Method for cascade recovery of tellurium from complex tellurium-containing material

Abstract

The invention discloses a method for cascade recovery of tellurium from a complex tellurium-containing material. The method comprises the steps of acid pickling, reduction neutralization, pyrogenic transformation, leaching and neutralization. According to the method, through cooperative treatment of a wet process and a pyrogenic process, the problem of slag phase wrapping is effectively solved, and tellurium with different valence states in a complex tellurium-containing material is converted into high-quality tellurium neutralization slag in a gradient mode. The selenium removal rate is not lower than 95%, the tellurium recovery rate reaches up to 90% or above, efficient separation of selenium and tellurium is achieved, and the produced tellurium dioxide neutralization slag can be used for further purification and refining.

Description

Technical Field

[0001] The present invention relates to the technical field of nonferrous metallurgy, and more particularly to a method for cascading tellurium recovery from complex tellurium-containing materials. Background Art

[0002] Tellurium is a rare metal with an abundance of approximately 1×10-7% in the Earth's crust. It is often found in association with pyrite, chalcopyrite, and sphalerite. No independent industrial minerals have been discovered. Tellurium is primarily extracted from anode mud from electrolytic copper, zinc smelting dust, and smelting tailings such as gold, silver, and lead. Current methods for separating and purifying tellurium include soda ash roasting, alkaline high-pressure leaching, sulfuric acid roasting, oxidative acid leaching, extraction, electrolytic refining, vacuum distillation, and zone melting refining.

[0003] Existing techniques involve subjecting tellurium copper materials to sodium chlorate acid leaching to separate copper; then alkaline leaching of the copper slag to separate tellurium; then removing impurities from the tellurium separation solution using sodium sulfide for primary removal and disodium EDTA for further removal; and finally, neutralizing the solution with a purified solution to adjust the pH to produce tellurium dioxide. This method requires the use of sodium chlorate, which releases chlorine gas during use, is environmentally unfriendly and requires high safety standards.

[0004] Existing techniques involve reacting tellurium-containing slag with sulfuric acid and sodium nitrate, allowing the copper in the tellurium-containing slag to enter the solution while retaining the tellurium in the leached residue. Hydrochloric acid is then used to leach the tellurium from the leached residue, followed by reduction with sulfur dioxide to produce crude tellurium powder. This method requires the introduction of nitrate and chloride ions, which is highly corrosive to wet process equipment and makes subsequent wastewater treatment difficult.

[0005] Other existing techniques involve grinding tellurium-containing materials and then subjecting them to oxygen-pressure alkali leaching to obtain a tellurium-containing alkali solution. The pH of the resulting tellurium-containing alkali solution is adjusted, and barium hydroxide is added to precipitate selenium. Sodium sulfide is then added to the selenium-precipitated solution to remove trace heavy metal ions and excess barium ions. The pH of the resulting purified solution is adjusted to neutralize tellurium precipitation, resulting in tellurium dioxide slag. This method is not adaptable to the raw materials used. If the tellurium-containing material contains a high proportion of hexavalent tellurium, the tellurium leaching rate will be low. Summary of the Invention

[0006] In view of this, the present invention provides a method for recovering tellurium from complex tellurium-containing materials in a stepwise manner to solve the above-mentioned problem.

[0007] The present invention provides a method for recovering tellurium from complex tellurium-containing materials in a stepwise manner, comprising:

[0008] Pickling: The complex tellurium-containing material to be processed is pickled, hexavalent tellurium is dissolved in acid, hexavalent tellurium is separated from tellurium in other valence states, and then liquid-solid separation is performed to obtain a pickling solution and a pickling residue, wherein the liquid-solid ratio of the total solution to the complex tellurium-containing material is (3-8):1, sulfuric acid is added to adjust the pH to less than 3, the temperature is raised to 50°C to 95°C, and the reaction is carried out for 1h to 4h;

