Method for synchronously removing aluminum and arsenic from tellurium electrolyte

Abstract

The invention relates to a method for synchronously removing aluminum and arsenic from a tellurium electrolyte, which comprises the following steps: S1, adjusting the pH value of the tellurium electrolyte to be acidic to obtain an acidic tellurium electrolyte; s2, adding a precipitator into the acidic tellurium electrolyte, and carrying out precipitation reaction to obtain a mixed solution; the precipitator is a mixture of sodium sulfide and ferric salt; and S3, performing solid-liquid separation on the mixed solution to complete synchronous aluminum and arsenic removal of the tellurium electrolyte. According to the method, the aluminum and arsenic impurities in the tellurium electrolyte can be efficiently removed while the tellurium loss rate is low, especially the precipitant is added at the same time, the mutual promotion effect on synchronous aluminum and arsenic removal is achieved, the aluminum content in the electrolyte after impurity removal is lower than 0.01 mg / L, the arsenic content in the electrolyte after impurity removal is lower than 0.05 mg / L, and the purity and quality of tellurium are effectively improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of electrolyte treatment, in particular to a method for simultaneously removing aluminum and arsenic from tellurium electrolyte. BACKGROUND

[0002] Tellurium is a rare metal, which is widely used in the fields of electronics, metallurgy, chemical industry, etc. For example, it is used to manufacture semiconductor materials in the field of electronics, and to improve alloy performance in the field of metallurgy. In the process of electrolytic refining of tellurium, the tellurium electrolyte often contains impurities such as aluminum and arsenic. The presence of these impurities not only affects the purity and quality of tellurium, but also may have a negative impact on the electrolysis process, such as reducing current efficiency and increasing energy consumption.

[0003] Common methods for removing aluminum and arsenic include adding sulfide, hydroxide and other precipitants to make aluminum and arsenic ions form insoluble compounds and precipitate; or selecting appropriate cation exchange resins or anion exchange resins according to the properties of the electrolyte, and using the affinity difference of ion exchange resins for different ions to exchange and remove aluminum and arsenic ions from the electrolyte; or using amine extractants, phosphine extractants, etc. to extract aluminum and arsenic ions from the electrolyte into the organic phase by taking advantage of the difference in solubility of solutes in two mutually insoluble solvents, and then separating them by back extraction.

[0004] Currently, there are various methods for removing impurities from tellurium electrolyte, but there are relatively few studies on simultaneously and efficiently removing aluminum and arsenic. The traditional chemical precipitation method is simple to operate, but has problems such as incomplete precipitation or high tellurium loss rate; the ion exchange method is costly, and the regeneration and maintenance of the resin are complex; the solvent extraction method requires high equipment, and the selection and recovery of the extractant are key difficulties. Therefore, it is of great practical significance to develop an efficient, economical and environmentally friendly method for removing aluminum and arsenic from tellurium electrolyte. SUMMARY

[0005] The purpose of the present application is to overcome the above technical deficiencies, and to provide a method for simultaneously removing aluminum and arsenic from tellurium electrolyte, which solves the technical problems of incomplete removal or high tellurium loss rate in the prior art when removing aluminum and arsenic from tellurium electrolyte.

[0006] To achieve the above technical purpose, the technical solution provided by the present application is as follows: In a first aspect, the present application provides a method for simultaneously removing aluminum and arsenic from tellurium electrolyte, comprising the following steps: S1, adjusting the pH of the tellurium electrolyte to be acidic to obtain an acidic tellurium electrolyte; S2, adding a precipitant to the acidic tellurium electrolyte to obtain a mixed solution after a precipitation reaction; the precipitant is a mixture of sodium sulfide and iron salt; S3, the mixed solution is subjected to solid-liquid separation to complete the simultaneous removal of aluminum and arsenic from the tellurium electrolyte.

