A process for the extraction and separation of zinc and cadmium

Abstract

The application belongs to the field of hydrometallurgy, and particularly discloses a method for extracting and separating zinc and cadmium, which comprises the following steps: mixing a solution containing zinc and cadmium to be separated with an extraction organic phase to obtain a zinc-loaded organic phase and a cadmium-containing raffinate; the extraction active component in the extraction organic phase comprises component A and component B in a volume ratio of 1:2.5-5.5; wherein, the component A is a compound of formula 1; the component B is a compound of formula 2; and the pH of the extraction process is 1-5.5. The application has the advantages of good zinc-cadmium separation effect, high recovery rate, simple process and the like.

Description

Technical Field

[0001] This invention belongs to the field of hydrometallurgical technology, specifically relating to the extraction and separation of zinc and cadmium. Background Technology

[0002] In the fields of copper smelting flue dust, smelting tailings treatment, and waste zinc-cadmium battery recycling, acidic zinc-cadmium solutions with similar zinc and cadmium concentrations are often generated during the separation and extraction of valuable metals. Zinc and cadmium are adjacent elements in the periodic table, and their similar properties in solution make them difficult to separate. Current methods for separating zinc and cadmium in solution mainly include zinc powder displacement, concentration crystallization, and selective precipitation.

[0003] For example, patent document CN121380564A discloses a method for selectively separating zinc and cadmium in a zinc-cadmium solution that is difficult to separate due to low concentration difference. The method involves co-precipitating the zinc-cadmium solution with an alkaline precipitant to obtain a co-precipitated residue enriched with zinc and cadmium. The co-precipitated residue is then slurried with water, and the pH of the slurry is controlled at 6-7.1 for selective cadmium dissolution. Subsequently, solid-liquid separation is performed to obtain zinc-rich slag and cadmium-rich leachate.

[0004] For example, patent document CN116004991A discloses a method for separating and recovering zinc, cadmium, and cobalt from zinc smelting residue, comprising the following steps: S1, feeding zinc smelting residue into a reaction tank, adding waste electrolyte to adjust the acid for leaching, and heating to fully leach zinc, cadmium, and cobalt from the residue; S2, adding zinc slag to replace and remove cadmium; S3, using a filter press for liquid-solid separation to obtain sponge cadmium residue and filtrate, the sponge cadmium residue entering the cadmium recovery process; S4, adding NaOH solution to the filtrate obtained after filtration in step S4 to adjust the pH; S5, adding reagent A for reaction; reagent A includes sodium thiram; S6, adding reagent B for reaction to remove cobalt; reagent B includes sodium nitrite; S7, using a filter press for liquid-solid separation to obtain cobalt residue.

[0005] Patent document CN103468963A discloses a method for crystallizing and separating zinc and cadmium from zinc-containing waste residue, which includes the following steps: S1. Raw material slurrying; S2. Neutral leaching; S3. Filtration; S4. Germanium precipitation; S5. Indium precipitation; S6. Copper precipitation; S7. Concentration crystallization; S8. Electrode enrichment.

[0006] Zinc powder displacement is a simple process for cadmium removal, but it is only suitable for treating high-zinc, low-cadmium solutions. Concentration and crystallization are only effective for solutions with high zinc and low cadmium or high cadmium and low zinc concentrations. When dealing with zinc and cadmium solutions of similar concentrations, both will precipitate simultaneously during concentration, making effective separation impossible. Selective precipitation can only achieve coarse separation of zinc and cadmium.

[0007] Extraction methods are simple to operate and easy to apply industrially. However, for zinc and cadmium solutions, the properties of the two elements are similar, making it difficult to achieve efficient and highly selective extraction and separation of zinc and cadmium based on extraction methods. Summary of the Invention

[0008] To address the problems existing in the current separation and extraction of zinc and cadmium under near-concentration systems, the present invention aims to provide a method for extracting and separating zinc and cadmium, which is designed to effectively separate and extract zinc and cadmium from the solution, thereby achieving efficient separation and recovery of both.