[0009] Reduction and neutralization: Heat the pickling solution to 50°C to 95°C, add a reducing agent in an amount equal to 0.8 to 1.5 times the theoretical amount of tellurium in the pickling solution, adjust the pH to neutral, and react for 1 to 4 hours to reduce hexavalent tellurium to tetravalent tellurium. After the reaction is complete, separate the liquid and solid to obtain tellurium neutralization slag and neutralized liquid. Taking sodium sulfite as the reducing agent, the chemical reaction equation is:

[0010] TeO4 2- +2H + +Na2SO3==TeO2↓+Na2SO4+H2O;

[0011] Pyrometallurgical transformation, subjecting the pickling slag to pyrometallurgical transformation to obtain transformed slag;

[0012] Leaching, subjecting the transformation slag to leaching treatment to obtain a leachate and a leach residue;

[0013] Neutralization: neutralizing the leaching solution to obtain tellurium neutralized slag and neutralized liquid.

[0014] Optionally, the reducing agent is at least one of sodium sulfite, sulfur dioxide, sodium sulfide, and sodium hydrosulfide.

[0015] Optionally, when the pickling solution contains heavy metal ions of copper and lead, sodium sulfide or sodium hydrosulfide is added in the reduction and neutralization step as a sulfiding agent to solidify the heavy metal ions of copper and lead into sulfide form. The chemical reaction equation is:

[0016] Cu 2+ +Na2S==CuS↓+2Na + ,

[0017] Pb 2+ +Na2S==PbS↓+2Na + .

[0018] Optionally, the process further includes separating tellurium from copper and lead, which includes adding alkali to the tellurium-neutralized slag and leaching it into a liquid phase, with CuS and PbS remaining in the slag phase. The chemical reaction equation is:

[0019] TeO2+2NaOH=Na2TeO3+H2O.

[0020] Optionally, the pyrometallurgical transformation includes: placing the pickling slag in pyrometallurgical equipment, heating it to 80°C~100°C, removing moisture from the pickling slag, and then continuing to heat it to 320°C~600°C, keeping it warm and controlling the air intake for 4h~12h. After the reaction is completed, the transformed slag is obtained, and the air intake is 1 to 10 times the theoretical amount of oxygen consumption reaction of the elements in the pickling slag, and the air intake is air or oxygen.

[0021] Optionally, the leaching includes: controlling the liquid-solid ratio of the total solution to the input transformation slag to be (3-8):1, the free alkalinity to be 20g / L-100g / L, the sulfide alkali concentration to be less than or equal to 2g / L, the reaction time to be 1h-4h, the reaction temperature to be 50°C-95°C, deepening the removal of heavy metal ions, and reducing a small amount of hexavalent tellurium in the transformation slag to tetravalent tellurium. After the reaction is completed, the liquid and solid are separated to obtain leaching slag and leachate.

[0022] Optionally, the neutralization includes: adding sulfuric acid to the leachate to adjust the pH to 3-6.5, controlling the temperature to 50°C-95°C, and the reaction time to 1h-4h. After the reaction is completed, liquid-solid separation is performed to obtain tellurium neutralization slag and neutralized liquid.

[0023] Compared with the prior art, the method for recovering tellurium from complex tellurium-containing materials provided by the present invention achieves at least the following beneficial effects:

[0024] The present invention first adopts the step of pickling to effectively separate hexavalent tellurium from tellurium in other valence states, thereby reducing its wrapping on the slag phase and improving the transformation effect of tellurium in the later stage.

[0025] This method, through the coordinated treatment of hydrometallurgy and pyrometallurgy, effectively overcomes the slag phase encapsulation problem, transforming tellurium gradients of varying valence states in complex tellurium-containing materials into high-quality tellurium-neutralized slag. The selenium removal rate is no less than 95%, and the tellurium recovery rate is over 90%, achieving highly efficient separation of selenium and tellurium. The resulting tellurium dioxide-neutralized slag can be further purified and refined to produce 4N tellurium.

[0026] The method of the present invention has strong adaptability to raw materials, a short process, uses fewer chemical agents, produces fewer intermediates, is environmentally friendly, and is easy to industrialize.

