Method for measuring trace gold in copper smelting slag flotation iron tailings

Abstract

The invention discloses a method for measuring trace gold in copper smelting slag flotation iron tailings, which comprises the following steps of: firstly, carrying out pretreatment including square magnetic boat pretreatment and sample pretreatment, and putting a sample into a square magnetic boat for staged heating; carrying out dissolution and suction filtration on the sample, and discarding filtrate; and heating the filter residue by using a clay crucible, preserving heat and cooling. And then performing pyrogenic assay enrichment, including the steps of melting, soot blowing, washing, gold separation, preparation of a gold solution and the like after proportioning the sample, and finally completing the determination of the gold content by an atomic absorption method. According to the method, the reducing power of the iron tailings is firstly removed, the influence of iron, flotation oil and sulfide is eliminated, enrichment is performed by adopting a pyrogenic process test, and a quantitative silver standard solution is added, so that gold is captured by silver, and the determination of trace gold in the copper smelting slag flotation iron tailings can be quickly and effectively completed; and the process cost is low, and the operation process is simple, flexible, rapid and accurate.

Description

Technical Field

[0001] This invention relates to the field of precious metal content determination technology, and in particular to a method for enriching and determining trace gold in iron tailings from copper smelting slag flotation. Background Technology

[0002] Copper concentrate is smelted using pyrometallurgical processes to produce copper-gold smelting slag. This slag undergoes slow cooling, crushing, and flotation to obtain flotation concentrate and flotation tailings. The flotation tailings are then magnetically separated to obtain iron concentrate and iron tailings, which are products of mineral processing. Many tailings contain trace amounts of heavy metals; for example, trace gold is found in iron tailings from copper smelting slag flotation. Gold does not react with hydrochloric acid, sulfuric acid, or nitric acid alone, but it dissolves in hydrochloric acid-nitric acid mixtures and hydrochloric acid solutions containing oxidizing agents. Common alkaline solutions do not react with gold, but the introduction of chlorine gas has a strong corrosive effect on it. Furthermore, gold dissolves in complexing agents such as cyanides, thiocyanates, thiourea, and thiosulfates to form corresponding stable complexes. Therefore, these properties of gold are often utilized in hydrometallurgical and analytical techniques for gold. However, the grade of trace gold in iron tailings is very low, making accurate determination of its content impossible using conventional hydrometallurgical methods. Meanwhile, the iron content of iron tailings (40-50%) makes traditional pyrometallurgical assays ineffective. Furthermore, the low silver content in iron tailings makes it difficult to capture gold using silver. These factors limit the determination of trace gold in iron tailings from copper smelting slag flotation. Therefore, there is an urgent need to develop a method that overcomes these limitations to achieve rapid and accurate determination of trace gold in iron tailings. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a simple, easy-to-implement, convenient and flexible, low-cost method for determining trace gold in iron tailings from copper smelting slag flotation, which can effectively enrich trace gold in iron tailings and eliminate the negative impact of iron.

[0004] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: a method for determining trace gold in iron tailings from copper smelting slag flotation, wherein the gold content in the iron tailings is 0.010 to 1.00 g / t.

[0005] I. Sample Pretreatment 1) Pretreatment of square magnetic boat: The clean square magnetic boat is gradually heated and calcined at room temperature, and then the power is turned off and it is allowed to cool naturally to room temperature for later use. 2) Sample pretreatment: Place pre-cut ordinary filter paper in a square magnetic boat, the size of which is flattened at the bottom of the boat. Weigh the sample into the square magnetic boat and then perform staged heating. 3) Sample dissolution: Transfer the sample treated in step 2 to a beaker, rinse the beaker wall with water to completely wet the sample; add hydrochloric acid along the beaker wall, heat at low temperature to dissolve completely; filter using a vacuum filtration pump with a glass frit funnel and filter membrane, and discard the filtrate. 4) Place the filter residue in a clay crucible, heat and keep it warm, then remove and cool it.