[0009] A method for extracting and separating zinc and cadmium involves mixing a solution containing zinc and cadmium to be separated with an extractive organic phase for extraction, thereby obtaining a zinc-loaded organic phase and a cadmium-containing raffinate.

[0010] The extractable active ingredients in the extracted organic phase include component A and component B in a volume ratio of 1:2.5~5.5; wherein component A is a compound of formula 1; and component B is a compound of formula 2.

[0011] The pH range for the extraction process is 1 to 5.5;

[0012] Formula 1

[0013] Formula 2

[0014] In Equation 1, R1 is C6~C 14 Alkyl group; R2 is C6~C 14 The alkyl or alkoxy group; M is at least one of hydrogen ion, sodium ion, potassium ion, ammonium ion, and cadmium ion, and m is the valence number of M;

[0015] In Formula 2, R3 is H or a hydroxyl group; R4 is H, a C1-C6 alkyl group, a C1-C6 alkoxy group, a halogen, or an amino group; R5 is H or a C1-C3 alkyl group; N is at least one of hydrogen ion, sodium ion, potassium ion, ammonium ion, and cadmium ion, and n is the valence number of N.

[0016] To address the problem that zinc and cadmium have similar properties and are difficult to extract and separate efficiently and selectively, this invention innovatively uses a combination of extractants from Formula 1 and Formula 2 for joint extraction. By coordinating the ratio of the two extractants and controlling the extraction pH, a synergistic effect is unexpectedly achieved, enabling efficient and highly selective extraction and separation of zinc and cadmium.

[0017] In this invention, the solution to be separated is a sulfuric acid solution of zinc and cadmium. For example, it can be a sulfuric acid leachate containing solid components such as slag or minerals containing zinc and cadmium.

[0018] In this invention, there are no special requirements for the concentrations of zinc ions and cadmium ions in the solution to be separated. For example, the concentration of zinc ions is 0.4~25 g / L; the concentration ratio of zinc ions to cadmium ions is 1:0.5~1.5.

[0019] In this invention, for the objects to be separated with similar zinc and cadmium concentrations, especially for objects with similar cadmium concentrations (zinc ion to cadmium ion concentration ratio of 1:1 to 1.5), the process described in this invention can also achieve the expected separation efficiency and selectivity.

[0020] In this invention, the pH of the solution to be separated can be controlled to be between 1.5 and 5 before extraction.

[0021] In this invention, the alkyl group in Formula 1 and Formula 2 can be a straight-chain or branched alkyl group.

[0022] In this invention, in component A, R1 is C7~C 10 Alkyl group; R2 is C7~C 10 The alkyl or alkoxy group; M is Cd.

[0023] In this invention, Formula 2 is Formula 2A;

[0024] Formula 2A

[0025] In Formula 2A, R3 is a hydroxyl group; R4 is H, a C1-C3 alkyl group, or a C1-C3 alkoxy group; R5 is H or a methyl group; and N is Cd.

[0026] In this invention, the extracted organic phase also contains a hydrophobic diluent;

[0027] Preferably, the hydrophobic diluent includes at least one of sulfonated kerosene, No. 200 solvent oil, and aviation kerosene.

[0028] In this invention, the volume content of component A in the extracted organic phase is 5% to 25%.

[0029] Preferably, in the extracted organic phase, the volume ratio of component A to component B is 1:3~5.

[0030] Furthermore, in the extracted organic phase, the volume content of the extracted active ingredient can be 25-85%, and more specifically, 30-80%.

[0031] In this invention, the pH regulator used to control the pH during the extraction process includes one or more of sodium hydroxide, sodium carbonate, ammonium carbonate, ammonia, calcium hydroxide, calcium oxide, magnesium hydroxide, and magnesium oxide.

[0032] The O / A volume ratio during the extraction process is 1:2~0.2.

[0033] The extraction process is carried out at a temperature of 15~50℃, and can be further carried out at 30~40℃.

[0034] In this invention, zinc and cadmium can be recovered from the zinc-loaded organic phase and the cadmium-containing raffinate, respectively, using known methods.

[0035] For example, as an optional method, the zinc-loaded organic phase is back-extracted using an acid solution to obtain a zinc-rich back-extraction solution, which is then evaporated to obtain the zinc product. The acid solution can be a sulfuric acid solution.

