Tin extraction and regeneration method for nitric acid type system tin stripping waste liquid

Abstract

The invention relates to a tin extraction and regeneration method for nitric acid type system tin stripping waste liquid, and belongs to the technical field of resource recovery. The method comprises the following steps: S1, adding industrial nitric acid into the nitric acid type system tin stripping waste liquid to enable the H < + > concentration to be 4.8-5.0 mol / L, and filtering to obtain first filtrate; s2, the first filtrate is heated to 65-70 DEG C to react for 1-2 h, tin mud and regenerated tin stripping liquid are obtained through filtering, and the regenerated tin stripping liquid is returned to the production line to be continuously used; and S3, alkali liquor is added into the tin sludge until the pH value is 13 or above, heating is performed to enable the tin sludge to be completely dissolved, CO2 is introduced until the pH value is smaller than 9, filtering is performed to obtain a sodium stannate solid, and the sodium stannate solid is calcined at the temperature of 300-350 DEG C to obtain a tin dioxide solid.

Description

Technical Field

[0001] The present invention relates to the technical field of resource recovery, and particularly relates to a method for tin extraction and regeneration of nitric acid-based tin stripping waste liquid. Background Art

[0002] In the production process of printed circuit boards (PCBs), nitric acid-based tin-containing water is commonly used to remove the tin plating layer on the circuit board. When the tin etching ability of the tin-containing water decreases, it becomes tin stripping waste liquid. Tin stripping waste liquid is an acidic wastewater and belongs to hazardous waste. The tin content in the tin stripping waste liquid generally reaches more than 90 g / L, the copper content is 5 - 10 g / L, the nitric acid residue is 15 - 20%, and it also contains heterocyclic compounds, polycyclic aromatic hydrocarbon compounds and polymers. Therefore, the tin stripping waste liquid has strong corrosiveness and pollution. If it is directly discharged without reasonable treatment, it will inevitably cause serious pollution to water resources and the ecological environment; at the same time, the valuable metals tin and copper in the tin-containing waste liquid have high contents and high recovery values.

[0003] Currently, the treatment methods for tin-containing waste liquid mainly include: neutralization method, distillation method, metal ion removal and recycling method, diffusion dialysis method and solvent extraction method. For example, Chinese Patent CN113651480A reports a method for regenerating tin-containing waste liquid, which includes the following steps: performing heat treatment on the tin-containing waste liquid to convert the tin component in the tin-containing waste liquid into metastannic acid; performing the first solid-liquid separation on the heat-treated tin-containing waste liquid to obtain tin mud and a first filtrate; adding a impurity removal agent to the first filtrate, and performing the second solid-liquid separation to obtain copper salt and a second filtrate; performing regeneration mother liquor preparation on the second filtrate, and adding tin stripping components to the second filtrate and then returning it to the tin stripping line for reuse as a tin stripping reagent. This method requires adding a large amount of impurity removal agent and cannot extract tin. Summary of the Invention

[0004] Aiming at the deficiencies of the prior art, the present invention provides a method for tin extraction and regeneration of nitric acid-based tin stripping waste liquid. 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] A method for tin extraction and regeneration of nitric acid-based tin stripping waste liquid provided by the present invention includes the following steps: S1. Adding industrial nitric acid to the nitric acid-based tin stripping waste liquid to make the concentration of H + be 4.8 - 5.0 mol / L, and filtering to obtain a first filtrate; S2. Heating the first filtrate to 65 - 70 °C and reacting for 1 - 2 h, filtering to obtain tin mud and a regenerated tin stripping liquid, and the regenerated tin stripping liquid is returned to the production line for continued use; S3. Adding alkali solution to the tin mud until the pH is above 13, heating to completely dissolve, filtering and introducing CO 2To pH < 9, filter to obtain sodium stannate solid, and calcine the sodium stannate solid at 300 - 350 °C to obtain tin dioxide solid.

[0006] Preferably, in step S1, the filtration is through a 5 μm precision filter.

[0007] Preferably, in step S2, nitric acid or other tin stripping solution components are added before the regenerated tin stripping solution returns to the production line.

[0008] Preferably, in step S3, the alkaline solution is a sodium hydroxide solution.

[0009] Preferably, in step S1, the concentration of the industrial nitric acid is 40 - 50%.

[0010] Preferably, in step S2, stirring is performed when heating the first filtrate, and the stirring rate is 200 - 250 r / min.

[0011] Preferably, in step S3, stirring is performed during heating and dissolution, and the stirring rate is 200 - 250 r / min.

[0012] The present invention uses waste tin stripping solution as a raw material. Among them, stannic acid is divided into α - stannic acid and β - stannic acid, with the general formula xSnO 2 .yH 2 O. Add industrial nitric acid (concentrated nitric acid), heat and react to cause a molecular structure change of the dissolved stannic nitrate. The reaction equation is: xSnO 2 .yH 2 O + HNO 3 (concentrated) → (SnO) 5 (OH) 10 ·5H 2 O↓ + 20NO 2 ↑. When the tin mud has a pH > 13, the tin in it will dissolve to form sodium stannate, while impurities such as copper and iron remain in the mud, thus realizing the separation of tin from other impurity ions.

