Method for recovering tellurium dioxide from tellurium electrolysis anode slime

Abstract

The invention belongs to the technical field of tellurium recovery, and discloses a method for recovering tellurium dioxide from tellurium electrolysis anode slime, which comprises the following steps: step 1, carrying out acid dissolution treatment on the tellurium electrolysis anode slime to completely dissolve sodium tellurate to obtain a solution A; step 2, adding alkali liquor into the solution A to enable the pH value of the system to be 1.5-2.5, completely reacting to obtain a solution B, and continuously stirring in the process; 3, sodium sulfite is added into the solution B, the system potential is controlled to range from-50 mV to-80 mV, solid-liquid separation is conducted after the reaction is completed, and tellurium dioxide is obtained. According to the method for recovering the tellurium dioxide from the tellurium electrolysis anode slime, the tellurium element in the tellurium electrolysis anode slime is dissolved through the acid liquor, then the pH value of the system is adjusted to a specific range through the alkali liquor, then the sodium sulfite is added for reacting to obtain the tellurium dioxide, and the method has the advantages of being high in tellurium recovery rate and good in safety.

Description

Technical Field

[0001] The invention relates to the technical field of tellurium recovery, and in particular to a method for recovering tellurium dioxide from tellurium electrolysis anode mud. Background Art

[0002] The anode mud produced in the process of tellurium electrolysis is mainly composed of sodium salt of tellurium, and the content of other impurities is relatively low. The reasons for its formation and its existence are complex. The main component of anode mud is sodium tellurate. During the electrolysis process, oxygen is produced at the anode, and TeO3 in the electrolyte 2- Will be oxidized to TeO4 2- Tellurate is insoluble in alkali solution. It precipitates in the electrolytic cell to form crystal nuclei and is dispersed near the anode plate or attached to the plate and gradually grows to form particles. It settles to the bottom of the cell due to its own gravity. Some of them adhere to the cell wall and grow. A small amount of them adhere to the cathode plate surface. With the continuous precipitation of tellurium and the flushing of the circulating electrolyte, most of them will return to the electrolyte, and a few will remain. If the particles formed on the cathode are not cleaned for a long time, they will be coated in the precipitated tellurium sheets. The particle cleaning work is not only labor-intensive but also easy to affect the quality of the final tellurium sheets. Since the tellurium content of sodium tellurate produced in the electrolytic refining process accounts for about 3% to 20% of the total tellurium content, it is necessary to clean the electrolytic cell regularly and recover the tellurium in the anode mud, so as to improve the tellurium recovery rate while ensuring the quality of the tellurium sheets. This is of great significance for the comprehensive utilization of resources and reducing production costs.

[0003] Prior art: Chinese patent 201610310326.3 discloses a method for recovering tellurium from tellurium anode mud. The technical scheme adopted is: first, the tellurium anode mud is washed with distilled water, and the unwashed Na2TeO3 is completely oxidized to Na2TeO4 with hydrogen peroxide. Then, dilute sulfuric acid is slowly added to the tellurium anode mud to leach tellurium, and the tellurium leachate is filtered to obtain the tellurium leachate. Then, Na2SO3 is used to oxidize the Te 6+ Reduce the crude tellurium powder, then use nitric acid solution to dissolve the crude tellurium powder, add the waste liquid regularly discharged from tellurium electrolysis or tellurium anode mud washing water to neutralize the solution, control the pH value of the reaction end point to 5-6, and completely convert the tellurium into tellurium dioxide, and remove impurities from the neutralized liquid.

[0004] The existing technology can timely replenish the tellurium in the anode mud produced by tellurium electrowinning to produce refined tellurium in the process, thereby improving the utilization efficiency of resources. The process is reasonable, easy to operate and implement, and the tellurium recovery rate is high. However, this method has a long processing flow, the addition of nitric acid will produce a large amount of acid mist, the auxiliary material consumption is relatively large, and the safety is relatively low. Summary of the invention

[0005] One of the purposes of the present invention is to provide a method for recovering tellurium dioxide from tellurium electrolysis anode mud. After the tellurium electrolysis anode mud is completely dissolved by acid dissolution treatment, sodium sulfite is added under a specific pH environment to react to obtain tellurium dioxide. The process does not generate acid mist and has a high recovery rate. It has the advantages of high safety and a short production process.