[0036] In this invention, cadmium-containing raffinate can be treated with an organic phase containing component C to obtain a cadmium-loaded organic phase. Then, the cadmium-loaded organic phase is back-extracted with acid to obtain a cadmium-rich raffinate. The cadmium-rich raffinate is then evaporated to obtain a cadmium product.

[0037] Component C is a compound of formula 3;

[0038] Formula 3

[0039] The selection ranges of R1 and R2 in Equation 3 are the same as those in Equation 1.

[0040] In an organic phase containing component C, the volume content of component C can be 5% to 30%.

[0041] Furthermore, the conditions for cadmium extraction can be adjusted as needed; for example, the O / A ratio for extraction can be 1:2 to 3:1.

[0042] Beneficial effects

[0043] This invention innovatively employs a combined extractant of Formula 1 and Formula 2 for joint extraction. By coordinating the ratio of the two extractants and controlling the extraction pH, a synergistic effect is unexpectedly achieved, enabling efficient and highly selective extraction and separation of zinc and cadmium. Detailed Implementation

[0044] The following examples are intended to illustrate the present invention, and not to further limit the scope of protection of the present invention.

[0045] The method for extracting and separating zinc and cadmium in a solution containing zinc and cadmium as described in this invention includes the following steps:

[0046] (1) Solution modification: Add alkali to an acidic zinc-cadmium solution to adjust the pH of the solution to 1~5.5 to obtain a modified solution;

[0047] The alkali mentioned is one or more of sodium hydroxide, sodium carbonate, ammonium carbonate, ammonia, calcium hydroxide, calcium oxide, magnesium hydroxide, and magnesium oxide.

[0048] (2) Selective extraction of zinc: The modified solution is mixed with an organic phase O containing a certain proportion of component A and component B to selectively extract zinc, resulting in an organic phase O1 loaded with zinc and a cadmium-containing raffinate.

[0049] Organic phase O1 is subjected to 2-4 stages of countercurrent back-extraction with 150-200 g / L sulfuric acid solution at a flow ratio (organic phase to aqueous phase) of 1:3-3:1 to obtain back-extracted zinc sulfate solution and back-extracted organic phase O1'. The back-extracted solution is then concentrated by evaporation to prepare zinc sulfate product, and the back-extracted organic phase O1' is recycled back to the zinc extraction process for reuse.

[0050] In the organic phase O, the volume percentage concentration of component A is 5% to 25%.

[0051] The aforementioned proportions of component A and component B refer to the mixing of component A and component B at a volume ratio of 1:2.5~5.5;

[0052] The organic phase O also contains a diluent; the diluent is at least one of sulfonated kerosene, No. 200 solvent oil, and aviation kerosene.

[0053] The selective extraction refers to 3 to 8 stages of countercurrent extraction under a flow ratio (organic to aqueous phase) of 1:2 to 0.2.

[0054] (3) Preparation of cadmium products:

[0055] The cadmium-containing raffinate is subjected to 3-6 stages of countercurrent extraction with an organic phase O2 containing a certain proportion of carbon at a flow ratio of 1:2-3:1 to obtain a cadmium-loaded organic phase O2'. After washing the organic phase O2', it is subjected to 2-4 stages of countercurrent back-extraction with a 50-120 g / L sulfuric acid solution at a flow ratio of 1:2-2:1 to obtain a cadmium-containing back-extraction solution and a back-extracted organic phase O2''. The cadmium-containing back-extraction solution is concentrated by evaporation to prepare cadmium sulfate product, and the back-extracted organic phase O2'' is recycled back to the cadmium extraction process for reuse.

[0056] The organic phase O2 also contains a diluent; the diluent is at least one of sulfonated kerosene, No. 200 solvent oil, and aviation kerosene.

[0057] In the organic phase O2, the volume percentage concentration of component C is 5%~30%, and the remainder is a diluent.

[0058] Example 1

[0059] Step 1: Using the acidic zinc and cadmium-containing solution generated during the comprehensive utilization of copper smelting flue dust as raw material, the solution contains 23.4 g / L of Zn, 31.8 g / L of Cd, and has a pH of 0.1.

