Method for arsenic-tellurium cooperation short-range recovery and valuable metal enrichment in arsenic alkali residue

Abstract

The application belongs to the technical field of metallurgy, and particularly relates to a method for cooperatively short-range recovery of arsenic and tellurium and enrichment of valuable metals in arsenic alkali slag, which comprises the following steps: mixing the arsenic alkali slag with a sodium hydroxide solution, introducing oxygen, and performing oxygen pressure alkali leaching at 0.2-0.4 MPa and 115-135 DEG C to obtain a conversion liquid and a conversion residue; S2 mixing the conversion residue obtained in step S1 with a sulfidizing agent and a sodium hydroxide solution, and performing sulfidizing leaching at 75-95 DEG C to obtain a leaching liquid and a leaching residue; S3 mixing the conversion liquid obtained in step S1 with the leaching liquid obtained in step S2, adjusting the pH to 5.0-6.0, and reacting to obtain crude tellurium dioxide and arsenic-containing wastewater. The application realizes efficient dissociation of tellurium in the arsenic alkali slag and synchronous solidification of arsenic by using a'mild oxygen pressure alkali leaching-strengthened alkaline sulfidizing leaching' cooperative process, and realizes cooperative separation and short-range recovery of arsenic and tellurium.

Description

Technical Field

[0001] This invention relates to the field of metallurgical technology, specifically to a method for the synergistic short-range recovery of arsenic and tellurium and the enrichment of valuable metals in arsenic-alkali slag. Background Technology

[0002] Arsenic-alkali slag is a typical hazardous solid waste generated during antimony smelting. It is complex in composition, highly toxic, and difficult to treat. This slag mainly consists of excess alkali (such as sodium hydroxide and sodium carbonate) and various valuable metals such as arsenic, tellurium, gold, silver, and antimony, making it a secondary resource with both environmental hazards and high value. Therefore, developing technologies that can effectively remove and solidify arsenic, neutralize excess alkali, and simultaneously and efficiently recover high-value metals such as gold, silver, antimony, and tellurium is of paramount practical significance for achieving the "harmlessness, reduction, and resource utilization" of hazardous waste, promoting the development of a circular economy, and protecting the environment.

[0003] Currently, the treatment processes for arsenic-alkali slag mainly revolve around two technical routes: pyrometallurgical and hydrometallurgical processes. Pyrometallurgical processes typically return the arsenic-alkali slag as a feedstock to the main lead-antimony smelting system for co-smelting within the larger system. While this method can recover some valuable metals to a certain extent, it generally suffers from drawbacks such as high energy consumption, high production costs, a high risk of secondary pollution from arsenic in the flue gas, and a long investment payback period. Hydrometallurgical processes mainly use water leaching and acid leaching to introduce arsenic and alkali into the solution phase, and then recover them separately through evaporation crystallization and precipitation separation. However, existing hydrometallurgical technologies often suffer from problems such as lengthy process flows, low reaction efficiency, and loss of valuable metals due to dispersion; and while they may achieve preliminary removal of arsenic, they generally lack effective solutions for the efficient extraction and selective enrichment of the rare metal tellurium, resulting in extremely low recovery rates for this high-value metal.

[0004] Patent document CN106834711B discloses a method for recovering and preparing high-purity selenium from arsenic-selenium-containing flue dust, employing a complex process of oxygen-pressure alkali leaching-neutralization-selective reduction-hydrogen reduction-vacuum distillation. This technology targets flue dust materials, where the oxygen-pressure conditions are more severe (temperature 120~300℃, pressure 0.1~3.5MPa), requiring subsequent costly hydrogen reduction and vacuum distillation steps. This places high demands on equipment, making it difficult to promote and apply in actual production processes and unsuitable for the economical treatment of arsenic-alkali residue. Patent application CN120589696A discloses a method for the graded recovery of tellurium from complex selenium-containing materials, employing a wet pyrometallurgical synergistic process of acid washing-reduction neutralization-pyrometallurgical transformation-leaching-neutralization, achieving selenium removal and graded tellurium recovery. This method is primarily designed for selenium-containing materials; its pyrometallurgical transformation stage requires high-temperature treatment, resulting in high energy consumption and stringent requirements for equipment corrosion resistance. Patent document CN114920208B discloses a method for efficiently separating tellurium selenium from tellurium-containing materials, which uses an alkaline sulfidation leaching system. However, the technology cannot effectively break down the complex telluride phases in arsenic-alkali slag. It does not provide an effective solution for the synergistic treatment and safe opening of arsenic in arsenic-alkali slag, and it ignores the comprehensive recovery of precious metals such as gold and silver in the leaching residue. When treating arsenic-alkali slag with multiple metals, it is difficult to achieve full resource recovery, thus limiting its application scope.

