CN115108576A - A kind of purification method of copper sulfate pentahydrate crystal and application thereof - Google Patents

Abstract

The invention belongs to the technical field of compound purification, and in particular relates to a purification method of copper sulfate pentahydrate crystals and application thereof. In the present invention, seed crystals of a certain size and addition rate are added to the crude copper sulfate solution for cultivation, and a four-stage cooling strategy is adopted to control the cooling rate to keep the solution in a metastable state, and gradually cool to 25-34° C. to obtain pentahydrate Copper sulfate crystal; the purity of the obtained copper sulfate pentahydrate crystal reaches the electroplating level, and the crystal morphology of the copper sulfate pentahydrate crystal is also greatly improved, the average crystal particle size is large, the particle size distribution is relatively concentrated, and it is not easy to agglomerate; at the same time, The method has simple process, greatly shortened preparation time, does not need to use strong acid and strong alkali solution, is green and environmentally friendly, has low resource consumption, and is favorable for large-scale production.

Description

A kind of purification method of copper sulfate pentahydrate crystal and its application

technical field

The invention belongs to the technical field of compound purification. More specifically, it relates to a purification method of copper sulfate pentahydrate crystal and its application.

Background technique

Copper sulfate pentahydrate, commonly known as blue vitriol, bile vitriol or copper vitriol, is an important inorganic chemical product. In the field of electroplating, the demand for electroplating-grade copper sulfate with good quality and high purity is increasing. Most of the products are industrial grade products with low purity and poor quality, fine particles, uneven particle size, poor crystal shape, not dense, and easy to break in the drying and screening process. Therefore, the preparation of high-purity copper sulfate pentahydrate crystals is of great significance.

In industry, some crude copper sulfate pentahydrate is often produced, and the application of crude copper sulfate pentahydrate is limited due to its low content of copper sulfate. The utilization rate of copper crude products, such as Yu Yaoping et al. studied the method of increasing copper sulfate crystal particles in the crude copper sulfate purification experiment, specifically adding sodium hydroxide and hydrogen peroxide to the copper sulfate solution to remove impurities such as ferrous sulfate, After adding seed crystals, sulfuric acid solution was added for acidification, followed by evaporation and natural cooling to precipitate crystals. It can effectively increase the size of copper sulfate crystals and remove impurities such as ferrous sulfate in crude copper sulfate, but it needs to add strong acid and strong alkali solution sulfuric acid in the purification process, which does not conform to the concept of green chemistry, and natural cooling is in the crystallization process. In the initial stage, the supersaturation of the solution increases sharply, reaches a certain peak, and then decreases sharply, so that the supersaturation of the crystallization process is maintained at a very low level for a long period of time, resulting in the occurrence of primary nucleation. And the problem of low production capacity (Yu Yaoping. The method of increasing the crystal particles of copper sulfate in the purification experiment of crude copper sulfate [J]. Journal of Huaihua University, 2003.). Therefore, there is an urgent need to provide a method for purifying copper sulfate pentahydrate crystals from copper sulfate pentahydrate crude product, which is environmentally friendly and has good primary nucleation production capacity.

SUMMARY OF THE INVENTION

The technical problem to be solved by the present invention is to overcome the defects and deficiencies that the existing method for purifying copper sulfate pentahydrate crystals from crude copper sulfate pentahydrate does not conform to the concept of green chemistry, the primary nucleation phenomenon is poorly controlled, and the production capacity is low. The invention discloses a method for purifying copper sulfate pentahydrate crystals, which is green and environmentally friendly, has high yield, high purity of copper sulfate, narrow crystal particle size distribution range, regular crystal morphology, and can greatly shorten the purification time.

The purpose of this invention is to provide the application of a kind of purification method of copper sulfate pentahydrate crystal in purifying copper sulfate pentahydrate crystal.

