A method for recovering tin from tin slag and a process for coupling tin recovery with Fenton reaction

Abstract

The present invention provides a method for recovering tin from tin slag and a process method for coupling tin recovery with Fenton reaction, wherein the tin slag is immersed in acid to dissolve the tin, filtered to obtain a mixed solution containing tin salt and stannous salt, and Fe-containing 3+ The solution is adjusted to pH 0.5-3. After the reaction, the solid-liquid separation is carried out and the obtained solid is roasted to obtain SnO2. Using the above method, the effluent of the Fenton reaction can be used as the Fe-containing 3+ The solution is introduced into the above tin recovery process, and after the reaction, Fe 3+ Reduced to Fe 2+ At the same time, the pH of the reaction solution is low, and the filtrate can be directly reused in the Fenton reaction, and the two reaction processes are coupled. The tin recovery method of the present invention can be summarized by controlling the reaction pH conditions. 4+ Most of the tin slag is even completely precipitated, with extremely high recovery rate and purity, which not only saves the cost of solid waste treatment, but also achieves the purpose of tin slag recycling and reuse, and can also realize coupling with the Fenton reaction process.

Description

Technical Field

[0001] The invention belongs to the technical field of solid waste resource utilization, and particularly relates to a method for recovering tin from tin slag and a process method for coupling tin recovery with Fenton reaction. Background Art

[0002] In recent years, with the continuous development of the electronics and electrical industries and the gradual introduction of lead-free soldering processes, tin consumption has increased dramatically. As a solid waste, the cost of handling tin slag has also increased significantly. In this context, recycling tin slag is undoubtedly a good option for saving resources and costs.

[0003] Solder slag is a source of tin residue. This residue is formed when electronics factories use lead-free tin wire to solder electronic components. The tin in the soldering furnace oxidizes after being subjected to high temperatures, leaving residue on the surface of the molten tin. Common treatment processes for solder slag include pyrometallurgy or melting treatment. These processes typically involve heating the solder to melt it into a liquid form. Residue recovery utilizes gravity to separate the liquid solder from the oxides, which remain insoluble. However, slag heats slowly, and heating to 240°C wastes energy and is inefficient. Therefore, effective solder slag recovery is a key method for reducing reaction costs.

[0004] Patent CN110872649A discloses a method for recovering tin from tin-lead slag, using a chlorination-water leaching-alkali fusion-water leaching-concentration crystallization process to produce sodium stannate. This invention effectively reuses the tin slag, but the introduction of a chlorination reagent into the reaction, which involves multiple volatilization and condensation processes, produces chlorinated residues and filtrate that can cause secondary pollution, and subsequent processing increases reaction costs.

[0005] Patent CN111573715A discloses a method for preparing tin dioxide from tin oxide slag. The reaction involves adding sulfuric acid and tin oxide slag in a ratio of 4 to 8:1 into a sealed container, and introducing oxygen into the container. The reaction pressure is ≥0.5 MPa, the reaction temperature is 130-200°C, and the reaction time is 4-8 hours. Using sulfuric acid as a carrier, the tin in the tin oxide slag reacts with oxygen to form tin dioxide until the reaction is complete. However, in this invention, the tin slag and oxygen do not react completely, resulting in the product being susceptible to heteroatoms and the generation of harmful gases. Summary of the Invention

[0006] In order to solve the deficiencies of the prior art, the present invention provides a method for recovering tin from tin slag and a method for coupling tin recovery with Fenton reaction. 3+ After the reaction and calcination, SnO2 solid is finally obtained, achieving a higher tin recovery rate; this method is coupled with the Fenton reaction, which can not only utilize the Fe 3+ , and can also reduce it to Fe required for the Fenton reaction2+ , and based on the control of reaction conditions, it has the pH required for the Fenton reaction and can be directly returned to the Fenton reaction unit for utilization, thus realizing the clever coupling of the two units.

[0007] The present invention achieves the above technical objectives through the following technical solutions:

[0008] The first aspect of the present invention provides a method for recovering tin from tin slag, comprising the following steps: immersing the tin slag in acid to dissolve the tin, filtering to obtain a mixed solution containing tin salt and stannous salt, and adding Fe 3+ The solution is adjusted to pH 0.5-3, and after the reaction, the solid-liquid is separated and the obtained solid is calcined to obtain SnO2.

[0009] Furthermore, the acid is sulfuric acid or hydrochloric acid, and the concentration of the hydrochloric acid is 20%-38% by mass, and the concentration of the sulfuric acid is 40%-60%, preferably 40%-50%. Sulfuric acid is preferred.