[0005] Therefore, developing a new technology that can directly process raw arsenic-alkali slag, achieve efficient synergistic separation and short-range recovery of arsenic and tellurium, and simultaneously enrich valuable metals is the key to solving the current problem of arsenic-alkali slag treatment. Summary of the Invention

[0006] This invention addresses the shortcomings of existing technologies by providing a method for the synergistic short-range recovery of arsenic and tellurium and the enrichment of valuable metals in arsenic-alkali slag.

[0007] The specific technical solution is as follows:

[0008] A method for the synergistic short-range recovery of arsenic and tellurium and the enrichment of valuable metals in arsenic-alkali slag includes the following steps:

[0009] S1 Arsenic-alkali residue is mixed with sodium hydroxide solution, oxygen is introduced, and oxygen pressure alkali leaching is carried out at 0.2~0.4MPa and 115~135℃ to obtain conversion solution and conversion residue;

[0010] S2 The conversion residue obtained in step S1 is mixed with a sulfiding agent and sodium hydroxide solution, and sulfidation leaching is carried out at 75~95℃ to obtain leachate and leaching residue;

[0011] S3. The conversion solution obtained in step S1 is mixed with the leachate obtained in step S2, and the pH is adjusted to 5.0~6.0. The reaction yields crude tellurium dioxide and arsenic-containing wastewater.

[0012] Among them, arsenic-alkali slag comes from hazardous solid waste generated during the antimony smelting process, and its main components are: As 10wt%~20wt%, Te 5wt%~15wt%, Sb 5wt%~15wt%, Ag 1wt%~5wt%, Bi 1wt%~5wt%, Cu 0.1wt%~1wt%, and Au 100~500g / t.

[0013] The reaction mechanism is as follows:

[0014] Arsenic-alkali residue is initially separated from tellurium and antimony during oxygen-pressure alkaline leaching to obtain conversion solution and conversion residue. Subsequently, tellurium and antimony are separated during sulfidation leaching of the conversion residue to obtain leachate and leachate residue. After mixing the conversion solution and leachate, arsenic and tellurium are separated by precisely adjusting the pH.

[0015] In step S1, during the oxygen-pressure alkaline leaching process, under low temperature and low pressure conditions, some of the insoluble tellurides in the arsenic-alkali residue react with sodium hydroxide to transform into readily soluble tellurate, which dissolves in the conversion solution (Te). 2- →TeO3 2- →TeO4 2- This process initially fixes arsenic from the arsenic-alkali slag into the conversion solution, achieving preliminary arsenic solidification and efficient tellurium enrichment, while sodium antimonate and some unreactable tellurides remain in the conversion slag. The main reactions are:

[0016] 2Te+4NaOH+3O2=2Na2TeO4+2H2O;

[0017] TeO2 + 2NaOH = Na2TeO3 + H2O;

[0018] 2Na₂TeO₃ + O₂ = 2Na₂TeO₄;

[0019] As₂O₃ + 6NaOH = 2Na₃AsO₃ + 3H₂O;

[0020] 2Na3AsO3 + O2 = 2Na3AsO4.

[0021] Furthermore, in step S1, the molar ratio of sodium hydroxide to the total amount of As and Te in the arsenic alkali residue is (2.0~4.0):1; the liquid-solid mass ratio is (4.0~5.0):1.

[0022] Furthermore, in step S1, the oxygen pressure alkali leaching time is 2.5~3.5h.