[0060] Take 5L of the above solution, add calcium oxide and stir to adjust the pH of the solution to 1.5, then mix with the zinc extraction organic phase O, and perform 8-stage countercurrent extraction at 40℃ and O / A flow ratio of 1:1 to obtain zinc-loaded organic phase O1 and raffinate L1.

[0061] The zinc extraction organic phase O comprises an extraction active ingredient and a diluent in a volume ratio of 80:20; the extraction active ingredient comprises component A and component B in a volume ratio of 1:3.

[0062] Component A is represented by formula 1a: ;

[0063] Component B is represented by formula 2a: ;

[0064] Step 2:

[0065] After washing the zinc-loaded organic phase O1, it was subjected to a two-stage countercurrent back-extraction with 200 g / L sulfuric acid solution at an O / A flow ratio of 3:1 to obtain the back-extracted organic phase O1' and the back-extract solution. The back-extract solution was evaporated and crystallized to obtain zinc sulfate monohydrate product, whose quality meets the requirements of superior grade in HG / T2326-2015. During the extraction process, the zinc extraction rate was 99.1%, and the cadmium extraction rate was 0.5%.

[0066] Step 3:

[0067] The cadmium-containing extract L1 was mixed with the cadmium-containing organic phase and subjected to three-stage countercurrent extraction at an O / A ratio of 3:1 to obtain the cadmium-loaded organic phase O2'. After washing the organic phase O2', it was subjected to two-stage countercurrent back-extraction with 120 g / L sulfuric acid solution at an O / A ratio of 2:1 to obtain the cadmium-containing back-extraction solution and the back-extraction organic phase O2''.

[0068] The organic phase of the cadmium extraction comprises component C and sulfonated kerosene in a volume ratio of 3:7;

[0069] Wherein, component C is from formula 3a ( );

[0070] Cadmium sulfate (8 / 3 hydrate) was prepared by evaporation and concentration of the cadmium-containing back-extraction solution, and its quality met the requirements of GB 1286-1977. The cadmium recovery rate during the extraction and back-extraction process was 98.9%.

[0071] Comparative Example 1

[0072] Compared with Example 1, the only difference is that the organic phase O used for zinc extraction in step 1 is changed. The experimental groups are as follows:

[0073] Group A: In the zinc extraction organic phase O, only component B is missing. The amount of component A and other operations and parameters are the same as in Example 1.

[0074] The zinc extraction rate was 58.6%, and the cadmium extraction rate was 56.9%.

[0075] Group B: In the zinc extraction organic phase O, component B is missing, and the missing component B is supplemented by an equal volume of component A, so that the volume content of the extracted active ingredient is still 80%; other operations and parameters are the same as in Example 1.

[0076] The zinc extraction rate was 92.4%, and the cadmium extraction rate was 91.9%.

[0077] Comparative Example 2

[0078] Compared with Example 1, the only difference is that the organic phase O used for zinc extraction in step 1 is changed. The experimental groups are as follows:

[0079] Group A: In the zinc extraction organic phase O, component A is missing, while the amount of component B and other operations and parameters are the same as in Example 1;

[0080] During the extraction process, the zinc extraction rate was 0.5% and the cadmium extraction rate was 0.2%.

[0081] Group B: In the zinc extraction organic phase O, component A is missing, and the missing component A is supplemented by component B in equal volume, so that the volume content of the extracted active ingredient is still 80%; other operations and parameters are the same as in Example 1.

[0082] The zinc extraction rate was 0.38%, and the cadmium extraction rate was 0.14%.

[0083] Comparative Example 3

[0084] Compared with Example 1, the only difference is that in step 1, the total content of the extracted active ingredients remains unchanged by controlling the zinc extraction organic phase O, and the volume ratio of component A to component B is controlled at 1:2; other operations and parameters are the same as in Example 1.

[0085] The zinc extraction rate was 87.7%, and the cadmium extraction rate was 49.5%.