[0010] Furthermore, after the tin slag is immersed in acid, the temperature is adjusted to 40-80°C, preferably 50-60°C, to fully dissolve the tin. The treatment time is 1-2 hours. During this process, the tin in the tin slag is converted into Sn 2+ and Sn 4+ To improve efficiency, the mixing ratio of tin slag and acid solution is controlled so that the mass concentration of tin salt and stannous salt is 80%-98%, preferably 90%-95%.

[0011] Furthermore, the Fe-containing 3+ Fe in solution 3+ The concentration is 5mg / L~100mg / L, and the added amount is based on the molar ratio of Fe to Sn being 3:1-2:1.

[0012] Furthermore, Fe 3+ After the solution is prepared, the pH is preferably adjusted to 1-2, more preferably to 1.1-1.3. At least 90% of Sn can be precipitated in the form of Sn(OH)4. In the preferred technical solution, more than 98% of Sn can be precipitated in the form of Sn(OH)4. SnO2 is then obtained through subsequent separation and roasting processes, and the purity of SnO2 reaches more than 95%.

[0013] Furthermore, Fe 3+ After the solution is prepared, the pH is adjusted using at least one of sulfuric acid, NaOH solution or ammonia water.

[0014] Furthermore, the calcination temperature is 400-700°C, preferably 600-650°C; and the calcination time is 2-5h, preferably 2.5-3.5h.

[0015] Furthermore, the tin slag generally refers to solid waste containing tin in industrial production. In addition, it may also contain other metal impurities including copper. The technical solution of the present invention is preferably used to treat solder slag, which is a substance remaining on the surface of the tin liquid after the tin in the welding furnace is oxidized after high temperature when the electronics factory uses lead-free tin wire to solder electronic components. Usually, the tin content of tin slag is 90%-98%, and it also contains miscellaneous metals such as copper, antimony, and silver. Since the recovery rate of tin in pyrometallurgical refining is limited, the tin slag is directly acidified and alkali precipitated to remove the impurities in the tin slag while ensuring its recovery rate.

[0016] In the above technical solution of the present invention, the solid tin solvent is first made into an ionic state by acidification treatment, and then the solid tin solvent is made into an ionic state by Fe 3+ By adjusting the pH, more than 90% of Sn is calcined into SnO2 in the form of Sn(OH)4, thus realizing tin recovery.

[0017] The technical purpose of the second aspect of the present invention is to provide a process method for coupling tin recovery and Fenton reaction, comprising: immersing tin slag in sulfuric acid to dissolve the tin, filtering to obtain a mixed solution containing tin salt and stannous salt, adding the effluent of the Fenton reaction to the mixed solution, adjusting the pH to 0.5-3, after the reaction, separating the solid and the liquid, roasting the obtained solid to obtain SnO2, and passing the obtained liquid into the Fenton reaction.

[0018] Furthermore, the mass concentration of the sulfuric acid is 40%-60%, preferably 40%-50%. The mass concentration of the mixed solution of the tin salt and the stannous salt is 80%-98%, preferably 90%-95%.

[0019] Furthermore, after the solder slag is immersed in sulfuric acid, the temperature is adjusted to 40-80°C, preferably 50-60°C, to fully dissolve the tin. The treatment time is 1-2 hours.

[0020] Furthermore, the effluent of the Fenton reaction is wastewater after organic wastewater is treated by Fenton oxidation, with a COD lower than 150 mg / L, preferably lower than 50 mg / L; the iron ion concentration is 10 mg / L-30 mg / L, preferably 15-20 mg / L, and the added amount is according to a molar ratio of Fe to Sn of 3:1-2:1.

[0021] Furthermore, the mixing ratio of tin slag and sulfuric acid solution is controlled so that the mass concentration of tin salt and stannous salt is 80%-98%, preferably 90%-95%; the effluent from the Fenton reaction is mixed with the mixed solution containing tin salt and stannous salt in a volume ratio of 3:1-6:1.

[0022] Furthermore, after adding the effluent from the Fenton reaction, the pH is preferably adjusted to 1-2, more preferably to 1.1-1.3. The reaction time is 0.5-1 h.

[0023] Furthermore, the pH is adjusted using at least one of sulfuric acid, NaOH solution or ammonia water.

[0024] Furthermore, the calcination temperature is 400-700°C, preferably 600-650°C; and the calcination time is 2-5h, preferably 2.5-3.5h.

