Method for efficiently removing arsenic from crude germanium tetrachloride solution based on arsenic hydride reduction

Abstract

The invention discloses a method for efficiently removing arsenic from a crude germanium tetrachloride solution based on arsenic hydride reduction, and belongs to the technical field of rare and noble metal metallurgy. According to the method, arsenic hydride gas is introduced into a crude germanium tetrachloride solution containing arsenic impurities under the protection of inert atmosphere and under the mild condition of 20-80 DEG C; the arsenic hydride and arsenic compounds such as arsenic trichloride, arsenious acid and arsenic acid in the solution are subjected to selective reduction reaction to generate simple substance arsenic solid precipitate. Then a germanium tetrachloride solution subjected to deep arsenic removal can be obtained through simple solid-liquid separation operation, obtained arsenic-containing solids are washed and dried, and resource recycling of crude arsenic products is synchronously achieved. The method provided by the invention initiates a new arsenic removal path of reduction-precipitation, has the outstanding advantages of high arsenic removal efficiency, good selectivity, short process flow, no secondary pollution and capability of realizing arsenic resource utilization, and provides a brand new solution for green and efficient preparation of high-purity germanium tetrachloride.

Description

Technical Field

[0001] This invention belongs to the field of rare and precious metal metallurgy technology, specifically relating to a method for efficient removal of arsenic from crude germanium tetrachloride solution based on arsine reduction, which is used for the preparation of high-purity germanium tetrachloride and the resource recovery of arsenic impurities. Background Technology

[0002] High-purity germanium materials are typically produced from germanium concentrate or germanium-containing waste through steps such as chlorination leaching and distillation to obtain high-purity germanium tetrachloride (GeCl4). The final high-purity germanium product is then obtained through processes such as hydrolysis, reduction, and zone melting. In this production chain, while conventional distillation can effectively separate most impurities with significantly different boiling points, its separation efficiency is limited for arsenic compounds with physical properties highly similar to GeCl4 (such as AsCl3, with a boiling point of 130.2℃, which is close to GeCl4's 84℃), making it difficult to reduce the arsenic content to 0.1 × 10⁻⁶. -4 Arsenic levels below a certain percentage are a critical factor limiting the deep purification of germanium tetrachloride. Therefore, developing a novel method for efficiently and selectively removing arsenic from germanium tetrachloride solution before the distillation process is of great value.

[0003] Germanium tetrachloride (GeCl4) is a key precursor for the preparation of high-purity germanium materials, and its purity directly affects the performance of germanium materials in fields such as optical fibers, infrared optics, and semiconductor devices. With the increasing demands for transmission loss in optical fiber communication (especially in specialized fields such as military and submarine cables), the market demand for ultra-high purity germanium tetrachloride is becoming increasingly urgent. However, arsenic impurities commonly found in raw materials exist in various forms, including arsenic trichloride (AsCl3), arsenous acid (H3AsO3), and arsenic acid (H3AsO4). Due to their similar physicochemical properties to germanium tetrachloride, these impurities become the most difficult bottleneck to remove during the purification process.

[0004] In the field of oxidative separation, the mainstream technology involves adding an oxidant to a germanium tetrachloride solution to convert lower-boiling-point trivalent arsenic compounds (such as arsenic trichloride, boiling point 130.2℃) into higher-boiling-point pentavalent arsenic compounds, followed by distillation to separate them from germanium tetrachloride (boiling point 84℃). For example, Chinese invention patent CN117819593B discloses a method and apparatus for removing arsenic from germanium tetrachloride by oxidizing hydrogen peroxide. This method uses hydrogen peroxide as an oxidant to oxidize arsenic trichloride to arsenic pentachloride in a hydrochloric acid medium, followed by multi-stage extraction, distillation, and rectification to obtain high-purity germanium tetrachloride. Although this method avoids the use of highly toxic chlorine gas and is relatively environmentally friendly and safe, the process is lengthy, involving multiple oxidation steps, static separation, and heating distillation, resulting in high energy consumption. Furthermore, the arsenic-containing waste acid solution generated still requires further treatment, failing to achieve the resource utilization of arsenic.