[0023] Furthermore, in step S1, the particle size of the arsenic-alkali slag is 100~300 mesh.

[0024] During the oxygen-pressure alkaline leaching process in step S1, the generated Na2TeO4 is soluble in the alkaline solution, and most of it enters the conversion liquid. However, a small amount of Na2TeO4 may still exist in the conversion slag for the following reasons: 1. The concentration of Na2TeO4 in the solution exceeds its solubility in the alkaline medium, or local fluctuations in temperature and pH may cause a small amount of Na2TeO4 to precipitate into the slag phase; 2. Fine tellurate particles may be encapsulated or adsorbed by other solid phases and not completely enter the solution. Therefore, these residual tellurium components in the slag can be further treated during the sulfide leaching process in step S2 to ensure efficient tellurium recovery. Meanwhile, the conversion slag obtained in step S1 will contain a small amount of As2O3 for the following reasons: During the oxygen-pressure alkaline leaching process, some trace amounts of As2O3 are encapsulated by other substances, making it difficult to fully contact the sodium hydroxide solution, thus preventing it from fully participating in the reaction; at the same time, as the reaction proceeds, sodium hydroxide is continuously consumed, and if mixing or mass transfer is insufficient, the local concentration may drop to a level insufficient to maintain the continuous reaction of As2O3, thus causing As2O3 to fail to achieve complete reaction.

[0025] Similarly, during the oxygen-pressure alkaline leaching process in step S1, the generated Na3AsO4 is soluble in the alkaline solution, and most of it enters the conversion liquid. However, a small amount of Na3AsO4 may still exist in the conversion residue for the following reason: during solid-liquid separation after the conversion reaction, the solubility of sodium arsenate (Na3AsO4) decreases with decreasing temperature. As the system temperature drops during the separation process, a small amount of sodium arsenate precipitates due to supersaturation and becomes mixed with the solid phase.

[0026] In step S2, during the atmospheric pressure alkaline sulfidation leaching process, the sulfiding agent reacts with the insoluble tellurides in the conversion slag to generate soluble tellurite Na2TeO3, which dissolves in the leachate. Simultaneously, antimony compounds in the conversion slag are converted into antimony sulfide, which is enriched and retained in the leaching slag. Valuable metals such as gold and silver in the conversion slag are also enriched in the leaching slag. Furthermore, in the alkaline sulfidation system of step S2, residual arsenic in the conversion slag undergoes a "sulfidation-complexation" reaction to form a soluble and stable compound, thereby ensuring its retention in the liquid-phase leachate and achieving deep separation from the target enriched slag. The main reactions are:

[0027] Na3AsO4+4Na2S+4H2O=Na3AsS4+8NaOH;

[0028] As₂O₃ + 6NaOH = 2Na₃AsO₃ + 3H₂O;

[0029] 4Na3SbO4+8Na2S+13H2O=2Sb2S3+26NaOH+Na2S2O3;

[0030] 9Na2TeO4+4Na2S+3H2O=9Na2TeO3+Na2S4O6+6NaOH.

[0031] Furthermore, in step S2, the molar ratio of sodium hydroxide to the total amount of As and Te in the conversion slag is (3.0~6.0):1, the molar ratio of S in the sulfiding agent to the total amount of As, Te, and Sb in the conversion slag is (1.5~2.5):1, and the liquid-solid mass ratio is (3.5~5.0):1. The sodium hydroxide in step S2 can create a safe and stable reaction environment: the addition of sodium hydroxide can effectively maintain the alkaline conditions of the system, avoiding the formation of an acidic environment when sodium sulfide is added, thereby completely inhibiting the generation of the toxic gas hydrogen sulfide and ensuring operational safety; at the same time, it can regulate the hydrolysis equilibrium of sodium tellurite: sodium hydroxide can significantly increase the OH- ions in the solution. - Concentration strongly inhibits the hydrolysis reaction of sodium tellurite (Na2TeO3), shifting the hydrolysis equilibrium to the left and stabilizing TeO3. 2- The presence of ions in solution effectively prevents precipitation caused by the hydrolysis of sodium tellurite to form insoluble tellurite acid (H₂TeO₃) or its acid salts, thus ensuring that tellurium species remain highly soluble in solution. In summary, sodium hydroxide, by indirectly participating in the reaction process, not only ensures process safety but also significantly improves the stability and solubility of sodium tellurite, ultimately contributing to increased leaching rates of the target components.

