Method for improving tellurium recovery by strengthening sulfidation leaching of copper anode slime

Abstract

The present application relates to a kind of copper anode slime strengthening sulphidation leaching method for improving tellurium recovery rate, the process steps are as follows: copper anode slime is slurried with concentrated sulfuric acid according to certain proportion at room temperature, after slurry, sulfuric acid roasting is carried out to produce calcine, after ball milling, water leaching is carried out to produce copper removal residue, copper removal residue is used to produce tellurium leaching agent into reaction kettle to produce tellurium removal residue and tellurium leaching solution, tellurium leaching solution is produced by adding sulfuric acid to adjust pH value to produce tellurium dioxide, tellurium removal residue is put into silver separation furnace to carry out fire refining, sodium carbonate is added during refining process to produce tellurium residue, tellurium residue is synchronously added with tellurium reducing agent in the process of ball milling to improve tellurium leaching rate, then acid-base neutralization is carried out to produce tellurium dioxide, and it is sent to tellurium refining process to produce tellurium ingot product.The production process proposed in the present application is suitable for comprehensive recovery of tellurium from high-impurity copper anode slime, and has the advantages of clear process, easy operation, strong process adaptability, high tellurium recovery rate and the like.

Description

Technical Field

[0001] This invention belongs to the field of combined hydrometallurgical and pyrometallurgical processes, and relates to a method for improving tellurium recovery rate through enhanced sulfidation leaching of copper anode mud. Through experimental demonstration and process optimization, technological innovation has been achieved. In the process of extracting tellurium from copper anode mud, a hydrometallurgical process is preferentially used to leach tellurium from the copper anode mud, and the optimal leaching agent is selected to achieve efficient tellurium leaching. Then, a pyrometallurgical process is used to further enrich and recover the remaining tellurium. This invention can significantly improve the tellurium recovery rate, has good economic benefits, and the process is simple to operate, highly efficient, and suitable for industrial production. Background Technology

[0002] Tellurium and its compounds possess excellent photoelectric properties and are increasingly important and widely used in solar cells, thermoelectric materials, and semiconductor devices. Currently, 70% of the world's tellurium is used in the production of CdTe thin-film solar cells. With the rapid development of the photovoltaic industry, the demand and price of tellurium are showing a continuous upward trend. Tellurium has an abundance of only 0.001–0.005 g / t in the Earth's crust and no independent deposits with industrial mining value; it mainly occurs as a homogeneous associated mineral in copper, lead, and other sulfide ores. Currently, tellurium is mainly recovered from copper anode slime smelting byproducts (accounting for over 90%). Copper anode slime is composed of various substances insoluble in the electrolyte during the electrolytic refining of anode copper, typically containing elements such as Au, Ag, Cu, Pb, Se, Te, Sn, and As. Currently, there are many methods for separating and extracting tellurium from copper anode slime, mainly divided into pure wet recovery processes and pyrometallurgical-wet combined recovery processes. Among them, the pure wet recovery process is mainly divided into chlorination extraction of tellurium, acidic oxidation leaching, and pressurized alkaline leaching. For example, CN104944387A, proposed by Yang Hongying et al. of Northeastern University, describes a method for recovering tellurium from copper anode mud under normal pressure and closed oxygenation. The method involves adding a mixed acid of dilute sulfuric acid and dilute nitric acid to the copper anode mud for slurry preparation, controlling the weight-to-volume ratio of copper anode mud in the slurry to be 15-25 g / mL, and the concentration of dilute sulfuric acid in the mixed acid to be 0.5-2 mol / L and the concentration of dilute nitric acid to be 0.03-0.1 mol / L. The prepared slurry is placed in a closed container, oxygen is introduced to remove air, the leaching temperature is 100-115℃, the stirring speed is 300-500 r / min, and leaching is carried out under normal pressure for 0.5-1.5 h, followed by solid-liquid separation. Although the invention has a high leaching rate, it has several drawbacks. First, it mainly uses nitric acid as the leaching agent. Although the invention mentions that only a small amount of nitric acid is used, harmful gases such as nitrogen oxides and a large amount of acidic wastewater will still be generated in the process, requiring additional treatment facilities and putting great pressure on environmental protection. Second, the invention only provides a method for leaching tellurium and does not describe the subsequent process for producing tellurium ingots. Regardless of the reduction process used, toxic and harmful gases will inevitably be generated in an acidic system. The combined pyrometallurgical and hydrometallurgical recovery processes mainly include sulfation roasting-alkali leaching, oxidative roasting-sulfuric acid leaching, and soda ash roasting-sulfuric acid leaching. For example, a method for efficient stepwise separation and extraction of selenium, copper, and tellurium from copper anode mud was proposed by Liu Degang et al. of Jiangxi University of Science and Technology, with publication number CN115449637A. The method proposes O2-SO2 roasting to separate selenium, obtaining roasted sand and selenium-enriched material; water leaching or acid leaching of roasted sand to separate copper, obtaining copper-separating slag and copper sulfate-rich solution, and drying the copper-separating slag in an oven; and alkaline leaching of copper-separating slag to separate tellurium, obtaining tellurium slag and sodium tellurite-containing solution, and drying the tellurium slag in an oven for subsequent gold and silver recovery.This invention uses O2-SO2 roasting and wet stepwise leaching to recover tellurium. However, the invention has the following drawbacks: First, the direct use of gaseous SO2 roasting and copper anode mud for roasting results in uneven mixing of gas and solid, leading to poor roasting effect. Second, the equipment used in this invention is all laboratory equipment, which has low processing capacity and cannot be used for industrial production.

