Method for regenerating sodium sulfite silver recovery spent mother liquor

Abstract

The application relates to the technical field of comprehensive recovery of rare and precious metals, and discloses a method for regenerating a sodium sulfite silver separation scrapped mother liquor. The method can remove impurity metals such as chlorine ions, copper, bismuth and selenium from the sodium sulfite silver separation waste liquid, and can completely regenerate the sodium sulfite silver separation waste liquid, so that the environmental risk caused by the discharge of the chlorine-containing waste liquid and the loss of the entrained precious metals are avoided, the dechlorination agent can be regenerated and utilized, the cost is low, and the output hydrochloric acid can be used in industry.

Description

Technical Field

[0001] This invention relates to the field of comprehensive recycling technology of rare and precious metals, and more specifically to a method for regenerating waste mother liquor from sodium sulfite silver separation. Background Technology

[0002] Copper and lead anode slimes are enriched with precious metals such as silver and gold. In wet processing, sodium sulfite is often used to separate silver, dissolving silver chloride and producing silver powder through formaldehyde reduction, thus separating and enriching the silver. The mother liquor from silver separation is then recycled back to the mother liquor after silver precipitation. However, with each cycle, the concentration of chloride ions and impurities such as antimony, bismuth, copper, and arsenic in the sodium sulfite mother liquor increases, causing a continuous decline in its silver-separating ability. To ensure the silver recovery rate, a certain proportion of the mother liquor must be periodically disposed of and fresh sodium sulfite solution prepared. Disposal typically involves evaporation and crystallization, causing sodium sulfite, sodium sulfide, and a small amount of sodium sulfate in the solution to evaporate and crystallize, forming a mixed waste salt. This waste salt also contains arsenic and must be treated as hazardous waste, sent to a landfill for disposal, which is very expensive. Currently, the conventional methods for treating waste mother liquor from sodium silver sulfite are all to discard it, and there is no existing research on the treatment and reuse of waste mother liquor from sodium silver sulfite.

[0003] Therefore, how to provide a simple and efficient method for treating waste mother liquor from sodium sulfite silver separation is a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0004] In view of this, the present invention provides a method for regenerating waste mother liquor from sodium silver sulfite, which can remove impurities such as chloride ions, copper, bismuth, and selenium from the waste sodium silver sulfite, and completely regenerate the waste sodium silver sulfite, avoiding the environmental risks caused by the discharge of chlorine-containing waste liquor and the loss of precious metals it carries. Furthermore, the dechlorinating agent is recyclable, has low cost, and the produced hydrochloric acid can be used in industry.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A method for regenerating waste mother liquor from sodium sulfite silver separation, characterized by comprising the following steps: (1) Acidification: In a closed reactor, sulfur dioxide is introduced into the sodium sulfite silver waste liquid to maintain the gas pressure in the reactor and obtain an acidic liquid; (2) Chlorine precipitation: Add bismuth trioxide to the acidic solution, then slowly add sodium hydroxide until the pH of the acidic solution rises to 5-6. Filter to obtain white bismuth oxychloride and the precipitated solution; the specific reaction process is as follows: Bi 3+ +Cl - +2OH - =BiOCl+H2O; (3) Roasting and regeneration: First, bismuth oxychloride is mixed with water, then concentrated sulfuric acid is added and mixed. After mixing, it is sent to the roasting furnace for two-stage roasting. The slag produced during the roasting process is bismuth trioxide, and the acid mist produced contains sulfur trioxide, hydrogen chloride gas and water vapor. (4) Absorption: The acid mist produced in step (3) is absorbed by 98% concentrated sulfuric acid to absorb sulfur trioxide. The tail gas produced during the absorption process is hydrogen chloride gas. (5) Condensation: Cool the hydrogen chloride gas produced in step (4) and absorb it with dilute hydrochloric acid to produce concentrated hydrochloric acid; (6) Removing impurity metals: Add sodium sulfide to the chlorine-precipitated liquid obtained in step (2) to remove copper, bismuth, selenium and tellurium from the solution, and filter to obtain sulfide slag and sulfide liquid; (7) Desulfate removal: Add barium hydroxide to the sulfidation solution obtained in step (6), filter and obtain barium sulfate precipitate and sulfate-precipitated solution; (8) Alkalization: Sodium hydroxide is added to the sulfate precipitate obtained in step (7) to adjust the pH value to 9, thereby regenerating the sodium sulfite silver precipitate waste liquid and producing regenerated sodium sulfite silver precipitate solution.

