A method for extracting germanium from germanium-rich lignite

Abstract

The present application belongs to the technical field of semiconductor germanium material production process, and discloses a method for extracting germanium from germanium-rich lignite. In view of the problems of high energy consumption, low germanium recovery rate, poor comprehensive utilization rate of resources and great environmental protection pressure of traditional fire roasting, the present application adopts a short process wet method of wet ball milling alkalization, surfactant intensified leaching, secondary countercurrent leaching and germanium recovery by ferric chloride precipitation. The germanium-rich lignite, water and sodium hydroxide are added into a wet ball mill for synchronous grinding, and the low alkali amount and particle size are controlled, then the surfactant is used to intensify the low-temperature leaching, the leaching slag is used as coal after secondary countercurrent leaching, and the secondary leaching filtrate is returned to the ball milling process for recycling; the primary leaching filtrate is directly co-precipitated with ferric chloride after alkali adjustment to extract germanium. The present application is completed under the conditions of liquid phase, normal pressure and low temperature, the germanium leaching rate and the germanium precipitation rate are both more than 90%, the leaching slag can still be used as industrial coal for further utilization, and the comprehensive and efficient utilization of germanium-rich lignite resources and the synergy of coal quality preservation are realized.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor germanium material production technology, specifically relating to a method for extracting germanium from germanium-rich lignite by combined activation leaching with sodium hydroxide solution and surfactant and co-precipitation with ferric chloride. Background Technology

[0002] Germanium is a scarce strategic resource and a non-renewable resource, widely used in strategic emerging industries such as national defense, aerospace, digital communications, and high-end equipment. It is a key mineral for ensuring national technological and defense security. Unlike ordinary non-ferrous metals, although the market size of germanium is not large, its industrial chain is irreplaceable, making it a typical "small metal, big strategy" material. With the upgrading of infrared detection technology, the iteration of optical communication, and the development of the aerospace industry, the market demand for high-purity germanium and functional germanium materials continues to grow steadily, and its strategic importance continues to rise.

[0003] Germanium is a typical rare and dispersed metal with almost no independent deposits. Its abundance in the Earth's crust is only about 7 ppm, lower than that of precious metals such as gold and silver. There are no independently exploitable rich deposits, and it rarely exists in elemental form. The vast majority of it occurs as a byproduct in lead-zinc, copper, coal, and some sulfide deposits, and is recovered and extracted as a byproduct of non-ferrous metal smelting and coal processing. Current mainstream processes are divided into two main categories: pyrometallurgical enrichment and hydrometallurgical extraction, both requiring high-purity extraction and purification. Mining and purification are difficult and production capacity is limited. Global germanium resources are highly concentrated, with China, the United States, and Russia being the core resource countries. my country not only ranks among the world's top in germanium reserves but is also the world's largest producer, processor, and exporter of germanium. Its industrial chain completeness and production capacity are globally leading, making it a strategic mineral resource in which my country has a competitive advantage.

[0004] Low-grade lignite germanium ore is mostly bound in organic matter, with only a small amount in silicate and sulfide bound states. Lignite has high moisture content, low calorific value, high volatile matter, and high ash content. Traditional direct hydrochloric acid or sulfuric acid leaching results in low germanium dissolution rate, many leached impurities, and great difficulty in separation. Therefore, in industry, germanium is generally enriched into smoke dust / coal ash through high-temperature volatilization, transforming low-grade germanium-containing raw coal into high-germanium-enriched coal ash, and then carrying out subsequent deep purification. Currently, the mainstream traditional route for extracting germanium from low-grade germanium-containing lignite in China involves high-temperature combustion and volatilization to obtain germanium-containing flue ash, followed by extraction through concentrated hydrochloric acid chlorination and distillation, and purification by rectification. Although the process is mature and easy to scale up, it has many drawbacks, such as low resource utilization, heat waste, high energy consumption, heavy pollution, difficulty in subsequent separation and purification, and poor overall returns. Furthermore, lignite needs to be oxidized and burned at 1000℃-1100℃ for a long time to allow the organic germanium to fully volatilize. The germanium-containing lignite itself has a low calorific value and high moisture content, requiring additional fuel. Overall, the energy consumption per unit of germanium product is high, and the emissions of carbon dioxide and nitrogen oxides are large, making it difficult to achieve low-carbon and clean extraction of germanium metal. Germanium-rich lignite typically contains 0.005%-0.07% germanium. At high temperatures, some germanium forms silicate solid solutions with silicon, aluminum, and iron, which cannot volatilize and enter the flue dust. The germanium grade in the flue dust is only 0.2%-1.0%, with limited enrichment multiples. Subsequent purification processes require significantly increased processing capacity, and the overall germanium recovery rate is generally 60%-70%. The recovery rate for low-grade germanium containing less than 0.02% germanium is less than 60%, down to 50%.