[0006] II. Fire-based Alchemy Enrichment (1) Ingredients: Stir the sample after ashing in step (4) with a sample spoon until it is loose, and then prepare the ingredients. The ingredients are: 35-40g of anhydrous sodium carbonate, 10-12g of silicon dioxide, 10-12g of borax, 100-120g of lead oxide, and 5-6g of soluble starch. After mixing the sample evenly, add 1-2mL of 0.1% silver standard solution and cover with a small amount of lead oxide. (2) Melting: Place the sample obtained in step (1) in a muffle furnace, heat it to 1100℃ for 40~50min, hold it for 10~15min, take it out, pour it into a cast iron mold, and cool it. (3) Ash blowing: Place the bright lead buckle obtained in step (2) into a magnesium sand ash dish that has been preheated at 920℃ for 30 minutes, close the furnace door to remove the film, wait for the black film to be removed and the melt to turn bright red, open the furnace door slightly to blow the ash, wait for the flash point to pass for 2~3 minutes, take it out, cool it, and obtain gold and silver granules. (4) Washing: Transfer the above gold and silver granules into a porcelain crucible, add glacial acetic acid, and boil gently on a low-temperature electric hot plate to wash the granules. When there are no more impurities on the surface of the granules, wash them with water and keep the granules in the porcelain crucible. (5) Gold separation: Add nitric acid (1+5) to a porcelain crucible containing the gold particles, place it on a hot plate to dissolve at low temperature, and continue heating for 5-10 minutes after the silver is completely dissolved. Remove the porcelain crucible and wash the porcelain crucible and gold particles with hot water. (6) Gold solution: Add fresh aqua regia solution to a magnetic crucible containing gold particles, heat at low temperature until completely dissolved, transfer to a colorimetric tube with water, make up to volume and shake well; (7) Determination of gold: The absorbance of the gold solution prepared above was measured at a wavelength of 242.8 nm using an atomic absorption spectrophotometer. The working curve was plotted with the mass concentration of the gold standard solution as the abscissa and the corresponding absorbance as the ordinate, and the gold content was calculated accordingly. Standard solution: Gold standard stock solution 1 mg / mL: Accurately weigh 0.1000 g of 99.99% pure gold and place it in a 50 mL beaker. Add 10 mL of fresh aqua regia and heat on a hot plate until completely dissolved. Then add 10 mL of hydrochloric acid and warm to dissolve. Finally, dilute to 100 mL in a volumetric flask with water and shake well. Gold standard working solution 100µg / mL: Accurately transfer 10.00mL of gold standard stock solution into a 100mL volumetric flask, add 10mL of hydrochloric acid, and dilute to 100mL with water. Shake well. Gold standard solution: Accurately transfer 0, 0.10, 0.20, 0.30, 0.40, and 0.50 mL of the gold standard working solution into 100 mL volumetric flasks, add 10 mL of hydrochloric acid, and dilute to 100 mL with water. Shake well.

[0007] Step 2) involves a four-stage heating process: Stage 1: Heat the sample from room temperature to 200°C, hold for 0.5 hours, stir with a glass rod to loosen the sample, wipe the glass rod with filter paper, and then place it in a square magnetic boat for ignition; Stage 2: Continue heating to 400°C, hold for 0.5 hours, stir with a glass rod to loosen the sample, wipe the glass rod with filter paper, and then place it in a square magnetic boat for ignition; Stage 3: Continue heating to 600°C, hold for 0.5 hours, stir with a glass rod to loosen the sample, wipe the glass rod with filter paper, and then place it in a square magnetic boat for ignition; Stage 4: Continue heating to 650°C, hold the edge of the square ceramic boat with crucible tongs, shake to disperse the sample, hold for 3 hours, then turn off the power, allow it to cool naturally to room temperature, and then remove and cool.

[0008] Step 4) Place the filter residue in a clay crucible and heat it to 650°C for 1 hour.

[0009] Step 1) The Chinese magnetic boat is gradually heated from room temperature to 900℃ and calcined for 2 hours.