[0005] In the area of ​​reduction-separation methods, there is limited research on related technologies. Chinese patent document CN102531043A proposes a method for removing arsenic using oxidants such as manganese dioxide and ferric chloride. However, this method essentially falls under the category of oxidation methods and carries the risk of introducing new metallic impurities such as manganese and iron. Furthermore, there are no mature reports on methods that directly convert arsenic impurities into easily separable forms through reduction reactions. An ideal reduction method should possess high selectivity, meaning it should only reduce arsenic impurities without affecting the germanium tetrachloride matrix, while simultaneously converting arsenic into an economically valuable form for recovery, thereby achieving clean production and resource recycling.

[0006] Therefore, existing technologies generally suffer from problems such as lengthy process flows, potential introduction of new impurities, generation of arsenic-containing waste liquid, and failure to achieve resource recovery of arsenic impurities. There is an urgent need in this field for a new method that can directly reduce, separate, and convert arsenic into a valuable element in one step. Summary of the Invention

[0007] To address the aforementioned shortcomings in existing germanium tetrachloride purification technologies, the present invention aims to provide a method for efficient arsenic removal from crude germanium tetrachloride solution based on arsine reduction. This method utilizes a selective reduction reaction to convert arsenic impurities in the solution into elemental arsenic solid in situ, achieving deep arsenic removal from the germanium tetrachloride solution and resource recovery of arsenic in one step.

[0008] To achieve the above-mentioned objectives, the technical solution adopted by this invention is as follows: A method for efficient arsenic removal from crude germanium tetrachloride solution based on arsine reduction, comprising the following steps: (1) Reduction reaction: Under the protection of an inert atmosphere, the reaction temperature is controlled within the range of 20℃~80℃. Arsine gas is introduced into a crude germanium tetrachloride solution containing arsenic impurities. The arsine reacts with the arsenic compounds in the solution to generate a solid precipitate of elemental arsenic. (2) Solid-liquid separation: After the reaction is completed, the reaction system is subjected to solid-liquid separation to obtain a germanium tetrachloride solution after deep arsenic removal and a solid containing elemental arsenic; (3) Product recovery: The solid containing elemental arsenic is washed and dried to recover crude arsenic.

[0009] Furthermore, the arsenic compound includes at least one of arsenic trichloride, arsenous acid, and arsenic acid; Furthermore, to ensure complete reaction, the molar amount of arsine gas introduced is preferably 5.0 to 8.0 times the total molar amount of arsenic in the crude germanium tetrachloride solution; Furthermore, to enhance gas-liquid mass transfer, the reduction reaction is preferably carried out under stirring conditions; Furthermore, the reaction temperature is preferably controlled between 20°C and 50°C to achieve a highly efficient reaction under mild conditions; Furthermore, the gas in the inert atmosphere is nitrogen or argon; Furthermore, the solid-liquid separation can be achieved by filtration, centrifugal sedimentation, or natural sedimentation.

[0010] The basic principle of this invention lies in utilizing the strong reducing property of arsine (AsH3) on various arsenic compounds. Under mild conditions, arsine can reduce arsenic compounds in different valence states (such as AsCl3, H3AsO3, H3AsO4) in solution to elemental arsenic (As), which is insoluble in the germanium tetrachloride system. The main chemical reaction equations are as follows: AsCl3 + AsH3 → 2As↓ + 3HCl H3AsO3 + AsH3 → 2As↓ + 3H2O H3AsO4 + 2AsH3 → 3As↓ + 3H2O + O2↑ Thermodynamic analysis shows that the Gibbs free energy change (ΔG) of the above reaction is significantly lower than 0 in the experimental temperature range, indicating that the reaction has a very strong spontaneous tendency and can proceed very thoroughly, thus ensuring that arsenic impurities are efficiently and completely reduced and converted into solid crude arsenic for separation.

[0011] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. A method for selectively removing arsenic from crude germanium tetrachloride solution using arsine as a reducing agent was proposed, fundamentally transforming the impurity removal path from the traditional "oxidation-distillation separation" to "reduction-precipitation separation", providing a completely new technical approach and solution for the removal of arsenic from germanium tetrachloride.

