Silicon germanium waste recycling treatment process
By using high-pressure hydrogen peroxide to decompose silicon material under alkaline conditions, combined with gradient acid precipitation and tannin precipitation, the problem of efficient recovery of germanium and silicon in silicon-germanium waste has been solved, achieving a high recovery rate and low-cost environmentally friendly process.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- HUNAN HENGGUANG TECH
- Filing Date
- 2025-08-05
- Publication Date
- 2026-07-24
AI Technical Summary
Existing technologies for recovering germanium and silicon from silicon-germanium solar thin film waste suffer from high pollution, low recovery rates, and waste of silicon resources. In particular, the hydrofluoric acid method and the high-temperature alkaline fusion roasting method cause serious environmental pollution, high costs, and low recovery rates.
Silicon material is decomposed by high-pressure hydrogen peroxide under alkaline conditions, combined with gradient acid precipitation and recycling. Low-cost tannins are used to replace tannins for precipitation. High-purity germanium and silicon products are obtained through solid-liquid separation and calcination.
This has resulted in a significant increase in germanium recovery rate, high-value utilization of silicon resources, reduced reagent consumption and environmental pollution, and simplified subsequent purification processes.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of metal recycling technology, specifically to a recycling process for efficiently and environmentally friendly recovering silicon and germanium from germanium-containing silicon-based waste, particularly silicon-germanium solar thin film waste. Background Technology
[0002] The large-scale application of silicon-germanium thin-film solar cells has resulted in the generation of a large amount of waste containing 2-3% germanium and 95-98% silicon. Germanium has significant value as a strategic rare metal, while the efficient recovery of silicon as the main component is also of resource significance. Current technologies for recovering silicon and germanium from this type of waste suffer from systemic flaws:
[0003] 1. Significant Environmental Risks in Leaching Processes: Existing technologies primarily rely on hydrofluoric acid and high-temperature alkaline fusion methods to dissolve silicon substrates and release germanium. The hydrofluoric acid method releases germanium through the reaction of HF with the silicon substrate, but this process generates large quantities of highly toxic fluoride wastewater, which is difficult and costly to treat, and is highly corrosive to equipment, posing serious environmental pollution and operational safety risks. The high-temperature alkaline fusion roasting method involves alkaline roasting at temperatures above 600℃ to generate hydrochloric acid-soluble metasilicates, which are then extracted through acidification and distillation. This process has the following significant drawbacks: Firstly, during acidification, germanium is easily encapsulated by silica colloids, resulting in a recovery rate typically below 60%. Secondly, this process consumes large amounts of sulfuric acid, requiring 0.8-1.0 tons of sulfuric acid per ton of raw material processed, significantly increasing production costs and causing substantial loss of germanium resources. Furthermore, the residue after distillation requires neutralization, and its products are classified as hazardous waste, further increasing environmental disposal costs.
[0004] 2. Precipitation process restricts economic efficiency: The iron salt precipitation method produces low-grade ferric germanate containing 10% germanium, which requires subsequent hydrochloric acid chlorination and distillation refining. Every 100 kg of germanium concentrate requires 700 L of 30% hydrochloric acid. The residue after distillation is classified as hazardous waste after neutralization, resulting in high disposal costs. The dissolving tannin method requires heating to prepare the tannin solution, which forms a colloid after precipitation, leading to slow filtration speed and making reagent recycling difficult.
[0005] 3. Existing processes generally focus on germanium recovery, lacking pathways for the high-value utilization of silicon components. While wet acid leaching systems (such as HF systems) can dissolve silicon, they completely destroy the silicon structure, making recycling difficult. Although pyrometallurgical processes can recover germanium, they are energy-intensive at high temperatures, and germanium enters the silicon slag during acidification. Even after distillation and neutralization, the slag remains hazardous waste, making silicon recovery impossible and further reducing germanium recovery rates. Summary of the Invention
[0006] This invention aims to provide a clean process for the simultaneous and efficient recovery of germanium and silicon from silicon-germanium solar thin film waste, solving the technical defects of traditional processes such as high pollution, high cost, low recovery rate, and waste of silicon resources.
[0007] The technical solution adopted in this invention is as follows: a silicon-germanium waste recycling process, comprising the following steps:
[0008] S1. Raw material pretreatment: Crush the silicon-germanium waste to 120-200 mesh;
[0009] S2, Alkali leaching reaction and solid-liquid separation: Pure water and the crushed waste obtained in step S1 are added to the decomposition reactor. Liquid alkali is added to adjust the pH to 13-14. Hydrogen peroxide is slowly added through an immersion inlet pipe until the material dissolves and the liquid becomes clear and transparent. After cooling to 85-90°C, solid-liquid separation is performed to obtain germanium-containing mother liquor and filter residue. The filter residue is dried and returned to step S1 to be mixed with the silicon-germanium waste to be treated for recycling. The germanium-containing mother liquor enters step S3.