[0013] Compared with the prior art, the present invention has the following advantages: The method provided by the present invention has cheap and easily available raw materials, low cost; simple process, mild reaction conditions, and low energy consumption; there is no need to use a large amount of alkali to neutralize the waste tin stripping solution. Compared with the neutralization method, the alkali consumption is reduced by 50 - 70%. The obtained tin dioxide product has a tin recovery rate as high as 99% and does not produce tin - containing solid waste. Moreover, the regeneration of the tin stripping solution can be achieved through simple steps. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a process flow chart of a method for extracting tin and regenerating waste nitric acid - type tin stripping solution in the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0015] The technical solution of the present invention will be described below in conjunction with specific embodiments.

[0016] Unless otherwise specified, the raw materials, equipment, etc. involved in the present invention are all ordinary commercially available products.

[0017] The contents of each component in the nitric acid-based tin stripping waste liquid of the present invention are as follows: Nitric acid 4 ± 0.5 mol / L, tin ions 70 ± 20 g / L, copper 5 ± 2 g / L, iron 18 ± 3 g / L.

[0018] Example 1 A method for recovering and regenerating tin from nitric acid-based tin stripping waste liquid, as Figure 1 shown, the steps are as follows: S1. Add 50% industrial nitric acid to the nitric acid-based tin stripping waste liquid to make the concentration of H + 5.0 mol / L, and filter to obtain the first filtrate; S2. Heat the first filtrate to 70 °C and react for 1 h, filter to obtain tin mud and regenerated tin stripping liquid, and after replenishing components such as nitric acid and ferric chloride, return it to the production line for continued use; S3. Add alkali solution to the tin mud until the pH is 13.5, heat to completely dissolve it, filter the remaining insoluble substances (copper, iron, etc.), and then pass in CO 2 to make the pH 8, filter to obtain a solid, and calcine the solid at 300 °C to obtain tin dioxide solid, and the tin recovery rate is 99.3%.

[0019] Example 2 A method for recovering and regenerating tin from nitric acid-based tin stripping waste liquid, as Figure 1 shown, the steps are as follows: S1. Add 40% industrial nitric acid to the nitric acid-based tin stripping waste liquid to make the concentration of H + 4.8 mol / L, and filter to obtain the first filtrate; S2. Heat the first filtrate to 65 °C and react for 2 h, filter to obtain tin mud and regenerated tin stripping liquid, replenish components such as nitric acid and ferric chloride, and return it to the production line for continued use; S3. Add alkali solution to the tin mud until the pH is 14, heat to completely dissolve it, filter the remaining insoluble substances, and then pass CO 2 into the solution to make the pH 8.5, filter to obtain a solid, and calcine the solid at 350 °C to obtain tin dioxide solid, and the tin recovery rate is 99.1%.

[0020] Comparative Example 1 The difference from Example 1 is that industrial nitric acid is not added in step S1, and the tin recovery rate is 85%.

[0021] Comparative Example 2 The difference from Example 1 is that industrial nitric acid is added to make the concentration of H + 4.5 mol / L, and the tin recovery rate is 90%.

[0022] Comparative Example 3 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%.

[0023] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Any other modifications or equivalent replacements made by those of ordinary skill in the art to the technical solutions of the present invention should be covered within the scope of the claims of the present invention as long as they do not depart from the principles and scope of the technical solutions of the present invention.

Claims

1. A method for regenerating tin from tin stripping waste liquid in a nitric acid system, characterized in that: The following steps are involved: S1. Add industrial nitric acid to the tin stripping wastewater of the nitric acid type system to make H + The concentration is 4.8-5.0 mol / L, and the first filtrate is obtained by filtration; S2, the first filtrate is heated to 65-70℃ for 1-2 hours, and the tin sludge and regenerated tin stripping liquid are filtered out, and the regenerated tin stripping liquid is returned to the production line for continued use; S3. Add alkali solution to the tin mud until the pH is above 13, heat to completely dissolve it, filter it, introduce CO2 until the pH is less than 9, filter to obtain solid sodium stannate, and calcine the solid sodium stannate at 300-350° C. to obtain solid tin dioxide.

2. The nitric acid type system tin stripping waste liquid tin extraction regeneration method according to claim 1, characterized in that, In step S1, the filtration is performed through a 5 um precision filter.

3. The nitric acid type system tin stripping waste liquid tin extraction regeneration method according to claim 1, characterized in that, In step S2, industrial nitric acid is added to the regenerated tin stripping solution before it returns to the production line.

4. The nitric acid type system tin stripping waste liquid tin extraction regeneration method according to claim 1, characterized in that, In step S3, the alkali solution is a sodium hydroxide solution.

5. The method for regenerating tin from nitric acid type tin stripping waste liquid according to claim 1, characterized in that: In step S1, the concentration of the industrial nitric acid is 40-50%.

6. The method for regenerating tin from tin stripping waste liquid of a nitric acid type 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 regenerating tin from nitric acid type tin stripping waste liquid 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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