[0012] 2. This method has high selectivity, reducing only arsenic compounds without affecting the germanium tetrachloride matrix, with a germanium recovery rate of over 99.9% (as shown in the examples), and can stably reduce the arsenic content from the initial thousands of mg / L (e.g., 2617 mg / L, 1756 mg / L) to below 10 mg / L (e.g., 8 mg / L, 5 mg / L), achieving deep purification.

[0013] 3. Arsenic impurities that are treated and discharged as "pollutants" in traditional processes are transformed into economically valuable "products"—crude arsenic (purity ≥99.5%), truly realizing the resource recovery and clean production of arsenic, which is in line with the principles of green chemistry and circular economy.

[0014] 4. The core process of "one-step reduction reaction + solid-liquid separation" replaces the complex multi-stage oxidation, extraction and distillation processes in the existing technology, which significantly shortens the process flow, reduces equipment investment and energy consumption, and improves the overall economic benefits. Attached Figure Description

[0015] Figure 1 This is a process flow diagram of the method of the present invention; Figure 2 This is a schematic diagram of the chemical reaction equations for the method of the present invention. The diagram shows the chemical equations for the reduction reaction of hydrogen arsine with impurities such as arsenic trichloride, arsenous acid, and arsenic acid to produce crude arsenic. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. However, it should be understood that the scope of protection of this invention is not limited thereto, and any modifications, equivalent substitutions, or improvements made based on the spirit of this invention should be covered within the scope of protection of this invention.

[0017] The method of this invention combines chemical reaction and physical purification, using a germanium tetrachloride solution with an arsenic content ≥1300 mg / L as raw material. The process is as follows: S1: Detection of germanium and arsenic content in germanium tetrachloride solution; S2: Add the crude germanium tetrachloride solution to the reactor and start stirring. Purge the reactor with inert gas to replace the air and maintain positive pressure. S3: After gas replacement is completed, start heating and control the process temperature below 50℃. Based on 5.0-8.0 times the total molar amount of arsenic in the solution, control the molar amount of arsine gas passing through by the gas flow meter and the reaction time. S4: Control the reaction time of the solution according to the reaction situation. A black solid precipitate will be produced during the reaction. S5: After the reaction is complete, the mixed solution is transferred to a solid-liquid separation device under the protection of an inert gas to perform solid-liquid separation, and a germanium tetrachloride solution after deep arsenic removal and crude arsenic after washing with anhydrous ethanol and drying under low temperature vacuum are obtained. S6: The obtained germanium tetrachloride solution is tested. If the test result is qualified, it is stored in the next step. If it is unqualified, S2 to S6 are repeated. Example

[0018] This embodiment follows Figure 1 The process flow shown is as follows.

[0019] 1) Take 10L of crude germanium tetrachloride solution with an arsenic content of 2617mg / L (calculated as As) and place it in a 20L sealed reactor with stirring and temperature control functions. Purge nitrogen gas to fully replace the air in the reactor and maintain a slightly positive pressure inert atmosphere.

[0020] 2) Set the reaction temperature to 25℃ and start stirring. Slowly introduce arsine gas into the solution through a mass flow meter, controlling the total gas flow to be 6.6 times the total molar amount of arsenic in the solution. During the reaction, a black solid precipitate can be observed to gradually form in the solution.

[0021] 3) After the reaction is complete, the reaction mixture is transferred to a solid-liquid separation device for filtration under nitrogen protection to obtain a clear filtrate and a black filter cake.

[0022] Analysis results showed that the arsenic content in the filtrate (germanium tetrachloride solution after arsenic removal) decreased to 8 mg / L, and the germanium recovery rate was 99.93%. After washing with anhydrous ethanol and low-temperature vacuum drying, the black filter cake yielded approximately 47.8 g of crude arsenic solid, which was tested to have a purity ≥99.5% (main impurity content: Sb≤0.20%, Bi≤0.08%, S≤0.10%). Example

[0023] This embodiment follows Figure 1 The process flow shown is as follows.

[0024] 1) Take 10L of crude germanium tetrachloride solution with an arsenic content of 1756mg / L (calculated as As) and place it in the same reaction vessel as in Example 1. Purge the air with nitrogen to maintain a slightly positive pressure inert atmosphere.

