Process for recovering refined tin from tin-containing material

Abstract

The invention discloses a process for recovering refined tin from a tin-containing material, which comprises the following steps: acid leaching: leaching the tin-containing material by using a first acid solution to obtain a leachate; a reducing agent is added into the leaching solution, ferric iron in the leaching solution is reduced into ferrous iron, then an extracting agent is added for extraction, and the tin element is extracted to enter an organic phase; a second acid solution is added into the organic phase for reverse extraction, and tin-rich reverse extraction liquid is obtained; and electrolytic refining is conducted, specifically, the tin-rich strip liquor is electrolyzed, and refined tin is obtained. According to the method, the tin-containing material can be fully utilized, the leaching rate of tin is high, the purity of tin in the finally produced tin product is larger than or equal to 99.9%, high-efficiency conversion from the tin-containing material to the high-purity tin product is achieved, and good economic value and application prospects are achieved.

Description

Technical Field

[0001] This invention relates to the field of tin recycling technology, and more specifically to a process for recovering refined tin from tin-containing materials. Background Technology

[0002] Tin is widely used in electronic solders, tinplate, alloys, and chemicals. Smelting waste from tin-containing materials such as lead concentrate and intermediate leaching mud is a significant source of tin. However, current technologies for tin recovery from tin-containing materials still face numerous technical challenges, limiting practical applications. Firstly, pretreatment technologies are limited and have poor adaptability to complex phases: for example, conventional sulfuric acid leaching processes have extremely low leaching rates for tin tightly encapsulated in lead sulfate or existing in crystalline SnO2 form. While some patented technologies propose roasting pretreatment, these methods are energy-intensive, may generate harmful fumes, and risk tin volatilization, hindering green and low-carbon production. Secondly, leaching systems lack specificity and selectivity: existing processes mostly focus on simple acid leaching, resulting in low tin concentrations in the leachate, which often coexists with large amounts of impurity ions such as lead, iron, copper, and arsenic, placing a significant burden on subsequent separation and purification. Although some patents have attempted to use alkaline leaching systems, they face new challenges such as high reagent consumption, strong corrosiveness to equipment, and complex processing procedures for coexisting metals like lead. Furthermore, the extraction and back-extraction processes have inherent technical bottlenecks: despite using extractants such as P204 to extract Sn from acidic media... 4+ It is already an industry consensus, but existing patented technologies are generally limited by two core challenges: one is Fe 3+ While impurities such as Sn can be pretreated, they increase process complexity and are difficult to completely separate during continuous operation, still interfering with extraction; and more importantly, Sn... 4+ -P204 complexes are extremely stable, resulting in low back-extraction efficiency. They often require high concentrations of strong alkalis or complex reagents under harsh conditions, which can easily cause aging of the extractant, difficulty in phase separation, and the generation of large amounts of difficult-to-treat back-extraction wastewater.

[0003] In summary, existing patented technologies generally suffer from technical challenges when processing complex tin-containing materials, especially tin-containing lead sludge, including incomplete pretreatment, poor leaching selectivity, low efficiency in extraction and back-extraction processes, and incomplete processes, making it difficult to directly obtain high-purity and high-value-added refined tin ingots. Therefore, developing a fully integrated wet process that is compact, has a high recovery rate, is environmentally friendly, and can directly produce high-purity tin products is of great practical significance. Summary of the Invention

[0004] The technical problem solved by this invention is to provide a process for recovering refined tin from tin-containing materials, so as to achieve efficient and high-purity tin recovery.

[0005] The technical problem solved by this invention is achieved by the following technical solution:

[0006] A process for recovering refined tin from tin-containing materials includes the following steps:

[0007] Acid leaching: The tin-containing material is leached with a first acid solution to obtain a leachate;

[0008] Extraction: A reducing agent is added to the leachate to reduce the ferric iron in the leachate to ferrous iron, and then an extractant is added for extraction, in which the tin element is extracted into the organic phase;

[0009] Back-extraction: A second acid solution is added to the organic phase for back-extraction to obtain a tin-rich back-extraction solution;

[0010] Electrolytic refining: Electrolyze the tin-rich back-extraction solution to obtain refined tin.

[0011] Furthermore, in the acid leaching step, the solid-liquid ratio of the tin-containing material to the first acid solution is 1:4 to 6, and the first acid solution is a hydrochloric acid solution with a concentration of 3 to 8 mol / L.

