Method for preparing large-particle copper sulfate from circuit board copper-containing waste liquid through crystallization

Abstract

The invention relates to a method for preparing large-particle copper sulfate from circuit board copper-containing waste liquid through crystallization, which comprises the following steps: S1, adding an oxidizing agent into the waste liquid, adding alkali to adjust the pH value to 2-3.5, filtering, adding sulfuric acid, heating and boiling to obtain a primary purified solution; s2, performing multi-stage counter-current extraction on the solution obtained in the step S1 by using a copper extraction agent, and then performing reverse extraction by using concentrated sulfuric acid to obtain copper sulfate reverse extraction liquid; s3, taking part of the copper sulfate strip liquor obtained in the S2, and carrying out rapid cooling or spray granulation to obtain copper sulfate fine grains; s4, carrying out sectional controllable evaporative crystallization on the copper sulfate strip liquor obtained in S2 to obtain copper sulfate crystals; and S5, washing and drying the copper sulfate crystal to obtain a final product. The copper sulfate crystal obtained by the method for preparing the large-particle copper sulfate from the copper-containing waste liquid of the circuit board through crystallization is large in particle size, the average particle size can reach 0.5-2.0 mm, the particle size distribution is concentrated, the crystal form is complete, and the purity is high.

Description

Technical Field

[0001] This invention belongs to the field of industrial wastewater treatment and resource recycling technology, specifically relating to a method for preparing large-particle copper sulfate from copper-containing waste liquid from circuit boards. Background Technology

[0002] The production of printed circuit boards generates a large amount of copper-containing waste liquid (such as acidic copper chloride etching waste liquid, micro-etching waste liquid, etc.), which has a high copper content. Direct discharge of such waste liquid will cause serious environmental pollution and resource waste. Therefore, recycling the copper resources generated from these waste liquids is of great significance.

[0003] Currently, the mainstream methods for recovering copper from this type of waste liquid include electrolysis, displacement, and precipitation-redissolution-evaporation crystallization. Among these, evaporation crystallization is an important way to produce copper sulfate, a high-value-added product. However, copper sulfate crystals obtained by existing technologies generally suffer from the following problems: (1) Fine grains: mostly powdery or fine needle-like crystals, with poor flowability, easy to generate dust, resulting in large losses during subsequent filtration, washing, drying, packaging and transportation, and easy to caking, affecting the product appearance and market value.

[0004] (2) Limited purity: The waste liquid contains Cl - Fe 2+ / Fe 3+ Ni 2+ Zn 2+ Impurity ions, such as complex ions, are easily trapped in copper sulfate crystals during the crystallization process in the form of complexes or co-crystallization, resulting in low product purity, which usually makes it difficult to meet industrial grade or higher standards (such as electroplating grade) requirements.

[0005] (3) Balance between crystallization rate and energy consumption: Pursuing a high crystallization rate often requires deep evaporation, which can easily lead to the simultaneous concentration and precipitation of impurities and high energy consumption; while controlling impurities may reduce the copper recovery rate.

[0006] (4) Poor process stability: Due to the fluctuation of waste liquid composition, the conventional crystallization process parameters are not very adaptable, making it difficult to continuously and stably produce large-particle, high-purity products.

[0007] Therefore, developing a key technology that can stably and efficiently prepare large-particle, high-purity copper sulfate crystals from complex copper-containing waste liquid from circuit boards has significant environmental and economic value. Summary of the Invention

[0008] The purpose of this invention is to provide a method for preparing large-particle copper sulfate from copper-containing waste liquid of circuit boards. The prepared copper sulfate crystals are large, with an average particle size of 0.5-2.0 mm, concentrated particle size distribution, complete crystal shape, and high purity.

