阅读说明：本技术 一种高纯度三分之八水合硫酸镉的生产方法 (Production method of high-purity one-third cadmium sulfate octahydrate ) 是由 张佳 王波 于 2021-04-14 设计创作，主要内容包括：本发明公开了一种高纯度三分之八水合硫酸镉的生产方法,包括如下步骤：将氧化镉溶于硫酸溶液中得到硫酸镉溶液,然后调pH值至2～5,再过滤,将滤液蒸发至比重为1.6～1.7g/mL；向蒸发后的滤液中加入有机溶剂醇或乙酸乙酯或乙醚,进行搅拌萃取,待萃取后进行离心,然后将离心所得晶体晾干,即得到三分之八水合硫酸镉。本发明的生产方法生产效率高、工艺步骤简单、成本低且安全、环境友好,且制备的三分之八水合硫酸镉产品产率和纯度高,适用于大规模生产。(The invention discloses a production method of high-purity one-third cadmium sulfate octahydrate, which comprises the following steps: dissolving cadmium oxide in a sulfuric acid solution to obtain a cadmium sulfate solution, then adjusting the pH value to 2-5, filtering, and evaporating the filtrate until the specific gravity is 1.6-1.7 g/mL; adding organic solvent alcohol or ethyl acetate or diethyl ether into the evaporated filtrate, stirring and extracting, centrifuging after extraction, and then drying the crystal obtained by centrifuging to obtain the trisection cadmium sulfate octahydrate. The production method has the advantages of high production efficiency, simple process steps, low cost, safety and environmental friendliness, and the prepared one-third octahydrate cadmium sulfate product has high yield and purity and is suitable for large-scale production.)

1. A production method of high-purity one-third cadmium sulfate octahydrate is characterized by comprising the following steps:

(1) dissolving cadmium oxide in a sulfuric acid solution to obtain a cadmium sulfate solution, then adjusting the pH value to 2-5, filtering, and evaporating the filtrate until the specific gravity is 1.6-1.7 g/mL;

(2) adding organic solvent alcohol or ethyl acetate or diethyl ether into the evaporated filtrate, stirring and extracting, centrifuging after extraction, and then drying the crystal obtained by centrifuging to obtain the trisection cadmium sulfate octahydrate.

2. The method for producing high-purity cadmium sulfate octahydrate of claim 1, wherein in step (2), the volume ratio of the organic solvent to the cadmium sulfate solution is 0.8-1.5: 1.

3. The method for producing high-purity cadmium sulfate octahydrate of claim 1, wherein in step (2), the stirring extraction time is 0.1-1 hour.

4. The method for producing high-purity cadmium sulfate octahydrate according to claim 1, wherein in the step (2), the centrifugation is carried out for 0.5 to 2 hours.

5. The method for producing high-purity cadmium sulfate octahydrate according to any one of claims 1 to 4, wherein in the step (1), the sulfuric acid solution is prepared by mixing concentrated sulfuric acid and water in a volume ratio of 1: 4.8-5.0; the mass concentration of the concentrated sulfuric acid is 98%.

6. The method for producing high-purity cadmium sulfate octahydrate according to any one of claims 1 to 4, wherein cadmium oxide or sulfuric acid is used to adjust the pH in step (1).

7. The method for producing high-purity cadmium sulfate octahydrate according to any one of claims 1 to 4, wherein in the step (2), the air-drying temperature is 25 to 30 ℃, and the air-drying relative humidity is 30 to 60 percent; the airing time is 8-36 hours.

8. The method for producing high-purity cadmium sulfate octahydrate of any one of claims 1 to 4, wherein after the step (2), the method further comprises the step of re-dissolving the prepared cadmium sulfate octahydrate and cadmium sulfate, and then performing secondary extraction crystallization to obtain cadmium sulfate crystals with higher purity.

9. The method for producing high-purity cadmium sulfate octahydrate according to any one of claims 1 to 4, wherein in step (2), the alcohol is ethanol.