[0027] Of course, any product implementing the present invention does not necessarily need to achieve all of the technical effects described above at the same time.

[0028] Further features and advantages of the present invention will become apparent from the following detailed description of exemplary embodiments of the present invention with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.

[0030] Figure 1 The present invention provides a method for recovering tellurium from complex tellurium-containing materials in a stepwise manner. DETAILED DESCRIPTION

[0031] Various exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. It should be noted that unless otherwise specifically stated, the relative arrangement of components and steps, numerical expressions and numerical values ​​set forth in these embodiments do not limit the scope of the present invention.

[0032] The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the invention, its application, or uses.

[0033] Technologies, methods, and equipment known to ordinary technicians in the relevant art may not be discussed in detail, but where appropriate, the technologies, methods, and equipment should be considered part of the specification.

[0034] In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not limiting. Therefore, other examples of the exemplary embodiments may have different values.

[0035] It should be noted that like reference numerals and letters refer to like items in the following figures, and therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0036] Reference Figure 1 The present invention provides a method for recovering tellurium from complex tellurium-containing materials in a stepwise manner, comprising the following steps:

[0037] S101, pickling, pickling the complex tellurium-containing material to be processed, dissolving hexavalent tellurium in acid, separating hexavalent tellurium from tellurium in other valence states, and then performing liquid-solid separation to obtain a pickling solution and pickling residue, wherein the liquid-solid ratio of the total solution to the complex tellurium-containing material is (3-8):1, sulfuric acid is added to adjust the pH to less than 3, the temperature is raised to 50°C to 95°C, and the reaction is carried out for 1 hour to 4 hours;

[0038] S102, reduction and neutralization, raising the temperature of the pickling solution to 50°C to 95°C, adding a reducing agent in an amount of 0.8 to 1.5 times the theoretical amount of tellurium in the pickling solution, adjusting the pH to neutral, and reacting for 1 to 4 hours to reduce hexavalent tellurium to tetravalent tellurium. After the reaction is completed, liquid-solid separation is performed to obtain tellurium neutralization slag and neutralized liquid;

[0039] S103, pyrometallurgical transformation, subjecting the pickling slag to pyrometallurgical transformation to obtain transformed slag;

[0040] S104, leaching, leaching the transformation slag to obtain a leachate and leaching slag;

[0041] S105, neutralization, neutralizing the leaching solution to obtain tellurium neutralized slag and neutralized liquid.

[0042] The method first performs pickling treatment on the complex tellurium-containing material to be treated, and performs liquid-solid separation to obtain pickling liquid and pickling residue; the obtained pickling liquid is subjected to reduction neutralization treatment to obtain tellurium-neutralized residue; the obtained pickling residue is subjected to pyrometallurgical transformation treatment to obtain transformation residue; the obtained transformation residue is subjected to leaching treatment to obtain leachate and leaching residue; and the obtained leachate is subjected to neutralization treatment to obtain tellurium-neutralized residue.

[0043] In the prior art, directly washing complex tellurium-containing materials with water before pyrometallurgical transformation can lead to slag entrapment. The present invention utilizes step S101, which utilizes the acid-soluble nature of hexavalent tellurium. Tetravalent tellurium (TeO2) and zero-valent tellurium (Te) have low solubility in acidic conditions and remain in the slag as solids. This effectively separates hexavalent tellurium from other tellurium valences, reducing its entrapment in the slag and improving subsequent tellurium transformation. Because selenium in complex tellurium-containing materials primarily exists in elemental form, it remains unreacted in this step and remains in the pickling slag.

[0044] Optionally, the liquid-to-solid ratio of the total solution to the complex tellurium-containing material is (3-8):1. This liquid-to-solid ratio ensures that the acid solution fully contacts the complex tellurium-containing material, promoting the dissolution of hexavalent tellurium. A low liquid-to-solid ratio may result in incomplete dissolution, while a high liquid-to-solid ratio increases subsequent processing costs.