[0005] Traditional pyrometallurgical germanium extraction processes rely on high energy and input consumption to achieve germanium enrichment, at the cost of high pollution, resource waste, and high environmental protection and maintenance costs. This disadvantage is further amplified when extracting germanium from low-grade germanium-rich lignite. Therefore, there is a need to research and develop a method with a simple process, high recovery rate, and suitable for extracting germanium from germanium-rich lignite. Summary of the Invention

[0006] The purpose of this invention is to overcome the problems of high energy consumption, long process, low germanium recovery rate, poor resource utilization and high environmental pressure in the existing pyrometallurgical germanium extraction process, and to provide a method for extracting germanium from germanium-rich lignite, which achieves efficient dissociation and enrichment of germanium under low alkali content, normal pressure and low temperature conditions.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A method for extracting germanium from germanium-rich lignite includes the following steps:

[0009] 1) Wet ball mill alkalization: After coarsely crushing germanium-rich lignite to a particle size of less than 5 mm, add it to a wet ball mill with water and sodium hydroxide in proportion and grind it simultaneously. The amount of water added is 4-6 times the weight of lignite, and the amount of sodium hydroxide added is 0.05-0.2 times the weight of lignite. Grind to a particle size of 60-120 mesh to obtain the ground raw material.

[0010] 2) Surfactant-enhanced leaching: The milled raw material is put into the leaching tank and a surfactant is added. The amount of surfactant added is 0.5‰–1‰ of the weight of the raw material. The mixture is heated to 70℃–90℃ under stirring conditions at a speed of 100 r / min–150 r / min and kept at this temperature for 2 h–5 h.

[0011] 3) Solid-liquid separation: The leached slurry is cooled to 40℃–60℃ and filtered to obtain primary leaching filtrate and primary leaching residue;

[0012] 4) Secondary countercurrent leaching: The primary leaching residue is added to water for secondary leaching, and the residue and filtrate are obtained by filtration. The secondary leaching filtrate is returned to step 1) and used as the solution for the next batch of wet ball milling.

[0013] 5) Precipitation and recovery of germanium: Take the first leaching filtrate and stir it at a speed of 100 r / min-150 r / min for 5 min-15 min. Then adjust the pH to 8-10, add ferric chloride, the amount of ferric chloride added is 50-100 times the amount of germanium metal in the filtrate, heat to 40℃-60℃, keep the reaction at this temperature for 1 h-2 h, let it stand to precipitate for 8 h-12 h, and filter to obtain germanium-containing precipitate.

[0014] Preferably, in step 1), the sodium hydroxide is in the form of fine particles, and the amount added is 0.1 times the weight of germanium-rich lignite, with a particle size not exceeding 3 mm.

[0015] Preferably, in step 2), the surfactant is hexadecyltrimethylamine bromide.

[0016] Preferably, in step 5), concentrated sulfuric acid is used to adjust the pH to 9.0, the amount of ferric chloride added is 75 times the amount of germanium metal in the filtrate, the reaction temperature is 50°C, the holding time is 2 h, and the standing time is 12 h.