[0032] Furthermore, in step S2, the sulfidation leaching time is 3.0~4.0h.

[0033] Furthermore, in step S2, the sulfiding agent is sodium sulfide and / or sulfur.

[0034] Preferably, in step S2, the leaching residue is returned to the pyrometallurgical system to recover valuable metals such as gold, silver, and antimony.

[0035] In step S3, the conversion solution and leachate are combined. Utilizing the complementary nature of acids and bases, dilute sulfuric acid is used to neutralize the precipitation in one step, precisely controlling the endpoint pH (5.0~6.0). This achieves selective precipitation of tellurium in the form of high-purity tellurium dioxide (tellurium recovery rate >97%), while arsenic remains in the solution to form a stable compound, achieving a clean open circuit. The main reactions are:

[0036] Na2TeO4+H2SO4=Na2SO4+TeO2+H2O+1 / 2O2;

[0037] Na2TeO3+H2SO4=Na2SO4+TeO2+H2O.

[0038] Furthermore, in step S3, the reaction time is 0.5~1.5h.

[0039] Furthermore, in step S3, the pH is adjusted to 5.0-6.0 using dilute sulfuric acid with a concentration of 5wt%-15wt%.

[0040] Preferably, in step S3, the arsenic-containing wastewater is returned to the wastewater treatment system.

[0041] The beneficial effects of this invention are as follows:

[0042] This invention utilizes a two-step synergistic process of "mild oxygen-pressure alkaline leaching - enhanced alkaline sulfidation leaching" to achieve efficient dissociation of tellurium and simultaneous solidification of arsenic in arsenic-alkali slag, providing high-quality raw materials for subsequent pyrometallurgical recovery. Furthermore, the process does not introduce harmful impurities, and the enriched slag can be directly returned to the smelting system, realizing the full-element recovery of multi-metal resources from hazardous waste, which meets the circular economy requirements of "harmlessness, reduction, and resource utilization." This process simplifies the traditional multi-step separation process, improves the direct recovery rate of tellurium, and achieves the harmless disposal of arsenic. Detailed Implementation

[0043] The embodiments of the present invention will be described in further detail below with reference to the examples. The following examples are for illustrative purposes only and should not be construed as limiting the scope of the invention. Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, the materials and reagents used in the following examples are commercially available.

[0044] Example 1

[0045] A method for synergistic short-range recovery of arsenic and tellurium and enrichment of valuable metals in arsenic-alkali slag.

[0046] Among them, the arsenic alkali slag comes from hazardous solid waste generated during the antimony smelting process, and its main components are: As 13.55wt%, Te 9.93wt%, Sb 10.20wt%, Ag 1.86wt%, Bi 2.46wt%, Cu 0.65wt%, and Au 286g / t.

[0047] Includes the following steps:

[0048] S1 Arsenic-alkali residue was ball-milled to a particle size of 200 mesh, then mixed with sodium hydroxide solution to a liquid-solid mass ratio of 4.0:1. Oxygen was introduced to adjust the system pressure to 0.2 MPa, and oxygen pressure alkali leaching was carried out at 135℃. After reacting for 3 hours, solid-liquid separation was performed to obtain conversion liquid and conversion residue. The molar ratio of sodium hydroxide to the total amount of As and Te in the arsenic-alkali residue was 2.0:1.

[0049] S2 The conversion slag obtained in step S1 is mixed with sodium sulfide and sodium hydroxide solution at a liquid-to-solid mass ratio of 4.0:1. Sulfide leaching is carried out at 75°C for 4.0 h. After solid-liquid separation, leachate and leaching slag are obtained. The leaching slag is returned to the pyrometallurgical system to recover valuable metals gold, silver, and antimony. The molar ratio of sodium hydroxide to the total amount of As and Te in the conversion slag is 3.0:1, and the molar ratio of S in the sulfiding agent to the total amount of As, Te, and Sb in the conversion slag is 2.1:1.