10. The method for producing high-purity cadmium sulfate octahydrate according to any one of claims 1 to 4, wherein in the step (2), mother liquor obtained by centrifugation is subjected to reduced pressure distillation, ethanol obtained by distillation is recycled, and the obtained mother liquor can be used as a raw material preparation solution for producing low-purity cadmium sulfate crystals.

Technical Field

The invention relates to a preparation method of a chemical product, in particular to a production method of high-purity one-third cadmium sulfate octahydrate.

Background

Cadmium sulfate octahydrate of three thirds (3 CdSO)₄·8H₂O) is an unstable hydrate of cadmium sulfate. Readily soluble in water and practically insoluble in alcohol and ethyl acetate and diethyl ether. The solubility of the cadmium sulfate solution is insensitive to temperature, and crystallization dissolution change can not occur due to temperature change, so that the cadmium sulfate solution can be used for preparing standard battery cadmium. In addition, in the aspects of chemical analysis, electroplating and batteriesAll have wide application.

At present, in the traditional method, cadmium metal is used as a raw material, nitric acid is used as an oxidant, the acidity is adjusted by sulfuric acid to be dissolved, reaction is carried out, ferric ions are removed by cadmium nitrate, then filtration, acidification, evaporation to dryness and ignition are carried out, water and ethanol are added for dissolution after cooling, suction filtration crystallization is carried out, crystals are washed by ethanol, and the products are obtained after drying. However, the method has low production efficiency, complex process, high cost, large amount of hydrogen generated, potential safety and environmental protection hazards, and the yield and purity of the produced product are required to be further improved in the industrial process.

Disclosure of Invention

The technical problem to be solved by the invention is to overcome the defects and defects mentioned in the background technology, and provide a production method of high-purity one-third of cadmium sulfate octahydrate, which has the advantages of high product yield and purity, high production efficiency, simple process steps, low cost, safety and environmental friendliness.

In order to achieve the above purpose, the invention adopts the following technical scheme:

a production method of high-purity one-third cadmium sulfate octahydrate comprises the following steps:

(1) dissolving cadmium oxide in a sulfuric acid solution to obtain a cadmium sulfate solution, then adjusting the pH value to 2-5, filtering, and evaporating the filtrate until the specific gravity is 1.6-1.7 g/mL;

(2) adding organic solvent alcohol or ethyl acetate or diethyl ether into the evaporated filtrate, stirring and extracting, centrifuging after extraction, and then drying the crystal obtained by centrifuging to obtain the trisection cadmium sulfate octahydrate.

In the above production method of high-purity cadmium sulfate octahydrate, preferably, in the step (2), the volume ratio of the organic solvent to the cadmium sulfate solution is 0.8-1.5: 1.

In the above production method of high-purity cadmium sulfate octahydrate, preferably, in step (2), the stirring extraction time is 0.1-1 hour.

In the above method for producing high-purity cadmium sulfate octahydrate, preferably, in step (2), the centrifugation time is 0.5-2 hours.

In the above production method of high-purity cadmium sulfate octahydrate, preferably, in the step (1), the sulfuric acid solution is prepared by mixing concentrated sulfuric acid and water in a volume ratio of 1: 4.8-5.0; the mass concentration of the concentrated sulfuric acid is 98%.

In the method for producing high-purity cadmium sulfate octahydrate, cadmium oxide or sulfuric acid is preferably used for adjusting the pH value in the step (1).

Preferably, in the step (2), the airing temperature is 25-30 ℃, and the airing relative humidity is 30-60%; the airing time is 8-36 hours.

Preferably, after the step (2), the method for producing high-purity cadmium sulfate octahydrate comprises the step of re-dissolving the prepared cadmium sulfate octahydrate and cadmium trisulfide and then carrying out secondary extraction and crystallization to obtain cadmium sulfate crystals with higher purity.