Above-mentioned purpose of the present invention is achieved through the following technical solutions:

The present invention protects a method for purifying copper sulfate pentahydrate crystals, comprising the following steps:

Mix the crude copper sulfate with water and heat to 85-100°C to dissolve, filter while hot, cool down to 56-63°C at a rate of 0.05°C/min-0.25°C/min for the first time, add seed crystals for 0.5-1h , and then the second cooling at a rate of 0.2 °C/min ~ 0.3 °C/min to 50 ~ 55 °C, the third cooling at a rate of 0.3 °C/min ~ 0.4 °C/min to 35 ~ 45 °C, the fourth cooling Cool down to 25-34°C at a rate of 0.4°C/min～0.5°C/min, let stand, and post-processing;

When the particle size of the seed crystal is 50-85 mesh, the seed crystal addition rate is 8%-12%; when the particle size of the seed crystal is 90-100 mesh, the seed crystal addition rate is 6%-12%.

The invention creatively adopts a four-stage grading cooling strategy, and keeps the solution in a metastable state by controlling the cooling rate. The growth rate is completely controlled by the cooling rate, which effectively avoids the primary nucleation phenomenon that occurs when the solution enters the unstable zone. If the natural cooling operation is adopted, the supersaturation of the solution increases sharply at the initial stage of the crystallization process, reaches a certain peak, and then decreases sharply, so that the supersaturation of the crystallization process remains at a very high level for a long period of time. Low levels, leading to problems with low primary nucleation productivity. As for the constant rate cooling operation, the disadvantages similar to the free cooling operation still exist.

The seed crystal formulation design is the key to the success of crystallization. The higher the seed crystal addition rate, the higher the cost. In addition, the growth rate of the single crystal will be inhibited and the average size of the product will be reduced. rate, resulting in the occurrence of primary nucleation and irregular product particle size.

The narrower the particle size distribution of the crystal seed, the narrower the particle size distribution of the obtained product, and the more uniform the particle size distribution of the product; the smaller the size of the seed crystal (less than 100 mesh) can improve the output of the product, but the resulting crystal particle size is smaller, Larger size (greater than 50 mesh) is conducive to the formation of crystals with larger particle size, but the product yield is lower. Only within the particle size range of the present invention, a large crystal particle size and a high yield can be achieved.

Preferably, the concentration of the copper sulfate crude product mixed with water is 750g/L～890g/L.

Preferably, the copper sulfate crude product is industrial copper sulfate crude product.

Preferably, stirring is also required during the first cooling, and the stirring rate is 80-150 r/min.

Preferably, stirring is also required during the second cooling, and the stirring rate is 300-400 r/min.

Preferably, stirring is also required during the third cooling, and the stirring rate is 300-400 r/min.

Preferably, stirring is also required during the fourth cooling, and the stirring rate is 300-400 r/min.

Preferably, the temperature is lowered to 36-40° C. for the third time.

Preferably, the temperature is lowered to 28-32° C. for the fourth time.

Preferably, the seed crystals are sieved through a sample sieve.

Preferably, the seed crystal needs to be washed with an appropriate amount of water after passing through the sample sieve.

Washing with an appropriate amount of water can dissolve the fine particles adhering to the seed crystal, making the surface of the seed crystal smoother and the particle size distribution more uniform.

Preferably, the water comprises deionized water.

Preferably, the standing time is 0.5-1.5 h.

The present invention further protects the application of the method for purifying copper sulfate pentahydrate crystals in the preparation of copper sulfate pentahydrate crystals.

The present invention has the following beneficial effects:

In the present invention, seed crystals with a certain size and addition rate are added to the crude copper sulfate solution for cultivation, and a four-stage cooling strategy is adopted to control the cooling rate to keep the solution in a metastable state, and gradually cool to 25-34° C. to obtain pentahydrate Copper sulfate crystal; the purity of the obtained copper sulfate pentahydrate crystal reaches the electroplating level, and the crystal morphology of the copper sulfate pentahydrate crystal is also greatly improved, the average crystal particle size is large, the particle size distribution is relatively concentrated, and it is not easy to agglomerate; at the same time, The method has the advantages of simple process, greatly shortened preparation time, no need to use strong acid and strong alkali solution, green environmental protection, low resource consumption, and is favorable for large-scale production.