[0010] In step (4), 30% by volume of glacial acetic acid is added to wash the gold and silver granules.

[0011] Preparation of silver standard solution: Weigh 0.1000g of high-purity silver with a purity of 5N into a 250mL beaker, add 10mL of nitric acid with a volume ratio of 1:1, heat at low temperature to dissolve completely, evaporate the nitrogen oxides, remove and cool, then dilute to 100mL in a volumetric flask, shake well, and store in a brown bottle.

[0012] This invention first removes the reducing power of iron tailings, eliminating the influence of iron, flotation oil, and sulfides. It then uses a pyrometallurgical method for enrichment and adds a quantitative silver standard solution to achieve silver capture of gold. This allows for the rapid and effective determination of trace gold in iron tailings from copper smelting slag flotation. The process is low-cost, simple, flexible, fast, and accurate.

[0013] This invention first removes the reducing power of iron tailings, eliminating the influence of iron, flotation oil, and sulfides. It then uses a pyrometallurgical method for enrichment and adds a quantitative silver standard solution to achieve silver capture of gold. This allows for the rapid and effective determination of trace gold in iron tailings from copper smelting slag flotation. The process is low-cost, simple, flexible, fast, and accurate. Detailed Implementation

[0014] The following is a further explanation with reference to specific implementation methods: In this embodiment, the entire measurement process is carried out according to the following steps: Measurement range: Trace gold in iron tailings from copper smelting slag flotation, with gold content ranging from 0.010 to 1.00 g / t.

[0015] Silver standard solution (0.1%): Accurately weigh 0.1000g of high-purity silver (5N, i.e., 99.999%) into a 250mL beaker, add 10mL of nitric acid (1:1 ratio), heat at low temperature until completely dissolved, evaporate nitrogen oxides, remove from heat, cool, and dilute to 100mL in a volumetric flask, then shake well. Store in a brown bottle.

[0016] I. Sample Pretreatment 1. Pretreatment of square magnetic boat: The clean square magnetic boat is gradually heated to 900℃ at room temperature and calcined for 2 hours. The power is turned off and the boat is allowed to cool naturally to room temperature for later use. 2. Sample pretreatment: Place two layers of cut ordinary filter paper in a square magnetic boat, the size of which should be enough to cover the bottom of the magnetic boat. Weigh 50g of sample (iron tailings) into the square magnetic boat and perform staged heating according to Table 1. Raise the temperature from room temperature to 200°C, stir the loose sample with a glass rod, wipe the glass rod with filter paper, and then place it in a square magnetic boat for ignition. Continue heating to 400°C, stir the loose sample with a glass rod, wipe the glass rod with filter paper, and then place it in a square magnetic boat for ignition. Continue heating to 600°C, stir the loose sample with a glass rod, wipe the glass rod with filter paper, and then place it in a square magnetic boat for ignition. Continue heating to 650°C, hold the edge of the square ceramic boat with crucible tongs, shake to disperse the sample, keep it at this temperature for 3 hours, then turn off the power and allow it to cool naturally to room temperature. Remove and cool. 3. Sample Dissolution: Transfer the above sample to a 500mL beaker, rinse the beaker wall with a small amount of water to ensure complete wetting of the sample. Add 120mL of hydrochloric acid along the beaker wall and heat at a low temperature until completely dissolved. Filter the solution using a vacuum filtration pump with a glass frit funnel and a 0.45µm filter membrane, discarding the filtrate. 4. Place the filter residue in a 500mL clay crucible, heat it from a low temperature to 650℃ and keep it at that temperature for 1 hour, then remove and cool it. II. Fire-based Alchemy Enrichment Preparation: Stir the previously ashed sample with a sample spoon until it reaches a loose state. Prepare the ingredients according to Table 2. After mixing the sample thoroughly, add 1.00 mL of 0.1% silver standard solution and cover with a small amount of lead oxide. Perform a blank test along with the sample. The blank test starts from the ingredients in Table 2 and does not require sample pretreatment. Melting: Place the prepared sample in a muffle furnace at 900℃, heat to 1100℃ for 40~50 min, hold for 10~15 min, remove, pour into a cast iron mold, and cool. Ash blowing: Place the bright lead clasp obtained after melting into a magnesia ash dish preheated to 920℃ for 30 minutes, close the furnace door and remove the film. After the black film is removed and the melt turns bright red, slightly open the furnace door and perform ash blowing. After the flash point has passed for 2-3 minutes, remove and cool. Gold and silver granules are obtained. Washing: Transfer the above gold and silver granules into a 30 mL porcelain crucible, add 15-20 mL of glacial acetic acid (30% by volume), and gently boil on a low-temperature hot plate to wash the granules. Once there are no more impurities on the surface of the granules, wash them with water and keep the granules in the porcelain crucible. Gold separation: Add 15-20 mL of nitric acid (1+5) to a porcelain crucible containing the gold particles, place it on a hot plate to dissolve at a low temperature, and continue heating for 5-10 minutes after the silver is completely dissolved. Remove the porcelain crucible and wash the porcelain crucible and gold particles 3 times with hot water. Gold solution: Add 4 mL of fresh aqua regia solution to a magnetic crucible containing gold particles, heat at low temperature until completely dissolved, transfer to a 25 mL colorimetric tube with water, make up to volume and shake well; Determination of gold: The absorbance of the gold solution prepared above was measured at a wavelength of 242.8 nm using an atomic absorption spectrophotometer. A working curve was plotted with the mass concentration of the gold standard solution on the x-axis and the corresponding absorbance on the y-axis, and the gold content was calculated accordingly. Determination of gold: The absorbance of the gold solution prepared above was measured at a wavelength of 242.8 nm using an atomic absorption spectrophotometer. A working curve was plotted with the mass concentration of the gold standard solution on the x-axis and the corresponding absorbance on the y-axis, and the gold content was calculated accordingly.

