resulting in reagent waste.

[0004] Therefore, a full-process analysis method that takes into account accuracy, environmental protection and economy is needed. Summary of the Invention

[0005] To address the above technical issues, the present invention provides a method for analyzing gold content in ore. This method first optimizes ore sample pretreatment techniques, enabling accurate and efficient dissolution of gold from ore samples, avoiding gold ion loss during sample processing and ensuring reliable test results. Secondly, it recovers large and fine free gold particles in stages, and quantitatively analyzes the total gold content through oxidation and desulfurization, followed by a dissolution-complexation reduction system. Furthermore, it enables efficient gold refining and recovery, achieving an integrated "analysis-recovery" process.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0007] The present invention provides a method for analyzing the gold content in ore, comprising the following steps:

[0008] S1. Take ore samples from different mining sites and use mineral dissociation analysis (MLA) to determine the type of sulfide in the ore samples, determine the occurrence state and particle size distribution of gold, and thus determine the analysis method;

[0009] S2, take an ore sample of mass m, dry and crush it to a particle size of <2mm, sieve it, collect the free gold with a particle size ≥2mm, record it as m1; ball mill the first sieve under the sieve to <0.5mm, sieve it for the second time, collect the free gold with a particle size ≥0.5mm, record it as m2; and continue to ball mill the second sieve under the sieve to <-400 mesh to obtain ore pulp;

[0010] S3, mixing the slurry with peracetic acid, adjusting the pH to ≤ 3, and heating the reaction for at least 6 hours to fully decompose the sulfide and release the encapsulated gold to obtain a mixed solution;

[0011] S4, placing the mixed solution in a high-temperature, high-pressure oxygen environment and reacting for at least 2 hours to completely destroy the sulfide lattice, and obtaining a solid by solid-liquid separation;

[0012] S5, adding the solid to the NaI / I2 solution and heating it in microwave for at least 2h, using the I3 formed by NaI and I2 - Oxidizes sulfides and dissolves gold (oxidizes Au 0 →Au + ), thereby dissolving solid gold to form stable [AuI4]- complex ions, and obtaining [AuI4]- complex ions through solid-liquid separation. - The target solution;

[0013] S6. Measure the gold content in the target solution by spectrophotometry, which is recorded as m3;

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

[0015] The present invention first analyzes the sulfide type of the ore sample and determines the analysis method. Secondly, through staged grinding and screening, large-particle free gold, small-particle free gold and ore pulp are collected in stages to ensure that the free gold is not lost, the gold ore is fully dissociated, and the sulfide-bound gold is completely released. Finally, the gold content in the ore pulp is analyzed by a wet method. The ore pulp is then oxidized to sulfide using mild and environmentally friendly peracetic acid in an acidic environment to destroy the sulfide encapsulation structure and expose the gold particles. If undissolved minerals still exist, the mixed solution is further placed in a high-temperature and high-pressure oxygen atmosphere for high-pressure oxidation to oxidize the sulfide (for example, pyrite, arsenopyrite, etc.) into soluble sulfate (Fe2(SO4)3, H2SO4), and arsenic is converted into scorodite (FeAsO4·2H2O), fully releasing the encapsulated gold. Then, an environmentally friendly, cyanide-free NaI / I2 solution (non-cyanide gold leaching system) is used for leaching and microwave-assisted dissolution to obtain soluble [AuI4] - The target solution of the complex; finally, the gold content of the target solution is calculated by spectrophotometry at 548 nm.

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

[0017] In summary, this method is easy to operate, does not require large equipment such as ICP-MS, has low investment cost, and is a full-process analysis method that takes into account accuracy, environmental protection, and economy.

[0018] Preferably, the specific steps of step S3 are: mixing the ore pulp with peracetic acid, and adding 1-3 mol / l sulfuric acid or hydrochloric acid to accurately adjust the pH to ≤ 3, and reacting at 60-80°C and 300-500 r / min for 6-12 hours, so that the peracetic acid fully oxidizes the ore pulp and destroys the sulfide structure to obtain a mixed solution.

[0019] Preferably, the solid-to-liquid ratio of the ore pulp to the 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 heat release and reduce reagent consumption.

[0022] Preferably, the specific steps of step S4 are: placing the mixed solution in an oxygen environment at 200-250°C and 2-3Mpa, reacting for 1-2 hours to ensure that the sulfide is completely converted into soluble sulfate, separating the solid, washing the solid with deionized water until the pH of the washing liquid is 7-8, removing soluble impurities, and preventing residual acid on the solid from affecting subsequent operations; at the same time, recovering copper / arsenic from the waste liquid.

[0023] Preferably, step S5 specifically comprises the following steps: adding the solid to a NaI / I2 solution, pH 7-9, 40-60° C., and microwave heating for 1-2 h, followed by solid-liquid separation, 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 is as follows: potassium iodide (NaI) and iodine (I2) are used to form an oxidation-coordination system to oxidize and dissolve the elemental gold, and a stable gold-iodine [AuI4] - The complex ions dissolve into the solution to complete the leaching of gold, that is, Au+2I-+I2→[AuI4]-.