[0003] To address the problems existing in the prior art, this invention provides a method for enhancing tellurium recovery rate through enhanced sulfidation leaching of copper anode mud. The aim is to shorten the processing time of copper anode mud, increase the processing volume, improve the tellurium leaching rate, and make other valuable metals in the copper anode mud more rational and concentrated, which is conducive to comprehensive recovery. This method reduces energy consumption, does not require special high-pressure equipment, has a faster leaching speed, alleviates environmental pressure, achieves comprehensive recovery of valuable elements, and creates better economic and social benefits. Summary of the Invention

[0004] To overcome the problems existing in the above-mentioned technologies, the purpose of this invention is to provide a method for improving tellurium recovery rate through enhanced sulfidation leaching of copper anode mud. The technical solution of this invention is achieved as follows: A method for improving tellurium recovery rate through enhanced sulfidation leaching of copper anode mud includes the following steps:

[0005] a. Copper anode mud and concentrated sulfuric acid are pulped at a ratio of copper anode mud: concentrated sulfuric acid = 1:0.7~1.0. After pulping, the pulp is transported to a rotary kiln by a quantitative feeder for sulfation roasting to produce roasted sand. During the roasting process, the selenium element in the copper anode mud undergoes an oxidation-reduction reaction to produce crude selenium, thereby achieving the separation of selenium and tellurium in the copper anode mud.

[0006] b. The calcined sand is first finely ground using a ball mill. After the slurry is pumped into the reactor, it is subjected to water leaching to remove copper at a liquid-to-solid ratio of 4-6:1 and 45-60℃ to obtain copper-removed slag and copper-containing liquid. The copper element in the calcined sand enters the liquid phase in the form of copper sulfate. Liquid alkali is added to adjust the pH of the copper-containing liquid to 5-6. Copper is precipitated as copper hydroxide and transferred to the copper smelting system to recover copper.

[0007] c. The copper-removing slag and water are slurried at a liquid-solid ratio of 4-6:1. After slurrying, a tellurium leaching agent is added to obtain tellurium-removing slag and tellurium leachate. Under the enhancement of the tellurium leaching agent, tellurium in the copper-removing slag is efficiently leached into the liquid phase. The tellurium leachate is neutralized by adding sulfuric acid at a temperature of 75℃-80℃, and the pH value is adjusted to 5-6 to produce tellurium dioxide. The product is then refined to produce qualified tellurium ingots.

[0008] d. The tellurium-depleted slag produced in step c is transferred to a silver-separating furnace for pyrometallurgical refining. The furnace temperature is controlled within the range of 800℃ to 1250℃. Sodium carbonate is added at a ratio of tellurium-depleted slag: sodium carbonate = 1:0.05 to 0.08, while tellurium slag is produced by blowing.