[0017] Traditional pyrometallurgical roasting relies on temperatures above 1000℃ to volatilize germanium. However, at high temperatures, germanium readily forms non-volatile silicate solid solutions with silicon, aluminum, and iron, and completely destroys the organic matter of lignite, resulting in a germanium recovery rate of only 60%–70% and low resource utilization. This application utilizes wet ball milling, simultaneously adding low-concentration sodium hydroxide during the grinding process. Through the synergistic effect of mechanical shearing and alkaline hydrolysis, the organic chelate structure of germanium bound by humic acid is destroyed, allowing germanium to selectively dissolve in the liquid phase as sodium germanate. The low alkalinity also inhibits the simultaneous dissolution of silicon, preventing the formation of silica gel and preserving the coal quality of the leaching residue. A surfactant is added to reduce the solid-liquid interfacial tension, promote the penetration of alkaline solution into the micropores of lignite, and enhance mass transfer. After a second countercurrent leaching process, the filtrate is returned to the ball milling process to achieve a closed-loop circulation of the alkali solution. Then, the co-adsorption of germanium by the ferric hydroxide colloid generated by the hydrolysis of ferric chloride is used to complete the precipitation and enrichment. The entire process is carried out under liquid phase, atmospheric pressure, and low temperature conditions, without the need for high-temperature roasting and reducing atmosphere control. This fundamentally eliminates the problems of heavy metal dust and carbon emissions from pyrometallurgical processes and achieves synergy between efficient germanium extraction and coal quality preservation.

[0018] Compared with existing pyrometallurgical enrichment and extraction technologies for germanium, this invention has the following advantages:

[0019] The process is simple and the alkali consumption is low: wet ball milling and simultaneous alkalization combine grinding and alkalization into one step. The amount of sodium hydroxide used is only 0.05-0.2 times the weight of lignite, which reduces alkali consumption and subsequent neutralization costs. The low alkali content also inhibits the large-scale dissolution of silicon, avoiding silica gel clogging of equipment and affecting subsequent germanium extraction.

[0020] High leaching rate: Surfactants reduce the solid-liquid interfacial tension, promote the penetration of low-concentration alkaline solution into the pores of lignite, and effectively dissociate organic chelated germanium. Under normal pressure conditions of 70℃–90℃, the germanium leaching rate can reach more than 90%.

[0021] High germanium recovery rate and good reagent recycling rate: Secondary countercurrent leaching further improves germanium recovery rate, and the secondary leaching filtrate is returned to the wet ball milling process as water for solution preparation, realizing a closed-loop circulation of alkali solution and residual germanium, and reducing reagent consumption.

[0022] Low energy consumption and short process: Germanium is directly enriched by pH adjustment and co-precipitation with ferric chloride in the alkaline leachate. The entire process is carried out at atmospheric pressure at 70℃–90℃, eliminating the steps of rotary evaporation concentration, hydrochloric acid leaching and high-temperature pyrolysis, resulting in a significant reduction in energy consumption.

[0023] The resulting germanium concentrate has qualified grade and significant environmental advantages: ferric chloride hydrolyzes under pH 8–10 conditions to generate ferric hydroxide colloid, which co-adsorbs germanium to form a precipitate with a germanium precipitation rate of over 90%. The resulting filter residue has a germanium grade of over 0.7%, which meets the standards for distillation-based germanium extraction raw materials. The germanium content in the filtrate is as low as 1 mg / L–5 mg / L, and it can meet emission standards after neutralization treatment, with no combustion flue gas or dust emissions. Attached Figure Description

[0024] Figure 1 This is a process flow diagram for extracting germanium from germanium-rich lignite. Detailed Implementation

[0025] Example 1: The raw material was 1000 kg of low-grade germanium-rich lignite, and the germanium content was found to be 0.0459% by sampling and testing. The steps for extracting germanium were as follows:

[0026] 1) Wet ball mill alkalization: Turn on the wet ball mill and put in 1000 kg of germanium-rich lignite that has been coarsely crushed to a particle size of less than 5 mm. Add 6000 L of tap water and 50 kg of sodium hydroxide (0.05 times the weight of lignite). Grind the raw material until the particle size can pass through a 90-mesh sieve to obtain a batch of ground raw material.