[0009] The technical solution adopted by this invention to solve the above problems is as follows: a method for preparing large-particle copper sulfate by crystallization from copper-containing waste liquid of circuit boards, comprising the following steps: S1. Add an oxidant to the copper-containing waste liquid of the circuit board to oxidize ferrous ions to ferric ions, and add alkali to adjust the pH to 2~3.5 so that impurities such as iron and aluminum precipitate in the form of hydroxides. Filter, add sulfuric acid and heat to boil to fully remove free chlorine and hydrogen chloride, and obtain a primary purified copper sulfate solution. S2. The solution obtained in S1 is subjected to multi-stage countercurrent extraction using a copper extractant, allowing copper to selectively enter the organic phase and react with residual Cl. - Ni 2+ Zn 2+ After the impurities are thoroughly separated, concentrated sulfuric acid is used for back-extraction to obtain a high-purity, high-concentration copper sulfate back-extraction solution. This step can fundamentally separate the impurities and lay the foundation for the growth of high-purity, large-particle crystals. S3. Take a portion of the copper sulfate back-extraction solution obtained in S2 and use rapid cooling or spray granulation to obtain uniform copper sulfate fine crystals with a particle size of 50-150 micrometers, which are used as seed crystals for later use. S4. The copper sulfate back-extraction solution obtained in S2 is used to obtain copper sulfate crystals by a segmented controlled evaporation crystallization method, specifically as follows: S4-1 Concentration Stage: The copper sulfate back-extraction solution obtained in S2 is initially concentrated to bring the solution concentration to a state close to saturation but without crystallization. S4-2 Seed crystal growth stage: Add the seed crystals prepared in step S3, control the evaporation rate at a low level, maintain the solution in a slightly metastable state, allow the seed crystals to grow slowly, and inhibit the formation of new crystal nuclei; S4-3 Crystal growth stage: After the seed crystals have grown uniformly, the evaporation rate is gradually increased and the temperature is slowly reduced. By utilizing the dual driving forces of concentration and temperature, the crystals continue to grow in layers on the existing seed crystals to obtain large-particle crystals. S4-4 Crystal growth and discharge: When the average particle size of the crystals reaches the target size, evaporation is stopped, and the crystals are grown by stirring at a constant temperature. Then, solid-liquid separation is carried out to obtain large copper sulfate crystals. S5. Wash the separated large copper sulfate crystals and then dry them under low-temperature airflow to obtain the final product.

[0010] Preferably, the oxidant in step S1 is hydrogen peroxide, and the heating and boiling time is 30-90 minutes.

[0011] Preferably, the copper extractant in step S2 is a hydroxyoxime extractant or an M5640 extractant.

[0012] Preferably, the copper sulfate solution obtained by back-extraction in step S2 contains Cu 2+ The concentration should be controlled at 120-180 g / L.

[0013] Preferably, step S4 is carried out in a forced circulation evaporation crystallizer, which is equipped with a fine crystal collection-dissolution circuit, an online particle size monitoring device, and an automatic control system (DCS / PLC).

[0014] Preferably, the online particle size monitoring device is an online particle size analyzer or an image analysis system.

[0015] Preferably, the S4-2 seed crystal growth stage specifically involves: adjusting the solution temperature to 40-55℃, adding the seed crystals prepared in step S3, and controlling the evaporation rate to 0.5-1.5 kg water / (m³). 2 •h) maintains the solution in a slightly metastable state, allowing the seed crystals to grow slowly and inhibiting the formation of new crystal nuclei.

[0016] Preferably, the S4-3 crystal growth stage specifically involves: after the seed crystals have grown uniformly, gradually increasing the evaporation rate to 1.5–3.0 kg water / (m³). 2 ·h), and slowly cool at a rate of 0.1~0.5℃ / hour, using the dual driving force of concentration and temperature to promote the continuous layered growth of crystals on the existing seed crystals, and obtain large-particle crystals.

[0017] Preferably, in step S4-4, the crystals are grown under constant temperature for 0.5-2 hours.

[0018] Compared with the prior art, the advantages of the present invention are as follows: (1) The present invention uses extraction and back-extraction and segmented controllable crystallization process to prepare copper sulfate crystals with large particles, an average particle size of 0.5-2.0 mm, concentrated particle size distribution, complete crystal shape and high purity. The segmented strategy of "first nucleation and then growth" combined with seed technology, fine crystal elimination and online monitoring and control effectively inhibits secondary nucleation, promotes the directional growth of crystals, improves crystallization rate and product yield, and reduces energy consumption.