[0007] Preferably, in step (1), the composition range of the sodium sulfite silver-containing waste liquid is: Cl - ≥5g / L, sulfate 0.5~5g / L, copper, bismuth, selenium and tellurium ≤0.2g / L.

[0008] Preferably, in step (1), the gas pressure inside the reactor is 0.05-0.1 MPa, and the pH of the acidic liquid is 1.5-3.

[0009] Preferably, in step (2), the ratio of the molar amount of bismuth in the bismuth trioxide to the molar amount of chloride ions in the acidic solution is 1:1.

[0010] Preferably, in step (3), the weight ratio of bismuth oxychloride, water, and concentrated sulfuric acid is 1:0.5:0.5~0.7.

[0011] Preferably, in step (3), the specific operation of the two-stage roasting is as follows: first, a low-temperature roasting is performed at 200℃~500℃ for 0.5~1.5 hours, and then a high-temperature roasting is performed at 500℃~800℃ for 0.5~1 hour. The specific reaction process is as follows: 2BiOCl + 3H2SO4 = Bi2(SO4)3 + 2HCl + 2H2O (Temperature: 200~500℃) Bi2(SO4)3=Bi2O3+3SO3 (Temperature:>500℃).

[0012] Preferably, in step (3), the vacuum degree of the roasting atmosphere during the two-stage roasting is controlled to be 1500Pa~2000Pa.

[0013] Preferably, in step (5), the hydrogen chloride gas produced in step (4) is cooled to less than 40°C and absorbed by 5%~10% dilute hydrochloric acid to produce concentrated hydrochloric acid with a concentration of 10%~19%.

[0014] Preferably, in step (6), the method for determining the amount of sodium sulfide is as follows: prepare a 35g / L sodium sulfide solution as a determination reagent, take the solution out of the reaction vessel and filter it to obtain a clear liquid, add the determination reagent to the clear liquid, and when no more precipitation is observed, it is the endpoint, and stop adding sodium sulfide to the reaction vessel.

[0015] Preferably, in step (7), the amount of barium hydroxide used is 10 g / L of the sulfided solution; the Cl in the regenerated sodium sulfite silver separation solution... - <2g / L, SO4 2- <0.2g / L.

[0016] In step (7), barium sulfate precipitate is generated, thereby removing sulfate ions from the solution. This is based on the principle that barium sulfite (Ksp is 5.3 × 10⁻⁶) has a Ksp concentration of 5.3 × 10⁻⁶. -7 ) and barium sulfate (Ksp is 1.1×10 -10 The solubility product difference is three orders of magnitude, making it easier to form barium sulfate salts with even smaller solubility products. This allows for the preferential removal of sulfate ions from sodium sulfite solutions, thus achieving the removal of sulfate ions from silver-containing sodium sulfite solutions. The resulting barium sulfate, after drying, can be used as a release agent for copper anode plate casting.