[0025] Furthermore, solder slag is the residue left on the surface of the molten tin after the tin in the welding furnace is oxidized after being exposed to high temperatures when soldering electronic components with lead-free tin wire in electronics factories. Typically, the slag contains 90%-98% tin and may also contain miscellaneous metals such as copper, antimony, and silver.

[0026] Compared with the prior art, the present invention has the following advantages:

[0027] (1) The present invention uses the tin slag produced in welding as raw material, directly treats the solid waste, first acidifies it, and then uses Fe 3+ As an oxidant, Sn 2+ Oxidized to Sn 4+ By controlling the pH conditions of the reaction, Sn 4+ Most of the tin slag is even completely precipitated, with extremely high recovery rate and purity. The recovery rate reaches more than 80%, and the purity reaches more than 95% as calculated by SnO2; it not only saves the cost of solid waste treatment, but also achieves the purpose of recycling and reusing tin slag.

[0028] (2) In particular, the solder slag recovery of the present invention is coupled with the Fenton reaction, and the Fe 3+ Sn in the mixed solution 2+ Oxidation was successfully performed to convert it to Sn 4+ , realizing the reuse of Fenton effluent. At this time, Fe 3+ Reduced to Fe 2+ At the same time, the pH of the reaction liquid is low, and the liquid after solid-liquid separation is directly reused in the Fenton reaction, providing a divalent iron source and good acidic conditions for the Fenton reaction, effectively reducing the cost of the Fenton reaction.

[0029] Other features and advantages of the present invention will be described in detail in the following detailed description. DETAILED DESCRIPTION

[0030] The following non-limiting examples may enable those skilled in the art to more fully understand the present invention, but are not intended to limit the present invention in any way.

[0031] The experimental methods in the following examples, unless otherwise specified, are all conventional methods in the art. The experimental materials used in the following examples, unless otherwise specified, were purchased from conventional biochemical reagent stores.

[0032] The pH value in the present invention is determined by the "Water Quality - Determination of pH - Glass Electrode Method" (GB / T6920), the COD is determined by the "Water Quality - Determination of COD - Potassium Dichromate Method" (GB / T 11914), and the metal ions are determined by the "Microwave Digestion / Inductively Coupled Plasma Mass Spectrometry" (ICP-MS) method.

[0033] Example 1

[0034] When an electronics factory uses lead-free solder wire for soldering, it produces solder slag containing 90%-95% tin. Organic wastewater from a coal chemical plant undergoes Fenton oxidation, resulting in a pH of 4.2, a COD of 80 mg / L, and an iron content of 17 mg / L.

[0035] Solder slag was immersed in 50% sulfuric acid and heated with stirring at 60°C and 100 rpm for 2 hours. The slag was fully dissolved, solid-liquid separation was performed, and the insoluble material at the bottom was filtered out. The mass concentration of tin salts and stannous salts in the filtrate was 90%. The Fenton oxidation effluent and filtrate were mixed in a 4:1 volume ratio, with a molar ratio of Fe to Sn of 2:1. The reaction was continued for 0.5 hours. The pH was adjusted to 2.0 with sodium hydroxide, and the solid-liquid separation was performed. The residue was dried for later use, and the filtrate was reused in the Fenton reaction system. The dried residue was calcined at 600°C for 3 hours to obtain a SnO2 solid with a mass percentage of over 98%, and the calculated Sn recovery rate was 86%.

[0036] Example 2

[0037] When an electronics factory uses lead-free solder wire for soldering, it produces solder slag containing up to 90% tin. Organic wastewater from a coal chemical plant undergoes Fenton oxidation, resulting in a pH of 3.9, a COD of 50 mg / L, and an iron content of 16 mg / L.

[0038] Solder slag was immersed in 50% sulfuric acid and heated with stirring at 60°C and 100 rpm for 2 hours. The slag was fully dissolved, solid-liquid separation was performed, and the insoluble material at the bottom was filtered out. The mass concentration of tin salts and stannous salts in the filtrate was 88%. The Fenton oxidation effluent and filtrate were mixed in a volume ratio of 6:1, with a molar ratio of Fe to Sn of 3:1. The reaction was continued for 1 hour. The pH was adjusted to 2.0 with sodium hydroxide, and the solid-liquid separation was performed. The residue was dried for later use, and the filtrate was reused in the Fenton reaction system. The dried residue was calcined at 600°C for 3 hours to obtain a SnO2 solid with a mass percentage of over 99%, and the calculated Sn recovery rate was 85%.