[0086] Comparative Example 4

[0087] Compared with Example 1, the only difference is that in step 1, the pH of the extraction process is 0.1, and all other operations and parameters are the same as in Example 1.

[0088] During the extraction process, the zinc extraction rate was 4.1%, and the cadmium extraction rate was 0.13%.

[0089] Comparative Example 5

[0090] Compared with Example 1, the only difference is that the structure of component B in the zinc extraction organic phase O of step 1 is changed. Specifically, comparative formula a ( Replace component B with an equal volume;

[0091] All other operations and parameters are the same as in Example 1.

[0092] During the extraction process, the zinc extraction rate was 94.1%, and the cadmium extraction rate was 10.8%. It is evident that the combination of components A and B in this application unexpectedly achieves synergy, enhancing the selective extraction and separation of zinc and cadmium.

[0093] Example 2

[0094] The solution obtained by removing other impurities from the leachate of waste zinc-cadmium batteries was used as raw material. The solution contained 14.2 g / L of Zn, 9.1 g / L of Cd, and had a pH of 3.5.

[0095] Take 5L of the above solution and mix it with component A (Formula 1b) which has a composition of 10%. )+40% component B (Formula 2b: The organic phase of zinc sulfate was mixed with 50% of No. 200 solvent oil and subjected to three-stage countercurrent extraction at 15℃ and an O / A flow ratio of 1:2 to obtain a zinc-loaded organic phase O1 and raffinate L1. After washing the zinc-loaded organic phase O1, it was subjected to four-stage countercurrent back-extraction with 150 g / L sulfuric acid solution at an O / A flow ratio of 1:3 to obtain a back-extracted organic phase O1' and back-extract. The back-extract was evaporated and crystallized to obtain zinc sulfate monohydrate, which met the requirements of superior grade HG / T2326-2015. During the extraction process, the zinc extraction rate was 99.3%, and the cadmium extraction rate was 0.4%.

[0096] The cadmium-containing extract L1 was mixed with an organic phase consisting of 15% component C (Formula 1b) + 85% No. 200 solvent oil. A six-stage countercurrent extraction was performed at an O / A flow ratio of 1:1 to obtain a cadmium-loaded organic phase O2'. After washing the organic phase O2', a four-stage countercurrent back-extraction was performed using a 50 g / L sulfuric acid solution at an O / A flow ratio of 1:2 to obtain a cadmium-containing back-extraction solution and the back-extracted organic phase O2''. The cadmium-containing back-extraction solution was concentrated by evaporation to prepare cadmium sulfate (8 / 3 hydrate) product, whose quality met the requirements of GB 1286-1977. The cadmium recovery rate during the extraction and back-extraction processes was 98.4%.

[0097] Example 3

[0098] The acidic leachate from copper smelting tailings was used as raw material. The solution contained 0.4 g / L of Zn, 0.6 g / L of Cd, and had a pH of 0.3.

[0099] Take 5L of the above solution, add sodium hydroxide and stir to adjust the pH of the solution to 5.0, then mix with a solution containing 5% component A (Formula 1a) + 25% component B (Formula 2c). The organic phase of zinc sulfate (O1) was mixed with 70% aviation kerosene and subjected to 8-stage countercurrent extraction at an O / A flow ratio of 5:1 to obtain a zinc-loaded organic phase O1 and raffinate L1. After washing the zinc-loaded organic phase O1, it was subjected to 4-stage countercurrent back-extraction with 180 g / L sulfuric acid solution at an O / A flow ratio of 2:1 to obtain a back-extracted organic phase O1' and back-extract solution. The back-extract solution was evaporated and crystallized to obtain zinc sulfate monohydrate, which met the requirements of superior grade HG / T2326-2015. During the extraction process, the zinc extraction rate was 98.2%, and the cadmium extraction rate was 0.12%.