In the above method for producing high-purity cadmium sulfate octahydrate, preferably, in step (2), the alcohol is ethanol.

In the above method for producing high-purity cadmium sulfate octahydrate, preferably, in step (2), the mother liquor obtained by centrifugation is subjected to reduced pressure distillation, the ethanol obtained by distillation is returned for use, and the obtained mother liquor can be used as a raw material preparation solution for producing low-purity cadmium sulfate crystals.

Compared with the prior art, the invention has the following beneficial effects:

the invention takes cadmium oxide and sulfuric acid as raw materials, and prepares a cadmium sulfate octahydrate product of three thirds by the steps of dissolving, filtering, adjusting the pH value, extracting, centrifuging at medium speed, airing and the like. The method has the advantages of simple operation, short flow, less required equipment, low production cost and high production efficiency, can directly obtain the high-purity cadmium sulfate octahydrate trisection, avoids the generation of the cadmium sulfate monohydrate, can be used for large-scale production, can obtain the cadmium sulfate octahydrate trisection with the purity of more than 5N, and has higher yield compared with the existing preparation method.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate an embodiment of the invention and, together with the description, serve to explain the invention and not to limit the invention.

FIG. 1 shows 3CdSO according to the present invention₄·8H₂A preparation process flow chart of O.

Detailed Description

The present invention will now be described in detail with reference to the drawings, which are given by way of illustration and explanation only and should not be construed to limit the scope of the present invention in any way. Furthermore, features from embodiments in this document and from different embodiments may be combined accordingly by a person skilled in the art from the description in this document.

Aiming at the existing 3CdSO₄·8H₂The applicant, after a great deal of research, prepares a 4N-6N one-third octahydrate cadmium sulfate product by taking cadmium oxide and sulfuric acid as raw materials and performing the steps of dissolving, filtering, adjusting the pH value, extracting, centrifuging, airing and the like, and the specific implementation mode is as follows:

1. dissolution reaction

Mixing sulfuric acid and water according to the proportion of 1: 4.8-5.0, adding cadmium oxide powder with the molar ratio of 1.01-1.1: 1.00, and stirring for dissolving for 3-10 hours. And (3) adjusting the pH value of the cadmium sulfate solution to 2-5 by using cadmium oxide or sulfuric acid, filtering, evaporating at 90-110 ℃ until the specific gravity is 1.6-1.8 g/mL. In the step, impurities insoluble in sulfuric acid can be removed by filtration and then evaporated to improve the yield.

2. Extracting, crystallizing and drying in air

Cooling to normal temperature, adding ethanol with the volume ratio of 0.8-1.5: 1 to the cadmium sulfate solution, stirring and extracting for 0.1-1 hour, centrifuging at medium speed for 0.5-2 hours, and airing the centrifuged crystal in a ventilated place (normal temperature is 25-30 ℃, and relative humidity is 30% -60%) for 8-36 hours to obtain the product, namely the trisection cadmium sulfate octahydrate. Low speed centrifugation can meet the requirement. One third of the cadmium sulfate octahydrate can be directly obtained by ethanol extraction and airing, and the generation of the cadmium sulfate monohydrate is avoided.

Example 1

The preparation method of the one-third octahydrate cadmium sulfate comprises the following steps:

(1) taking 2.6L of water, putting the water into a beaker, slowly adding 540mL of analytically pure sulfuric acid (98%), stirring, then adding cadmium oxide in batches, wherein the total amount is 1.275kg, the molar ratio of the cadmium oxide to the sulfuric acid is 1.02:1.00, reacting for 3 hours, controlling the pH value of a reaction end point to be 2.5-3 by supplementing sulfuric acid, performing suction filtration, evaporating at 90 ℃, and evaporating until the specific gravity is 1.62 g/mL;

(2) after cooling to normal temperature, according to the volume ratio of the cadmium sulfate solution: mixing the two solutions at the ratio of 1:1 with ethanol, mixing the two solutions at normal temperature under ventilation, stirring the mixture by an explosion-proof motor, stirring the mixture for 0.5 hour, centrifuging the mixture at medium speed for 1 hour, distilling the ethanol in the obtained mother solution under reduced pressure for recycling, airing the obtained crystals in a ventilation position, and airing the crystals for 8 hours at the temperature of 28 ℃ and the relative humidity of 30% to obtain the trisection cadmium sulfate octahydrate.