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

[0026] Microwave heating at 40-60°C accelerates the dissolution of gold, but when the temperature is >70°C, it is easy to cause I2 to volatilize.

[0027] Preferably, in the NaI / I2 solution, the concentration of the NaI solution is (1-3) mol / L, the mass concentration is (149.9–449.7) g / L, and the excess I - , ensure I3 - Stable existence.

[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). Excessive NaI can avoid excessive I2, which may lead to side reactions, and can also maintain the advantage of the NaI system to ensure the solubility of I2, thereby ensuring the complete dissolution of gold.

[0030] The present invention found that the NaI / I2 solution system has a higher solubility than KI / I2 and can be used to prepare high concentration I - , reducing solution consumption, and NaI is cheaper than KI, making it suitable for industrial-scale applications. The wastewater is free of cyanide contamination, and a reducing agent (such as Na2S2O3 or ascorbic acid) can be used to recover gold and regenerate I-.

[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, and using deionized water as a blank reference; then testing the absorbance of the target solution, and substituting the absorbance into the gold standard solution-absorbance standard curve to obtain the gold content in the target solution.

[0032] The present invention, at 548nm [AuI4] - The molar absorptivity is high, with a linear range of 0.1-5 g / L; after blank subtraction of matrix interference, the RSD is <2%.

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

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

[0035] (2) Electrolysis-Smelting: After washing and desorbing the gold adsorbed on the activated carbon with a mixed solution of 1% NaOH and 1% NaI by mass for 3-5 times, the mixture is added to the electrolytic cell of the electrolysis system and electrolytically reduced to obtain gold mud; the gold mud is then dissolved with dilute hydrochloric acid to remove impurities, washed to neutrality, dried at 105°C, and smelted at 1200°C to obtain a gold ingot with a purity of ≥99.5%.

[0036] Preferably, in step (1), the waste liquid obtained is reduced and precipitated with Na2S2O3 having a mass concentration of 5%-10% to achieve the recycling of I2, and I2<5mg / L meets the emission standards. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 This is a flow chart for analyzing the gold content in the ore of the present invention;

[0038] Figure 2 It is the linear relationship diagram of absorbance-concentration of the gold standard solution of the present invention. DETAILED DESCRIPTION

[0039] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0040] The product models cited in the present invention description are for illustration only and have no connection with the right holder or manufacturer.

[0041] Example 1

[0042] 1. Analysis methods for gold content in ore, including:

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

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

[0045] The first screened material was then ground to 0.5 mm using a ball mill and screened for the second time to collect the free gold with a particle size ≥ 0.5 mm, which was recorded as m 2＝ 0.08g; then the second sieve was further ground with a ball mill to -400 mesh to obtain a slurry to ensure that the gold ore was fully dissociated;

[0046] S3. Add the slurry and 10% v / v peracetic acid at a solid-to-liquid ratio of 1:5 into a reaction vessel, wherein the peracetic acid is added in three batches to avoid burns caused by the violent exotherm 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° C. for 6 h, fully oxidize the sulfide coating the gold surface, destroy the sulfide structure, and release the naked gold particles to obtain a mixed solution;

[0047] If there is still undissolved sulfide, place the mixed solution in an autoclave, introduce 3Mpa of oxygen at 250℃, and oxidize for 2 hours to further completely oxidize the sulfide into soluble sulfate (SO4 2- ), stop the oxygen flow, open the reactor, centrifuge the reaction solution at 10000r / min for 50min to separate the solid and liquid, wash the solid with deionized water, and adjust the washing solution to pH 7 to remove impurities such as soluble sulfate and prevent residual acid on the solid from affecting subsequent operations;

[0048] S5. The washed solid and 2500 ml of NaI / I2 solution (in the NaI / I2 solution, the concentration of NaI solution is 3 mol / l, the concentration of I2 is 1 mol / l, and the molar ratio of NaI / I2 is 1:3, ensuring that I2 is excessive and fully dissolves the gold) are added to a closed reaction, and heated to 60°C using a microwave at pH 7 for 2 h to fully dissolve the gold particles into soluble ([AuI4] - The soluble gold solution was placed in a centrifuge and centrifuged at 10,000 r / min for 30 minutes to separate the solid and liquid. The residue was washed with deionized water for 5 times to improve the gold recovery rate. The washing liquid and the filtrate were collected to obtain the target solution.

[0049] S6. Spectrophotometrically test the gold content in the target solution, including: testing the absorbance of the gold standard solution at 548 nm at 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, and calculating a gold standard solution-absorbance standard curve, with deionized water used as a blank reference; then testing the absorbance of the target solution to be 0.377, and substituting the absorbance of 0.377 into the gold standard solution-absorbance standard curve y = 0.2157x, R 2 =0.9989, y is the absorbance, x is the mass of gold, and the gold content in the target solution is obtained, which is recorded 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] The present invention [AuI4] at 548nm - The molar absorptivity is high, with a linear range of 0.1-5.0 g / L; after blank subtraction of matrix interference, the RSD is <2%.