[0009] e. The tellurium slag produced in step d is processed by ball milling, and a tellurium reducing agent is added to leach tellurium from the slag. Sulfuric acid is added for acid-base neutralization, and the pH value is adjusted to the range of 5-6 to produce tellurium dioxide. The tellurium is then refined to produce qualified tellurium ingots.

[0010] Preferably, the tellurium leaching agent involved in step c is sodium carbonate or a mixture of sodium hydroxide and sodium sulfide, with a ratio of sodium carbonate or sodium hydroxide:sodium sulfide = 5:1. The alkalinity of the leaching solution is 4%–6%. The role of adding sodium sulfide is that Na2TeO4 is almost insoluble in aqueous and alkaline solutions, but under the action of Na2S, Na2TeO4 can generate soluble Na2TeS4. Tellurium itself has a good affinity for sulfur. Telluride, Te, and TeO2 can also react with Na2S during the leaching process to form Na2TeS3. The reaction principle is as follows:

[0011] Me₂Te + Na₂S + 3S = Na₂TeS₃ + Me₂S

[0012] TeO2+3Na2S+2H2O=Na2TeS3+4NaOH

[0013] Te + Na₂S + 2S = Na₂TeS₃

[0014] Na2TeO4+4Na2S+4H2O=Na2TeS4+8NaOH;

[0015] Preferably, in step d, the tellurium-depleted slag is pyrometallurgically refined in a silver separation furnace. During the process of adding sodium carbonate and blowing it to form tellurium slag, the blowing gas is nitrogen at a pressure of 0.1 MPa. The purpose of using nitrogen is primarily to stir the mixture, as sodium carbonate is more likely to combine with tellurium. The most important function is to reduce the oxidizing atmosphere in the silver separation furnace and prevent the tellurium element in the tellurium-depleted slag from undergoing a peroxidation reaction to form +6 valence tellurium under high temperature conditions, thus increasing the burden on the subsequent wet leaching of tellurium slag.

[0016] Preferably, the tellurium reducing agent in step e is a mixture of sodium sulfite and sodium hydroxide, with a mixing ratio of sodium sulfite:sodium hydroxide = 1:3. The tellurium reducing agent is added while ball milling, and the ball milling action is used to enhance the reducing effect of the tellurium reducing agent and improve the tellurium leaching rate.

[0017] Preferably, in step b, the wastewater generated during the acid-base neutralization process by adding liquid alkali to adjust the pH value of the copper-containing solution is recycled for calcined sand ball milling; in step c, the acid-base neutralization is carried out by adding sulfuric acid, and the resulting neutralized liquid is recycled for water leaching copper removal in step b. By recycling wastewater in two steps, the amount of wastewater generated in this process is reduced, alleviating the environmental pressure of wastewater treatment.

[0018] To fully verify the feasibility of the sulfidation process involved in this invention, XPS analysis was performed on the materials produced before and after the copper removal slag was sulfidated, as shown in Figures 1 and 2.

[0019] As shown in XPS plot 1 of the copper slag removal, the valence state distribution of tellurium is mainly Te. 6+ and Te 4+ Mainly, and Te 6+ The characteristic peak area (the area enclosed by the pink curve) is greater than Te. 4+ (The area enclosed by the green curve) is the Te in the tellurium leaching residue. 6+ The proportion is greater than Te 4 + Therefore, simply using alkaline leaching cannot achieve the leaching of tellurium from copper-removing slag.

[0020] As can be seen from XPS plot 2 of the tellurium-de-tellurized slag, the valence state distribution of tellurium is mainly Te. 4+ And Te is the main component, and Te 4+ The area of ​​the characteristic peak (the region enclosed by the red curve) is much larger than that of Te (the region enclosed by the blue curve). Therefore, the enhanced sulfidation process can reduce the +6 valence state of tellurium to the +4 valence state, and then the alkaline leaching process can be used to leach the tellurium.