[0027] 2) Surfactant-enhanced leaching: The milled raw material is placed into a leaching tank equipped with stirring and steam heating. The stirring speed is adjusted to 125 r / min, and 7.4 kg of hexadecyltrimethylamine bromide surfactant is added (approximately 0.75‰ of the raw material weight). Steam heating is then initiated, raising the temperature to 80℃ and maintaining this temperature for 3 hours. After the holding period, heating is stopped, and stirring continues to cool the solution in the leaching tank to 50℃. During this process, germanium in germanium-rich lignite exists in the solution as sodium germanate, and its chemical reaction equation is as follows:

[0028] GeO₂ + 2NaOH → Na₂GeO₃ + H₂O

[0029] 3) Solid-liquid separation: The filter press is turned on, and the solution in the leaching tank is pumped into the filter press through the sewage pump to start filtration, so that the solid and liquid are separated to obtain the primary leaching filtrate and the primary leaching residue. The weight of the primary leaching residue is 2018.5 kg and the weight of the primary leaching filtrate is 6497 L. The filtrate is sampled and tested, and its germanium content is found to be 44.61 mg / L.

[0030] 4) Secondary countercurrent leaching: Add 6000 L of tap water to the leaching tank, turn on the agitator, and repeat the above operation with the primary leaching residue in the leaching tank for secondary leaching. 1996.50 kg of secondary leaching residue was obtained, and sampling analysis showed that its germanium content was 0.0017%. 6903 L of secondary leaching filtrate was obtained, and analysis of its germanium content showed a result of 18.94 mg / L. Based on the data, the leaching rate after two leaching processes under these conditions reached 91.63%, and the metal balance rate reached 99.02%. The secondary leaching filtrate was collected and returned to step 1) as the water for preparing the solution for the next batch of wet ball milling.

[0031] 5) Precipitation and recovery of germanium: 10,000 L of the primary leaching filtrate was added to a neutralization tank equipped with stirring and steam heating. The stirrer was turned on and the speed was adjusted to 125 r / min. Stirring was carried out for 15 min to ensure thorough mixing. The germanium content was measured to be 49.61 mg / L. Concentrated sulfuric acid was slowly added to the neutralization tank to adjust the pH to 9.5. 50 kg of ferric chloride was added, and steam heating was turned on to raise the temperature to 50℃. After holding at this temperature for 2 h, heating was stopped, the stirrer was turned off, and the mixture was allowed to stand for 12 h before pressure filtration to separate the solid and liquid. 53.8 kg of neutralized germanium precipitate filter residue was obtained, with a germanium content of 0.843%. After calcination at 500℃, the germanium content was 1.41%. 9973 L of filtrate was also collected, with a germanium content of 3.8 mg / L. Based on the data, the germanium precipitation rate under these conditions reached 91.42%, and the metal balance rate reached 99.24%.

[0032] The chemical reaction equation involved in step 5) is:

[0033] Na₂GeO₃ + 3H₂SO₄ → Ge(SO₄)₂ + Na₂SO₄ + 3H₂O Ge(SO₄)₂ + 4NaOH → Ge(OH)₄↓ + 2Na₂SO₄ FeCl₃ + 3H₂O → Fe(OH)₃ (colloid)↓ + 3HCl

[0034] Example 2: The raw material was 1000 kg of germanium-rich lignite, and the germanium content was found to be 0.0515% by sampling and testing. The steps for extracting germanium were as follows:

[0035] 1) Wet ball mill alkalization: Turn on the wet ball mill, put in 1000 kg of germanium-rich lignite that has been coarsely crushed to a particle size of less than 5 mm, add 6000 L of tap water and 100 kg of sodium hydroxide (0.1 times the weight of lignite), grind the raw material until the particle size can pass through a 100-mesh sieve, and obtain a batch of ground raw material.

[0036] 2) Surfactant-enhanced leaching: The milled raw material is put into a leaching tank equipped with stirring and steam heating. The stirring speed is turned on and adjusted to 125 r / min. 3.6 kg of hexadecyltrimethylamine bromide surfactant is added (the amount added is about 0.5‰ of the raw material weight). Steam heating is turned on and the temperature is raised to 90℃ and kept at that temperature for 3 h. After the holding time is completed, the heating is stopped and stirring is continued to cool the temperature of the solution in the leaching tank to 50℃.