[0010] S3. Primary Desilication: In a primary desilication reactor, the germanium-containing mother liquor obtained in step S2 is diluted with pure water and heated to 90-95°C. Under rapid stirring, 10-20% dilute sulfuric acid is slowly added to adjust the pH to 10.2-10.4, and a primary desilication reaction is carried out. After the reaction is completed, the mixture is filtered to separate the silicon-containing solid and the germanium-containing filtrate. The silicon-containing solid is washed with pure water until the germanium content in the wash water is <50 mg / L, and then output as a silicon by-product. The wash water is returned to step S2 as supplementary process water for the decomposition reactor. The germanium-containing filtrate proceeds to step S4.
[0011] S4. Secondary Desilication: In a secondary desilication reactor, the germanium-containing filtrate obtained in step S3 is heated to 90-95°C and maintained. 10-20% dilute sulfuric acid is slowly added to adjust the pH to 9.2-9.5, and a secondary desilication reaction is carried out. Silicon is removed stepwise by gradually decreasing the pH. After the reaction is completed, the filtrate is filtered to separate the silicon-containing solid and the germanium-containing filtrate. The silicon-containing solid is washed with pure water until the germanium content in the wash water is <200 mg / L. The wash water is returned to step S3 as makeup water for diluting the germanium-containing mother liquor. The germanium-containing filtrate proceeds to step S5.
[0012] S5, Primary Germanium Precipitation: Water is first added to the primary germanium precipitation reactor, followed by pre-acidification with 10-20% dilute sulfuric acid to a pH of 0.3-0.5 as the base solution. Then, the secondary desilication germanium-containing filtrate obtained in step S4 is slowly added, controlling the overall pH of the system to 1-2. 20-25 times the mass of germanium is added to tannin solid powder, and after stirring and reacting fully, the mixture is filtered to obtain tannin germanium solid and the primary germanium precipitation post-filtrate. The tannin germanium solid is calcined to obtain germanium concentrate, and the primary germanium precipitation post-filtrate proceeds to step S6.
[0013] S6. Secondary germanium precipitation and wastewater treatment: In the secondary germanium precipitation reactor, 40 to 50 times the mass of germanium is added to the filtrate after primary germanium precipitation obtained in step S5. The mixture is stirred until the germanium content in the liquid phase is <1 mg / L, and then filtered to obtain secondary germanium precipitate and final wastewater. The final wastewater is neutralized to a pH of 7 to 8 and then discharged for further treatment.
[0014] Furthermore, the silicon-germanium waste is silicon-germanium solar thin film waste, containing 2-3 wt% germanium and 95-98 wt% silicon.
[0015] Furthermore, the mass ratio of pure water to crushed waste added in step S2 is (9.5~10.5):1.
[0016] Furthermore, the liquid alkali mentioned in step S2 is a sodium hydroxide solution.
[0017] Further, in step S2, after adjusting the pH to 13-14 with added alkali, the decomposition reactor is heated to 95-100°C with steam, and then hydrogen peroxide is slowly added through an immersion inlet pipe. The pressure is increased to 0.55-0.6 MPa, and the temperature is increased to 150-160°C and maintained.
[0018] Further, the germanium-containing mother liquor described in step S3 is diluted at a volume ratio of 1:(3.8-4.2).
[0019] Further, in step S4, the silicon-containing solid after secondary desilication is returned to step S3 and added to the diluted germanium-containing mother liquor. After stirring evenly, the temperature is raised.
[0020] Furthermore, in step S4, the first 30% of the washing water from the secondary desilication of silicon-containing solids and the secondary desilication of germanium-containing filtrate enter step S5 together, and the remaining 70% of the washing water is returned to step S3 as supplementary water for diluting the germanium-containing mother liquor.
[0021] Furthermore, the calcination conditions for the tannin-germanium solid in step S5 are as follows: calcination at 500–650°C under an oxygen-rich atmosphere to obtain a germanium concentrate with a content of 50–55%.
[0022] Furthermore, in step S6, the secondary germanium solid is returned to the system in step S5 after the overall pH is 1-2 and then added back for recycling.