[0017] In the formula: Gold standard stock solution 1 mg / mL: Accurately weigh 0.1000 g of pure gold (99.99%) and place it in a 50 mL beaker. Add 10 mL of fresh aqua regia and heat on a hot plate until completely dissolved. Then add 10 mL of hydrochloric acid and warm to dissolve. Finally, dilute to 100 mL in a volumetric flask with water and shake well. Gold standard working solution 100µg / mL: Accurately transfer 10.00mL of gold standard stock solution into a 100mL volumetric flask, add 10mL of hydrochloric acid, and dilute to 100mL with water in the volumetric flask. Shake well. Gold standard solution: Accurately transfer 0, 0.10, 0.20, 0.30, 0.40, and 0.50 mL of the gold standard working solution into 100 mL volumetric flasks, add 10 mL of hydrochloric acid, and dilute to 100 mL with water. Shake well.

[0018] The gold content in the iron tailings from copper smelting slag flotation was measured to be 0.18 g / t.

[0019] The residual gold content in the assay crucible and slag in the method of this invention is detected. The touch crucible and separated slag used in the melting process in the embodiment were crushed. The crushed powder was made into lead buckles according to the method of the present invention. After the lead buckles were blown with ash, gold was separated and no gold particles appeared.

[0020] The above experiments demonstrate that the method of this invention can completely enrich gold in iron tailings from copper smelting slag flotation without requiring a secondary gold extraction process. This reduces detection costs and improves work efficiency.

[0021] The copper smelting slag flotation iron tailings mentioned in this invention refers to copper-gold-containing smelting slag produced by pyrometallurgical smelting of copper concentrate. The smelting slag is slowly cooled, crushed, and flotated to obtain flotation concentrate and flotation tailings. The iron tailings after magnetic separation of iron concentrate from the flotation tailings have a low gold content of 3g / t.

[0022] The innovative aspects of this invention are explained below: 1. Roasting removes volatile substances such as carbon, sulfur, and flotation oil. Otherwise, adding a large amount of hydrochloric acid during the sample dissolution process will cause a violent and exothermic reaction. At the same time, the volatile substances generated, such as hydrogen sulfide and carbon dioxide, will be mixed with the sample and overflow the beaker during the discharge process, resulting in sample loss.