[0037] 3) Solid-liquid separation: The filter press is turned on, and the solution in the leaching tank is pumped into the filter press through the sewage pump to start filtration, so that the solid and liquid are separated to obtain the primary leaching filtrate and the primary leaching residue. The weight of the primary leaching residue is 2030.05 kg and the weight of the primary leaching filtrate is 6594 L. The filtrate is sampled and tested, and its germanium content is found to be 50.11 mg / L.

[0038] 4) Secondary countercurrent leaching: Add 6000 L of tap water to the leaching tank, turn on the agitator, and repeat the above operation with the primary leaching residue in the leaching tank for secondary leaching. 2040.51 kg of secondary leaching residue was obtained, and sampling analysis showed that its germanium content was 0.0019%. 7271 L of secondary leaching filtrate was obtained, and its germanium content was analyzed to be 20.07 mg / L. Based on the data, the leaching rate after two leaching processes under these conditions reached 92.49%, and the metal balance rate reached 98.73%. The secondary leaching filtrate was collected and returned to step 1) as the water for preparing the solution for the next batch of wet ball milling.

[0039] 5) Precipitation and recovery of germanium: 10,000 L of the primary leaching filtrate was added to a neutralization tank equipped with stirring and steam heating. The stirrer was turned on and the speed was adjusted to 125 r / min. Stirring was carried out for 15 min to ensure thorough mixing. The germanium content was measured to be 51.35 mg / L. Concentrated sulfuric acid was slowly added to the neutralization tank to adjust the pH to 8.5. 45 kg of ferric chloride was added, and steam heating was turned on to raise the temperature to 50℃. After holding at this temperature for 2 h, heating was stopped, the stirrer was turned off, and the mixture was allowed to stand for 12 h before pressure filtration to separate the solid and liquid. 54.39 kg of neutralized germanium precipitate filter residue was obtained, with a germanium content of 0.8618%. After calcination at 500℃, the germanium content was 1.40%. 9846 L of filtrate was also collected, with a germanium content of 4.12 mg / L. Based on the data, the germanium precipitation rate under these conditions reached 91.28%, and the metal balance rate reached 98.18%.

[0040] Example 3: The raw material was 1000 kg of germanium-rich lignite, and the germanium content was measured to be 0.0492%. The steps for extracting germanium were as follows:

[0041] 1) Wet ball mill alkalization: Turn on the wet ball mill and put in 1000 kg of germanium-rich lignite that has been coarsely crushed to a particle size of less than 5 mm. Add 6000 L of tap water and 200 kg of sodium hydroxide (0.2 times the weight of lignite) to grind the raw material until the particle size can pass through an 80-mesh sieve to obtain a batch of ground raw material.

[0042] 2) Surfactant-enhanced leaching: The milled raw material is put into a leaching tank equipped with stirring and steam heating. The stirring speed is turned on and adjusted to 125 r / min. 7.4 kg of polyvinyl alcohol surfactant is added (the amount added is about 0.75‰ of the raw material). Steam heating is turned on and the temperature is raised to 85℃ and kept at that temperature for 3 h. After the holding time is completed, the heating is stopped and stirring is continued to cool the temperature of the solution in the leaching tank to 50℃.

[0043] 3) Solid-liquid separation: The filter press is turned on, and the solution in the leaching tank is pumped into the filter press through the sewage pump to start filtration, so that the solid and liquid are separated to obtain the primary leaching filtrate and the primary leaching residue. The weight of the primary leaching residue is 2230.95 kg and the weight of the primary leaching filtrate is 5853 L. The filtrate is sampled and tested, and its germanium content is found to be 56.09 mg / L.

[0044] 4) Secondary countercurrent leaching: Add 6000 L of tap water to the leaching tank, turn on the agitator, and repeat the above operation with the primary leaching residue in the leaching tank for secondary leaching. 2101.06 kg of secondary leaching residue was obtained, and sampling analysis showed a germanium content of 0.0008%. 6895 L of secondary leaching filtrate was obtained, and analysis of its germanium content showed a result of 21.02 mg / L. Based on the data, the leaching rate after two leaching processes under these conditions reached 96.18%, and the metal balance rate reached 99.60%. The secondary leaching filtrate was collected and returned to step 1) as the water for preparing the solution for the next batch of wet ball milling.