Description of drawings

FIG. 1 is a crystal morphology diagram obtained by magnifying 40 times of the copper sulfate pentahydrate crystals obtained in Examples 1 to 3 by an optical microscope. From left to right, they are Example 1, Example 2, and Example 3.

2 is a particle size distribution diagram of the copper sulfate pentahydrate crystals obtained in Examples 1 to 3 obtained by a laser particle size analyzer. From left to right, they are Example 1, Example 2, and Example 3.

3 is a crystal morphology diagram obtained by magnifying 40 times of the copper sulfate pentahydrate crystals obtained in Comparative Examples 1 to 2 of the present invention by an optical microscope, from left to right are Comparative Example 1 and Comparative Example 2.

4 is a particle size distribution diagram of the copper sulfate pentahydrate crystals obtained in Comparative Examples 1 to 2 of the present invention obtained by a laser particle size analyzer, from left to right are Comparative Example 1 and Comparative Example 2.

5 is a crystal morphology diagram of the copper sulfate pentahydrate crystals obtained by the comparative examples 3 to 5 of the present invention, which are obtained by magnifying 40 times by an optical microscope.

6 is a particle size distribution diagram of the copper sulfate pentahydrate crystals obtained in Comparative Examples 3 to 5 of the present invention obtained by a laser particle size particle shape analyzer, from left to right are Comparative Example 3, Comparative Example 4, and Comparative Example 5.

Fig. 7 is the crystal morphology of the copper sulfate pentahydrate crystal obtained in Comparative Example 6 obtained by magnifying 40 times by an optical microscope and the particle size distribution diagram obtained by a laser particle size analyzer. From left to right are the crystal morphology. Graph, particle size distribution graph.

Detailed ways

The present invention is further described below with reference to the accompanying drawings and specific embodiments, but the embodiments do not limit the present invention in any form. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the technical field.

Unless otherwise specified, the reagents and materials used in the following examples are commercially available.

Main component and content of industrial copper sulfate crude product used in the present invention are as shown in table 1:

Table 1 Main components and content of industrial copper sulfate crude product

project Industrial copper sulfate Copper sulfate (CuSO₄·5H₂O) content w/% 95.63 Arsenic (As) content w/% 0.00011 Lead (Pb) content w/% 0.00002 Calcium (Ca) content w/% 0.00700 Iron (Fe) content w/% 0.01364 Cobalt (Co) content w/% 0.00002 Nickel (Ni) content w/% 0.00002 Zinc (Zn) content w/% 0.00006 Cadmium (Cd) content w/% 0.00000 Manganese (Mn) content w/% 0.00010 Aluminum (Al) content w/% 0.00319 Chromium (Cr) content w/% 0.00066 Chloride (as Cl) content w/% 0.01250 Water insoluble content w/% 0.01630 pH(50g/L solution) 3.60

The preparation of embodiment 1 copper sulfate pentahydrate crystal

Take 84.48g of industrial copper sulfate crude product and mix it with 100ml of deionized water and heat it to 85°C, suction filtration while hot to obtain a clear solution, cool down to 58.5°C with a cooling rate of 0.2°C/min and a stirring rate of 120r/min, add 65 The seed crystals were sieved and washed with water, the seed crystal addition rate was 10%, the stirring rate was maintained at 120 r/min, and the crystals were grown at a constant temperature of 58.5 °C for 0.5 h. The obtained seed crystals were evenly and regularly suspended in the entire solution, followed by The cooling rate of 0.2°C/min and the stirring rate of 350r/min were cooled to 50°C, the cooling rate of 0.3°C/min and the stirring rate of 350r/min were cooled to 38°C, and the cooling rate of 0.4°C/min, 350r/min The stirring rate of min was cooled to 30 °C, left for 1 h, vacuum filtered, washed with deionized water, and the washed crystals were vacuum dried for 3 h to obtain copper sulfate pentahydrate crystals.