[0050] S3. The conversion solution obtained in step S1 is mixed with the leachate obtained in step S2. Under stirring conditions, 5 wt% dilute sulfuric acid is slowly added to adjust the pH to 5.0. After reacting for 1 hour, crude tellurium dioxide and arsenic-containing wastewater are obtained by solid-liquid separation. The arsenic-containing wastewater is then returned to the wastewater treatment system.

[0051] Example 2

[0052] A method for synergistic short-range recovery of arsenic and tellurium and enrichment of valuable metals in arsenic-alkali slag.

[0053] Among them, the arsenic alkali slag comes from hazardous solid waste generated during the antimony smelting process, and its main components are: As 14.35wt%, Te 10.63wt%, Sb 9.52wt%, Ag 1.85wt%, Bi 3.10wt%, Cu 0.55wt%, and Au 270g / t.

[0054] Includes the following steps:

[0055] S1 Arsenic-alkali residue was ball-milled to a particle size of 200 mesh, then mixed with sodium hydroxide solution to a liquid-solid mass ratio of 5.0:1. Oxygen was introduced to adjust the system pressure to 0.3 MPa, and oxygen pressure alkali leaching was carried out at 120℃ for 2.5 h. After solid-liquid separation, conversion liquid and conversion residue were obtained. The molar ratio of sodium hydroxide to the total amount of As and Te in the arsenic-alkali residue was 4.0:1.

[0056] S2 The conversion slag obtained in step S1 is mixed with sodium sulfide and sodium hydroxide solution at a liquid-to-solid mass ratio of 3.5:1. Sulfide leaching is carried out at 80°C for 3.5 hours. After solid-liquid separation, leachate and leaching slag are obtained. The leaching slag is returned to the pyrometallurgical system to recover valuable metals gold, silver, and antimony. The molar ratio of sodium hydroxide to the total amount of As and Te in the conversion slag is 6.0:1, and the molar ratio of S in the sulfiding agent to the total amount of As, Te, and Sb in the conversion slag is 1.5:1.

[0057] S3. The conversion solution obtained in step S1 is mixed with the leachate obtained in step S2. Under stirring conditions, 15wt% dilute sulfuric acid is slowly added to adjust the pH to 5.5. After reacting for 1.5 hours, crude tellurium dioxide and arsenic-containing wastewater are obtained by solid-liquid separation. The arsenic-containing wastewater is then returned to the wastewater treatment system.

[0058] Example 3

[0059] A method for synergistic short-range recovery of arsenic and tellurium and enrichment of valuable metals in arsenic-alkali slag.

[0060] Among them, the arsenic alkali slag comes from hazardous solid waste generated during the antimony smelting process, and its main components are: As 11.25wt%, Te 12.35wt%, Sb 8.63wt%, Ag 2.10wt%, Bi 1.63wt%, Cu 0.48wt%, and Au 235g / t.

[0061] Includes the following steps:

[0062] S1 Arsenic-alkali residue was ball-milled to a particle size of 200 mesh, then mixed with sodium hydroxide solution to a liquid-solid mass ratio of 4.5:1. Oxygen was introduced to adjust the system pressure to 0.4 MPa, and oxygen pressure alkali leaching was carried out at 115℃ for 3.5 h. After solid-liquid separation, conversion liquid and conversion residue were obtained. The molar ratio of sodium hydroxide to the total amount of As and Te in the arsenic-alkali residue was 3.0:1.

[0063] S2 The conversion slag obtained in step S1 is mixed with sodium sulfide and sodium hydroxide solution at a liquid-to-solid mass ratio of 5.0:1. Sulfide leaching is carried out at 95°C for 3.0 h. After solid-liquid separation, leachate and leaching slag are obtained. The leaching slag is returned to the pyrometallurgical system to recover valuable metals gold, silver, and antimony. The molar ratio of sodium hydroxide to the total amount of As and Te in the conversion slag is 5.0:1, and the molar ratio of S in the sulfiding agent to the total amount of As, Te, and Sb in the conversion slag is 2.5:1.