[0023] The beneficial effects of this invention are as follows:
[0024] (1) This invention uses an alkaline environment immersion method with hydrogen peroxide and high pressure to decompose silicon material in one step, with a decomposition rate of over 99%. The undecomposed material is mainly uncrushed silicon-germanium particles. Through gradient acid precipitation desiliconization and recycling, the total desiliconization rate of the first desiliconization reaches about 90%, and the germanium loss rate is about 2-5%. The total desiliconization rate of the second desiliconization reaches about 95%. The lost germanium is returned to the first desiliconization, and the germanium recovery rate is greatly improved. Silicon-containing solids with a silicon content of ≥99% (the main component of which is hydrated silicon dioxide) are directly output as industrial silicon raw materials after being washed with pure water, realizing the high-value recovery of silicon resources. The silicon-germanium loss is no more than 5%, which is significantly higher than that of traditional processes.
[0025] (2) Replace tannin with low-cost rubber tannin (the cost of rubber tannin is only 1 / 3 to 1 / 5 of that of tannin), and combine it with solid powder direct injection technology to avoid the colloids generated after adding liquid after water dissolution, which leads to slow filtration and inability to be recycled. After precipitation, it is a particulate solid, which is easy to filter and can be recycled, reducing the amount of reagent consumed by 30%.
[0026] (3) After roasting, germanium concentrate with a content of 50-55% can be obtained directly, simplifying the subsequent purification process. Detailed Implementation
[0027] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.
[0028] Example 1
[0029] The silicon-germanium solar thin film waste recycling process provided in this embodiment includes the following steps:
[0030] S1. Waste pretreatment:
[0031] Waste silicon-germanium solar thin films (containing 2.7% germanium and 95-98% silicon) are mechanically ground to a particle size range of 120-200 mesh to ensure sufficient contact and efficient execution of subsequent chemical reactions.
[0032] S2. Alkali leaching reaction and solid-liquid separation:
[0033] Traditional processes often involve leaching with hydrofluoric acid or calcining with sodium bicarbonate at 800–900°C, or calcining with sodium hydroxide at 600–700°C. These methods suffer from significant environmental hazards, complex processes, high energy consumption, and low recovery rates (only 50–60%). This process employs a modified alkaline leaching method: 5000... L of deionized water was added, followed by 500 kg of crushed raw material. The pH of the system was adjusted to 13-14 by adding 32% sodium hydroxide solution. The decomposition reactor was heated to 95-100°C using steam. 27.5% hydrogen peroxide was slowly added through a metering pump and an immersion inlet pipe (subsurface immersion inlet prevents direct surface decomposition). At the same time, the pressure was increased to 0.56 MPa, and the temperature was raised to 150-160°C and maintained at a constant temperature. After reacting for 30 minutes, the material was confirmed to be completely dissolved through the observation hole, and the solution was clear and transparent. Then, after the system temperature dropped to 90°C, solid-liquid separation was performed using a filter press. The resulting germanium-containing mother liquor was transferred to a primary desilication reactor. The filter residue was dried and then mixed back into the raw material for crushing to achieve recycling.
[0034] S3, First Desilication:
[0035] In a desilication reactor, 1000 L of germanium-containing mother liquor was diluted to 5000 L to prevent excessive silicon concentration from causing polymerization caking and stirring jamming. The system was heated to 90℃ and maintained at a constant temperature (to ensure that silica crystallizes during desilication and prevents the formation of a gel-like substance that adsorbs large amounts of germanium). The stirring device was started and stirred rapidly (stirring speed 160 rpm; high speed helps prevent silica slag polymerization and caking, and can break up large polymer particles). A 10-20% sulfuric acid solution was slowly added to adjust the pH of the system to 10.4, causing 90% of the silicon in the solution to be converted into white hydrated silica particles (silicon content ≥99%, germanium content 375 g / t). The silicon-containing solids were separated by a filter press, and the filter cake was washed with pure water to ensure that the germanium content in the washing water was below 50%. mg / L; the first 30% of the washing water and the first desiliconization germanium-containing filtrate were transferred to the second-stage germanium precipitation reactor, and the last 70% of the washing water was returned to the decomposition reactor as supplementary process water. The silicon-containing solids after washing were sold to silicon plants as silicon by-products.