[0023] Because iron tailings contain 40-50% iron, traditional pyrometallurgical assays cannot completely capture gold. Furthermore, due to the very low gold content in iron tailings, conventional hydrometallurgical methods cannot achieve accurate determination. Therefore, currently, there are no relevant gold detection technologies available in the industry for materials with a high iron matrix, such as iron ore, iron concentrate, and iron tailings.

[0024] This invention adds a large amount of hydrochloric acid during the sample dissolution process, which converts sulfides into volatile hydrogen sulfide gas that escapes, dissolves iron to form ions that are separated from the residue, and reduces the reducing power of sulfur and iron elements in the pyrometallurgical assay process. This eliminates the need for reducing power experiments, reduces detection costs, and improves work efficiency.

[0025] Conventional pyrometallurgical assays require a secondary assay to correct the residual gold content in the assay crucible and slag. The method of this invention can completely enrich gold in iron tailings from copper smelting slag flotation without a secondary assay, thus reducing detection costs and improving work efficiency.

[0026] There is a lack of methods for enriching and determining trace gold in iron tailings from copper smelting slag flotation. This invention first removes the reducing power of the sample and then removes the influence of iron, eliminating the need for a reducing power test. By using a single fire assay to correct the amount of silver, lead can be used to capture gold and silver to form a suitable lead clasp, which can completely separate gold and silver and obtain the accurate quality of gold.

[0027] Because the sample contained low levels of silver, silver could not effectively capture gold. Therefore, a measured amount of silver nitrate solution was added during the experiment to achieve silver-gold capture. This eliminated the negative effects of iron and sulfides, and improved the silver-gold capture efficiency even with trace amounts of silver.

[0028] The present invention has been described in detail above. The above description is only a preferred embodiment of the present invention and should not be construed as limiting the scope of the present invention. All equivalent changes and modifications made in accordance with the scope of this application should still fall within the scope of the present invention.