[0045] Optionally, sulfuric acid is added to adjust the pH to less than 3. The strong acidic environment can maintain the solubility of hexavalent tellurium.

[0046] Optionally, the pickling temperature is raised to any value among 50°C, 60°C, 70°C, 75°C, 80°C, 85°C, 95°C, or any range between any two of the above values. It is understood that high temperatures can maintain the solubility of hexavalent tellurium, but excessively high temperatures can increase energy consumption and equipment corrosion.

[0047] Optionally, the pickling reaction time is any value among 1h, 1.5h, 2h, 2.5h, 3h, 3.5h, 4h or any range of values ​​between any two of the above points.

[0048] Optionally, the pickling liquid (containing hexavalent tellurium) and the pickling residue (containing tellurium in other valence states) are separated by filtration or centrifugation, which is not specifically limited here.

[0049] Specifically, for S102, the purpose of adding a reducing agent in this step is to 6+ Reduction to Te 4+ .

[0050] When the pickling solution contains heavy metal ions such as copper and lead, it is necessary to add appropriate sodium sulfide or sodium hydrosulfide as a sulfiding agent to solidify the heavy metal ions such as copper and lead into sulfide form. In the subsequent tellurium neutralization and slag purification process, efficient separation of tellurium from heavy metal ions such as copper and lead can be achieved. The main chemical reaction equation is:

[0051] TeO4 2- +2H + +Na2SO3==TeO2↓+Na2SO4+H2O

[0052] Cu 2+ +Na2S==CuS↓+2Na +

[0053] Pb 2+ +Na2S==PbS↓+2Na +

[0054] In the subsequent neutralization slag extraction process, tellurium in the neutralization slag is leached into the liquid phase by adding alkali, while copper sulfide and lead sulfide remain in the slag phase, achieving the separation of tellurium from copper and lead. The main chemical equation is:

[0055] TeO2+2NaOH=Na2TeO3+H2O

[0056] Optionally, the reducing agent is at least one of sodium sulfite, sulfur dioxide, sodium sulfide, and sodium hydrosulfide.

[0057] Optionally, in the reduction and neutralization step, the pickling solution is heated to any of 50° C., 55° C., 60° C., 65° C., 70° C., 75° C., 80° C., 85° C., 90° C., and 95° C., or any range between any two of the above values. High temperatures can accelerate the reduction reaction.

[0058] Optionally, the amount of reducing agent added during the reduction and neutralization step is 0.8 to 1.5 times the theoretical amount of tellurium in the pickling solution, such as any value among 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, and 1.5, or any range between any two of the aforementioned values. It should be noted that too little reducing agent will result in an incomplete reaction, while a sufficient amount will ensure a complete reaction. However, too much reducing agent may increase subsequent processing costs.

[0059] Optionally, the reduction and neutralization step adjusts the pH to neutral (6-8), which promotes the precipitation of TeO2 and can avoid the co-precipitation of metal ions.

[0060] Optionally, the reaction time of the reduction neutralization step is any value among 1h, 1.5h, 2h, 2.5h, 3h, 3.5h, 4h, or any range between any two of the above points.

[0061] Specifically, S103, pyrometallurgical transformation, is to subject the pickling slag to pyrometallurgical transformation treatment to obtain transformed slag, including: placing the pickling slag in pyrometallurgical equipment, heating it to 80°C to 100°C, removing moisture from the pickling slag, and then continuing to heat it to 320°C to 600°C, keeping it warm and controlling the air intake for 4h to 12h. After the reaction is completed, the transformed slag is obtained, and the air intake is 1 to 10 times the theoretical amount of oxygen consumption reaction of the elements in the pickling slag, and the air intake is air or oxygen.