[0036] S4, Secondary Desilication:
[0037] In the secondary desilication reactor, the system is heated to 90℃ and maintained at a constant temperature. A 10-20% sulfuric acid solution is slowly added to adjust the pH to 9.2, promoting the further conversion of the remaining 10% of silicon into white hydrated silica particles (silicon content ≥99%, germanium content approximately 2000-3000 g / t). The silicon-containing solids are separated by a filter press, and the filter cake is washed with pure water, ensuring that the germanium content in the wash water is below 200 mg / L. The first 30% of the wash water, along with the secondary desilication germanium-containing filtrate, is transferred to the primary germanium precipitation reactor. The remaining 70% of the wash water is returned to the primary desilication reactor as makeup water for diluting the germanium-containing mother liquor. The secondary desilication produces very few silicon-containing solid particles, but the germanium content is relatively high. Therefore, it can be directly returned to the primary desilication reactor and added to the diluted germanium-containing mother liquor for further dissolution and desilication recovery of germanium.
[0038] S5, Grade 1 Germanium precipitate:
[0039] In the primary germanium precipitation reactor, an appropriate amount of industrial water is first added, followed by pre-acidification with 10-20% dilute sulfuric acid to a pH of 0.3-0.5 as the base solution. Then, the secondary desilication germanium-containing filtrate with a pH of 9.2-9.5 is slowly added, ensuring the overall pH of the system is maintained within the range of 1-2. Preparing the acid solution before adding the desilication germanium-containing solution to the acidic environment prevents residual silicon from further precipitating as the pH drops from 9 to 2, thus avoiding impact on the final product quality. Finally, the germanium-containing solution is cooled to 35-40°C using the reactor jacket cooling water (to prevent the added solids from precipitating). (Dissolve tannin powder in a tannin-rubber compound). Based on the germanium content in the solution, add 25 times the amount of tannin-rubber solid powder. React thoroughly for 4 hours under stirring. After the reaction is complete, separate the tannin-germanium solid and the first-stage germanium-precipitated filtrate using a filter press. Wash the filter cake with industrial water, ensuring the pH of the wash water is 5-6. Transfer the wash water and the first-stage germanium-precipitated filtrate together to the second-stage germanium-precipitated reactor. After calcining the tannin-germanium solid at 500℃ with oxygen, a germanium concentrate with a content of 50-55% can be obtained.
[0040] S6, Secondary germanium precipitation and wastewater treatment:
[0041] In the secondary germanium precipitation reactor, based on the germanium content in the filtrate after primary germanium precipitation, 50 times the amount of tannin solid powder was added. The mixture was stirred and reacted for 4 hours. After testing, the germanium content in the liquid phase was found to be less than 1 mg / L. After separation by a filter press, the secondary germanium solid (tannin germanium) obtained could still adsorb a lot of germanium and could be added back to the primary germanium precipitation reactor for reuse, reducing the amount of tannin solid powder used in the primary germanium precipitation reactor. The filtrate was neutralized to a pH of 7-8 and then sent to the industrial park's wastewater treatment plant for further treatment.
[0042] Examples 2-4
[0043] Examples 2-4 respectively provide alkaline leaching reactions of pretreated waste materials. The treatment steps are the same as in Example 1, but the difference lies in the specific process control conditions. The specific process control conditions and data of the alkaline leaching reactions in Examples 1-4 are shown in Appendix Table 1.
[0044] Appendix 1:
[0045]
[0046] As can be seen from the comparison in Appendix 1, applying pressure during the alkaline leaching reaction can shorten the reaction time and increase the germanium leaching rate.
[0047] Examples 5-7
[0048] Examples 5-7 respectively provide the first desilication, second desilication, first-stage germanium precipitation, and second-stage germanium precipitation treatments of the germanium-containing mother liquor obtained by the alkaline leaching reaction in Example 1. The treatment steps are the same as in Example 1, but the difference lies in the specific process control conditions. The specific process control conditions and data of Example 1 and Examples 5-7 are shown in Appendix Table 2.
[0049] Appendix 2:
[0050]
[0051] The above description is merely an example and illustration of the structure of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described, or use similar methods to replace them, as long as they do not deviate from the structure of the present invention or exceed the scope defined in the claims, all of which should fall within the protection scope of the present invention.
