Method for directly preparing stannous oxalate from tin-containing waste materials

Abstract

The invention provides a method for directly preparing stannous oxalate from tin-containing waste materials. The method comprises the following steps: (1) adding hydrochloric acid into water to prepare a solution A; (2) adding tin tetrachloride into the solution A for dissolving to prepare a selective tin dissolving solution B; (3) adding the tin-containing waste material into the solution B, and dissolving tin to obtain a solution C; (4) adjusting the pH value of the solution C, and then adding oxalic acid to generate stannous oxalate precipitate; and (5) standing, filtering, chlorinating the filtrate, returning to the solution B prepared in the step (2), and washing, filtering and drying the filter residue to obtain the stannous oxalate product. The tin dissolving process is a disproportionation reaction and has the advantages of being good in selectivity, high in reaction speed and good in product quality. Besides, compared with an existing method for preparing stannous oxalate with reagents such as metal tin and tin compounds which are high in price as raw materials, the method has the advantages that the raw materials are tin-containing waste materials, and the method is wide in source, low in cost and good in benefit.

Description

Technical Field

[0001] This invention relates to a technology for preparing stannous oxalate from tin-containing waste materials, specifically a low-cost method for directly preparing stannous oxalate from tin-containing waste materials. Background Technology

[0002] Tin plays a vital role in people's production and daily life, widely used in tin-plated tinplate materials for food and beverage packaging, tin alloy materials, tin soldering materials, and tin plating of metal surfaces. This widespread use of tin generates a large amount of tin-containing waste materials, such as scrap circuit boards, tin-coated iron needles, tin-coated copper particles, tin-tungsten electrical alloys, and tin-tungsten carbide electrical alloys. These are valuable secondary resources of tin, and given that tin is an expensive metal, its green and efficient recycling is essential. Currently, the recycling of tin-containing waste materials mainly uses inorganic acids as solvents for tin leaching. This method suffers from poor selectivity, high impurity content in the leaching solution, and increased difficulty in subsequent purification. The solvent concentration is also high, often requiring an acid concentration of 2 mol / L or higher, placing higher demands on equipment corrosion resistance. Furthermore, the reaction rate is slow, exceeding 24 hours at room temperature, often requiring heating to temperatures above 50°C to improve the reaction rate. Ultimately, this results in high costs and difficulty in achieving good economic benefits, necessitating improvement.

[0003] Stannous oxalate is a high-value-added divalent tin fine chemical product that has emerged in recent years. It is a white powder, insoluble in water but soluble in dilute hydrochloric acid. Due to its high catalytic activity and environmental friendliness, it is widely used in metallurgy, resins, coal chemicals, printing and dyeing, and other fields as a catalyst for acetylation reactions, a catalyst for coal hydrogenation, and for the exposure of blueprint paper. Demand for it is increasing year by year. Currently, stannous oxalate is mainly produced by preparing a solution of stannous salt from commercially available industrial tin compounds, followed by a precipitation reaction with an oxalate solution. The main problem is the high cost of raw materials, resulting in persistently high production costs.

[0004] This invention was proposed in response to the problems existing in the prior art. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for directly preparing stannous oxalate from tin-containing waste materials.

[0006] This invention can be achieved through the following technical solutions:

[0007] This invention discloses a method for directly preparing stannous oxalate from tin-containing waste materials.

[0008] Includes the following steps:

[0009] 1. Dissolve hydrochloric acid in water to prepare an aqueous solution A with a concentration of 0.1–0.5 mol / L;

[0010] 2. Add tin tetrachloride (SnCl4) to solution A while stirring to dissolve the tin tetrachloride, thus preparing a selective tin-dissolving solution B with a tin tetrachloride concentration of 0.1-1.0 mol / L, consisting of tin tetrachloride, hydrochloric acid, and water.

[0011] 3. First, clean the tin-containing waste material with water, then add it to solution B. This allows the tin in the waste material to undergo a disproportionation reaction with tin tetrachloride to generate stannous chloride (stannin dichloride, SnCl2). Once the concentration of stannous chloride in the solution reaches 0.2–2.0 mol / L, stop adding the tin-containing waste material. Filter the solution to obtain stannous chloride, hydrochloric acid aqueous solution C, and filter residue 1. Wash filter residue 1 with water, and combine the wash water with solution C. Filter residue 1 is used to recover other valuable components.