[0021] The method for enhancing tellurium recovery through enhanced sulfidation leaching of copper anode mud according to the present invention represents a significant improvement over existing processes:

[0022] The production process proposed in this invention has significant advantages such as clear process, easy operation, excellent environment, and strong process adaptability. This invention addresses the problem that conventional alkaline leaching processes cannot leach +6 valence tellurium from copper anode mud by proposing an enhanced sulfidation process to convert high valence tellurium into low valence tellurium for efficient leaching. Furthermore, for the tellurium remaining after wet leaching, a pyrometallurgical process is used for enrichment and recovery, thereby improving the tellurium recovery rate and achieving high economic benefits. Attached Figure Description

[0023] Figure 1 This is a process flow diagram of the present invention;

[0024] Figure 2 XPS image of copper slag removal;

[0025] Figure 3 XPS graph for detellurized residue. Detailed Implementation

[0026] To better understand and implement this invention and to verify the outstanding role of the process optimization proposed in the treatment of copper anode sludge, the contents of this invention are described in detail with reference to the following examples. The contents of this invention are not limited to the examples below.

[0027] Example 1:

[0028] The following details a method for enhancing tellurium recovery through sulfidation leaching of copper anode mud: The elemental contents of the copper anode mud are shown in Table 1.

[0029] Table 1. Element content (%) in copper anode mud

[0030]

[0031] The following steps are used:

[0032] Step 1: Copper anode mud and concentrated sulfuric acid are pulped at a mass ratio of copper anode mud: concentrated sulfuric acid = 1:0.76. After pulping, the pulp is fed to a rotary kiln by a quantitative feeder for sulfation roasting to produce roasted sand. The element content of the produced roasted sand is shown in Table 2.

[0033] Table 2. Element content (%) in calcined ore produced by sulfation roasting

[0034]

[0035] After sulfation and roasting, the selenium separation rate of copper anode mud can reach over 98%, and the remaining elements Au, Ag, Cu, Te, Bi, and Sb are enriched in the roasted mud with a recovery rate of over 99%.

[0036] Step 2: The roasted sand is first finely ground using a ball mill. The slurry is then pumped into the reactor and subjected to water leaching at 50°C at a liquid-to-solid ratio of 4:1 to remove copper, yielding copper-removing slag and copper-containing liquid. The pH of the copper-containing liquid is adjusted to 5.5 by adding liquid alkali, resulting in copper hydroxide precipitate, which is then transferred to the copper smelting system for copper recovery. The elemental contents of the copper-removing slag and copper hydroxide slag are shown in the figure. Figure 3 Table 4.

[0037] Table 3. Element content (%) in copper removal slag

[0038]

[0039] Table 4. Element content (%) in copper hydroxide slag

[0040]

[0041] Note: Elements marked with * are in g / t.

[0042] After copper removal by water leaching, the copper separation rate in the calcined sand can reach over 95%, and the remaining elements Au, Ag, Cu, Te, Bi, and Sb are enriched in the copper removal slag, with recovery rates all above 99%.

[0043] Step 3: The copper-removing slag and water are slurried at a liquid-solid ratio of 5:1. After slurrying, a tellurium leaching agent is added to obtain tellurium-removing slag and tellurium leaching solution. The tellurium leaching agent is a mixture of sodium hydroxide and sodium sulfide at a mixing ratio of 5:1. The tellurium leaching solution is neutralized by adding sulfuric acid at a temperature of 75℃ to adjust the pH to 5.5 to produce tellurium dioxide. This product is then refined in tellurium to produce qualified tellurium ingots.

[0044] Step 4: The detellurized slag is transferred to a silver separation furnace for pyrometallurgical refining. The furnace temperature is controlled at 1050℃. Sodium carbonate is added at a ratio of detellurized slag: sodium carbonate = 1:0.06. At the same time, nitrogen gas is blown in to form tellurium slag.

[0045] Step 5: The tellurium slag is processed by ball milling. During the ball milling process, a tellurium reducing agent is added. The tellurium leachate is neutralized by adding sulfuric acid to adjust the pH to 5.5 to produce tellurium dioxide.