[0012] Furthermore, in the acid leaching step, the leaching temperature is 50–70°C, and the leaching time is 1–2 hours.

[0013] Furthermore, stirring is maintained during the acid leaching step at a speed of 300–500 r / min.

[0014] Furthermore, in the extraction step, the reducing agent is ascorbic acid or iron powder.

[0015] Furthermore, in the extraction step, the extractant is an acidic phosphorus extractant, which includes one or both of P204 and tributyl phosphate. The P204 is diluted in sulfonated kerosene, and the volume concentration of P204 is 20-35%, with an O / A ratio of 0.5-1.5.

[0016] Furthermore, in the back-extraction step, the second acid solution is a hydrochloric acid solution with a concentration of 8-12 mol / L, and the O / A ratio of the back-extraction is 0.5-1.5.

[0017] Furthermore, in the electrolytic refining step, the electrolyte temperature is 30–50°C; and the electrolysis time is 4–12 hours.

[0018] Furthermore, in the electrolytic refining step, the cathode is made of stainless steel or titanium, and the anode is made of graphite or titanium-plated ruthenium electrode; the current density during electrolysis is 100-300 A / m. 2 .

[0019] Furthermore, in the acid leaching step, the tin-rich back-extraction solution is adjusted before electrolysis to make the tin ion concentration 10-20 g / L and the pH adjusted to 1.5-2.5.

[0020] Beneficial effects: The process for recovering and refining tin from tin-containing materials described in this invention improves the tin leaching rate through an optimized acid leaching system and reduces Fe. 3+ It significantly improves extraction selectivity, while high-acid back-extraction effectively dissociates the Sn-P2O4 complex, providing a pure feed solution for electrolysis. Furthermore, it creatively introduces an electrolytic refining step, which, combined with the overall process, results in a high tin leaching rate. The final tin product has a tin purity of ≥99.9%, achieving a high-efficiency conversion from tin-containing materials to high-purity tin products, which has great economic value and application prospects.

[0021] This invention features thorough pretreatment, strong leaching selectivity, high efficiency in extraction and back-extraction processes, a compact process, high recovery rate, and environmental friendliness, making it of significant practical importance for improving the comprehensive utilization level of tin-containing materials. Detailed Implementation

[0022] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below with reference to specific embodiments.

[0023] Example 1

[0024] A process for recovering refined tin from tin-containing materials includes the following steps:

[0025] Acid leaching: 500g of lead concentrate with a tin content of 0.67% was added to a 6mol / L hydrochloric acid solution at a solid-liquid ratio of 1:4. The leaching reaction was carried out at a temperature of 60℃ and a stirring speed of 400r / min for 1h. After the reaction was completed, the solid and liquid were separated to obtain the leachate. The tin leaching rate was measured to be 98.6%.

[0026] Extraction: Add 1.2 times the theoretical amount of ascorbic acid to the leachate and stir at room temperature for 30 min to reduce the ferric iron in the leachate to ferrous iron. Then add the P204-kerosene system, in which the volume concentration of P204 is 33%. Extract for 5 min under the condition of O / A = 1. Tin element is extracted into the organic phase. In this step, the extraction rate of tin is 96%.

[0027] Back-extraction: Add 10 mol / L hydrochloric acid solution to the organic phase for back-extraction. Under the condition of O / A = 1, back-extract for 10 min. In this step, the tin back-extraction rate is 95.3%, and a tin-rich back-extraction solution with a tin concentration of 1.35 g / L is obtained.

[0028] Electrolytic refining: The tin-rich back-extraction solution is concentrated and Sn is adjusted.2+ The concentration was adjusted to 15 g / L, pH = 2.0, and then injected into the electrolytic cell as the electrolyte. A stainless steel plate was used as the cathode, and graphite as the anode, at a current density of 200 A / m². 2 Electrolysis was performed at 40℃ for 6 hours. A dense tin plating layer was deposited on the cathode. After peeling off, the plating was cleaned and dried to obtain refined tin. The purity of the refined tin was tested and found to be 99.9%.