The preparation of embodiment 2 copper sulfate pentahydrate crystal

Take 84.48g of industrial copper sulfate crude product and mix it with 100ml of deionized water and heat it to 85°C, suction filtration while hot to obtain a clear solution, cool down to 58.5°C with a cooling rate of 0.2°C/min and a stirring rate of 120r/min, and add 100 The seed crystals were sieved and washed with water, the seed crystal addition rate was 6%, the stirring rate was maintained at 120 r/min, and the crystals were grown at a constant temperature of 58.5 °C for 0.5 h. The obtained seeds were uniformly and regularly suspended in the whole solution, followed by The cooling rate of 0.2°C/min and the stirring rate of 350r/min were cooled to 50°C, the cooling rate of 0.3°C/min and the stirring rate of 350r/min were cooled to 38°C, and the cooling rate of 0.4°C/min, 350r/min The stirring rate of min was cooled to 30 °C, left for 1 h, vacuum filtered, washed with deionized water, and the washed crystals were vacuum dried for 3 h to obtain copper sulfate pentahydrate crystals.

The difference from Example 1 is that the seed crystals pass through a 100-mesh screen, and the seed crystal addition rate is 6%.

The preparation of embodiment 3 copper sulfate pentahydrate crystal

Take 84.48g of industrial copper sulfate crude product and mix it with 100ml of deionized water and heat it to 85°C, suction filtration while hot to obtain a clear solution, cool down to 58.5°C with a cooling rate of 0.2°C/min and a stirring rate of 120r/min, and add 100 The seed crystals were sieved and washed with water, the seed crystal addition rate was 10%, the stirring rate was maintained at 120 r/min, and the crystals were grown at a constant temperature of 58.5 °C for 0.5 h. The obtained seed crystals were evenly and regularly suspended in the entire solution, followed by The cooling rate of 0.2°C/min and the stirring rate of 350r/min were cooled to 50°C, the cooling rate of 0.3°C/min and the stirring rate of 350r/min were cooled to 38°C, and the cooling rate of 0.4°C/min, 350r/min The stirring rate of min was cooled to 30 °C, left for 1 h, vacuum filtered, washed with deionized water, and the washed crystals were vacuum dried for 3 h to obtain copper sulfate pentahydrate crystals.

The difference from Example 1 is that the seed crystals pass through a 100-mesh screen.

Comparative Example 1 Preparation of copper sulfate pentahydrate crystals

Take 84.48g of industrial copper sulfate crude product and mix it with 100ml of deionized water and heat it to 85°C, suction filtration while hot to obtain a clear solution, cool down to 58.5°C with a cooling rate of 0.2°C/min and a stirring rate of 120r/min, add 65 The seed crystals were sieved and washed with water, the seed crystal addition rate was 2%, the stirring rate was maintained at 120 r/min, and the crystals were grown at a constant temperature of 58.5 ° C for 0.5 h. The obtained seed crystals were uniformly and regularly suspended in the entire solution, followed by The cooling rate of 0.2°C/min and the stirring rate of 350r/min were cooled to 50°C, the cooling rate of 0.3°C/min and the stirring rate of 350r/min were cooled to 38°C, and the cooling rate of 0.4°C/min, 350r/min The stirring rate of min was cooled to 30 °C, left for 1 h, vacuum filtered, washed with deionized water, and the washed crystals were vacuum dried for 3 h to obtain copper sulfate pentahydrate crystals.

The difference from Example 1 is that the seed crystal addition rate is 2%.

