A method for recovering tin from a nitric acid type system tin stripping waste liquid

Abstract

The application relates to a tin recovery and regeneration method for a nitric acid type system tin stripping waste liquid, and belongs to the technical field of resource recovery. + The concentration is 4.8-5.0 mol / L, and first filtrate is obtained through filtration; S2, the first filtrate is heated to 65-70 DEG C and reacts for 1-2 hours, tin mud and regenerated tin stripping liquid are obtained through filtration, and the regenerated tin stripping liquid is returned to a production line for continuous use; S3, alkali is added to the tin mud until the pH is above 13, heating is carried out to completely dissolve the tin mud, CO2 is introduced until the pH is less than 9, sodium stannate solid is obtained through filtration, and the sodium stannate solid is calcined at 300-350 DEG C to obtain tin dioxide solid.

Description

Technical Field

[0001] This invention relates to the field of resource recycling technology, and in particular to a method for regenerating tin from tin-removing waste liquid in a nitric acid-based system. Background Technology

[0002] In the production of printed circuit boards (PCBs), nitric acid-based tin-containing solutions are commonly used to remove the tin plating layer from the circuit boards. When the tin-removing ability of the solution decreases, it becomes tin stripping wastewater. Tin stripping wastewater is an acidic wastewater and is classified as hazardous waste. The tin content in tin stripping wastewater generally reaches over 90 g / L, the copper content is 5–10 g / L, and the nitric acid residue is 15–20%. It also contains heterocyclic compounds, polycyclic aromatic hydrocarbons, and polymers. Therefore, tin stripping wastewater is highly corrosive and polluting. If discharged directly without proper treatment, it will inevitably cause serious pollution to water resources and the ecological environment. At the same time, the tin-containing wastewater has a high content of valuable metals tin and copper, making it highly valuable for recycling.

[0003] Currently, the main methods for treating tin-containing waste liquid include neutralization, distillation, metal ion removal and recycling, diffusion dialysis, and solvent extraction. For example, Chinese patent CN113651480A reports a method for regenerating tin-containing waste liquid, comprising the following steps: heat-treating the tin-containing waste liquid to convert the tin component into metastannic acid; performing a first solid-liquid separation on the heat-treated tin-containing waste liquid to obtain tin sludge and a first filtrate; adding a purifying agent to the first filtrate, followed by a second solid-liquid separation to obtain copper salt and a second filtrate; preparing a regenerated sub-liquid from the second filtrate, adding a tin-removing component to the second filtrate, and returning it to the tin-removing line for reuse as a tin-removing agent. This method requires the addition of a large amount of purifying agent and cannot extract the tin. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a method for regenerating tin from tin stripping waste liquid in a nitric acid-based system. The tin stripping waste liquid can be regenerated through acidification filtration and heat treatment, and tin can be prepared into tin dioxide through a simple process. The process route is simple and the cost is low.

[0005] This invention provides a method for tin extraction and regeneration of tin-removing waste liquid in a nitric acid-based system, comprising the following steps:

[0006] S1. Industrial nitric acid is added to the tin stripping waste liquid in the nitric acid type system to make H + The concentration was 4.8-5.0 mol / L, and the first filtrate was obtained by filtration.

[0007] S2. The first filtrate is heated to 65-70℃ and reacted for 1-2 hours. After filtration, tin mud and regenerated tin stripping solution are obtained. The regenerated tin stripping solution is returned to the production line for continued use.

[0008] S3. Add alkaline solution to the tin slurry until the pH is above 13, heat to completely dissolve, filter and pass CO2 through until the pH is < 9, filter to obtain sodium stannate solid, calcine the sodium stannate solid at 300-350℃ to obtain tin dioxide solid.

[0009] Preferably, in step S1, the filtration is performed using a 5µm precision filter.

[0010] Preferably, in step S2, nitric acid or other tin stripping solution components are added before the regenerated tin stripping solution is returned to the production line.

[0011] Preferably, in step S3, the alkaline solution is a sodium hydroxide solution.

[0012] Preferably, in step S1, the concentration of the industrial nitric acid is 40-50%.

[0013] Preferably, in step S2, the first filtrate is stirred while being heated, and the stirring rate is 200-250 r / min.

[0014] Preferably, in step S3, stirring is performed during heating and dissolving, and the stirring rate is 200-250 r / min.

[0015] This invention uses tin stripping waste liquid as raw material, in which stannic acid is divided into α-stannic acid and β-stannic acid, with the general formula xSnO2.yH2O. Industrial nitric acid (concentrated nitric acid) is added, and the reaction is heated to cause a change in the molecular structure of the dissolved tin nitrate. The reaction equation is: xSnO2.yH2O + HNO3 (concentrated) → (SnO)5(OH) 10 • 5H₂O↓ + 20NO₂↑. When the pH of tin sludge is greater than 13, the tin in it will dissolve to form sodium stannate, while impurities such as copper and iron will remain in the sludge, thus achieving the separation of tin from other impurity ions.

[0016] Compared with the prior art, the present invention has the following advantages:

[0017] The method provided by this invention uses inexpensive and readily available raw materials, resulting in low cost; the process is simple, the reaction conditions are mild, and energy consumption is low; it eliminates the need for large amounts of alkali to neutralize the tin stripping waste liquid, reducing alkali usage by 50-70% compared to the neutralization method. The obtained tin dioxide product has a tin recovery rate of up to 99%, and no tin-containing solid waste is generated. Furthermore, the tin stripping solution can be regenerated through simple steps. Attached Figure Description

[0018] Figure 1 This is a process flow diagram of a method for regenerating tin from tin-removing waste liquid in a nitric acid-based system according to the present invention. Detailed Implementation

[0019] The technical solution of the present invention will be described below with reference to specific embodiments.