[0012] 4. First, add one or more of ammonia, sodium hydroxide, and alkaline chloride to solution C to adjust the pH value to 4-7. Then, add oxalic acid to solution C in portions, stirring and monitoring the pH value and stannous chloride concentration while adding the acid. Maintain the pH value at 4-7. When the stannous chloride concentration in the solution drops to ≤0.05mol / L, stop adding oxalic acid. The reaction will produce stannous oxalate precipitate.

[0013] 5. Let stand for ≥2 hours, then start filtration. The filtrate is solution D with a low concentration of stannous chloride. Chlorine gas is then introduced into solution D to convert the stannous chloride in solution D into stannous tetrachloride, which is then returned to step 2 to prepare solution B. Filter residue 2 is stannous oxalate precipitate. Filter residue 2 is washed with water, and the wash water is combined with solution D. After drying, stannous oxalate (SnC2O4) product is obtained.

[0014] Preferably, the tin in the tin-containing waste material in step 3 exists in a metallic state, an oxidized state, or a combination of both. The tin-containing waste material includes tin waste material, tin-coated iron waste material, tin-coated copper waste material, tin-tungsten electrical alloy waste material, and tin-tungsten carbide electrical alloy waste material, but is not limited to these. The tin in the waste material structure is not completely covered, and it can be completely or partially exposed.

[0015] Preferably, in step 3, the amount of tin-containing waste material added is determined according to the chemical reaction. The amount of waste material added should be 1.01 to 1.05 times the theoretical value of the tin content in the waste material, so that the tin content is excessive and the tin tetrachloride in the solution reacts completely. The chemical reaction formula is as follows:

[0016] Sn + SnCl₄ = 2SnCl₂

[0017] Preferably, in step 4, the pH value of the solution is monitored and maintained at 4–7. After monitoring, the pH value is maintained at 4–7 by adding one or more of ammonia, sodium hydroxide, and alkaline chloride.

[0018] Preferably, after solution D in step 5 is circulated more than 3 times, when the concentration of other components reaches 0.01 mol / L, solution D is not directly returned to step 2 for the preparation of solution B. After the extraction of stannous chloride, the remaining solution is sent for water treatment, and the extracted stannous chloride is returned to step 3 to dissolve in solution C and enter the process for preparing stannous oxalate.

[0019] Compared with existing technologies, the present invention has the following advantages:

[0020] 1. High production efficiency: The dissolution process of tin in tin-containing waste materials is a disproportionation reaction of tin, which is very fast. It can shorten the reaction time of the traditional inorganic acid tin dissolution process, which requires more than 24 hours under strong acid and high temperature conditions, to less than 2 hours at room temperature.

[0021] 2. The product quality is good. As mentioned above, the dissolution process of tin in tin-containing waste materials is a disproportionation reaction of tin. The disproportionation reaction is a reaction between substances of different valence states of the same element. It has a strong selectivity. When tin in tin-containing waste materials dissolves, non-tin components will not dissolve, which ensures that a high-purity stannous chloride solution is obtained. This provides an inherently favorable condition for preparing high-purity and high-quality stannous oxalate products.

[0022] 3. Low production cost: This invention uses tin-containing waste materials to prepare stannous oxalate, while existing methods use commercially available industrial tin compounds for preparation, and the cost of raw materials is the main cost of preparing stannous oxalate, so the preparation cost is high. However, the raw material of this invention is tin-containing waste materials, most of which have a tin content of less than 5% and can be disregarded, so the raw material procurement cost is greatly reduced and the production cost is low. Attached Figure Description

[0023] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings, wherein:

[0024] Figure 1 This is a process flow diagram of the present invention; Detailed Implementation

[0025] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings:

[0026] Example 1:

[0027] (1) Take 10L of concentrated hydrochloric acid and add it to water to prepare approximately 600L of hydrochloric acid aqueous solution A with a concentration of 0.2mol / L;

[0028] (2) Take 157 kg of industrial grade tin tetrachloride (SnCl4) solid powder and add it to solution A while stirring to dissolve the tin tetrachloride solid. Prepare about 600 L of tin tetrachloride, hydrochloric acid and water selective tin dissolution solution B with a tin tetrachloride concentration of 1.0 mol / L.

[0029] (3) First, the waste circuit board was crushed and reselected to obtain tin-copper particles with a tin content of 4.5% and then washed with water. Then, it was added to solution B while stirring to dissolve the tin in the waste material. When the concentration of stannous chloride in the solution reached 2.0 mol / L, the addition of waste material was stopped. The amount of waste material added was 1600 kg. After filtration, stannous chloride, hydrochloric acid aqueous solution C and filter residue 1 were obtained. Filter residue 1 was washed with water and the wash water was combined with solution C. Filter residue 1 was used to recover copper.