[0007] Compared with the prior art, the present application has the following advantages: The pH value of the tellurium electrolyte is first adjusted to be acidic, the aluminum ions form a precursor of aluminum hydroxide precipitate, and the arsenic ions exist in the form of specific acid radical ions; then a precipitant is added to the tellurium electrolyte after the pH value is adjusted, the aluminum ions and the arsenic ions form a precipitate through a precipitation reaction, and the separation of aluminum and arsenic from the tellurium electrolyte is realized through solid-liquid separation; the present application can efficiently remove the aluminum and arsenic impurities in the tellurium electrolyte while ensuring a low tellurium loss rate, especially when the precipitant is added at the same time, the simultaneous removal of aluminum and arsenic has a mutual promotion effect, the aluminum content in the electrolyte after impurity removal is less than 0.01 mg / L, and the arsenic content is less than 0.05 mg / L, thereby effectively improving the purity and quality of tellurium. DETAILED DESCRIPTION

[0008] In order to make the purpose, technical scheme and advantages of the present application clearer, the present application will be further described in detail below with examples. It should be understood that the specific examples described herein are only used to explain the present application and not to limit the present application.

[0009] In view of the defects that the removal of aluminum and arsenic in the tellurium electrolyte is incomplete or the tellurium loss rate is high at present, the present application provides a method for simultaneously removing aluminum and arsenic from a tellurium electrolyte, which can efficiently remove aluminum and arsenic impurities in the tellurium electrolyte while ensuring a low tellurium loss rate.

[0010] In a first aspect, the present application provides a method for simultaneously removing aluminum and arsenic from a tellurium electrolyte, comprising the following steps: S1, adjusting the pH of the tellurium electrolyte to be acidic to obtain an acidic tellurium electrolyte; S2, adding a precipitant to the acidic tellurium electrolyte to obtain a mixed solution through a precipitation reaction; the precipitant is a mixture of sodium sulfide and iron salt; S3, the mixed solution is subjected to solid-liquid separation to complete the simultaneous removal of aluminum and arsenic from the tellurium electrolyte.

[0011] The pH value of the tellurium electrolyte is first adjusted to be acidic, the aluminum ions form a precursor of aluminum hydroxide precipitate, and the arsenic ions exist in the form of specific acid radical ions; then a precipitant is added to the tellurium electrolyte after the pH value is adjusted, the aluminum ions and the arsenic ions form a precipitate through a precipitation reaction, and the separation of aluminum and arsenic from the tellurium electrolyte is realized through solid-liquid separation; the present application can efficiently remove the aluminum and arsenic impurities in the tellurium electrolyte while ensuring a low tellurium loss rate, especially when the precipitant is added at the same time, the simultaneous removal of aluminum and arsenic has a mutual promotion effect, the aluminum content in the electrolyte after impurity removal is less than 0.01 mg / L, and the arsenic content is less than 0.05 mg / L, thereby effectively improving the purity and quality of tellurium.

[0012] Preferably, in step S1, the content of tellurium in the tellurium electrolyte is 10-30 g / L, and the content of arsenic element impurities and aluminum element impurities is both above 0.6 g / L.

[0013] Preferably, in step S1, the pH value of the acidic tellurium electrolyte is 4-6.

[0014] The present application first regulates the pH value of tellurium electrolyte to ensure the impurity removal effect. If the pH value is too low (<4), the acidity is too strong, and the sulfur ions are easy to combine with H + Combined with the escape of H2S, the generation of aluminum hydroxide is inhibited; the arsenate ion form changes, and the complexing efficiency with iron ions decreases, resulting in incomplete arsenic precipitation. If the pH value is too high (>6), the alkalinity increases, the aluminum hydroxide precipitate is dissolved back into aluminate, and the iron ions are easy to hydrolyze into Fe(OH)3 colloid, which adsorbs and wraps arsenic but is difficult to settle, resulting in an increase in the residues of aluminum and arsenic.

[0015] Preferably, in step S1, a 30wt%-50wt% sulfuric acid solution is used to adjust the pH of the tellurium electrolyte to be acidic.

[0016] Preferably, in step S2, the molar ratio of sodium sulfide to iron salt in the precipitant is (2-3):1, and the molar ratio of iron element in the iron salt to arsenic element in the tellurium electrolyte is (1.1-1.5):1. The molar amount of arsenic element = electrolyte volume (L) x arsenic ion concentration (g / L) / 75 (g / mol).