[0046] The final recovery rates of gold, silver, tellurium, and selenium in the copper anode mud are shown in Table 9.

[0047] Table 9 shows the recovery rates of gold, silver, tellurium, and selenium in copper anode slime:

[0048]

[0049] Comparative Example 1:

[0050] Steps 1 and 2 are the same as in Example 1. Step 3 is as follows: the copper removal slag and water are slurried at a liquid-solid ratio of 5:1. After slurrying, sodium hydroxide is added to obtain tellurium removal slag and tellurium leachate. The tellurium leachate is neutralized by adding sulfuric acid at a temperature of 75°C to adjust the pH to 5.5 and produce tellurium dioxide.

[0051] The comparison results of elements in the tellurium removal residue of Example 1 and Comparative Example 1 are shown in Table 5:

[0052] Table 5. Content of various elements in tellurium-depleted slag under different conditions (%)

[0053]

[0054] Comparative results: Compared with adding a tellurium leaching agent, under the same conditions, adding only sodium hydroxide to leach tellurium resulted in an unsatisfactory leaching effect, with a large portion of tellurium remaining in the residue and a leaching rate of less than 70%. After adding a tellurium leaching agent, the leaching rate of tellurium exceeded 90%, demonstrating a significant leaching effect.

[0055] Comparative Example 2:

[0056] Steps 1, 2, and 3 are the same as in Example 1. Step 4 is as follows: the detellurized slag is transferred to a silver separation furnace for pyrometallurgical refining. The furnace temperature is controlled at 1050℃. Sodium carbonate is added at a ratio of detellurized slag: sodium carbonate = 1:0.06. Tellurized slag is formed without blowing.

[0057] Comparative Example 3:

[0058] Steps 1, 2, and 3 are the same as in Example 1. Step 4 is as follows: the detellurized slag is transferred to a silver separation furnace for pyrometallurgical refining. The furnace temperature is controlled at 1050°C. Sodium carbonate is added at a ratio of detellurized slag: sodium carbonate = 1:0.06. Compressed air is blown in to produce tellurium slag.

[0059] The comparison results of Example 1 with Comparative Examples 2 and 3 are shown in Table 6.

[0060] Table 6. Element content (%) in tellurium slag under different conditions

[0061]

[0062] Comparison results: Under the same conditions, the tellurium slag produced without nitrogen blowing has a lower tellurium grade than the tellurium blowing produced without nitrogen blowing. Although the tellurium slag produced by blowing compressed air has a higher tellurium grade, it is still lower than that produced by blowing nitrogen.

[0063] Experiment: The tellurium content in the tellurium leaching residue after alkaline dissolution of the tellurium slag produced in Example 1, Comparative Example 2 and Comparative Example 3 was compared. The comparison results are shown in Table 7.

[0064] Table 7. Tellurium content (%) in tellurium leaching residue after alkali dissolution of tellurium slag under different conditions

[0065]

[0066]

[0067] Comparison results: The tellurium slag produced by blowing in nitrogen as a protective gas had the highest tellurium leaching rate after alkali dissolution, compared with the non-blowing and compressed air blowing methods.

[0068] Comparative Example 4:

[0069] Steps 1, 2, 3, and 4 are the same as in Example 1. Step 5 is as follows: the tellurium slag is processed by ball milling, the slurry is pumped into the reactor, sodium hydroxide is added to the reactor, and the tellurium leachate is neutralized by adding sulfuric acid to adjust the pH to 5.5 to produce tellurium dioxide.

[0070] Comparative Example 5:

[0071] Steps 1, 2, 3, and 4 are the same as in Example 1. Step 5 is as follows: the tellurium slag is treated by ball milling, and sodium hydroxide is added at the same time. The tellurium leachate is neutralized by adding sulfuric acid to adjust the pH to 5.5 to produce tellurium dioxide.

[0072] Comparative Example 6:

[0073] Steps 1, 2, 3, and 4 are the same as in Example 1. Step 5 is as follows: the tellurium slag is processed by ball milling, the slurry is pumped into the reactor, a tellurium reducing agent is added to the reactor, and the tellurium leachate is neutralized by adding sulfuric acid to adjust the pH to 5.5 to produce tellurium dioxide.