[0006] To achieve the above object, the present invention provides a method for recovering tellurium dioxide from tellurium electrolysis anode mud, comprising the following steps:

[0007] Step 1: subjecting tellurium electrolysis anode mud to acid dissolution treatment to completely dissolve sodium tellurate to obtain solution A;

[0008] Step 2: Add alkali solution to solution A to adjust the pH value of the system to 1.5-2.5, and react completely to obtain solution B, with continuous stirring during the process;

[0009] Step 3: Add sodium sulfite to solution B and control the system potential to -50 to -80 mV. After the reaction is complete, separate the solid and liquid to obtain tellurium dioxide.

[0010] Furthermore, the specific operation of step 1 is: mixing tellurium electrolysis anode mud with water, slowly adding acid solution to adjust the pH of the system to 0.4-0.6 and controlling the temperature to 70-80° C., and reacting for 0.5-1 h to obtain solution A.

[0011] Preferably, the solid-liquid ratio of the tellurium electrolysis anode mud to water is 1:1-4, and the acid liquid is sulfuric acid.

[0012] Furthermore, the specific operation of step 2 is: adding sodium hydroxide or potassium hydroxide to solution A to make the pH value of the system 1.5-2.5, heating to 70-80° C. and reacting for 0.5-1 h to obtain solution B, and continuously stirring at a stirring speed of 200-400 r / min during the process.

[0013] As a further preferred embodiment, the pH value of the system in step 2 is 2 to 2.2.

[0014] Furthermore, the molar amount of sodium sulfite added in step 3 is 1.5 to 2 times the molar amount of tellurium in the tellurium electrolysis anode mud.

[0015] Based on the subsequent need to configure tellurium dioxide into an electrolyte and return it to the electrowinning process to produce refined tellurium, the method of the present invention for recovering tellurium dioxide from tellurium electrolysis anode mud also includes step 4: mixing tellurium dioxide with water, slowly adding sodium hydroxide to adjust the pH of the system to 13-14, and obtaining solution D.

[0016] Beneficial Effects

[0017] Compared with the prior art, the present invention has the following advantages:

[0018] (1) The present invention provides a method for recovering tellurium dioxide from tellurium electrolysis anode mud, wherein the tellurium element in the tellurium electrolysis anode mud is first dissolved by acid solution, and then the pH value of the system is adjusted to a specific range by alkaline solution, and then sodium sulfite is added to react to obtain tellurium dioxide, which has the advantages of high tellurium recovery rate and good safety;

[0019] (2) The present invention adjusts the pH value of the system to a specific range by using alkaline solution, which can better reduce tellurium dioxide and also reduce the amount of sodium sulfite used, effectively reducing production costs. DETAILED DESCRIPTION

[0020] The present invention will be further described below in conjunction with the embodiments, but it does not constitute any limitation to the present invention. Any limited number of modifications made within the scope of the claims of the present invention are still within the scope of the claims of the present invention.

[0021] In order to explain the technical content of the present invention in detail, further description is given below in conjunction with the implementation modes.

[0022] Example 1

[0023] A method for recovering tellurium dioxide from tellurium electrolysis anode mud comprises the following steps:

[0024] Step 1: Add tellurium electrolysis anode mud and water into the reactor at a solid-liquid ratio of 1:3, stir evenly at a rate of 400 r / min, slowly add concentrated sulfuric acid to adjust the pH of the solution to 0.5, heat to 80°C and react for 1 hour to obtain solution A;

[0025] Step 2: maintaining the stirring speed, adding sodium hydroxide to solution A to adjust the pH of the system to 2.05, and heating to 75°C to react for 0.5h to obtain solution B;

[0026] Step 3: Maintaining the stirring speed, add sodium sulfite in an amount 1.8 times the molar amount of tellurium to solution B, the system potential is -65 mv, maintain the reaction at 75°C for 1 hour, filter, and obtain solution C and tellurium dioxide.

[0027] Example 2

[0028] A method for recovering tellurium dioxide from tellurium electrolysis anode mud comprises the following steps:

[0029] Step 1: Add tellurium electrolysis anode mud and water into the reactor at a solid-liquid ratio of 1:3, stir evenly at a rate of 400 r / min, slowly add concentrated sulfuric acid to adjust the pH of the solution to 0.55, heat to 80°C and react for 1 hour to obtain solution A;

[0030] Step 2: maintaining the stirring speed, adding sodium hydroxide to solution A to adjust the pH of the system to 2.08, and heating to 75°C to react for 0.5h to obtain solution B;

[0031] Step 3: Maintaining the stirring speed, add sodium sulfite twice the molar amount of tellurium to solution B, the system potential is -50 mv, maintain the reaction at 75°C for 1 hour, filter, and obtain solution C and tellurium dioxide.