[0017] In the present application, if the ratio of sodium sulfide to iron salt is <2:1 (excess of iron salt), the excess of iron ions will easily cause hydrolysis to generate Fe(OH)3 flocculation, which adsorbs arsenic but will wrap tellurium ions, resulting in an increase in tellurium loss; and the lack of sulfur ions will cause insufficient precipitation of aluminum ions. If the ratio is >3:1 (excess of sodium sulfide), the excess of sulfur ions will combine with tellurium ions to generate tellurium sulfide precipitate, causing loss of target elements; at the same time, the excess of sulfur ions may generate iron sulfide with iron ions, covering the surface of ferric arsenate and hindering arsenic precipitation. In addition, the Fe 3+ The excess of arsenic is 10-50%, more preferably 10-35%, to ensure complete precipitation of arsenic into ferric arsenate. The molar ratio set in the precipitant of the present application not only refers to the actual concentration of aluminum and arsenic ions in the electrolyte, but also is verified by thermodynamic calculation of the difference in solubility product of aluminum hydroxide to ensure simultaneous and efficient precipitation of aluminum hydroxide and ferric arsenate.

[0018] Preferably, in step S2, the iron salt is ferric sulfate or ferric chloride.

[0019] In the present application, the iron salt can be selected from ferric sulfate or ferric chloride. Ferric chloride has good solubility, fast reaction rate, and short formation time of precipitate, but Cl - may corrode the equipment; ferric sulfate has weak hydrolysis acidity and low corrosion to the equipment, so it is more preferred. Avoiding the use of ferrous salt (such as ferrous sulfate) is mainly because Fe 2+ needs to be oxidized to Fe 3+ before it is effective, which requires the introduction of an additional oxidizing agent, increasing the cost and impurity risk, and the stability of ferrous arsenate is poor, which is easy to dissolve back, and the arsenic removal rate is lower than that of ferric salt.

[0020] Preferably, in step S2, the temperature of the precipitation reaction is 40-50℃, and the time is 1.5-2.5h.

[0021] In the precipitation reaction of the present application, if the temperature is too low (<40℃): the reaction kinetics is slow, the crystallization of aluminum hydroxide and ferric arsenate is slow, the precipitate particles are fine, and the filter membrane is easily penetrated, resulting in excessive residual aluminum and arsenic in the filtrate. If the temperature is too high (>50℃): the aluminum hydroxide is partially dissolved, and the hydrolysis of the iron salt is accelerated to generate Fe(OH)3 colloid, which adsorbs arsenic but wraps tellurium, increasing the loss rate of tellurium, and the removal rate of aluminum and arsenic does not significantly improve.

[0022] Preferably, in step S2, the precipitation reaction is carried out under stirring, and the stirring rate is 100-300rpm.

[0023] In the precipitation reaction of the present application, if the stirring rate is too slow: the precipitant is not uniformly dispersed, the local concentration is too high, and sodium sulfide is agglomerated, resulting in aluminum precipitation wrapping arsenic ions, reducing the removal rate of arsenic, and the precipitate particles are easily settled and hardened, making solid-liquid separation difficult. If the stirring rate is too fast: the shear force is too large, which causes the precipitate particles to break, increasing the risk of membrane penetration, and the energy consumption increases, reducing the economic efficiency.

[0024] Preferably, in step S3, the solid-liquid separation is carried out by membrane filtration.

[0025] Further preferably, in the membrane filtration method, the pore size of the filter membrane is 0.1-0.5μm, and the filtration pressure is 0.15-0.25MPa.

[0026] In the present application, by selecting a filter membrane with appropriate pore size for filtration, it is ensured that the precipitate can be effectively retained, and the electrolyte can pass smoothly.