[0020] Unless otherwise specified, the raw materials and equipment involved in this invention are all commercially available products.

[0021] The content of each component in the tin stripping waste liquid of the nitric acid type system in this invention is as follows:

[0022] Nitric acid 4±0.5mol / L, tin ions 70±20g / L, copper 5±2g / L, iron 18±3g / L.

[0023] Example 1

[0024] A method for tin extraction and regeneration of tin-removing waste liquid in a nitric acid-based system, such as... Figure 1 As shown, the steps are as follows:

[0025] S1, 50% industrial nitric acid is added to the tin stripping waste liquid in the nitric acid type system to make H + The concentration was 5.0 mol / L, and the first filtrate was obtained by filtration.

[0026] S2. The first filtrate is heated to 70°C and reacted for 1 hour. After filtration, tin mud and regenerated tin stripping solution are obtained. The regenerated tin stripping solution is replenished with nitric acid, ferric chloride and other components and then returned to the production line for continued use.

[0027] S3. Add alkaline solution to the tin sludge until the pH is 13.5, heat to completely dissolve, filter out the remaining insoluble matter (copper, iron, etc.), then pass CO2 in to make the pH 8, filter to obtain a solid, and calcine the solid at 300℃ to obtain tin dioxide solid. The tin recovery rate is 99.3%.

[0028] Example 2

[0029] A method for tin extraction and regeneration of tin-removing waste liquid in a nitric acid-based system, such as... Figure 1 As shown, the steps are as follows:

[0030] S1. Add 40% industrial nitric acid to the tin stripping waste liquid in the nitric acid type system to make H... + The concentration was 4.8 mol / L, and the first filtrate was obtained after filtration.

[0031] S2. The first filtrate is heated to 65°C and reacted for 2 hours. After filtration, tin mud and regenerated tin stripping solution are obtained. After replenishing the components such as nitric acid and ferric chloride, the solution is returned to the production line for continued use.

[0032] S3. Add alkaline solution to the tin sludge until the pH is 14, heat to completely dissolve, filter out the remaining insoluble matter, and then pass CO2 into the solution to make the pH 8.5. Filter to obtain a solid, and calcine the solid at 350℃ to obtain tin dioxide solid. The tin recovery rate is 99.1%.

[0033] Comparative Example 1

[0034] The difference from Example 1 is that industrial nitric acid is not added in step S1, and the tin recovery rate is 85%.

[0035] Comparative Example 2

[0036] The difference from Example 1 is that industrial nitric acid was added, making H... + The concentration was 4.5 mol / L, and the tin recovery rate was 90%.

[0037] Comparative Example 3

[0038] The difference from Example 1 is that the concentration of industrial nitric acid in step S1 is 30%, and the tin recovery rate is 92%.

[0039] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Any other modifications or equivalent substitutions made by those skilled in the art to the technical solutions of the present invention, as long as they do not depart from the principles and scope of the technical solutions of the present invention, should be covered within the scope of the claims of the present invention.

Claims

1. A method for tin extraction and regeneration from tin-removing waste liquid in a nitric acid-based system, characterized in that, It consists of the following steps: S1. Industrial nitric acid is added to the tin stripping waste liquid in the nitric acid type system to make H + The concentration was 4.8-5.0 mol / L, and the first filtrate was obtained by filtration. S2. The first filtrate is heated to 65-70℃ and reacted for 1-2 hours. After filtration, tin mud and regenerated tin stripping solution are obtained. The regenerated tin stripping solution is returned to the production line for continued use. S3. Add alkaline solution to the tin slurry until the pH is above 13, heat it to completely dissolve it, filter it, and then pass CO2 through it until the pH is < 9. Filter to obtain sodium stannate solid. Calcine the sodium stannate solid at 300-350℃ to obtain tin dioxide solid.

2. The method for tin extraction and regeneration of tin-removing waste liquid in a nitric acid-based system according to claim 1, characterized in that, In step S1, the filtration is performed using a 5µm precision filter.

3. The method for tin extraction and regeneration of tin-removing waste liquid in a nitric acid-based system according to claim 1, characterized in that, In step S2, industrial nitric acid is added to the recycled tin stripping solution before it is returned to the production line.

4. The method for tin extraction and regeneration of tin-removing waste liquid in a nitric acid-based system according to claim 1, characterized in that, In step S3, the alkaline solution is a sodium hydroxide solution.

5. The method for tin extraction and regeneration of tin-removing waste liquid in a nitric acid-based system according to claim 1, characterized in that, In step S1, the concentration of the industrial nitric acid is 40-50%.

6. The method for tin extraction and regeneration of tin-removing waste liquid in a nitric acid-based system according to claim 1, characterized in that, In step S2, the first filtrate is stirred while being heated, and the stirring rate is 200-250 r / min.

7. The method for tin extraction and regeneration of tin-removing waste liquid in a nitric acid-based system according to claim 1, characterized in that, In step S3, stirring is performed during heating and dissolving, and the stirring rate is 200-250 r / min.

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