Comparative Example 2 Preparation of copper sulfate pentahydrate crystals

Take 84.48g of industrial copper sulfate crude product and mix it with 100ml of deionized water and heat it to 85°C, suction filtration while hot to obtain a clear solution, cool down to 58.5°C with a cooling rate of 0.2°C/min and a stirring rate of 120r/min, add 65 The seed crystals were sieved and washed with water, the seed crystal addition rate was 6%, the stirring rate was maintained at 120 r/min, and the crystals were grown at a constant temperature of 58.5 °C for 0.5 h. The obtained seeds were uniformly and regularly suspended in the whole solution, followed by The cooling rate of 0.2°C/min and the stirring rate of 350r/min were cooled to 50°C, the cooling rate of 0.3°C/min and the stirring rate of 350r/min were cooled to 38°C, and the cooling rate of 0.4°C/min, 350r/min The stirring rate of min was cooled to 30 °C, left for 1 h, vacuum filtered, washed with deionized water, and the washed crystals were vacuum dried for 3 h to obtain copper sulfate pentahydrate crystals.

The difference from Example 1 is that the seed crystal addition rate is 6%.

Comparative Example 3 Preparation of copper sulfate pentahydrate crystals

Take 84.48g of industrial copper sulfate crude product and mix it with 100ml of deionized water and heat it to 85°C, suction filtration while hot to obtain a clear solution, cool down to 58.5°C with a cooling rate of 0.2°C/min and a stirring rate of 120r/min, and add 100 The seed crystals were sieved and washed with water, the seed crystal addition rate was 2%, the stirring rate was maintained at 120 r/min, and the crystals were grown at a constant temperature of 58.5 ° C for 0.5 h. The obtained seed crystals were uniformly and regularly suspended in the entire solution, followed by The cooling rate of 0.2°C/min and the stirring rate of 350r/min were cooled to 50°C, the cooling rate of 0.3°C/min and the stirring rate of 350r/min were cooled to 38°C, and the cooling rate of 0.4°C/min, 350r/min The stirring rate of min was cooled to 30 °C, left for 1 h, vacuum filtered, washed with deionized water, and the washed crystals were vacuum dried for 3 h to obtain copper sulfate pentahydrate crystals.

The difference from Example 1 is that the seed crystals pass through a 100-mesh screen, and the seed crystal addition rate is 2%.

Comparative Example 4 Preparation of copper sulfate pentahydrate crystals

Take 84.48g of industrial copper sulfate crude product and mix it with 100ml of deionized water and heat it to 85°C, filter while hot to obtain a clear solution, cool down to 58.5°C with a cooling rate of 0.2°C/min and a stirring rate of 120r/min, add 120 The seed crystals were sieved and washed with water, the seed crystal addition rate was 2%, the stirring rate was maintained at 120 r/min, and the crystals were grown at a constant temperature of 58.5 ° C for 0.5 h. The obtained seed crystals were uniformly and regularly suspended in the entire solution, followed by Cool down to 50°C with a cooling rate of 0.2°C/min and stirring rate of 350r/min, cool down to 38°C with a cooling rate of 0.3°C/min and stirring rate of 350r/min, and cool down to 38°C with a cooling rate of 0.4°C/min to 350r/min The stirring rate was cooled to 30 °C, left standing for 1 h, vacuum filtered, washed with deionized water, and the washed crystals were vacuum dried for 3 h to obtain copper sulfate pentahydrate crystals.

The difference from Example 1 is that the seed crystals pass through a 120-mesh screen, and the seed crystal addition rate is 2%.