[0017] Compared with existing technologies, this invention can remove chloride ions, copper, bismuth, selenium and other impurity metals from sodium sulfite silver separation waste liquid, achieve complete regeneration of sodium sulfite silver separation waste liquid, and the dechlorinating agent can be recycled and reused at low cost. At the same time, it can recover chloride ions in silver separation waste liquid and produce hydrochloric acid, which can be used in the wet treatment process of copper anode mud. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0019] Figure 1 This is a process flow diagram of the regeneration method of the present invention. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] Example 1 For sodium sulfite silver separation waste liquid 1m 3 The components are: Cl - :5.27g / L, Na2SO3: 163.4g / L, SO4 2- The concentrations of sodium sulfite and silver sulfite in the waste liquid are: Cu: 0.08 g / L, Bi: 0.05 g / L, Te: 0.06 g / L, Se: 0.04 g / L. The regeneration treatment of the sodium sulfite silver sulfite waste liquid should be carried out according to the following steps: (1) Acidification: Sulfur dioxide is introduced into the sodium sulfite silver separation waste liquid, and the gas pressure in the reactor is maintained at 0.05 MPa until the pH is 3 to obtain an acidic solution; (2) Chlorine precipitation: Add bismuth trioxide to the acidic solution, and then slowly add sodium hydroxide until the pH of the acidic solution rises to 6. After filtration, a white bismuth oxychloride precipitate and the chlorine precipitation solution are obtained. (3) Calcination and regeneration: Bismuth oxychloride: water: concentrated sulfuric acid = 1:0.5:0.5 by weight ratio. First, mix bismuth oxychloride with water, then add 98% concentrated sulfuric acid and mix. After mixing, send the mixture into the calcination furnace. Control the vacuum degree of the calcination atmosphere to 1500 Pa. First, perform low-temperature calcination, control the temperature to rise uniformly from 200℃ to 500℃ for 1 hour. Then, perform high-temperature calcination, control the temperature to rise gradually from 500℃ to 800℃ for 0.5 hours. The calcination process produces 38.9 kg of bismuth trioxide. The acid mist produced by calcination contains sulfur trioxide, hydrogen chloride gas and water vapor. (4) Absorption: The acid mist is absorbed by 98% concentrated sulfuric acid to absorb sulfur trioxide. The tail gas produced during the absorption process is hydrogen chloride gas. (5) Condensation: The hydrogen chloride gas is cooled to below 40°C and absorbed by a 1m circulatory system using 6% dilute hydrochloric acid. 3 Afterwards, 1.08m was produced. 3 Concentrated hydrochloric acid with a concentration of 10.6%; (6) Removal of impurity metals: Sodium sulfide is added to the chlorine-precipitated liquid. The method and amount of sodium sulfide added are as follows: Prepare a sodium sulfide solution (35 g / L) as a test reagent. Take the solution out of the reactor and filter it to obtain a clear liquid. Add the test reagent to the clear liquid. When no more precipitation is observed, it is the endpoint, indicating that the sodium sulfide has been added in sufficient quantity and no more is added. After the sodium sulfide is added to the endpoint, filter out the sulfide slag and the sulfide-treated liquid. The sulfide slag contains 7.27% copper, 3.53% bismuth, 3.52% selenium, 2.15% tellurium, and 8.96% silver. The composition of the sulfide-treated liquid is: 0.03 g / L copper, 0.006 g / L bismuth, 0.001 g / L selenium, 0.001 g / L tellurium, and 0.001 g / L silver. (7) Desulfate removal: Add barium hydroxide to the sulfidation liquid. The amount of barium hydroxide is 10 kg per cubic meter of sulfidation liquid. After filtration, barium sulfate precipitate and sulfate-precipitated liquid are obtained, with a sulfate content of 0.17 g / L. (8) Alkalization: Sodium hydroxide is added to the solution after sulfate precipitation to adjust the pH to 9, thereby regenerating the sodium sulfite silver separation waste liquid and producing 0.86m of regenerated sodium sulfite silver separation solution. 3 The composition of the regenerated sodium sulfite silver solution is Cl. - : 1.3 g / L, sulfate: 0.17 g / L, copper, bismuth, selenium, and tellurium are all <0.01 g / L.

[0022] The regenerated sodium sulfite silver separation solution obtained after treatment using the method in Example 1 can be recycled as a silver separation mother liquor. This effectively removes impurities from the mother liquor, achieving regeneration of waste sodium sulfite wastewater, reducing the discharge of waste sodium sulfite silver separation wastewater, minimizing the environmental risks associated with chloride-containing waste salts, and avoiding the loss of precious metals carried over in the wastewater. Bismuth trioxide is regenerable and recyclable. During the recycling process, chloride ions in the waste sodium sulfite silver separation mother liquor are treated to ultimately form dilute hydrochloric acid, which can be returned to the precious metal recovery process, avoiding the risk of chloride ion discharge into the wastewater.

[0023] Comparative Example 1 The treatment process was the same as in Example 1, involving the treatment of sodium sulfite silver-containing waste liquid. Using conventional methods, the sodium sulfite silver-containing waste liquid underwent deep reduction with formaldehyde and was subsequently disposed of as waste. The resulting chlorine- and sodium-containing wastewater was distilled to produce 178 kg of chlorine- and sodium sulfite-containing waste salt. This waste salt contained approximately 0.3% arsenic and was classified as hazardous solid waste, requiring disposal in a dedicated hazardous waste disposal site, which incurred high disposal costs.

[0024] Example 2 For sodium sulfite silver separation waste liquid 1m 3 The component is Cl. - :36.4g / L, Na2SO3: 147.4g / L, SO4 2-The concentrations of sodium sulfite and silver sulfite in the waste liquid are: 4.88 g / L, Cu: 0.13 g / L, Bi: 0.2 g / L, Te: 0.08 g / L, Se: 0.07 g / L. The regeneration treatment of the sodium sulfite silver sulfite waste liquid should be carried out according to the following steps: (1) Acidification: Sulfur dioxide is introduced into the sodium sulfite silver separation waste liquid, and the gas pressure in the reactor is maintained at 0.1 MPa until the pH is 1.5 to obtain an acidic solution; (2) Chlorine precipitation: Add bismuth trioxide to the acidic solution, and then slowly add sodium hydroxide until the pH of the acidic solution rises to 5. After filtration, a white bismuth oxychloride precipitate and chlorine precipitation solution are obtained.