[0032] Example 3

[0033] A method for recovering tellurium dioxide from tellurium electrolysis anode mud comprises the following steps:

[0034] Step 1: Add tellurium electrolysis anode mud and water into the reactor at a solid-liquid ratio of 1:3, stir evenly at a rate of 400 r / min, slowly add concentrated sulfuric acid to adjust the pH of the solution to 0.48, heat to 80°C and react for 1 hour to obtain solution A;

[0035] Step 2: maintaining the stirring speed, adding sodium hydroxide to solution A to adjust the pH of the system to 2.1, and heating to 75°C for reaction for 0.5h to obtain solution B;

[0036] Step 3: Maintaining the stirring speed, add sodium sulfite in an amount 1.9 times the molar amount of tellurium to solution B, the system potential is -80 mv, maintain the reaction at 75°C for 1 hour, filter, and obtain solution C and tellurium dioxide.

[0037] Example 4

[0038] A method for recovering tellurium dioxide from tellurium electrolysis anode mud comprises the following steps:

[0039] Step 1: Add tellurium electrolysis anode mud and water into the reactor at a solid-liquid ratio of 1:3, stir evenly at a rate of 400 r / min, slowly add concentrated sulfuric acid to adjust the pH of the solution to 0.51, heat to 80°C and react for 1 hour to obtain solution A;

[0040] Step 2: maintaining the stirring speed, adding sodium hydroxide to solution A to adjust the pH of the system to 2.2, and heating to 75°C for reaction for 0.5h to obtain solution B;

[0041] Step 3: Maintaining the stirring speed, add sodium sulfite in an amount 1.6 times the molar amount of tellurium to solution B, the system potential is -70 mv, maintain the reaction at 75°C for 1 hour, filter, and obtain solution C and tellurium dioxide.

[0042] Comparative Example 1

[0043] A method for recovering tellurium dioxide from tellurium electrolysis anode mud comprises the following steps:

[0044] Step 1: Add tellurium electrolysis anode mud and water into the reactor at a solid-liquid ratio of 1:3, stir evenly at a rate of 400 r / min, slowly add concentrated sulfuric acid to adjust the pH of the solution to 2.1, heat to 80°C and react for 1 hour to obtain solution A;

[0045] Step 2: Maintaining the stirring speed, add sodium sulfite in an amount 1.6 times the molar amount of tellurium to solution A, the system potential is -70 mv, maintain the reaction at 75°C for 1 hour, filter, and obtain solution C and tellurium dioxide.

[0046] Comparative Example 2

[0047] A method for recovering tellurium dioxide from tellurium electrolysis anode mud comprises the following steps:

[0048] Step 1: Add tellurium electrolysis anode mud and water into the reactor at a solid-liquid ratio of 1:3, stir evenly at a rate of 400 r / min, slowly add concentrated sulfuric acid to adjust the pH of the solution to 0.51, heat to 80°C and react for 1 hour to obtain solution A;

[0049] Step 2: maintaining the stirring speed, adding sodium hydroxide to solution A to adjust the pH of the system to 1.1, and heating to 75°C for reaction for 0.5h to obtain solution B;

[0050] Step 3: Maintaining the stirring speed, add sodium sulfite in an amount 2.5 times the molar amount of tellurium to solution B, the system potential is -75 mv, maintain the reaction at 75°C for 1 hour, filter, and obtain solution C and tellurium dioxide.

[0051] Comparative Example 3

[0052] A method for recovering tellurium dioxide from tellurium electrolysis anode mud comprises the following steps:

[0053] Step 1: Add tellurium electrolysis anode mud and water into the reactor at a solid-liquid ratio of 1:3, stir evenly at a rate of 400 r / min, slowly add concentrated sulfuric acid to adjust the pH of the solution to 0.51, heat to 80°C and react for 1 hour to obtain solution A;

[0054] Step 2: maintaining the stirring speed, adding sodium hydroxide to solution A to adjust the pH of the system to 3.2, and heating to 75°C for reaction for 0.5h to obtain solution B;

[0055] Step 3: Maintaining the stirring speed, add sodium sulfite in an amount 1.6 times the molar amount of tellurium to solution B, the system potential is -70 mv, maintain the reaction at 75°C for 1 hour, filter, and obtain solution C and tellurium dioxide.

[0056] The tellurium dioxide obtained in Examples 1-4 and Comparative Examples 1-3 was used to prepare a solution D according to the following operation:

[0057] Tellurium dioxide and water were mixed at a solid-liquid ratio of 1:2, and sodium hydroxide was slowly added to adjust the pH of the system to 13.1 to obtain solution D.