[0062] Optionally, the pyrometallurgical transformation has two stages: a dehydration stage and a thermal transformation stage. The dehydration stage removes free water and crystal water in the pickling slag to avoid the rapid vaporization of water in the subsequent high-temperature stage, which may cause a sudden increase in equipment pressure or slag splashing. The thermal transformation stage converts elements such as tellurium and sulfur in the pickling slag into easily separable oxides or single substances through oxidation / reduction reactions, while removing volatile impurities (such as As and Sb). The main chemical reaction equation is:

[0063] 2MeTe+3O2==2TeO2+2MeO

[0064] Te+O2==TeO2

[0065] 2TeO2+O2==2TeO3 (a small amount of side reaction)

[0066] Se+O2==SeO2↑

[0067] Selenium is completely separated from tellurium in this step, with the tellurium remaining in the slag phase. Selenium is oxidized to selenium dioxide, which volatilizes into the flue gas. Because this step removes over 95% of the selenium, the selenium content in the transition slag is extremely low, and its reaction is no longer considered in subsequent steps.

[0068] During the dehydration phase, the heating rate should be increased slowly (5-10°C / min) to avoid local overheating. Atmosphere control can be achieved by introducing a small amount of inert gas (such as N2) or air to maintain a slightly positive pressure (0.01-0.05 MPa) to prevent premature introduction of an oxidizing atmosphere. The endpoint can be determined by maintaining the temperature for 1-2 hours until the slag quality no longer changes (moisture content <1%).

[0069] During the thermal transformation stage, excessive temperatures (>600°C) or excess oxygen may cause TeO2 to further oxidize to TeO3 (low volatility and difficult to recover). Therefore, the temperature needs to be controlled between 320°C and 600°C, and the air intake should be 1 to 10 times the theoretical amount of oxygen consumption reaction of the elements in the pickling slag to reduce the occurrence of side reactions.

[0070] Optionally, the thermal transition temperature is any value among 320°C, 350°C, 400°C, 450°C, 500°C, 550°C, 600°C or any range of values ​​between any two of the above points.

[0071] Optionally, the air intake volume can be 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 times the theoretical oxygen consumption of the elements in the pickling slag. The intake gas can be air or oxygen. Air is more cost-effective, but N2 dilutes the oxygen, requiring an increased intake volume. Oxygen intake provides higher reaction efficiency.

[0072] The reaction time is adjusted according to the slag thickness and reaction rate. The reaction time can be any value among 4h, 5h, 6h, 7h, 8h, 9h, 10h, 11h, 12h or any range between any two of the above points.

[0073] Specifically, S104, leaching, leaching the transformation slag to obtain a leachate and a leachate slag, including: controlling the liquid-solid ratio of the total solution to the input transformation slag to be (3-8):1, the free alkalinity to be 20g / L-100g / L, the sulfide alkali concentration to be less than or equal to 2g / L, the reaction time to be 1-4h, the reaction temperature to be 50°C-95°C, deepening the removal of heavy metal ions, and reducing a small amount of hexavalent tellurium in the transformation slag to tetravalent tellurium. After the reaction is completed, the liquid and solid are separated to obtain the leachate slag and the leachate.

[0074] The alkali sulfide is preferably sodium sulfide or sodium hydrosulfide.

[0075] The main chemical reaction equation is:

[0076] TeO2+2NaOH==Na2TeO3+H2O

[0077] TeO3+2NaOH==Na2TeO4+H2O

[0078] Na2TeO4+H2O+Na2S==Na2TeO3+S↓+2NaOH

[0079] MeO+Na2S+H2O==MeS↓+2NaOH

[0080] This step further removes heavy metal ions and reduces the small amount of overoxidized hexavalent tellurium produced in step S103 to tetravalent tellurium. The tellurium enters the liquid phase, while the small amount of heavy metal ions enter the slag phase.

[0081] Optionally, the liquid-to-solid ratio of the total solution to the input transition slag can be controlled to any ratio selected from 3:1, 4:1, 5:1, 6:1, 7:1, or 8:1, or any range between any two of the aforementioned values. The free alkalinity can be any value selected from 20 g / L, 30 g / L, 40 g / L, 50 g / L, 60 g / L, 70 g / L, 80 g / L, 90 g / L, or 100 g / L, or any range between any two of the aforementioned values. The concentration of sodium sulfide can be less than or equal to 2 g / L. The reaction time can be any value selected from 1 hour, 1.5 hours, 2 hours, 2.5 hours, 3 hours, 3.5 hours, or 4 hours, or any range between any two of the aforementioned values. The reaction temperature can be any value selected from 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, or 95°C, or any range between any two of the aforementioned values.