[0045] 5) Precipitation and recovery of germanium: 10,000 L of the primary leaching filtrate was added to a neutralization tank equipped with stirring and steam heating. The stirrer was turned on and the speed was adjusted to 125 r / min. Stirring was carried out for 15 min to ensure thorough mixing. The germanium content was measured to be 52.59 mg / L. Concentrated sulfuric acid was slowly added to the neutralization tank to adjust the pH to 9.0. 39 kg of ferric chloride was added, and steam heating was turned on to raise the temperature to 50°C. After a constant temperature precipitation reaction for 2 h, heating was stopped, the stirrer was turned off, and the mixture was allowed to stand for 12 h before pressure filtration to separate the solid and liquid. 59.75 kg of neutralized precipitated germanium filter residue was obtained, with a germanium content of 0.8526%. After calcination at 500°C, the germanium content was 1.47%. 9693 L of filtrate was also collected, with a germanium content of 1.46 mg / L. Based on the data, the germanium precipitation rate under these conditions reached 96.87%, and the metal balance rate reached 99.16%.

[0046] Comparing Examples 1, 2, and 3, Example 3 exhibits the best overall technical indicators: the sodium hydroxide input is 0.2 times the weight of the germanium-rich lignite, the leaching temperature is 85℃, and the leaching rate after two leaching cycles reaches 96.18%, with a metal balance rate of 99.60%. During germanium precipitation and recovery, concentrated sulfuric acid is used to adjust the pH to 9.0, the amount of ferric chloride added is approximately 75 times the amount of germanium metal in the filtrate, the germanium precipitation rate reaches 96.87%, the metal balance rate reaches 99.16%, and the final filtrate germanium content is as low as 1.46 mg / L. Under the same equipment and method, Example 3 demonstrates superior leaching rate, germanium precipitation rate, metal balance rate, and filtrate residue control compared to Examples 1 and 2. Furthermore, is it convenient to supplement with other examples?

[0047] Comparative Example 1, without surfactant leaching: The raw material was 1000 kg of low-grade germanium-rich lignite, and the germanium content was measured to be 0.0459%. The germanium extraction steps were as follows:

[0048] 1) Wet ball mill alkalization: Turn on the wet ball mill, put in 1000 kg of germanium-rich lignite, add 6000 L of tap water and 100 kg of sodium hydroxide, grind the raw material until the particle size can pass through a 90-mesh sieve, and obtain a batch of ground raw material.

[0049] 2) Leaching: The milled raw material is placed into a leaching tank equipped with stirring and steam heating. The stirring speed is adjusted to 125 r / min, and steam heating is started to raise the temperature to 80℃ and hold for 3 hours. After the holding period, heating is stopped, and stirring continues to cool the solution temperature in the leaching tank to 50℃. During this process, germanium in germanium-rich lignite exists in the solution as sodium germanate, and its chemical reaction equation is as follows:

[0050] GeO₂ + 2NaOH → Na₂GeO₃ + H₂O

[0051] 3) Solid-liquid separation: The filter press is turned on, and the solution in the leaching tank is pumped into the filter press through the sewage pump to start filtration, so that the solid and liquid are separated to obtain the primary leaching filtrate and the primary leaching residue. The weight of the primary leaching residue is measured to be 2010.6 kg and the weight of the primary leaching filtrate is 6465 L. The filtrate is sampled and tested to find that its germanium content is 32.48 mg / L.

[0052] 4) Secondary countercurrent leaching: Add 6000 L of tap water to the leaching tank, turn on the agitator, and repeat the above operation with the primary leaching residue in the leaching tank for secondary leaching. 1967.3 kg of secondary leaching residue was obtained, and sampling analysis showed that its germanium content was 0.0078%. 6936 L of secondary leaching filtrate was obtained, and analysis of its germanium content showed a result of 12.23 mg / L. Based on the data, the leaching rate under these conditions reached 64.51%, and the metal balance rate reached 97.65%.