Comparative Example 5 Preparation of copper sulfate pentahydrate crystals

Take 84.48g of industrial copper sulfate crude product and mix it with 100ml of deionized water and heat it to 85°C, filter while hot to obtain a clear solution, cool down to 58.5°C with a cooling rate of 0.2°C/min and a stirring rate of 120r/min, add 120 The seed crystals were sieved and washed with water, the seed crystal addition rate was 6%, the stirring rate was maintained at 120 r/min, and the crystals were grown at a constant temperature of 58.5 °C for 0.5 h. The obtained seeds were uniformly and regularly suspended in the whole solution, followed by The cooling rate of 0.2°C/min and the stirring rate of 350r/min were cooled to 50°C, the cooling rate of 0.3°C/min and the stirring rate of 350r/min were cooled to 38°C, and the cooling rate of 0.4°C/min, 350r/min The stirring rate of min was cooled to 30 °C, left for 1 h, vacuum filtered, washed with deionized water, and the washed crystals were vacuum dried for 3 h to obtain copper sulfate pentahydrate crystals.

The difference from Example 1 is that the seed crystals pass through a 120-mesh screen, and the seed crystal addition rate is 6%.

The preparation of comparative example 6 copper sulfate pentahydrate crystal

Take 84.48g of industrial copper sulfate crude product and mix it with 100ml of deionized water and heat it to 85°C, filter while hot to obtain a clear solution, cool down to 58.5°C with a cooling rate of 0.2°C/min and a stirring rate of 120r/min, add 120 The seed crystals were sieved and washed with water, the seed crystal addition rate was 2%, the stirring rate was maintained at 120 r/min, and the crystals were grown at a constant temperature of 58.5 ° C for 0.5 h. The obtained seed crystals were uniformly and regularly suspended in the entire solution, followed by The cooling rate of 0.2°C/min and the stirring rate of 350r/min were cooled to 50°C, the cooling rate of 0.3°C/min and the stirring rate of 350r/min were cooled to 38°C, and the cooling rate of 0.4°C/min, 350r/min The stirring rate of min was cooled to 30 °C, left for 1 h, vacuum filtered, washed with deionized water, and the washed crystals were vacuum dried for 3 h to obtain copper sulfate pentahydrate crystals.

The difference from Example 1 is that the seed crystals pass through a 120-mesh screen.

Experimental Example 1 Determination of the main component content of copper sulfate pentahydrate crystals

The copper sulfate pentahydrate crystals obtained in Examples 1 to 3 and Comparative Examples 1 to 6 are subjected to main component content determination, and the method used is derived from HG/T 3592-2020 "Copper Sulfate for Electroplating" (the standard of copper sulfate for electroplating is as follows. Table 4), the main components and content results of copper sulfate pentahydrate crystals are shown in Tables 2-3.

The main components and content of copper sulfate pentahydrate crystals obtained in Table 2 Examples 1-3

The main components and content of copper sulfate pentahydrate crystals obtained in Table 3 Comparative Examples 1 to 6

Table 4 HG/T 3592-2020 "Copper Sulfate for Electroplating"

As can be seen from Table 2, and the content of copper sulfate pentahydrate in Examples 1 to 3 is higher than that of the raw materials, it can be seen from Table 4 that Example 1 reaches the electroplating grade qualified product, which is close to the electroplating grade first-class product; Examples 2 and 3 reached the first-class electroplating grade, and Example 3 was close to the first-class electroplating grade; in terms of impurity content, the Fe content decreased from 0.0136% to 0.0020% to 0.0030% as a whole, meeting the requirements of the first-class electroplating grade; Ca The overall content has dropped from 0.0070% to 0.0002% to 0.0017%, and the quality is between the first-class and first-class electroplating grades; the chloride content has dropped from 0.0125% to 0.0009% to 0.0035%, and the quality is between the electroplating grades. Among the equal and superior products, in addition, the copper sulfate pentahydrate of the above embodiment is optimized to the electroplating grade copper sulfate, and the yield is also very consistent with the production efficiency, which are 92.6%, 90.51%, and 93.2%, respectively.

It can be seen from Table 3 that although the purity of Comparative Examples 1 to 3 is close to that of electroplating grade copper sulfate, the low yield is not suitable for actual production. It can be seen that only changing the combination of the mesh number of the crystal seed sieve and the seed crystal addition rate makes the The prepared copper sulfate pentahydrate crystals were unqualified products.