[0052] 2. Gold recovery: Use activated carbon adsorption and electrolysis to recover gold. The specific methods are:

[0053] (1) Activated carbon adsorption

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

[0055] (2) Electrolysis-Smelting

[0056] The gold mud is placed in an acid-resistant container and soaked in 10% dilute HCl for 1 hour to dissolve any impurities such as iron and copper. The mud is then washed with deionized water until neutral. The washed gold mud is dried at 105°C for 2 hours and then smelted at 1200°C to obtain a gold ingot with a purity of ≥99.4%. The weight of the gold ingot is 1.74g. This means that 1kg of ore corresponds to 1.75g ​​of gold in the target solution. After cyanidation-carbon slurry electrolysis, the 1.74g gold ingot is obtained with a purity of 99.4%.

[0057] This invention utilizes a closed-loop process consisting of "staged recovery of free gold - mild sulfide oxidation - efficient complex leaching of gold - spectrophotometric detection of gold content - and environmentally friendly recovery" to achieve quantitative analysis of total gold content and efficient gold refining and recovery, achieving an integrated "analysis-recovery" process. The total gold recovery rate is ≥99%, avoiding the operational risks and environmental pollution associated with traditional gold dissolution 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 in the scope of protection of the present invention.

Claims

1. A method for analyzing gold content in ore, characterized in that: The following steps are involved: S1. Take ore samples from different mining sites, analyze the types of sulfides in the ore samples using a mineral dissociation method, and determine the analysis method; S2, weighing the ore sample with a mass of m, drying and crushing it to a particle size of <2 mm, sieving, collecting free gold with a particle size of ≥2 mm, and recording it as m1; ball-milling the first sieve to <0.5 mm, and performing a second sieve to collect free gold with a particle size of ≥0.5 mm, and recording it as m2; and further ball-milling the second sieve to <-400 mesh to obtain a slurry; S3, mixing the slurry with peracetic acid, adjusting the pH to ≤ 3, and heating the mixture for at least 6 hours to obtain a mixed solution; S4, placing the mixed solution in a high-temperature, high-pressure oxygen environment, reacting for at least 1 hour, and separating to obtain a solid; S5, adding the solid to the NaI / I2 solution, heating with microwave for at least 2 h, and separating the solid and liquid to obtain the target solution; S6. Measure the gold content in the target solution by spectrophotometry, which is recorded as m3; S7. Gold content of the ore sample = (m1+m2+m3) / m*100%.

2. The method for analyzing gold content in ore according to claim 1, wherein: The specific steps of step S3 are: The ore pulp is mixed with peracetic acid, and 1-3 mol / L sulfuric acid or hydrochloric acid is added to adjust the pH to ≤ 3, and the mixture is reacted at 60-80° C. and 300-500 r / min for 6-12 hours to obtain a mixed solution.

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

4. The method for analyzing gold content in ore according to claim 1, wherein: The specific steps of step S4 are: The mixed solution is placed in an oxygen environment at 200-250° C. and 2-3 MPa, reacted for 1-2 hours, solid-liquid separation is performed, and the solid is washed with deionized water until the pH of the washing liquid is 7-8.

5. The method for analyzing gold content in ore according to claim 1, wherein: The specific steps of step S5 are: The solid is added to a NaI / I2 solution, pH 7-9, 40-60°C and microwave-heated for 2-4 hours, followed by solid-liquid separation, and the residue is washed with deionized water. The washing liquid and the filtrate are collected to obtain the target solution.

6. The method for analyzing gold content in ore according to claim 5, wherein: In the NaI / I2 solution, the concentration of the 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 according to any one of claims 1 to 5, characterized in that: The solid-liquid separation is performed by centrifugal filtration at 8000-10000 r / min for 30-50 minutes.

8. The method for analyzing gold content in ore according to claim 5, wherein: In step S6, the gold content in the target solution is tested by spectrophotometry, including: testing a 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 test the absorbance of the target solution, and bring the absorbance into the gold standard solution-absorbance standard curve to obtain the gold content in the target solution.

9. The method for analyzing gold content in ore according to claim 1, wherein: Also includes: The method for recovering gold in the target solution comprises 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 hours, and separate the solid to obtain activated carbon that adsorbs gold; (2) washing the gold-adsorbed activated carbon 3-5 times with a mixed solution of 1% NaOH and 1% NaI, adding the mixed solution to the electrolytic cell of the electrolysis system, and performing electrolytic reduction to obtain gold mud; The gold mud is then dissolved with dilute hydrochloric acid to remove impurities, washed until neutral, dried at 105°C, and smelted at 1200°C to obtain gold ingots with a purity of ≥99.5%.

10. The method for analyzing gold content in ore according to claim 9, wherein: In step (1), the waste liquid is reduced and precipitated with Na2S2O3 having a mass concentration of 5%-10% to obtain I2.

Images