[0030] (4) First, add ammonia water to solution C while stirring and measuring the pH value of the solution. Adjust the pH value to 5.0-5.5. Then, add industrial oxalic acid solid powder to solution C in portions while stirring and monitoring the pH value and stannous chloride concentration. Add ammonia water to maintain the pH value at 5.0-5.5. When the stannous chloride concentration in the solution drops to 0.01 mol / L, stop adding oxalic acid. The reaction will produce stannous oxalate precipitate.

[0031] (5) After standing for 3 hours, filter is started. The filtrate is solution D containing stannous chloride. Chlorine gas is then introduced into solution D to convert the stannous chloride in solution D into stannous tetrachloride, and then returned to step (2) to prepare solution B. Filter residue 2 is stannous oxalate precipitate. Filter residue 2 is washed with water, and the wash water is combined with solution D. After drying, stannous oxalate product is obtained. 230 kg of stannous oxalate product is obtained with a purity of 99.7%.

[0032] Example 2:

[0033] (1) Take 8.34 L of concentrated hydrochloric acid and add it to water to prepare approximately 1000 L of hydrochloric acid aqueous solution A with a concentration of 0.1 mol / L;

[0034] (2) Take 200 kg of industrial tin tetrachloride (SnCl4) solid powder and add it to solution A while stirring to dissolve the tin tetrachloride solid. Prepare about 1000 L of tin tetrachloride, hydrochloric acid and water selective tin dissolution solution B with a tin tetrachloride concentration of 0.77 mol / L.

[0035] (3) First, clean the tin-filled iron needles with water containing 0.5% tin. Then, add them to solution B in 10 batches while stirring to dissolve the tin coating on the outer layer of the waste material. Stop adding waste material when the concentration of stannous chloride in the solution reaches 1.5 mol / L. The amount of waste material added is 17680 kg. Filter to obtain stannous chloride, hydrochloric acid aqueous solution C and filter residue 1. Wash filter residue 1 with water and combine the wash water with solution C. Filter residue 1 is used to recover iron.

[0036] (4) First, add ammonia water to solution C while stirring and measuring the pH value of the solution. Adjust the pH value to 5.5-6.0. Then, add industrial oxalic acid solid powder to solution C in portions while stirring and monitoring the pH value and stannous chloride concentration. Add ammonia water to maintain the pH value at 5.5-6.0. When the stannous chloride concentration in the solution drops to 0.01 mol / L, stop adding oxalic acid. The reaction will produce stannous oxalate precipitate.

[0037] (5) After standing for 2.5 hours, filter is started. The filtrate is solution D containing stannous chloride. Chlorine gas is then introduced into solution D to convert the stannous chloride in solution D into stannous tetrachloride, and then returned to step (2) to prepare solution B. Filter residue 2 is stannous oxalate precipitate. Filter residue 2 is washed with water, and the wash water is combined with solution D. After drying, stannous oxalate product is obtained. 290 kg of stannous oxalate product is obtained with a purity of 99.3%.

[0038] Example 3:

[0039] (1) Take 10L of concentrated hydrochloric acid and add it to water to prepare approximately 240L of hydrochloric acid aqueous solution A with a concentration of 0.5mol / L;

[0040] (2) Take 644 kg of industrial tin tetrachloride (SnCl4) solid powder and add it to solution A while stirring to dissolve the tin tetrachloride solid. Prepare about 240 L of tin tetrachloride, hydrochloric acid and water selective tin dissolution solution B with a tin tetrachloride concentration of 1.0 mol / L.

[0041] (3) First, clean the tin-clad copper electrical alloy contacts containing 20% ​​tin with water, then add them to solution B while stirring to dissolve the tin coating on the outer layer of the waste material. Stop adding waste material when the concentration of stannous chloride in the solution reaches 2.0 mol / L. The amount of waste material added is 57.5 kg. Filter to obtain stannous chloride, hydrochloric acid aqueous solution C and filter residue 1. Wash filter residue 1 with water and combine the wash water with solution C. Filter residue 1 is used to recover copper.