[0029] Example 2

[0030] A process for recovering refined tin from tin-containing materials includes the following steps:

[0031] Acid leaching: 500g of medium-grade leaching mud with a tin content of 0.28% was added to a high-chlorine mother liquor (equivalent hydrochloric acid concentration of approximately 4mol / L) diluted three times and adjusted to pH=0.9 at a solid-liquid ratio of 1:4. The leaching reaction was carried out at a temperature of 70℃ and a stirring speed of 400r / min for 2 hours. After the reaction, the solid and liquid were separated to obtain the leaching solution, and the tin leaching rate was measured to be 86%.

[0032] Extraction: Add 1.2 times the theoretical amount of ascorbic acid to the leachate and stir at room temperature for 30 min to reduce the ferric iron in the leachate to ferrous iron. Then add the P204-kerosene system, in which the volume concentration of P204 is 25%. Extract for 5 min under the condition of O / A of 0.8. Tin is extracted into the organic phase. In this step, the extraction rate of tin is 97%.

[0033] Back-extraction: A 12 mol / L second acid solution was added to the organic phase for back-extraction. The back-extraction was carried out for 10 min under the condition that O / A was 1.1. In this step, the tin back-extraction rate was 96.5%, and a tin-rich back-extraction solution with a tin concentration of 1.48 g / L was obtained.

[0034] Electrolytic refining: The tin-rich back-extraction solution is concentrated and Sn is adjusted. 2+ The concentration was adjusted to 15 g / L and the pH value to 2.0, and then injected into the electrolytic cell as the electrolyte. A stainless steel plate was used as the cathode and graphite as the anode, at a current density of 200 A / m². 2 Electrolysis was performed at 50℃ for 4 hours. A dense tin plating layer was deposited on the cathode. After peeling off, the plating was cleaned and dried to obtain refined tin. The purity of the refined tin was tested and found to be 99.9%.

[0035] Example 3

[0036] A process for recovering refined tin from tin-containing materials includes the following steps:

[0037] Acid leaching: 500g of electronic solder waste with a tin content of 5.2% was added to an 8mol / L hydrochloric acid solution at a solid-liquid ratio of 1:5. The leaching reaction was carried out at a temperature of 70℃ and a stirring speed of 450r / min for 1.5h. After the reaction was completed, the solid and liquid were separated to obtain the leaching solution. The tin leaching rate was measured to be 98.2%.

[0038] Extraction: Add ascorbic acid at 1.1 times the theoretical amount to the leachate and stir at room temperature for 30 min to reduce the ferric iron in the leachate to ferrous iron. Then add the P204-kerosene system, in which the volume concentration of P204 is 30%. Extract for 8 min under the condition of O / A ratio of 1.1. Tin is extracted into the organic phase. In this step, the extraction rate of tin is 98.5%.

[0039] Back-extraction: A 12 mol / L second hydrochloric acid solution was added to the organic phase for back-extraction. The back-extraction was carried out for 12 min under the condition of O / A of 1.0. In this step, the tin back-extraction rate was 97.8%, and a tin-rich back-extraction solution with a tin concentration of 18.5 g / L was obtained.

[0040] Electrolytic refining: The tin-rich back-extraction solution is diluted and the Sn content is adjusted. 2+ The concentration was adjusted to 18 g / L, pH = 2.2, and then injected into the electrolytic cell as the electrolyte. A titanium plate was used as the cathode, and a ruthenium-plated titanium electrode as the anode, at a current density of 250 A / m². 2 Electrolysis was performed at 45℃ for 8 hours. A dense and bright tin plating layer was deposited on the cathode. After peeling off, the plating was cleaned and dried to obtain refined tin. The purity of the refined tin was tested to be as high as 99.95%.

[0041] Compare with Example 1

[0042] In this comparative example, equivalent sulfuric acid was used instead of hydrochloric acid for leaching, and the rest was the same as in Example 1. The tin leaching rate was only 32.5%, and subsequent extraction and back-extraction were inefficient. Even with enrichment, the minimum tin concentration of 10 g / L in the electrolyte could not be achieved, meaning an effective product could not be obtained.

[0043] Compare with Example 2

[0044] In this comparative example, the acid leaching step was as follows: 500g of lead concentrate with a tin content of 0.67% was added to a 12mol / L first acid solution at a solid-liquid ratio of 1:4. The leaching reaction was carried out at 80℃ and a stirring speed of 400r / min for 1 hour. After the reaction was completed, the solid and liquid were separated to obtain the leachate. The rest was the same as in the example. The concentration of impurity ions such as iron and aluminum in the leachate was found to be significantly increased, leading to a decrease in extraction selectivity and difficulty in subsequent back-extraction. Ultimately, the purity of the tin product obtained by electrolysis was only 91.5%.