[0082] Specifically, S105, neutralization, neutralizes the leachate to obtain tellurium neutralized slag and neutralized liquid, including: adding sulfuric acid to the leachate to adjust the pH to 3-6.5, controlling the temperature to 50°C-95°C, and the reaction time to 1h-4h. After the reaction is completed, liquid-solid separation is performed to obtain tellurium neutralized slag and neutralized liquid.

[0083] The main chemical reaction equation is:

[0084] Na2TeO3+H2SO4=TeO2↓+Na2SO4+H2O

[0085] Optionally, the pH is adjusted to 3-6.5 by sulfuric acid to precipitate tellurium in the form of TeO2 while avoiding co-precipitation of other metals (such as Cu, Fe, and Zn). The neutralization reaction time can be any value among 1h, 1.5h, 2h, 2.5h, 3h, 3.5h, and 4h, or any range between any two of the above points. A reaction time of 1h to 4h can ensure complete precipitation of tellurium while avoiding excessive reaction leading to slag particle refinement. The neutralization reaction temperature can be any value among 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, and 95°C, or any range between any two of the above points. Controlling the temperature between 50°C and 95°C can accelerate the tellurium precipitation reaction while controlling the solubility of impurities.

[0086] The above method can effectively separate selenium from tellurium, with a selenium removal rate of not less than 95% and a tellurium recovery rate of more than 90%.

[0087] The tellurium neutralization slag produced by the present invention has a main grade exceeding 50% and a selenium content of ≤0.1%, resulting in high-quality slag suitable for further purification and refining to produce 4N tellurium. The resulting leaching residue can be used to recover other valuable elements based on its composition. After tellurium is enriched, it can be returned to the process, achieving efficient tellurium recovery.

[0088] Example 1

[0089] Take 1 kg (dry weight) of impurity-free material 1 from the tellurium production process, containing 28.38% tellurium. Control the liquid-to-solid ratio to 3:1, adjust the pH to 2.5, raise the temperature to 95°C, and stir for 4 hours. After the reaction, separate the liquid and solid to produce a pickling solution and a pickling slag. Heat the pickling solution to 50°C, add the reducing agent Na2S at 0.8 times the theoretical amount required for the reaction with tellurium in the solution, adjust the pH to neutral, and react for 2.5 hours. After the reaction, separate the liquid and solid to produce a tellurium-neutralized slag and a neutralized liquid. Place the pickling slag in a pyrometallurgical process and heat it to 90°C to remove moisture from the pickling slag. Continue heating the temperature to 320°C, maintain the temperature, and control the air intake at 1 times the theoretical amount required for the oxygen consumption reaction of the elements in the pickling slag for 4 hours. After the reaction, a transition slag is obtained. The slag was added at a liquid-to-solid ratio of 3:1, with a free alkalinity of 100 g / L, an alkaline sulfide concentration of 0 g / L, and a reaction temperature of 50°C for 4 hours. After the reaction, the liquid and solid were separated to produce a leaching residue and a leachate. The leachate was adjusted to a pH of 3 by adding sulfuric acid, and the temperature was controlled at 50°C for 2.5 hours. After the reaction, the liquid and solid were separated to produce a tellurium neutralized slag and a neutralized solution.

[0090] In this embodiment, the tellurium neutralization slag contains tellurium (weighted average) of 56.73% and selenium of 0.012%, with a selenium removal rate of 96.13% and a tellurium recovery rate of 93.57%.