[0053] The leaching rate was 27.12% lower than that without the surfactant cetyltrimethylamine bromide, indicating a significant decrease in leaching efficiency. Therefore, it is necessary to add a surfactant to improve the leaching rate.

[0054] Comparative Example 2: Germanium recovery from the primary leaching solution without pH adjustment: 10,000 L of primary leaching filtrate was added to a sedimentation tank equipped with stirring and steam heating. The stirrer was turned on and the speed was adjusted to 125 r / min. Stirring was performed for 15 min to ensure thorough mixing. A sample was taken, and the germanium content was found to be 51.92 mg / L. Without pH adjustment, 50 kg of ferric chloride was slowly added directly to the sedimentation tank. Steam heating was turned on and the temperature was raised to 50℃. After maintaining this temperature for 2 h, heating was stopped, the stirrer was turned off, and the mixture was allowed to stand for 12 h before pressure filtration to separate the solid and liquid. 41.39 kg of neutralized precipitated germanium filter residue was obtained, with a germanium content of 0.762%. After calcination at 500℃, the germanium content was 1.431%. 9861 L of filtrate was also tested, and the germanium content was found to be 19.9 mg / L. Based on the data, the germanium precipitation rate under these conditions reached 59.75%, and the metal balance rate reached 98.53%.

[0055] Based on the above analysis of the germanium recovery rate obtained by directly precipitating germanium with a single alkaline leaching solution, the germanium precipitation recovery rate is at least 31.53% lower than that obtained by adjusting the pH to 8.5-9.5 before precipitating germanium. Therefore, it is necessary to adjust the pH of the germanium precipitation solution to 8.5-9.5.

Claims

1. A method for extracting germanium from germanium-rich lignite, characterized in that, Includes the following steps: 1) Wet ball mill alkalization: After coarsely crushing germanium-rich lignite to a particle size of less than 5 mm, add it to a wet ball mill with water and sodium hydroxide in proportion and grind it simultaneously. The amount of water added is 4-6 times the weight of lignite, and the amount of sodium hydroxide added is 0.05-0.2 times the weight of lignite. Grind to a particle size of 60-120 mesh to obtain the ground raw material. 2) Surfactant-enhanced leaching: The milled raw material is put into the leaching tank and a surfactant is added. The amount of surfactant added is 0.5‰–1‰ of the weight of the raw material. The mixture is heated to 70℃–90℃ under stirring conditions at a speed of 100 r / min–150 r / min and kept at this temperature for 2 h–5 h. 3) Solid-liquid separation: The leached slurry is cooled to 40℃–60℃ and filtered to obtain primary leaching filtrate and primary leaching residue; 4) Secondary countercurrent leaching: The primary leaching residue is added to water for secondary leaching, and the residue and filtrate are obtained by filtration. The secondary leaching filtrate is returned to step 1) and used as the solution for the next batch of wet ball milling. 5) Precipitation recovery of germanium: Take the first leaching filtrate and stir it at a speed of 100 r / min-150 r / min for 5 min-15 min. Then adjust the pH to 8-10, add ferric chloride, the amount of ferric chloride added is 50-100 times the amount of germanium metal in the filtrate, heat to 40℃-60℃, keep the reaction at this temperature for 1 h-2 h, let it stand to precipitate for 8 h-12 h, and filter to obtain germanium-containing precipitate.

2. The method according to claim 1, characterized in that, In step 1), the sodium hydroxide is in the form of fine particles, and the amount added is 0.1 times the weight of germanium-rich lignite, with a particle size not exceeding 3 mm.

3. The method according to claim 1, characterized in that, In step 2), the surfactant is hexadecyltrimethylamine bromide.

4. The method according to claim 1, characterized in that, In step 5), concentrated sulfuric acid is used to adjust the pH to 8.5-9.5, the amount of ferric chloride added is 75-100 times the amount of germanium metal in the filtrate, the reaction temperature is 50℃, the constant temperature precipitation reaction time is 2 h, and the standing time is 12 h.

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