Claims
1. A process for recycling and treating silicon-germanium waste, characterized in that, Includes the following steps: S1. Raw material pretreatment: Crush the silicon-germanium waste to 120-200 mesh; S2, Alkali leaching reaction and solid-liquid separation: Pure water and the crushed waste obtained in step S1 are added to the decomposition reactor. Liquid alkali is added to adjust the pH to 13-14. Hydrogen peroxide is slowly added through an immersion inlet pipe until the material dissolves and the liquid becomes clear and transparent. After cooling to 85-90°C, solid-liquid separation is performed to obtain germanium-containing mother liquor and filter residue. The filter residue is dried and returned to step S1 to be mixed with the silicon-germanium waste to be treated for recycling. The germanium-containing mother liquor enters step S3. S3. Primary Desilication: In a primary desilication reactor, the germanium-containing mother liquor obtained in step S2 is diluted with pure water and heated to 90-95°C. Under rapid stirring, 10-20% dilute sulfuric acid is slowly added to adjust the pH to 10.2-10.4, and a primary desilication reaction is carried out. After the reaction is completed, the mixture is filtered to separate the silicon-containing solid and the germanium-containing filtrate. The silicon-containing solid is washed with pure water until the germanium content in the wash water is <50 mg / L, and then output as a silicon by-product. The wash water is returned to step S2 as supplementary process water for the decomposition reactor. The germanium-containing filtrate proceeds to step S4. S4. Secondary Desilication: In a secondary desilication reactor, the germanium-containing filtrate obtained from the primary desilication in step S3 is heated to 90-95°C and maintained. 10-20% dilute sulfuric acid is slowly added to adjust the pH to 9.2-9.5 to carry out the secondary desilication reaction. After the reaction is completed, the filtrate is filtered to separate the secondary desilication silicon-containing solid and the secondary desilication germanium-containing filtrate. The secondary desilication silicon-containing solid is washed with pure water until the germanium content in the wash water is <200 mg / L. The wash water is returned to step S3 as makeup water for diluting the germanium-containing mother liquor. The secondary desilication germanium-containing filtrate proceeds to step S5. S5, Primary Germanium Precipitation: Water is first added to the primary germanium precipitation reactor, followed by pre-acidification with 10-20% dilute sulfuric acid to a pH of 0.3-0.5 as the base solution. Then, the secondary desilication germanium-containing filtrate obtained in step S4 is slowly added, controlling the overall pH of the system to 1-2. 20-25 times the mass of germanium is added to tannin solid powder, and after stirring and reacting fully, the mixture is filtered to obtain tannin germanium solid and the primary germanium precipitation post-filtrate. The tannin germanium solid is calcined to obtain germanium concentrate, and the primary germanium precipitation post-filtrate proceeds to step S6. S6. Secondary germanium precipitation and wastewater treatment: In the secondary germanium precipitation reactor, 40 to 50 times the mass of germanium is added to the filtrate after primary germanium precipitation obtained in step S5. The mixture is stirred until the germanium content in the liquid phase is <1 mg / L, and then filtered to obtain secondary germanium precipitate and final wastewater. The final wastewater is neutralized to a pH of 7 to 8 and then discharged for further treatment.
2. The silicon-germanium waste recycling process as described in claim 1, characterized in that, The silicon-germanium waste is silicon-germanium solar thin film waste, containing 2-3 wt% germanium and 95-98 wt% silicon.
3. The silicon-germanium waste recycling process as described in claim 1, characterized in that, The mass ratio of pure water to crushed waste added in step S2 is (9.5~10.5):
1.
4. The silicon-germanium waste recycling process as described in claim 1, characterized in that, The liquid alkali mentioned in step S2 is a sodium hydroxide solution.
5. The silicon-germanium waste recycling process as described in claim 1, characterized in that, In step S2, after adjusting the pH to 13-14 with added alkali, the decomposition reactor is heated to 95-100°C with steam, and then hydrogen peroxide is slowly added through an immersion inlet pipe. The pressure is increased to 0.55-0.6 MPa, and the temperature is increased to 150-160°C and maintained.
6. The silicon-germanium waste recycling process as described in claim 1, characterized in that, The germanium-containing mother liquor mentioned in step S3 is diluted at a volume ratio of 1: (3.8 to 4.2).
7. The silicon-germanium waste recycling process as described in claim 1, characterized in that, In step S4, the silicon-containing solids after secondary desilication are returned to step S3 and added to the diluted germanium-containing mother liquor. After stirring evenly, the temperature is raised.
8. The silicon-germanium waste recycling process as described in claim 1, characterized in that, In step S4, the first 30% of the washing water from the secondary desilication of silicon-containing solids and the secondary desilication of germanium-containing filtrate enter step S5 together, and the remaining 70% of the washing water is returned to step S3 as supplementary water for diluting the germanium-containing mother liquor.
9. The silicon-germanium waste recycling process as described in claim 1, characterized in that, The calcination conditions for tannin-germanium solid in step S5 are as follows: calcination at 500–650°C in an oxygen-rich atmosphere to obtain germanium concentrate with a content of 50–55%.
10. The silicon-germanium waste recycling process as described in claim 1, characterized in that, In step S6, the secondary germanium solid is returned to the system in step S5 after the overall pH is 1-2, and then added back for recycling.