[0045] Compare with Example 3

[0046] In this comparative example, during the back-extraction step, a 4 mol / L second acid solution was added to the organic phase for back-extraction, and the rest was the same as in Example 1. In this comparative example, due to the low concentration of the back-extraction acid, the tin back-extraction rate was only 65.8%, the tin concentration in the enriched back-extraction solution was low, the purity of the product after electrolysis was only 89.7%, and the electrolysis efficiency was low.

[0047] Compare with Example 4

[0048] In this comparative example, the tin-rich stripping solution was directly electrolyzed without pretreatment in the electrolytic refining step, and the rest was the same as in Example 1. Because the tin-rich stripping solution was directly electrolyzed without pretreatment in the electrolytic refining step, and the rest was the same as in Example 1, the current efficiency during electrolysis was low, the tin layer deposited at the cathode was loose and easily detached, the purity of the final product was only 90.3%, and the recovery rate was low.

[0049] Compare with Example 5

[0050] In this comparative example, ascorbic acid was not added as a reducing agent during the extraction step, and the remaining steps were the same as in Example 3. Due to the unreduced Fe... 3+ Fe 3+ Competition with tin for extraction led to a significant decrease in extraction selectivity, with the tin extraction rate at only 78.2%. Furthermore, the high iron content in the organic phase made subsequent back-extraction difficult, and the final purity of the tin product obtained by electrolysis was only 92.1%, which fully demonstrates the crucial role of the reduction step in obtaining high-purity products.

[0051] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A process for the recovery of refined tin from a tin-bearing material, characterized in that, The method comprises the following steps: acid leaching: using a first acid solution to leach the tin-containing material to obtain a leaching solution; extraction: adding a reducing agent to the leaching solution to reduce the ferric iron in the leaching solution to ferrous iron, and then adding an extractant to extract the tin into an organic phase; stripping: adding a second acid solution to the organic phase to obtain a tin-rich stripping solution; electrolytic refining: electrolyzing the tin-rich stripping solution to obtain refined tin.

2. Process for the recovery of refined tin from tin-bearing materials according to claim 1, characterized in that, In the acid leaching step, the solid-liquid ratio of the tin-containing material to the first acid solution is 1:4-6, and the concentration of the first acid solution is 3-8 mol / L.

3. Process for the recovery of refined tin from tin-bearing materials according to claim 1, characterized in that, In the acid leaching step, the leaching temperature is 50-70℃, and the leaching time is 1-2 h.

4. Process for the recovery of refined tin from tin-bearing materials according to claim 1, characterized in that, In the acid leaching step, stirring is maintained, and the stirring speed is 300-500 r / min.

5. The process for the recovery of refined tin from tin-bearing materials according to claim 1, characterized in that, In the extraction step, the reducing agent is ascorbic acid or iron powder.

6. The process for the recovery of refined tin from tin-bearing materials according to claim 1, characterized in that, In the extraction step, the extractant is an acidic phosphorus extractant, and the acidic phosphorus extractant comprises one or both of P204 or tributyl phosphate, the P204 is diluted in sulfonated kerosene, the volume concentration of P204 is 20-35%, and the O / A ratio of extraction is 0.5-1.

5.

7. The process for the recovery of refined tin from tin-bearing materials according to claim 1, characterized in that, In the stripping step, the concentration of the second acid solution is 8-12 mol / L, and the O / A ratio of stripping is 0.5-1.

5.

8. The process for the recovery of refined tin from tin-bearing materials according to claim 1, characterized in that, In the electrolytic refining step, the electrolyte temperature is 30-50℃, and the electrolysis time is 4-12 h.

9. The process for the recovery of refined tin from tin-bearing materials according to claim 1, characterized in that, In the electrolytic refining step, the cathode uses stainless steel plate or titanium plate, and the anode uses graphite electrode or titanium plated with ruthenium; the current density during electrolysis is 100-300 A / m 2 .

10. The process for the recovery of refined tin from tin-bearing materials according to claim 1, characterized in that, In the acid leaching step, the tin-rich stripping solution is adjusted before electrolysis to make the tin ion concentration 10-20 g / L and the pH 1.5-2.5.