[0091] Example 2

[0092] Take 1 kg (dry weight) of impurity-free material 2 from the tellurium production process, containing 14.22% tellurium. Control the liquid-to-solid ratio to 5:1, adjust the pH to 1, and heat to 70°C with stirring for 2.5 hours. After the reaction, separate the liquid and solid to produce a pickling solution and a pickling slag. Heat the pickling solution to 75°C, add a reducing agent (sodium sulfite + Na2S) in an amount theoretically required to react with the tellurium in the solution, adjust the pH to neutral, and allow the reaction to continue for 1 hour. After the reaction, separate the liquid and solid to produce a tellurium-neutralized slag and a neutralized liquid. The pickling slag is placed in a pyrometallurgical equipment and heated to 100°C to remove moisture from the pickling slag. The temperature is then raised to 450°C, maintaining the temperature while controlling the air intake to 5 times the theoretical amount required to react with the oxygen consumption of the elements in the pickling slag. The reaction continues for 8 hours. After the reaction, a transition slag is obtained. The slag was added at a liquid-to-solid ratio of 5.5:1, with a free alkalinity of 60 g / L, a sodium sulfide concentration of 1 g / L, and a reaction temperature of 70°C for 2.5 hours. After the reaction, the liquid and solid were separated to produce a leaching residue and a leachate. The leachate was adjusted to a pH of 6.5 by adding sulfuric acid, and the temperature was controlled at 95°C for 1 hour. After the reaction, the liquid and solid were separated to produce a tellurium neutralized slag and a neutralized solution.

[0093] In this embodiment, the tellurium neutralization slag contains tellurium (weighted average) of 53.22% and selenium of 0.056%, with a selenium removal rate of 95.89% and a tellurium recovery rate of 91.84%.

[0094] Example 3

[0095] Take 1 kg (dry weight) of impurity-free material 3 from the tellurium production process, containing 46.11% tellurium. Control the liquid-to-solid ratio to 8:1, adjust the pH to 0.5, and heat to 50°C with stirring for 1 hour. After the reaction, separate the liquid and solid to produce a pickling solution and a pickling slag. Heat the pickling solution to 95°C, add a reducing agent (SO₂ + NaHS) at 1.5 times the theoretical amount required for the reaction with tellurium in the solution, adjust the pH to neutral, and allow the reaction to continue for 4 hours. After the reaction, separate the liquid and solid to produce a tellurium-neutralized slag and a neutralized liquid. The pickling slag is placed in a pyrometallurgical equipment and heated to 80°C to remove moisture from the pickling slag. The temperature is then raised to 580°C, maintained at this temperature, and the air intake is controlled at 10 times the theoretical amount required for the oxygen consumption reaction of the elements in the pickling slag for 12 hours. After the reaction, a transition slag is obtained. The transformation slag was added at a liquid-to-solid ratio of 8:1, with a free alkalinity of 20 g / L and a sodium hydrosulfide concentration of 2 g / L at a reaction temperature of 95°C for 1 hour. After the reaction, the liquid and solid were separated to produce a leaching slag and a leachate. The leachate was then acidified to adjust its pH to 4.8, and the temperature was controlled at 75°C for 4 hours. After the reaction, the liquid and solid were separated to produce a tellurium neutralized slag and a neutralized liquid.

[0096] In this embodiment, the tellurium neutralization slag contains tellurium (weighted average) of 61.66%, selenium <0.01%, selenium removal rate of 98.17%, and tellurium recovery rate of 94.58%.

[0097] Although some specific embodiments of the present invention have been described in detail by way of examples, it should be understood by those skilled in the art that the above examples are for illustration only and are not intended to limit the scope of the present invention. It should be understood by those skilled in the art that modifications may be made to the above embodiments without departing from the scope and spirit of the present invention. The scope of the present invention is defined by the appended claims.