[0025] 2) Set the reaction temperature to 35℃, turn on the stirrer, and introduce arsine gas through a mass flow meter. The total amount of gas introduced is 6.3 times the total molar amount of arsenic in the solution. During the reaction, a black solid precipitate was also observed to form.

[0026] 3) After the reaction is complete, the reaction mixture is transferred to a solid-liquid separation device for filtration under nitrogen protection to obtain a clear filtrate and a black filter cake.

[0027] Analysis showed that the arsenic content in the filtrate decreased to 5 mg / L, and the germanium recovery rate was 99.91%. After washing and drying, the filter cake yielded approximately 32.4 g of crude arsenic solid, with a purity ≥99.5% (main impurity content: Sb≤0.20%, Bi≤0.08%, S≤0.10%). This example demonstrates that the method exhibits excellent reducing power for arsenic compounds of different concentrations and potentially different forms.

[0028] Comparative Example 1: To verify the technical effect of the present invention, the method described in publication number CN102531043A was used as a comparison, and the following experiment was conducted: A crude germanium tetrachloride solution from the same batch as in Example 2 of this invention was used, with an initial arsenic content of 1756 mg / L. Following the method described in CN102531043A, a certain amount of manganese dioxide was added to the crude germanium tetrachloride solution as an oxidant for oxidation treatment. After the reaction, the treated germanium tetrachloride solution was tested. The results showed that the arsenic content was reduced, indicating that the method has a certain degree of arsenic removal effect; however, the test also revealed the addition of manganese ion impurities in the solution, indicating that manganese dioxide partially dissolved and introduced new metallic impurities during the reaction.

[0029] This result indicates that although the method described in CN102531043A can reduce the arsenic content in germanium tetrachloride solution, it introduces manganese ions, which may lead to secondary pollution problems in the subsequent preparation of high-purity germanium and affect the recovery rate of germanium.

[0030] In contrast, the method described in this invention does not introduce new impurity elements during the processing, effectively avoids secondary pollution, and has higher purification effect and better process stability.

[0031] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for efficient arsenic removal from a crude germanium tetrachloride solution based on reduction of arsine, characterized in that, Includes the following steps: (1) Reduction reaction: Under the protection of an inert atmosphere, the reaction temperature is controlled within the range of 20℃~80℃. Arsine gas is introduced into a crude germanium tetrachloride solution containing arsenic impurities. The arsine reacts with the arsenic compounds in the solution to generate a solid precipitate of elemental arsenic. (2) Solid-liquid separation: After the reaction is completed, the reaction system is subjected to solid-liquid separation to obtain a germanium tetrachloride solution after arsenic removal and a solid containing elemental arsenic; (3) Product recovery: The solid containing elemental arsenic is washed and dried to recover crude arsenic.

2. The method for high-efficiency dearsenication of a crude germanium tetrachloride solution based on reduction of arsine according to claim 1, characterized in that, The arsenic compound includes at least one of arsenic trichloride, arsenous acid, and arsenic acid.

3. The method for high-efficiency dearsenication of a crude germanium tetrachloride solution based on reduction of arsine according to claim 1 or 2, characterized in that, The molar amount of arsine gas introduced is 5.0 to 8.0 times the total molar amount of arsenic in the crude germanium tetrachloride solution.

4. A method for efficient arsenic removal from crude germanium tetrachloride solution based on arsine reduction according to claim 1 or 2, characterized in that, The reduction reaction was carried out under stirring conditions.

5. A method for efficient arsenic removal from crude germanium tetrachloride solution based on arsine reduction according to claim 1 or 2, characterized in that, The reaction temperature is controlled between 20°C and 50°C.

6. A method for efficient arsenic removal from crude germanium tetrachloride solution based on arsine reduction according to claim 1 or 2, characterized in that, The gas in the inert atmosphere is nitrogen or argon.

7. A method for efficient arsenic removal from crude germanium tetrachloride solution based on arsine reduction according to claim 1 or 2, characterized in that, The solid-liquid separation is achieved by filtration, centrifugal sedimentation, or natural sedimentation.

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