[0100] The cadmium-containing extract L1 was mixed with an organic phase consisting of 5% component C (Formula 3a) + 95% sulfonated kerosene, and subjected to a 6-stage countercurrent extraction at an O / A flow ratio of 1:1 to obtain a cadmium-loaded organic phase O2'. After washing the organic phase O2', a 4-stage countercurrent back-extraction was performed using a 100 g / L sulfuric acid solution at an O / A flow ratio of 1:2 to obtain a cadmium-containing back-extraction solution and the back-extracted organic phase O2''. The cadmium-containing back-extraction solution was evaporated and concentrated to prepare cadmium sulfate (8 / 3 hydrate) product, the quality of which met GB 1286-1977. The cadmium recovery rate during the extraction and back-extraction processes was 97.8%.

Claims

1. A method for extracting and separating zinc and cadmium, characterized in that, The solutions containing zinc and cadmium to be separated are mixed with the extracting organic phase for extraction, resulting in a zinc-loaded organic phase and a cadmium-containing raffinate. The extractable active ingredients in the extracted organic phase include component A and component B in a volume ratio of 1:2.5~5.5; wherein component A is a compound of formula 1; and component B is a compound of formula 2. The pH range for the extraction process is 1 to 5.5; Formula 1 Formula 2 In Equation 1, R1 is C6~C 14 Alkyl group; R2 is C6~C 14 The alkyl or alkoxy group; M is at least one of hydrogen ion, sodium ion, potassium ion, ammonium ion, and cadmium ion, and m is the valence number of M; In Formula 2, R3 is H or a hydroxyl group; R4 is H, a C1-C6 alkyl group, a C1-C6 alkoxy group, a halogen, or an amino group; R5 is H or a C1-C3 alkyl group; N is at least one of hydrogen ion, sodium ion, potassium ion, ammonium ion, and cadmium ion, and n is the valence number of N.

2. The method for extracting and separating zinc and cadmium as described in claim 1, characterized in that, The solution to be separated is a sulfuric acid solution of zinc and cadmium.

3. The method for extracting and separating zinc and cadmium as described in claim 2, characterized in that, In the solution to be separated, the concentration of zinc ions is 0.3~25 g / L; the concentration ratio of zinc ions to cadmium ions is 1:0.5~1.

5.

4. The method for extracting and separating zinc and cadmium as described in claim 1, characterized in that, In component A, R1 is C7~C 10 Alkyl group; R2 is C7~C 10 The alkyl or alkoxy group; M is Cd.

5. The method for extracting and separating zinc and cadmium as described in claim 1, characterized in that, Equation 2 is Equation 2A; Formula 2A In Formula 2A, R3 is a hydroxyl group; R4 is H, a C1-C3 alkyl group, or a C1-C3 alkoxy group; R5 is H or a methyl group; and N is Cd.

6. The method for extracting and separating zinc and cadmium as described in claim 1, characterized in that, The extracted organic phase also contains a hydrophobic diluent; Preferably, the hydrophobic diluent includes at least one of sulfonated kerosene, No. 200 solvent oil, and aviation kerosene.

7. The method for extracting and separating zinc and cadmium as described in claim 6, characterized in that, In the extracted organic phase, the volume content of component A is 5% to 25%.

8. The method for extracting and separating zinc and cadmium as described in claim 1, characterized in that, pH regulators used to control pH during the extraction process include one or more of the following: sodium hydroxide, sodium carbonate, ammonium carbonate, ammonia, calcium hydroxide, calcium oxide, magnesium hydroxide, and magnesium oxide. The O / A volume ratio during the extraction process is 1:2~0.2; The extraction process is carried out at a temperature of 15~50℃.

9. The method for extraction and separation of zinc and cadmium according to any one of claims 1 to 8, characterized in that, The zinc-loaded organic phase was back-extracted with acid to obtain a zinc-rich back-extracting solution, which was then evaporated to obtain the zinc product.

10. The method for extraction and separation of zinc and cadmium according to any one of claims 1 to 8, characterized in that, The cadmium-containing raffinate is subjected to cadmium extraction treatment with an organic phase containing component C to obtain a cadmium-loaded organic phase. Subsequently, the cadmium-loaded organic phase is back-extracted with acid to obtain a cadmium-rich raffinate. The cadmium-rich raffinate is then evaporated to obtain the cadmium product. Component C is a compound of formula 3; Formula 3 The selection ranges of R1 and R2 in Equation 3 are the same as those in Equation 1.

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