[0042] (4) First, add ammonia water to solution C while stirring and measuring the pH value of the solution. Adjust the pH value to 6.0-6.5. Then, add industrial oxalic acid solid powder to solution C in portions while stirring and monitoring the pH value and stannous chloride concentration. Add ammonia water to maintain the pH value at 6.0-6.5. When the stannous chloride concentration in the solution drops to 0.005 mol / L, stop adding oxalic acid. The reaction will produce stannous oxalate precipitate.

[0043] (5) After standing for 2 hours, filter is started. The filtrate is solution D containing stannous chloride. Chlorine gas is then introduced into solution D to convert the stannous chloride in solution D into stannous tetrachloride and return to step (2) to prepare solution B. Filter residue 2 is stannous oxalate precipitate. Filter residue 2 is washed with water to obtain 136 kg of stannous oxalate product with a purity of 99.7%.

[0044] 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 the present invention is defined by the appended claims and their equivalents.

Claims

1. A process for the direct preparation of stannous oxalate from tin containing scrap material, characterized in that, The method comprises the following steps: Step (1): hydrochloric acid is added to water to prepare a hydrochloric acid aqueous solution A with a hydrochloric acid concentration of 0.1-0.5 mol / L; Step (2): tin tetrachloride is added to the solution A while stirring to dissolve the tin tetrachloride, so as to prepare a tin tetrachloride, hydrochloric acid and water selective tin dissolving solution B with a tin tetrachloride concentration of 0.1-1.0 mol / L; Step (3): the tin-containing waste material is first cleaned with water, and then added to the solution B, so that the tin in the waste material reacts with the tin tetrachloride to generate stannous chloride; when the stannous chloride concentration in the solution reaches 0.2-2.0 mol / L, the addition of the tin-containing waste material is stopped, and filtration is performed to obtain a stannous chloride, hydrochloric acid aqueous solution C and a filter residue 1; the filter residue 1 is cleaned with water, and the washing water is combined with the solution C; the filter residue 1 is used for recovering other valuable components; Step (4): one or more combinations of ammonia, sodium hydroxide and alkaline chloride are added to the solution C to adjust the pH value to 4-7; then oxalic acid is added to the solution C in batches while stirring and monitoring the pH value and the stannous chloride concentration of the solution, so as to maintain the pH value at 4-7; when the stannous chloride concentration in the solution is ≤0.05 mol / L, the addition of the oxalic acid is stopped, and stannous oxalate precipitate is generated; Step (5): standing for ≥2 h, and then starting filtration; the filtrate is a solution D with a low stannous chloride concentration; chlorine gas is introduced into the solution D to convert the stannous chloride in the solution D into tin tetrachloride, and the solution D is returned to step (2) for preparing the solution B; the filter residue 2 is the stannous oxalate precipitate, which is washed with water; the washing water is combined with the solution D; and the filter residue 2 is dried to obtain the stannous oxalate product.

2. The method for directly preparing stannous oxalate from tin-containing scrap material according to claim 1, characterized in that: The tin in the tin-containing waste material in step (3) exists in the form of metal state, oxide state or both states, and the tin-containing waste material includes tin waste material, tin-coated iron waste material, tin-coated copper waste material, tin-tungsten electrical alloy waste material, tin-carbide tungsten electrical alloy waste material, or tin in the waste material structure is not completely coated and is all or partially exposed.

3. The process for direct preparation of stannous oxalate from tin containing scrap material as claimed in claim 1 wherein: The addition amount of the tin-containing waste material in step (3) is determined according to the chemical reaction, and the addition amount of the waste material should be 1.01-1.05 times of the theoretical value of the tin content in the waste material, so that the tin is excessive and the reaction of the tin tetrachloride in the solution is complete, and the chemical reaction formula is as follows: Sn+SnCl4=2SnCl2.

4. The method for directly preparing stannous oxalate from tin-containing scrap material according to claim 1, characterized in that: In step (4), the pH value of the solution is monitored and maintained at 4-7; after monitoring, one or more combinations of ammonia, sodium hydroxide and alkaline chloride are added to maintain the pH value at 4-7.

5. The process for direct preparation of stannous oxalate from tin containing scrap material as claimed in claim 1 wherein: In step (5), the solution D is recycled for >3 times; when the concentration of other components reaches 0.01 mol / L, the solution D is not directly returned to step (2) for preparing the solution B; after the stannous chloride is extracted, the remaining solution is sent to water treatment; the extracted stannous chloride is returned to step (3) and dissolved in the solution C to enter the process of preparing stannous oxalate.

Images