[0064] S3. The conversion solution obtained in step S1 is mixed with the leachate obtained in step S2. Under stirring conditions, 10wt% dilute sulfuric acid is slowly added to adjust the pH to 6.0. After reacting for 0.5 hours, crude tellurium dioxide and arsenic-containing wastewater are obtained by solid-liquid separation. The arsenic-containing wastewater is then returned to the wastewater treatment system.

[0065] test

[0066] The As and Te contents in the leaching residues of Examples 1-3 were determined, and the tellurium recovery rate and arsenic removal rate were calculated. The results are shown in Table 1 and Table 2, respectively.

[0067] The As and Te contents in the leaching residue were tested using inductively coupled plasma atomic emission spectrometry (ICP-AES).

[0068] Table 1. As and Te content in leaching residue

[0069]

[0070] Table 2 Tellurium recovery rate and arsenic removal rate

[0071]

[0072] Among them, "arsenic removal rate" refers to the efficiency of arsenic removal from the original arsenic alkali residue to the final leaching residue.

[0073] The arsenic-alkali slag treatment method provided by this invention achieves phase reconstruction of tellurium and initial solidification of arsenic through mild oxygen-pressure alkaline leaching, followed by enhanced alkaline sulfidation leaching to achieve efficient dissociation of tellurium and deep arsenic removal, and finally achieves efficient precipitation of tellurium through pH control. Examples show that this method achieves a tellurium recovery rate >97% and an arsenic removal rate >93%, while valuable metals such as gold, silver, and antimony are enriched in the leaching residue by more than 1.5 times. This method achieves synergistic short-range recovery of arsenic and tellurium and efficient enrichment of valuable metals in arsenic-alkali slag, possessing comprehensive advantages such as short process, mild conditions, environmental friendliness, and high resource utilization.

[0074] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for the synergistic short-range recovery of arsenic and tellurium and the enrichment of valuable metals in arsenic-alkali slag, characterized in that, Includes the following steps: S1 Arsenic-alkali residue is mixed with sodium hydroxide solution, oxygen is introduced, and oxygen pressure alkali leaching is carried out at 0.2~0.4MPa and 115~135℃ to obtain conversion solution and conversion residue; S2 The conversion residue obtained in step S1 is mixed with a sulfiding agent and sodium hydroxide solution, and sulfidation leaching is carried out at 75~95℃ to obtain leachate and leaching residue; S3. The conversion solution obtained in step S1 is mixed with the leachate obtained in step S2, and the pH is adjusted to 5.0~6.

0. The reaction yields crude tellurium dioxide and arsenic-containing wastewater. Among them, arsenic-alkali slag comes from hazardous solid waste generated during the antimony smelting process, and its main components are: As 10wt%~20wt%, Te 5wt%~15wt%, Sb 5wt%~15wt%, Ag 1wt%~5wt%, Bi 1wt%~5wt%, Cu 0.1wt%~1wt%, and Au 100~500g / t; In step S1, the molar ratio of sodium hydroxide to the total amount of As and Te in the arsenic alkali residue is (2.0~4.0):1; In step S2, the molar ratio of sodium hydroxide to the total amount of As and Te in the conversion slag is (3.0~6.0):1, the molar ratio of S in the sulfiding agent to the total amount of As, Te and Sb in the conversion slag is (1.5~2.5):1, the liquid-solid mass ratio is (3.5~5.0):1, and the sulfidation leaching time is 3.0~4.0h.

2. The method according to claim 1, characterized in that, In step S1, the liquid-to-solid mass ratio is (4.0~5.0):

1.

3. The method according to claim 1, characterized in that, In step S1, the oxygen pressure alkali leaching time is 2.5~3.5h.

4. The method according to claim 1, characterized in that, In step S2, the vulcanizing agent is sodium sulfide and / or sulfur.

5. The method according to claim 1, characterized in that, In step S3, the reaction time is 0.5~1.5h.

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