Claims

1. A method for recovering tellurium from complex tellurium-containing materials in a stepwise manner, characterized in that: include: Pickling: The complex tellurium-containing material to be processed is pickled, hexavalent tellurium is dissolved in acid, hexavalent tellurium is separated from tellurium in other valence states, and then liquid-solid separation is performed to obtain a pickling solution and a pickling residue, wherein the liquid-solid ratio of the total solution to the complex tellurium-containing material is (3-8):1, sulfuric acid is added to adjust the pH to less than 3, the temperature is raised to 50°C to 95°C, and the reaction is carried out for 1h to 4h; Reduction neutralization: heating the pickling solution to 50° C. to 95° C., adding a reducing agent in an amount of 0.8 to 1.5 times the theoretical amount of tellurium in the pickling solution, adjusting the pH to neutral, and reacting for 1 to 4 hours to reduce hexavalent tellurium to tetravalent tellurium. After the reaction is completed, liquid-solid separation is performed to obtain tellurium neutralization slag and neutralized liquid; Pyrometallurgical transformation, subjecting the pickling slag to pyrometallurgical transformation to obtain transformed slag; Leaching, subjecting the transformation slag to leaching treatment to obtain a leachate and a leach residue; Neutralization: neutralizing the leaching solution to obtain tellurium neutralized slag and neutralized liquid.

2. The method for recovering tellurium from complex tellurium-containing materials according to claim 1, characterized in that: The reducing agent is at least one of sodium sulfite, sulfur dioxide, sodium sulfide, and sodium hydrosulfide.

3. The method for recovering tellurium from complex tellurium-containing materials according to claim 1, characterized in that: When the pickling solution contains heavy metal ions of copper and lead, sodium sulfide or sodium hydrosulfide is added as a sulfiding agent in the reduction and neutralization step to solidify the heavy metal ions of copper and lead into sulfide form. The chemical reaction equation is: <h2 style=";text-align:left;direction:ltr">Cu<h2 style=";text-align:left;direction:ltr"> 2+ <h2 style=";text-align:left;direction:ltr"> +Na2S==CuS↓+2Na<h2 style=";text-align:left;direction:ltr"> + <h2 style=";text-align:left;direction:ltr"> , <h2 style=";text-align:left;direction:ltr">Pb<h2 style=";text-align:left;direction:ltr"> 2+ <h2 style=";text-align:left;direction:ltr"> +Na2S==PbS↓+2Na<h2 style=";text-align:left;direction:ltr"> + <h2 style=";text-align:left;direction:ltr"> 。 4. The method for recovering tellurium from complex tellurium-containing materials according to claim 3, characterized in that: The process also includes a step of separating tellurium from copper and lead, which includes adding alkali to the tellurium neutralized slag to leach it into a liquid phase, with CuS and PbS remaining in the slag phase. The chemical reaction equation is: TeO2+2NaOH=Na2TeO3+H2O.

5. The method for recovering tellurium from complex tellurium-containing materials according to claim 1, characterized in that: The pyrometallurgical transformation comprises: placing the pickling slag in a pyrometallurgical device, heating it to 80° C. to 100° C., removing moisture from the pickling slag, and then continuing to heat it to 320° C. to 600° C., keeping it warm and controlling the air intake for 4 hours to 12 hours. After the reaction is completed, a transformed slag is obtained, and the air intake is 1 to 10 times the theoretical amount of oxygen consumption reaction of the elements in the pickling slag, and the air intake is air or oxygen.

6. The method for recovering tellurium from complex tellurium-containing materials according to claim 1, characterized in that: The leaching process includes: controlling the liquid-solid ratio of the total solution to the input transformation slag to be (3-8):1, the free alkalinity to be 20g / L-100g / L, the sulfide concentration to be less than or equal to 2g / L, the reaction time to be 1h-4h, the reaction temperature to be 50°C-95°C, deepening the removal of heavy metal ions, and simultaneously reducing a small amount of hexavalent tellurium in the transformation slag to tetravalent tellurium. After the reaction is completed, liquid-solid separation is performed to obtain leaching slag and leachate.

7. The method for recovering tellurium from complex tellurium-containing materials according to claim 1, characterized in that: The neutralization comprises: adding sulfuric acid to the leachate to adjust the pH to 3-6.5, controlling the temperature to 50° C.-95° C., and the reaction time to 1 hour-4 hours. After the reaction is completed, liquid-solid separation is performed to obtain tellurium neutralization slag and neutralized liquid.

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