Claims

1. A method for determining trace gold in iron tailings from copper smelting slag flotation, wherein the gold content in the iron tailings is 0.010–1.00 g / t, characterized in that: I. Sample Pretreatment 1) Pretreatment of square magnetic boat: The clean square magnetic boat is gradually heated and calcined at room temperature, and then the power is turned off and it is allowed to cool naturally to room temperature for later use. 2) Sample pretreatment: Place pre-cut ordinary filter paper in a square magnetic boat, the size of which is flattened at the bottom of the boat. Weigh the sample into the square magnetic boat and then perform staged heating. 3) Sample dissolution: Transfer the sample treated in step 2 to a beaker, rinse the beaker wall with water to completely wet the sample; add hydrochloric acid along the beaker wall, heat at low temperature to dissolve completely; filter using a vacuum filtration pump with a glass frit funnel and filter membrane, and discard the filtrate. 4) Place the filter residue in a clay crucible, heat and keep it at that temperature, then remove and cool it. II. Fire-based Alchemy Enrichment (1) Ingredients: Stir the sample after ashing in step (4) with a sample spoon until it is loose, and then prepare the ingredients. The ingredients are: 35-40g of anhydrous sodium carbonate, 10-12g of silicon dioxide, 10-12g of borax, 100-120g of lead oxide, and 5-6g of soluble starch. After mixing the sample evenly, add 1-2mL of 0.1% silver standard solution and cover with a small amount of lead oxide. (2) Melting: Place the sample obtained in step (1) in a muffle furnace and heat it to 1100℃ for 40~50 min. Keep warm for 10-15 minutes, then remove and pour into a cast iron mold to cool. (3) Ash blowing: Place the bright lead buckle obtained in step (2) into a magnesium sand ash dish that has been preheated at 920℃ for 30 minutes, close the furnace door to remove the film, wait for the black film to be removed and the melt to turn bright red, open the furnace door slightly to blow the ash, wait for the flash point to pass for 2~3 minutes, take it out, cool it, and obtain gold and silver granules. (4) Washing: Transfer the above gold and silver granules into a porcelain crucible, add glacial acetic acid, and boil gently on a low-temperature electric hot plate to wash the granules. When there are no more impurities on the surface of the granules, wash them with water and keep the granules in the porcelain crucible. (5) Gold separation: Add nitric acid (1+5) to a porcelain crucible containing the gold particles, place it on a hot plate to dissolve at low temperature, and continue heating for 5-10 minutes after the silver is completely dissolved. Remove the porcelain crucible and wash the porcelain crucible and gold particles with hot water. (6) Gold solution: Add fresh aqua regia solution to a magnetic crucible containing gold particles, heat at low temperature until completely dissolved, transfer to a colorimetric tube with water, make up to volume and shake well; (7) Determination of gold: The absorbance of the gold solution prepared above was measured at a wavelength of 242.8 nm using an atomic absorption spectrophotometer. The working curve was plotted with the mass concentration of the gold standard solution as the abscissa and the corresponding absorbance as the ordinate, and the gold content was calculated accordingly. Standard solution: Gold standard stock solution 1 mg / mL: Accurately weigh 0.1000 g of 99.99% pure gold and place it in a 50 mL beaker. Add 10 mL of fresh aqua regia and heat on a hot plate until completely dissolved. Then add 10 mL of hydrochloric acid and warm to dissolve. Finally, dilute to 100 mL in a volumetric flask with water and shake well. Gold standard working solution 100µg / mL: Accurately transfer 10.00mL of gold standard stock solution into a 100mL volumetric flask, add 10mL of hydrochloric acid, and dilute to 100mL with water. Shake well. Gold standard solution: Accurately transfer 0, 0.10, 0.20, 0.30, 0.40, and 0.50 mL of the gold standard working solution into 100 mL volumetric flasks, add 10 mL of hydrochloric acid, and dilute to 100 mL with water. Shake well.

2. The method for determining trace gold in copper smelting slag flotation iron tailings according to claim 1, characterized in that: Step 2) involves a four-stage heating process: Stage 1: Heat the sample from room temperature to 200°C, hold for 0.5 hours, stir with a glass rod to loosen the sample, wipe the glass rod with filter paper, and then place it in a square magnetic boat for ignition; Stage 2: Continue heating to 400°C, hold for 0.5 hours, stir with a glass rod to loosen the sample, wipe the glass rod with filter paper, and then place it in a square magnetic boat for ignition; Stage 3: Continue heating to 600°C, hold for 0.5 hours, stir with a glass rod to loosen the sample, wipe the glass rod with filter paper, and then place it in a square magnetic boat for ignition; Stage 4: Continue heating to 650°C, hold the edge of the square ceramic boat with crucible tongs, shake to disperse the sample, hold for 3 hours, then turn off the power, allow it to cool naturally to room temperature, and then remove and cool.

3. The method for determining trace gold in copper smelting slag flotation iron tailings according to claim 1, characterized in that: Step 4) Place the filter residue in a clay crucible and heat it to 650°C for 1 hour.

4. The method for determining trace gold in copper smelting slag flotation iron tailings according to claim 1, characterized in that: Step 1) The Chinese magnetic boat is gradually heated from room temperature to 900℃ and calcined for 2 hours.

5. The method for determining trace gold in copper smelting slag flotation iron tailings according to claim 1, characterized in that: In step (4), 30% by volume of glacial acetic acid is added to wash the gold and silver granules.

6. The method for determining trace gold in copper smelting slag flotation iron tailings according to claim 1, characterized in that: Preparation of silver standard solution: Weigh 0.1000g of high-purity silver with a purity of 5N into a 250mL beaker, add 10mL of nitric acid with a volume ratio of 1:1, heat at low temperature to dissolve completely, evaporate the nitrogen oxides, remove and cool, then dilute to 100mL in a volumetric flask, shake well, and store in a brown bottle.

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