[0019] (2) By integrating online particle size monitoring and automatic control system, the present invention achieves precise control of crystallization process, reduces human intervention, ensures product quality consistency, and is suitable for continuous and large-scale production. Detailed Implementation

[0020] The present invention will be further described in detail below with reference to the embodiments. Example 1

[0021] Take 10L of acidic copper chloride etching waste liquid from a PCB factory, containing Cu 2+ 85g / L, Cl - 120g / L, Fe 2+ 2.5g / L.

[0022] S1: Add concentrated sulfuric acid to adjust the pH to 2.0, heat and boil at 85℃ for 60 minutes with stirring. After cooling, add 5 ml of 30% hydrogen peroxide, stir for 30 minutes, then adjust the pH to 4.0 with NaOH solution, filter, and obtain purified solution A.

[0023] S2: Purified solution A was subjected to three-stage countercurrent extraction using a 30% M5640 sulfonated kerosene solution, followed by two-stage back-extraction using a 200 g / L sulfuric acid solution to obtain Cu-containing solution. 2+ 150g / L high-purity copper sulfate back-extraction solution B.

[0024] S3: Take a portion of solution B, rapidly cool and crystallize, and sieve to obtain uniform seed crystals of 80-120 micrometers.

[0025] S4: Pump the remaining solution B into an OSLO crystallizer and concentrate it to near the saturation point at 60°C and a low evaporation rate. Cool to 50°C, add seed crystals (0.5% w / w), and control the evaporation rate at 1.0 kg water / (m³). 2 • h) Crystallize for 2 hours, then slowly cool to 30°C at a rate of 0.3°C / hour, while gradually increasing the evaporation rate to 2.0 kg water / (m²) 2 ·h), crystallization continues for 8 hours. During the process, the crystal growth is monitored by an online particle size analyzer, and the fine crystal collector is automatically controlled to work. The crystals are discharged after 1 hour of crystal growth.

[0026] S5: Centrifuge, wash with saturated copper sulfate solution at 5℃, and dry with airflow at 35℃.

[0027] Results: Copper sulfate crystals were obtained with an average particle size of 0.82 mm, a D90 particle size of >1.2 mm, and regular blue orthorhombic crystals. The purity (CuSO4·5H2O) was 99.1%, and the copper recovery rate was 96.5%. Example 2

[0028] Take 10L of micro-etching waste liquid from a PCB factory, containing Cu 2+ 50g / L, Cl - 15g / L, H2SO4 balance.

[0029] S1: Add concentrated sulfuric acid to adjust the pH to 1.5, heat and boil at 90℃ for 40 minutes with stirring, cool, add 3 ml of 30% hydrogen peroxide to oxidize, then adjust the pH to 3.8 with NaOH solution to precipitate, filter, and obtain purified solution A.

[0030] S2: Because Cl - Since the content is low, the extraction step is omitted, and S1 purification solution A is used directly.

[0031] S3: Take a portion of solution B, rapidly cool and crystallize, and sieve to obtain uniform seed crystals of 100-150 micrometers.

[0032] S4: Crystallization is carried out in a forced circulation (FC) crystallizer, following the segmented temperature and evaporation control strategy of Example 1, but the crystal growth temperature is set to 45°C and the cooling rate during the growth stage is set to 0.2°C / hour.

[0033] S5: Same as Example 1.

[0034] Results: Copper sulfate crystals with an average particle size of 0.65 mm were obtained, with a purity of 98.7% and a copper recovery rate of 95.8%.

[0035] Comparative Example Using the same waste liquid as in Example 1, after only simple pretreatment in S1, the liquid was directly evaporated and concentrated under normal pressure until a large amount of crystals were precipitated, and then cooled, centrifuged, and dried.

[0036] Results: A mixture of fine needle-like and powdery particles was obtained, with an average particle size of <0.1 mm. It was prone to agglomeration, with a purity of only 96.5%, and contained obvious chloride ion impurities.

[0037] It is evident that the method of this invention can effectively produce large-particle, high-purity copper sulfate products from copper-containing waste liquid of circuit boards, which is significantly superior to conventional crystallization methods.

[0038] In addition to the above embodiments, the present invention also includes other embodiments. All technical solutions formed by equivalent transformation or equivalent substitution should fall within the protection scope of the claims of the present invention.