[0027] The present application mainly has the following advantages: (1) The method of the present application can efficiently remove aluminum and arsenic impurities in tellurium electrolyte by accurately adjusting the pH value and reasonably using precipitants, so that the aluminum content in the electrolyte after impurity removal is less than 0.01mg / L, and the arsenic content is less than 0.05mg / L, greatly improving the purity and quality of tellurium, and meeting the strict requirements of high-end application fields for tellurium materials.

[0028] (2) The precipitant used in the present application is a common chemical reagent and material, which is widely available and relatively low in price, and no secondary pollution is generated in the entire treatment process, which meets the environmental protection requirements and has good economic and environmental benefits.

[0029] (3) The method of the present application has strong adaptability and flexibility, and can realize efficient aluminum and arsenic removal treatment by adjusting the process parameters and equipment configuration according to tellurium electrolyte of different sources and compositions, which has a wide application prospect.

[0030] The application will be further described in detail by specific examples. In the examples, the tellurium electrolyte contains 15.2 g / L of tellurium, 1.8 g / L of arsenic impurities and 0.6 g / L of aluminum impurities.

[0031] Example 1 A method for simultaneously removing aluminum and arsenic from a tellurium electrolyte includes the following steps: S1, adjusting pH value: 100 L of tellurium electrolyte is placed in a mixing and stirring tank. 40% dilute sulfuric acid is slowly added to the tank while monitoring by a pH sensor, and a stirrer is turned on at a stirring speed of 200 rpm. When the pH value reaches 4, the addition of acid is stopped.

[0032] S2, precipitation reaction: a precipitant containing 6.48 mol of sodium sulfide and 3.24 mol of ferric chloride (molar ratio of sodium sulfide to ferric chloride is 2:1) is added from a precipitant storage tank to a reaction kettle through a pipeline and mixed with the tellurium electrolyte with adjusted pH value. A heating device of the reaction kettle is turned on to raise the temperature to 40℃, and continuous stirring is performed at a stirring speed of 200 rpm, and the reaction time is 2 hours.

[0033] S3, solid-liquid separation: after the reaction is completed, the mixed liquid in the reaction kettle is delivered to a filtration device through a filtration pump, the pore size of a filtration membrane is 0.1 microns, and the filtration pressure is controlled at 0.2 MPa. The precipitate after filtration is left on the filtration membrane, and the filtrate enters a filtrate collection tank. The detection results show that the tellurium content of the filtrate is 14.5 g / L, the aluminum content is 0.008 mg / L, and the arsenic content is 0.05 mg / L, all of which meet the requirements.

[0034] Example 2 A method for simultaneously removing aluminum and arsenic from a tellurium electrolyte includes the following steps: S1, adjusting pH value: 100 L of tellurium electrolyte is placed in a mixing and stirring tank. 40% dilute sulfuric acid is slowly added to the tank while monitoring by a pH sensor, and a stirrer is turned on at a stirring speed of 200 rpm. When the pH value reaches 6, the addition of acid is stopped.

[0035] S2, precipitation reaction: a precipitant containing sodium sulfide and 3.24 mol of ferric chloride (molar ratio of sodium sulfide to ferric chloride is 3:1) is added from a precipitant storage tank to a reaction kettle through a pipeline and mixed with the tellurium electrolyte with adjusted pH value. A heating device of the reaction kettle is turned on to raise the temperature to 50℃, and continuous stirring is performed at a stirring speed of 200 rpm, and the reaction time is 2 hours.

[0036] S3, solid-liquid separation: after the reaction, the mixed solution in the reactor was transported to the filter device through the filter pump, the pore size of the filter membrane was 0.5 microns, and the filtration pressure was controlled at 0.2 MPa. The precipitate after filtration was left on the filter membrane, and the filtrate entered the filtrate collection tank. The test results showed that the tellurium content of the filtrate was 14.3 g / L, the aluminum content was 0.006 mg / L, and the arsenic content was 0.03 mg / L, all of which met the requirements.

[0037] Example 3 A method for simultaneously removing aluminum and arsenic from a tellurium electrolyte, comprising the following steps: S1, adjusting pH value: take 100 L of tellurium electrolyte and put it into a mixing and stirring tank. Monitor through a pH sensor, slowly add 40% dilute sulfuric acid to the tank, and at the same time, start the stirrer with a stirring speed of 200 revolutions per minute. When the pH value reaches 5, stop adding acid.