[0039] Example 3

[0040] When an electronics factory uses lead-free solder wire for soldering, it produces solder slag containing 90%-95% tin. Organic wastewater from a coal chemical plant undergoes Fenton oxidation, resulting in a pH of 4.0, a COD of 65 mg / L, and an iron content of 20 mg / L.

[0041] Solder slag was immersed in 50% sulfuric acid and heated with stirring at 60°C and 100 rpm for 2 hours. The slag was fully dissolved, solid-liquid separation was performed, and the insoluble material at the bottom was filtered out. The mass concentration of tin salts and stannous salts in the filtrate was 89%. The Fenton oxidation effluent and filtrate were mixed in a volume ratio of 5:1, with a molar ratio of Fe to Sn of 2.5:1. The reaction was continued for 0.5 hours. The pH was adjusted to 3.0 with sodium hydroxide, and the solid-liquid separation was performed. The residue was dried for later use, and the filtrate was reused in the Fenton reaction system. The dried residue was calcined at 600°C for 3 hours to obtain a solid mixture of 92% SnO2 and 6% Fe2O3 by mass. The calculated Sn recovery rate was 78%.

[0042] From the above examples, it can be found that the tin dioxide produced by the present invention has a relatively high purity and can be used in subsequent industrial applications.

[0043] Example 4

[0044] The solder slag and process used were the same as in Example 1, except that after adding the Fenton oxidation effluent, the pH was adjusted to 2.7 with sodium hydroxide. Finally, a SnO2 solid with a mass percentage of more than 95% was obtained, and the calculated Sn recovery rate was 80%.

[0045] Example 5

[0046] The solder slag used and the process were the same as in Example 1, except that after adding the Fenton oxidation effluent, the pH was adjusted to 1.5 with sodium hydroxide. Finally, a SnO2 solid with a mass percentage of more than 99% was obtained, and the calculated Sn recovery rate was 88%.

[0047] Example 6

[0048] The solder slag used and the process were the same as in Example 1, except that after adding the Fenton oxidation effluent, the pH was adjusted to 1.3 with sodium hydroxide. Finally, a SnO2 solid with a mass percentage of more than 99% was obtained, and the calculated Sn recovery rate was 89%.

[0049] Comparative Example 1

[0050] The mixing ratio of solder slag and sulfuric acid was adjusted so that the mass concentration of tin salt and stannous salt in the obtained filtrate was 60%, and the other operating conditions were the same as those in Example 1. Finally, a SnO2 solid with a mass percentage of more than 97% was obtained, and the calculated Sn recovery rate was 55%.

[0051] Comparative Example 2

[0052] The solder slag and process used were the same as in Example 1, except that after adding the Fenton oxidation effluent, the pH was adjusted to 3.1 with sodium hydroxide. Finally, a SnO2 solid with a mass percentage of more than 90% was obtained, and the calculated Sn recovery rate was 75%.

Claims

1. A process for coupling tin recovery with Fenton reaction, comprising: Tin slag is immersed in sulfuric acid to dissolve the tin, and the solution is filtered to obtain a mixed solution containing tin salt and stannous salt. The mixing ratio of the tin slag and the sulfuric acid solution is controlled so that the mass concentration of the tin salt and the stannous salt is 80%-98%. The effluent of the Fenton reaction is added thereto in an amount according to a molar ratio of Fe to Sn of 3:1-2:1, and the pH is adjusted to 0.5-3. After the reaction, the solid and liquid are separated, and the obtained solid is roasted to obtain SnO2, and the obtained liquid is passed into the Fenton reaction.

2. The process according to claim 1, characterized in that: The concentration of the sulfuric acid is 40%-50%.

3. The process according to claim 1, characterized in that: After the tin slag is immersed in sulfuric acid, the temperature is adjusted to 40-80°C and the treatment time is 1-2 hours.

4. The process according to claim 1, characterized in that: The effluent of the Fenton reaction is wastewater after organic wastewater is treated by Fenton oxidation, with a COD lower than 150 mg / L and an iron ion concentration of 10 mg / L-30 mg / L.

5. The process according to claim 1, characterized in that: The effluent from the Fenton reaction is mixed with a mixed solution of tin salt and stannous salt in a volume ratio of 3:1-6:

1.

6. The process according to claim 1, characterized in that: After adding the effluent from the Fenton reaction, adjust the pH to 1-2.

7. The process according to claim 6, characterized in that: After adding the effluent from the Fenton reaction, adjust the pH to 1.1-1.

3.

8. The process according to claim 1, characterized in that: The pH is adjusted using at least one of sulfuric acid, NaOH solution, or ammonia solution.