[0025] (3) Calcination and regeneration: Bismuth oxychloride: water: concentrated sulfuric acid = 1:0.5:0.7 by weight ratio, first mix bismuth oxychloride with water, then add concentrated sulfuric acid and mix. After mixing, send it into the calcination furnace. Control the vacuum degree of the calcination atmosphere to 2000 Pa. First, perform low-temperature calcination, control the temperature to rise uniformly from 200℃ to 500℃ for 0.5 hours, and then perform high-temperature calcination, control the temperature to rise gradually from 500℃ to 800℃ for 1 hour. The calcination process produces 241.4 kg of bismuth trioxide. The acid mist produced by calcination contains sulfur trioxide, hydrogen chloride gas and water vapor. (4) Absorption: The acid mist is absorbed by 98% concentrated sulfuric acid to absorb sulfur trioxide. The tail gas produced during the absorption process is hydrogen chloride gas. (5) Condensation: The hydrogen chloride gas is cooled to below 40°C and absorbed by a 10% dilute hydrochloric acid cycle for 1m. 3 Afterwards, 1.32m was produced. 3 Concentrated hydrochloric acid with a concentration of 18.1%; (6) Removal of impurity metals: Sodium sulfide is added to the chlorinated liquid. The method and amount of sodium sulfide added are as follows: First, a prepared sodium sulfide solution (35 g / L) is used as a test reagent. The solution is taken out from the reactor and filtered to obtain a clear liquid. The test reagent is added dropwise to the clear liquid. When no more precipitation is observed, the endpoint is reached, indicating that the sodium sulfide has been added in sufficient quantity and no more is added. After the sodium sulfide is added to the endpoint, the sulfide slag and the sulfide liquid are filtered out. The sulfide slag contains 11.72% copper, 7.32% bismuth, 6.27% selenium, 7.65% tellurium, and 6.96% silver. The composition of the sulfide liquid is: 0.02 g / L copper, 0.05 g / L bismuth, 0.001 g / L selenium, 0.001 g / L tellurium, and 0.001 g / L silver. (7) Desulfate removal: Add barium hydroxide to the sulfidation liquid. The amount of barium hydroxide is 10 kg per cubic meter of sulfidation liquid. After filtration, barium sulfate precipitate and sulfate-precipitated liquid are obtained. The sulfate content is 0.18 g / L. (8) Alkalization: Sodium hydroxide is added to the solution after sulfate precipitation to adjust the pH to 9, thereby regenerating the sodium sulfite silver separation waste liquid and producing 0.89m of regenerated sodium sulfite silver separation solution.3 The composition of the regenerated sodium sulfite silver solution is Cl. - : 1.1 g / L, sulfate 0.12 g / L, copper, bismuth, selenium, and tellurium are all <0.01 g / L.

[0026] The regenerated sodium sulfite silver-removing solution obtained after treatment according to the method in Example 2 can be recycled as a silver-removing mother liquor, realizing the regeneration treatment of waste sodium sulfite wastewater, reducing the discharge of waste sodium sulfite silver-removing wastewater, reducing the environmental risks of chloride-containing waste salts, and avoiding the loss of precious metals entrained in the wastewater. Bismuth trioxide is regenerable and recyclable. During the recycling process, chloride ions in the waste sodium sulfite silver-removing mother liquor are treated to ultimately form dilute hydrochloric acid, which can be returned to the precious metal recovery process, avoiding the risk of chloride ion discharge in wastewater.

[0027] Comparative Example 2 The treatment process was the same as in Example 2, involving the treatment of sodium sulfite silver-containing waste liquid. Using conventional methods, the sodium sulfite silver-containing waste liquid underwent deep formaldehyde reduction followed by complete disposal. The resulting chlorine- and sodium-containing wastewater was distilled to produce 162 kg of chlorine- and sodium sulfite-containing waste salt. This waste salt contained approximately 0.4% arsenic and was classified as hazardous solid waste, requiring disposal at a dedicated hazardous waste disposal site, which incurred high costs.