[0038] S2, precipitation reaction: add the precipitant containing sodium sulfide and 3.24 mol of ferric chloride (molar ratio of sodium sulfide to ferric chloride is 2.5:1) from the precipitant storage tank to the reactor through the pipeline, and mix it with the tellurium electrolyte with adjusted pH value. Start the heating device of the reactor, raise the temperature to 45°C, and continue to stir at a stirring speed of 200 revolutions per minute, and the reaction time is 2 hours.

[0039] S3, solid-liquid separation: after the reaction, the mixed solution in the reactor was transported to the filter device through the filter pump, the pore size of the filter membrane was 0.2 microns, and the filtration pressure was controlled at 0.2 MPa. The precipitate after filtration was left on the filter membrane, and the filtrate entered the filtrate collection tank. The test results showed that the tellurium content of the filtrate was 14.6 g / L, the aluminum content was 0.007 mg / L, and the arsenic content was 0.04 mg / L, all of which met the requirements.

[0040] Comparative Example 1 Compared with Example 2, the only difference is that step S1 is removed; other steps and conditions are the same as Example 2. The test results showed that the tellurium content of the filtrate was 14.3 g / L, the aluminum content was 0.24 mg / L, and the arsenic content was 0.37 mg / L.

[0041] Comparative Example 2 Compared with Example 2, the only difference is that the pH value in step S1 is adjusted to 3; other steps and conditions are the same as Example 2. The test results showed that the tellurium content of the filtrate was 14.1 g / L, the aluminum content was 0.39 mg / L, and the arsenic content was 0.33 mg / L.

[0042] Comparative Example 3 The difference between Example 2 and Comparative Example 1 is that the iron salt is replaced by an equimolar amount of sodium sulfide (i.e., all sodium sulfide is used); other steps and conditions are the same as in Example 2. The test results show that the filtrate contains 13.9 g / L of tellurium, 0.057 mg / L of aluminum, and 1769 mg / L of arsenic.

[0043] Comparative Example 4 The difference between Example 2 and Comparative Example 4 is that the reaction temperature is 25°C; other steps and conditions are the same as in Example 2. The test results show that the filtrate contains 14.8 g / L of tellurium, 1.56 mg / L of aluminum, and 2.87 mg / L of arsenic.

[0044] Comparative Example 5 The difference between Example 2 and Comparative Example 5 is that the reaction temperature is 70°C; other steps and conditions are the same as in Example 2. The test results show that the filtrate contains 12.4 g / L of tellurium, 0.81 mg / L of aluminum, and 0.02 mg / L of arsenic.

[0045] Comparative Example 6 The difference between Example 2 and Comparative Example 6 is that the sodium sulfide and iron salt are added in two steps, i.e., the sodium sulfide is added first, and the iron salt is added after 1 hour; other steps and conditions are the same as in Example 2. The test results show that the filtrate contains 14.5 g / L of tellurium, 0.008 mg / L of aluminum, and 0.49 mg / L of arsenic.

[0046] The test results of Example 2 and Comparative Examples 1-6 are statistically analyzed, as shown in Table 1 below. Since the original composition and concentration of the tellurium electrolyte are fixed, and the amount of dilute sulfuric acid used in the pH adjustment process is not significantly different, the tellurium content, aluminum content, and arsenic content after treatment in each example and comparative example can be compared to determine the differences in aluminum and arsenic removal efficiency and the differences in tellurium content loss.