[0058] Then, solution C and solution D were tested. The results are shown in Table 1. The testing method is as follows:

[0059] The potential was detected by a potentiometer, and the tellurium content was detected by ICP;

[0060] Table 1 Tellurium recovery test results of Examples 1-4 and Comparative Examples 1-3

[0061]

[0062] According to the results in Table 1, we can see that:

[0063] It can be seen from the data of Examples 1-4 that the technical solution of the present invention can efficiently recover the tellurium element, and the recovery rate of the tellurium element is extremely high, among which the effect of Example 4 is the most obvious, indicating that Example 4 is a further preferred solution. Example 4 of the present invention uses acid to dissolve the tellurium element in the tellurium electrolysis anode mud, and then adjusts the pH value of the system to a specific value with alkaline solution, and then adds a specific amount of sodium sulfite to react to obtain tellurium dioxide. In this process, the reaction temperature, reaction time, system potential, system pH and other factors are strictly controlled, which can greatly improve the recovery rate of the tellurium element.

[0064] From the comparison of the data of Example 4 and Comparative Example 1, it can be seen that when the amount of acid used in step 1 is insufficient, although the tellurium content in solution C does not increase significantly, the tellurium recovery rate of solution D decreases significantly. Although Comparative Example 1 maintains the final reaction pH value of sodium sulfite to be the same as that of Example 4, due to the insufficient amount of acid used, many tellurium ions are not dissolved in the acid, resulting in a significant decrease in the yield of tellurium dioxide.

[0065] From the comparison of the data of Example 4 and Comparative Example 2, it can be seen that when the pH value in step 2 is too low, although the loss of tellurium ions from solution C in step 3 is effectively reduced, more sodium sulfite is also consumed. Moreover, when the pH value is too low, sodium sulfite directly reduces part of the tellurium element into tellurium powder, which is difficult to dissolve in solution D for the next step of refining. The tellurium powder obtained by reduction has more impurities and requires a longer process for purification.

[0066] According to the data comparison between Example 4 and Comparative Example 3, when the amount of sodium hydroxide used in step 2 is too high, resulting in too high pH, ​​it will affect the subsequent reduction reaction, resulting in incomplete reduction and a significant decrease in the recovery rate of tellurium.

[0067] The embodiments presented herein are only embodiments selected according to the combination of all possible embodiments. The appended claims should not be limited by the embodiments describing the present invention. Some numerical ranges used in the claims include sub-ranges therein, and the changes in these ranges should also be covered by the appended claims.

Claims

1. A method for recovering tellurium dioxide from tellurium electrolysis anode mud, characterized in that: The steps include: Step 1: subjecting tellurium electrolysis anode mud to acid dissolution treatment to completely dissolve sodium tellurate to obtain solution A; Step 2: Add alkali solution to solution A to adjust the pH value of the system to 1.5-2.5, and react completely to obtain solution B, with continuous stirring during the process; Step 3: Add sodium sulfite to solution B and control the system potential to -50 to -80 mV. After the reaction is complete, separate the solid and liquid to obtain tellurium dioxide.

2. The method for recovering tellurium dioxide from tellurium electrolysis anode mud according to claim 1, characterized in that: The specific operation of step 1 is: mixing tellurium electrolysis anode mud with water, slowly adding acid solution to adjust the pH of the system to 0.4-0.6 and controlling the temperature to 70-80° C., and reacting for 0.5-1 h to obtain solution A.

3. The method for recovering tellurium dioxide from tellurium electrolysis anode mud according to claim 2, characterized in that: The solid-to-liquid ratio of the tellurium electrolysis anode mud to water is 1:1-4, and the acid liquid is sulfuric acid.

4. The method for recovering tellurium dioxide from tellurium electrolysis anode mud according to claim 1, characterized in that: The specific operation of step 2 is: adding sodium hydroxide or potassium hydroxide to solution A to make the pH value of the system 1.5-2.5, heating to 70-80° C. and reacting for 0.5-1h to obtain solution B, and continuously stirring at a stirring speed of 200-400 r / min during the process.

5. The method for recovering tellurium dioxide from tellurium electrolysis anode mud according to claim 4, characterized in that: In the step 2, the pH value of the system is 2 to 2.

2.

6. The method for recovering tellurium dioxide from tellurium electrolysis anode mud according to claim 1, characterized in that: The molar amount of sodium sulfite added in step 3 is 1.5 to 2 times the molar amount of tellurium in the tellurium electrolysis anode mud.

7. The method for recovering tellurium dioxide from tellurium electrolysis anode mud according to claim 1, characterized in that: The method also includes step 4: mixing tellurium dioxide with water, and slowly adding sodium hydroxide to adjust the pH of the system to 13-14, to obtain solution D.

Images