In this example, the yield was 77.5% and the product purity reached 5N.

Example 2

The preparation method of the one-third octahydrate cadmium sulfate comprises the following steps:

(1) putting 2.7L of water into a beaker, slowly adding 540mL of analytically pure sulfuric acid (98%), stirring, then adding cadmium oxide in batches, wherein the total amount is 1.315kg, the molar ratio of the cadmium oxide to the sulfuric acid is 1.05:1.00, reacting for 10 hours, and the pH value at the end point of the reaction is 3.5-4, performing suction filtration, then evaporating at 110 ℃, and evaporating until the specific gravity is 1.65 g/mL;

(2) and after cooling to the normal temperature, mixing the cadmium sulfate solution and the ethanol according to the volume ratio of 1:1.5, mixing at the normal temperature under ventilation, stirring by using an explosion-proof motor, centrifuging at medium speed for 0.5 hour after stirring for 0.1 hour, carrying out reduced pressure distillation on alcohol in mother liquor for cyclic use, airing crystals at the ventilation position, and airing at the temperature of 25 ℃ and the relative humidity of 50% for 12-16 hours to obtain the cadmium sulfate octahydrate of three thirds.

In this example, the yield was 82.3% and the product purity reached 5N. In the actual large-scale production process, the reaction with the key pH value in the required range is difficult to realize in the step (1), and analytically pure sulfuric acid is required to be added to adjust the pH value.

Example 3

The preparation method of the one-third octahydrate cadmium sulfate comprises the following steps:

(1) putting 2.65L of water into a beaker, slowly adding 540mL of analytically pure sulfuric acid (98%), stirring, then adding 1.369kg of cadmium oxide in batches, wherein the molar ratio of the cadmium oxide to the sulfuric acid is 1.09:1.00, reacting for 7 hours, and controlling the pH to be 4.5-5 at the end point of the reaction, performing suction filtration, and then evaporating at 100 ℃ until the specific gravity is 1.7 g/mL;

(2) and after cooling to the normal temperature, mixing the cadmium sulfate solution and the ethanol according to the volume ratio of 1:0.8, mixing at the normal temperature under ventilation, stirring by using an explosion-proof motor, carrying out medium-speed centrifugation for 2 hours after stirring for 1 hour, carrying out reduced pressure distillation on alcohol in mother liquor for cyclic use, airing the obtained crystals at the ventilation position, and airing at the temperature of 30 ℃ and the relative humidity of 60% for 36 hours to obtain the trisection cadmium sulfate octahydrate.

The yield of this example was 79.7% and the product purity achieved a 5N rating. In the actual large-scale production process, the reaction with the key pH value in the required range is difficult to realize in the step (1), and analytically pure sulfuric acid is required to be added to adjust the pH value.

In the above embodiments, the mother liquor obtained by the centrifugation is distilled under reduced pressure, the ethanol obtained by distillation is returned for use, the obtained mother liquor can be used as a raw material preparation solution for producing low-purity cadmium sulfate crystals, and the primary mother liquor can also be returned to the step (1) for continuous use.

Typical analysis data of the one-third octahydrate cadmium sulfate product prepared by the method are shown in table 1, and as can be seen from table 1, compared with the existing enterprise standards, the method has the advantages that the prepared product has better quality, the impurity content is better controlled, the product prepared by the method has good stability, the single extraction rate reaches over 75 percent, and the cadmium solution in the obtained mother liquor can be recycled, so that the yield is higher, and the method is suitable for large-scale production.

Table 1 product analysis data

The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.