Claims

1. A process for the crystallization of large-grained copper sulfate from a copper-containing waste solution of a circuit board, characterized in that: The method comprises the following steps: S1. Adding an oxidizing agent to the copper-containing waste liquid of the circuit board to oxidize ferrous ions to ferric ions, and adding a base to adjust the pH to 2-3.5, filtering, and adding sulfuric acid for heating and boiling to obtain a primary purified copper sulfate solution; S2. The solution obtained in S1 is subjected to multi-stage countercurrent extraction with a copper extraction agent, and then subjected to back extraction with concentrated sulfuric acid to obtain a high-purity and high-concentration copper sulfate back-extraction solution; S3. A part of the copper sulfate back-extraction solution obtained in S2 is subjected to rapid cooling or spray granulation to obtain uniform copper sulfate fine crystals with a particle size of 50-150 microns, which are used as seed crystals for standby; S4. The copper sulfate back-extraction solution obtained in S2 is subjected to stepwise controllable evaporation crystallization to obtain copper sulfate crystals, specifically as follows: S4-1. Concentration stage: The copper sulfate back-extraction solution obtained in S2 is preliminarily concentrated to a state close to saturation but without crystallization; S4-2. Seed crystal growth stage: The seed crystals prepared in S3 are added, the evaporation rate is controlled at a low level, and the solution is maintained in a slightly metastable state, so that the seed crystals grow slowly and the generation of new crystal nuclei is inhibited; S4-3. Crystal growth stage: After the seed crystals grow uniformly, the evaporation rate is gradually increased, and the temperature is slowly decreased, so that the concentration and temperature double driving force is utilized to promote the continuous layer growth of the crystals on the existing seed crystals, and large particle crystals are obtained; S4-4. Crystal growth and discharge: When the average particle size of the crystals reaches the target size, the evaporation is stopped, the crystals are stirred at a constant temperature for a certain period of time, and then solid-liquid separation is performed to obtain large particle copper sulfate crystals; S5. The separated large particle copper sulfate crystals are washed and then dried under a low-temperature gas flow to obtain the final product.

2. The process for the crystallization of copper sulfate from a copper containing waste solution of a circuit board according to claim 1, characterized in that: The oxidizing agent in step S1 is hydrogen peroxide, and the heating and boiling time is 30-90 min.

3. The process for the crystallization of copper sulfate from a copper containing waste solution of a circuit board according to claim 1, characterized in that: The copper extraction agent in step S2 is a hydroxamic acid extraction agent or M5640 extraction agent.

4. The method of claim 1, wherein the method is characterized by: The Cu concentration in the copper sulfate solution obtained in step S2 2+ was controlled at 120-180 g / L.

5. The method of claim 1, wherein the method is characterized by: The step S4 is carried out in a forced circulation evaporation crystallizer, which is provided with a fine crystal trapping-dissolving circuit, an online particle size monitoring device, and an automatic control system.

6. The process for the crystallization of copper sulfate from copper containing waste solutions of printed circuit boards according to claim 1, characterized in that: The online particle size monitoring device is an online particle size analyzer or an image analysis system.

7. The process for the crystallization of copper sulfate from copper containing waste solutions of printed circuit boards according to claim 1, characterized in that: The S4-2 seed crystal growing stage is specifically as follows: the solution temperature is adjusted to 40-55°C, the seed crystal prepared in the S3 step is added, the evaporation rate is controlled to be 0.5-1.5 kg water / (m 2 ·h), the solution is kept in a slightly metastable state, the seed crystal is slowly grown, and the generation of new crystal nucleus is inhibited.

8. The process for the crystallization of copper sulfate from copper containing waste solutions from printed circuit boards according to claim 1, characterized by that: The S4-3 crystal growth stage specifically includes: after the crystal seeds grow uniformly, the evaporation rate is gradually increased to 1.5-3.0 kg water / (m 2 ·h), and the temperature is slowly decreased at a rate of 0.1-0.5 ℃ / h, so as to promote the crystal to continuously grow in layers on the existing crystal seeds by using the double driving force of concentration and temperature, and obtain large-grained crystals.

9. The process for the crystallization of copper sulfate from copper containing waste solutions from printed circuit boards according to claim 1, characterized by that: In step S4-4, the stirring and aging at a constant temperature is performed for 0.5-2 h.