[0074] The comparison results of tellurium grade in the tellurium leaching residue produced by Example 1 and Comparative Examples 4, 5 and 6 are shown in Table 8.

[0075] Table 8. Tellurium grade (%) in tellurium leaching residue under different conditions

[0076]

[0077] Comparative results: Adding a tellurium reducing agent during ball milling resulted in the best tellurium leaching effect compared to other experimental conditions.

Claims

1. A method for enhancing tellurium recovery rate through enhanced sulfidation leaching of copper anode mud, characterized in that: a. Copper anode slime and concentrated sulfuric acid are pulped at a ratio of copper anode slime: concentrated sulfuric acid = 1:0.7~1.

0. After pulping, the pulp is transported to a rotary kiln by a quantitative feeder for sulfation roasting to produce roasted sand. During the roasting process, the selenium element in the copper anode slime undergoes an oxidation-reduction reaction to produce crude selenium, thereby achieving the separation of selenium and tellurium in the copper anode slime. b. The calcined sand is first finely ground using a ball mill. After the slurry is pumped into the reactor, it is subjected to water leaching to remove copper at a liquid-to-solid ratio of 4-6:1 and 45-60℃ to obtain copper-removed slag and copper-containing liquid. The copper element in the calcined sand enters the liquid phase in the form of copper sulfate. Liquid alkali is added to adjust the pH of the copper-containing liquid to 5-6. Copper is precipitated as copper hydroxide and transferred to the copper smelting system to recover copper. c. The copper-removing slag and water are pulped at a liquid-solid ratio of 4-6:

1. After pulping, a tellurium leaching agent is added to obtain tellurium-removing slag and tellurium leachate. Under the enhancement of the tellurium leaching agent, tellurium in the copper-removing slag is efficiently leached into the liquid phase. The tellurium leachate is neutralized by adding sulfuric acid at a temperature of 75℃-80℃, adjusting the pH value to 5-6 to produce tellurium dioxide. This product is then refined to produce qualified tellurium ingots. The tellurium leaching agent is a mixture of sodium carbonate or sodium hydroxide and sodium sulfide, with a ratio of sodium carbonate or sodium hydroxide:sodium sulfide = 5:

1. The alkali concentration of the leachate is 4%-6%. The reaction principle is as follows: Me₂Te + Na₂S + 3S = Na₂TeS₃ + Me₂S TeO₂ + 3Na₂S + 2H₂O = Na₂TeS₃ + 4NaOH Te + Na₂S + 2S = Na₂TeS₃ Na2TeO4+4Na2S+4H2O=Na2TeS4+8NaOH; d. The tellurium-depleted slag produced in step c is transferred to a silver-separating furnace for pyrometallurgical refining. The furnace temperature is controlled within the range of 800℃~1250℃. Sodium carbonate is added according to the ratio of tellurium-depleted slag: sodium carbonate = 1:0.05~0.

08. At the same time, tellurium slag is produced by blowing gas. The blowing gas is nitrogen and the pressure is 0.1Mpa. e. The tellurium slag produced in step d is processed by ball milling, and a tellurium reducing agent is added to leach tellurium from the slag. Sulfuric acid is added for acid-base neutralization, and the pH value is adjusted to the range of 5-6 to produce tellurium dioxide. The product is then refined in tellurium to produce qualified tellurium ingots. The tellurium reducing agent is a mixture of sodium sulfite and sodium hydroxide in a ratio of sodium sulfite:sodium hydroxide = 1:

3. The tellurium reducing agent is added simultaneously with ball milling to enhance the reducing effect of the tellurium reducing agent and improve the tellurium leaching rate.

2. The method for enhancing tellurium recovery rate through enhanced sulfidation leaching of copper anode mud according to claim 1, characterized in that: In step b, the wastewater generated during the acid-base neutralization process by adding liquid alkali to adjust the pH value of the copper-containing solution is recycled for the calcined sand ball mill; in step c, the acid-base neutralization is carried out by adding sulfuric acid, and the resulting neutralized liquid is recycled for the water leaching copper removal process in step b.

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