Experimental Example 2 Morphology and particle size analysis of copper sulfate pentahydrate crystals

The copper sulfate pentahydrate crystals obtained in Examples 1 to 3 and Comparative Examples 1 to 6 were subjected to particle size distribution analysis, and crystal micromorphology was analyzed by an optical microscope.

As shown in Figures 1 to 7: the particle size distribution of copper sulfate pentahydrate crystals obtained in Examples 1 to 3 is relatively narrow, wherein Example 3 is a unimodal distribution, and the particle size is mainly distributed between 1000 and 1200um, and Example 1 is distributed The range is wide, but the particle size is mainly distributed between 1000 and 2000um. Example 2 is close to a unimodal distribution, and the particle size is mainly distributed in 900 to 1200um, indicating that the seed crystals in this seed crystal formula are screened. In the crystallization process, the probability of primary nucleation is small, so that the crystals precipitated during the cooling crystallization process can be regularly attached to the seed crystal and grow regularly, with a large average particle size, and can be seen from the crystal topography. It can be seen that the crystal forms of Examples 1 to 3 are very regular, and it is not easy to adhere to the mother liquor and entrain impurities, thereby improving the product purity.

The particle size distribution of copper sulfate pentahydrate crystals obtained in Comparative Examples 1 to 6 cannot be taken into account at the same time as the particle size and crystal morphology. For example, the particle size distribution of Comparative Examples 5 and 6 is narrow, showing a unimodal distribution, but the particle size distribution is mainly Between 250 and 300um, and from the crystal morphology, it can be seen that the crystal form is disordered, the primary nucleation phenomenon is serious, and the fine crystals are difficult to wash and filter, and it is easy to be mixed with the mother liquor to affect the purity.

The above-mentioned embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited by the above-mentioned embodiments, and any other changes, modifications, substitutions, combinations, The simplification should be equivalent replacement manners, which are all included in the protection scope of the present invention.

Claims (10)

1. A method for purifying copper sulfate pentahydrate crystals is characterized by comprising the following steps:

mixing a copper sulfate crude product with water, heating to 85-100 ℃ for dissolving, filtering while the mixture is hot, cooling to 56-63 ℃ at the rate of 0.05-0.25 ℃/min for the first time, adding seed crystals, and culturing for 0.5-1 h; cooling to 50-55 ℃ at the speed of 0.2-0.3 ℃/min for the second time, cooling to 35-45 ℃ at the speed of 0.3-0.4 ℃/min for the third time, cooling to 25-34 ℃ at the speed of 0.4-0.5 ℃/min for the fourth time, standing, and performing post-treatment to obtain the final product;

when the grain size of the seed crystal is 50-85 meshes, the seed crystal addition rate is 8% -12%; when the grain size of the seed crystal is 90-100 meshes, the seed crystal addition rate is 6% -12%.

2. The purification method of claim 1, wherein the concentration of the crude copper sulfate mixed with water is 750g/L to 890 g/L.

3. The purification method according to claim 1, wherein stirring is required during the first temperature reduction, and the stirring speed is 80-150 r/min.

4. The purification method according to claim 1, wherein stirring is further required during the second temperature reduction, and the stirring speed is 300-400 r/min.

5. The purification method according to claim 1, wherein stirring is further required during the third temperature reduction, and the stirring speed is 300-400 r/min.

6. The purification method according to claim 1, wherein stirring is further required during the fourth temperature reduction, and the stirring speed is 300-400 r/min.

7. The purification method according to claim 1, wherein the third temperature reduction is carried out to 36-40 ℃.

8. The purification method according to claim 1, wherein the fourth temperature reduction is carried out to 28-32 ℃.

9. The purification method according to claim 1, wherein the standing time is 0.5 to 1.5 hours.

10. Use of the method for purifying copper sulfate pentahydrate crystals as claimed in any one of claims 1 to 9 for the preparation of copper sulfate pentahydrate crystals.

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