[0028] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for regenerating waste mother liquor from sodium sulfite silver separation, characterized in that, Includes the following steps: (1) Acidification: In a closed reactor, sulfur dioxide is introduced into the sodium sulfite silver waste liquid to maintain the gas pressure in the reactor and obtain an acidic liquid; (2) Chlorine precipitation: Add bismuth trioxide to the acidic solution, and then slowly add sodium hydroxide until the pH of the acidic solution rises to 5-6. Filter to obtain white bismuth oxychloride and chlorine precipitation solution. (3) Roasting and regeneration: First, bismuth oxychloride is mixed with water, then concentrated sulfuric acid is added and mixed. After mixing, it is sent to the roasting furnace for two-stage roasting. The slag produced during the roasting process is bismuth trioxide, and the acid mist produced contains sulfur trioxide, hydrogen chloride gas and water vapor. (4) Absorption: The acid mist produced in step (3) is absorbed by 98% concentrated sulfuric acid to absorb sulfur trioxide. The tail gas produced during the absorption process is hydrogen chloride gas. (5) Condensation: Cool the hydrogen chloride gas produced in step (4) and absorb it with dilute hydrochloric acid to produce concentrated hydrochloric acid; (6) Removing impurity metals: Add sodium sulfide to the chlorine-precipitated liquid obtained in step (2) to remove copper, bismuth, selenium and tellurium from the solution, and filter to obtain sulfide slag and sulfide liquid; (7) Desulfate removal: Add barium hydroxide to the sulfidation solution obtained in step (6), filter and obtain barium sulfate precipitate and sulfate-precipitated solution; (8) Alkalization: Sodium hydroxide is added to the sulfate precipitate obtained in step (7) to adjust the pH value to 9, thereby regenerating the sodium sulfite silver precipitate waste liquid and producing regenerated sodium sulfite silver precipitate solution.

2. The method for regenerating waste mother liquor from sodium sulfite silver separation according to claim 1, characterized in that, In step (1), the composition range of the sodium sulfite silver separation waste liquid is: Cl - ≥5g / L, sulfate 0.5~5g / L, copper, bismuth, selenium and tellurium ≤0.2g / L.

3. The method for regenerating waste mother liquor from sodium sulfite silver separation according to claim 1, characterized in that, In step (1), the gas pressure inside the reactor is 0.05-0.1 MPa, and the pH of the acidic liquid is 1.5-3.

4. The method for regenerating waste mother liquor from sodium sulfite silver separation according to claim 1, characterized in that, In step (2), the ratio of the molar amount of bismuth in the bismuth trioxide to the molar amount of chloride ions in the acidic solution is 1:

1.

5. The method for regenerating waste mother liquor from sodium sulfite silver separation according to claim 1, characterized in that, In step (3), the weight ratio of bismuth oxychloride, water, and concentrated sulfuric acid is 1:0.5:0.5~0.

7.

6. The method for regenerating waste mother liquor from sodium sulfite silver separation according to claim 1, characterized in that, In step (3), the specific operation of the two-stage roasting is as follows: first, the low-temperature stage is roasted at 200℃~500℃ for 0.5~1.5 hours, and then the high-temperature stage is roasted at 500℃~800℃ for 0.5~1 hours.

7. The method for regenerating waste mother liquor from sodium sulfite silver separation according to claim 1, characterized in that, In step (3), the vacuum degree of the roasting atmosphere is controlled to be 1500Pa~2000Pa during the two-stage roasting.

8. The method for regenerating waste mother liquor from sodium sulfite silver separation according to claim 1, characterized in that, In step (5), the hydrogen chloride gas produced in step (4) is cooled to less than 40°C and absorbed by 5%~10% dilute hydrochloric acid to produce concentrated hydrochloric acid with a concentration of 10%~19%.

9. The method for regenerating waste mother liquor from sodium sulfite silver separation according to claim 1, characterized in that, In step (6), the method for determining the amount of sodium sulfide is as follows: prepare a 35g / L sodium sulfide solution as a determination reagent, take the solution out of the reaction vessel and filter it to obtain a clear liquid, add the determination reagent to the clear liquid, and when no more precipitation is observed, it is the endpoint, and stop adding sodium sulfide to the reaction vessel.

10. A method for regenerating waste mother liquor from sodium sulfite silver separation according to claim 1, characterized in that, In step (7), the amount of barium hydroxide used is 10 g / L of the sulfided solution; the Cl in the regenerated sodium sulfite silver separation solution... - <2g / L, SO4 2- <0.2g / L.

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