[0047] Table 1 Statistical results of Example 2 and Comparative Examples 1-6

[0048] As can be seen from Table 1, in Comparative Example 1, without pH control, the aluminum ion precipitation is insufficient, the arsenate form is unstable, and the precipitation efficiency is reduced; in Comparative Example 2, the acidity is too strong, the sulfur ion is easily combined with H +Combined with H2S escape, the generation of aluminum hydroxide is inhibited, the arsenate ion form is changed, the complexing efficiency with iron ions is reduced, and the arsenic precipitation is incomplete; in the comparative example 3, sodium sulfide has a certain effect on aluminum precipitation, but there is no iron ion in the solution, and arsenic cannot form ferric arsenate precipitation; in the comparative example 4, the reaction kinetics is slow, the aluminum hydroxide precipitation is insufficient, and the ferric arsenate crystallization is slow; in the comparative example 5, the solubility of aluminum hydroxide increases, the hydrolysis of iron salt intensifies, and tellurium is wrapped, causing the adverse phenomenon that although the arsenic content is lower, the tellurium loss increases; in the comparative example 6, the addition of sodium sulfide first removes aluminum completely, but the iron salt lags behind, the ferric arsenate precipitation is slow, the local arsenic concentration increases, and the final arsenic removal effect is poor, which shows that the simultaneous addition of the precipitant in the present application has a certain mutual promotion effect on the synchronous removal of aluminum and arsenic.

[0049] Therefore, the present application has good effect on the impurity removal of tellurium electrolyte, especially the removal rates of aluminum and arsenic are higher than those of the traditional sodium sulfide method, and the impact on tellurium is small, and the loss rate is controlled within 5%.

[0050] The specific embodiments of the present application described above do not constitute a limitation on the protection scope of the present application. Any various other corresponding changes and modifications made according to the technical concept of the present application shall be included in the protection scope of the claims of the present application.

Claims

1. A method for simultaneous removal of aluminum and arsenic from tellurium electrolyte, characterized in that, The method comprises the following steps: S1, adjusting the pH of tellurium electrolyte to be acidic to obtain acidic tellurium electrolyte; S2, adding a precipitant to the acidic tellurium electrolyte to obtain a mixed solution through a precipitation reaction; The precipitant is a mixture of sodium sulfide and iron salt; S3, the mixed solution is subjected to solid-liquid separation to complete the synchronous removal of aluminum and arsenic from the tellurium electrolyte.

2. The method for simultaneous removal of aluminum and arsenic from tellurium electrolyte according to claim 1, characterized in that, In step S1, the content of tellurium in the tellurium electrolyte is 10-30 g / L, and the content of arsenic impurities and aluminum impurities is both above 0.6 g / L.

3. The method for simultaneous removal of aluminum and arsenic from tellurium electrolyte according to claim 1, characterized in that, In step S1, the pH of the acidic tellurium electrolyte is 4-6.

4. The method for simultaneous removal of aluminum and arsenic from tellurium electrolyte according to claim 1, characterized in that, In step S1, sulfuric acid solution is used to adjust the pH of the tellurium electrolyte to be acidic.

5. The method for simultaneous removal of aluminum and arsenic from tellurium electrolyte according to claim 1, characterized in that, In step S2, the molar ratio of sodium sulfide to iron salt is (2-3):1, and the molar ratio of iron element in the iron salt to arsenic element in the tellurium electrolyte is (1.1-1.5):

1.

6. The method of simultaneous removal of aluminum and arsenic from tellurium electrolyte according to claim 1, characterized in that, In step S2, the iron salt is ferric sulfate or ferric chloride.

7. The method of simultaneous removal of aluminum and arsenic from tellurium electrolyte according to claim 1, characterized in that, In step S2, the temperature of the precipitation reaction is 40-50℃, and the time is 1.5-2.5 h.

8. The method of simultaneous removal of aluminum and arsenic from tellurium electrolyte according to claim 1, characterized in that, In step S2, the precipitation reaction is carried out under stirring at a stirring rate of 100-300 rpm.

9. The method of simultaneous removal of aluminum and arsenic from tellurium electrolyte according to claim 1, characterized in that, In step S3, the solid-liquid separation is carried out by membrane filtration.

10. The method of claim 9, wherein the Te electrolyte is synchronized to remove Al and As. In the membrane filtration, the pore size of the filtration membrane is 0.1-0.5 μm, and the filtration pressure is 0.15-0.25 MPa.

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