Method for preparing magnesium sulfate heptahydrate from magnesite flotation tailings

Abstract

The invention relates to the technical field of preparation of magnesium sulfate heptahydrate, in particular to a method for preparing magnesium sulfate heptahydrate from magnesite flotation tailings, which comprises the following steps: 1) crushing the magnesite flotation tailings until the granularity is less than or equal to 0.074 mm to obtain tailings powder; 2) mixing and stirring the tailing powder and sulfuric acid, and then filtering to obtain a crude magnesium sulfate solution; 3) adding sodium hydroxide into the crude magnesium sulfate solution, adjusting the pH value of the solution to 6, and filtering; 4) concentrating the concentration of magnesium sulfate to 30%-40%; (5) cooling the concentrated solution to 0-10 DEG C, and controlling the cooling speed to be 1-5 DEG C / h, so that magnesium sulfate heptahydrate is fully crystallized and separated out; 6) filtering the crystallized mixture, and separating out magnesium sulfate heptahydrate crystals; and 7) finally drying the filtered magnesium sulfate heptahydrate crystal to obtain a magnesium sulfate heptahydrate finished product. According to the method, high-purity magnesium sulfate heptahydrate can be obtained, so that the influence of tailings on the environment is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of preparing magnesium sulfate heptahydrate, and particularly to a method for preparing magnesium sulfate heptahydrate from the flotation tailings of magnesite ore. Background Art

[0002] Magnesite ore is a mineral resource rich in magnesium oxide, and a certain amount of magnesium resources still exist in its flotation tailings. At present, the utilization of the flotation tailings of magnesite ore is not sufficient. The accumulation of a large amount of tailings not only occupies land but also may have a certain impact on the environment.

[0003] As an important chemical raw material, magnesium sulfate heptahydrate has a wide range of applications in the fields of agriculture, food, medicine, etc. Therefore, developing a method for preparing magnesium sulfate heptahydrate from the flotation tailings of magnesite ore is of great significance for improving the resource utilization rate and reducing the accumulation of tailings. Summary of the Invention

[0004] To overcome the defects of the prior art, the technical problem solved by the present invention is to provide a method for preparing magnesium sulfate heptahydrate from the flotation tailings of magnesite ore, which can obtain magnesium sulfate heptahydrate with high purity, and further solve the impact of tailings on the environment.

[0005] To achieve the above object, the present invention is realized by adopting the following technical solutions:

[0006] A method for preparing magnesium sulfate heptahydrate from the flotation tailings of magnesite ore, comprising the following steps:

[0007] 1) Crushing the flotation tailings of magnesite ore to a particle size ≤ 0.074 mm to obtain tailings powder;

[0008] 2) Mixing and stirring the tailings powder with sulfuric acid, and then filtering to obtain a crude magnesium sulfate solution; wherein, the concentration of sulfuric acid is 35% - 45%;

[0009] 3) Adding sodium hydroxide to the crude magnesium sulfate solution to adjust the pH value of the solution to 6, and then filtering;

[0010] 4) Concentrating the solution filtered in step 3) to concentrate the concentration of magnesium sulfate to 30% - 40%;

[0011] 5) Cooling the concentrated solution to 0 - 10 °C, controlling the cooling rate at 1 - 5 °C / h to allow magnesium sulfate heptahydrate to fully crystallize and precipitate;

[0012] 6) Filtering the mixture after crystallization to separate out magnesium sulfate heptahydrate crystals;

[0013] 7) Finally, drying the filtered magnesium sulfate heptahydrate crystals to obtain the finished product of magnesium sulfate heptahydrate.

[0014] In step 2), the mass ratio of the tailings powder to sulfuric acid is 1:(1-5); the stirring time is 2-4 h, the stirring speed is 300-600 r / min; the stirring temperature is 60-80 °C.

[0015] In step 3), the concentration of sodium hydroxide is 10%-20%.

[0016] In step 5), the stirring speed during the concentration process is 200-400 r / min.

[0017] In step 7), the drying temperature is 40-60 °C, and the drying time is 0.5-3 h.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0019] 1) The present invention converts traditional waste flotation tailings into magnesium sulfate heptahydrate, reducing environmental pollution and land occupation caused by tailings accumulation.

[0020] 2) In the present invention, by adding sodium hydroxide to adjust the pH to 6, Fe 3+ , Al3+ form insoluble substances or complex precipitates, realizing efficient separation of impurities and avoiding magnesium loss.

[0021] 3) In the present invention, the solution concentrated to a concentration of 30%-40% is crystallized at a slow cooling rate, which can promote the formation of large crystal particles, reduce impurity entrapment, and improve the product purity and yield. Specific Embodiments

[0022] The following further describes the specific embodiments of the present invention:

[0023] Example 1

[0024] A method for preparing magnesium sulfate heptahydrate from magnesite flotation tailings, comprising the following steps:

[0025] 1) Crush the magnesite flotation tailings to a particle size of ≤0.074 mm to obtain tailings powder.

[0026] 2) Mix the tailings powder with sulfuric acid and stir, then filter to obtain a crude magnesium sulfate solution; wherein, the concentration of sulfuric acid is 40%. The mass ratio of the tailings powder to sulfuric acid is 1:3, the stirring time is 4 h, the stirring speed is 400 r / min, and the stirring temperature is 80 °C.

[0027] 3) Add sodium hydroxide with a concentration of 20% to the crude magnesium sulfate solution, adjust the pH value of the solution to 6, and then filter.

[0028] 4) Concentrate the solution filtered in step 3) to a concentration of 35% for magnesium sulfate.

[0029] 5) Cool the concentrated solution to 5°C at a cooling rate of 2°C / h to fully precipitate magnesium sulfate heptahydrate. The stirring speed during concentration is 350 r / min.

[0030] 6) Filter the crystallized mixture to separate the magnesium sulfate heptahydrate crystals.

[0031] 7) Finally, dry the filtered magnesium sulfate heptahydrate crystals to obtain the finished product of magnesium sulfate heptahydrate. The drying temperature is 55°C and the drying time is 2 h.

[0032] Example 2

[0033] A method for preparing magnesium sulfate heptahydrate from the flotation tailings of magnesite, comprising the following steps:

[0034] 1) Crush the flotation tailings of magnesite to a particle size of ≤0.074 mm to obtain tailing powder.

[0035] 2) Mix and stir the tailing powder with sulfuric acid, and then filter to obtain a crude magnesium sulfate solution; wherein, the concentration of sulfuric acid is 42%. The mass ratio of the tailing powder to sulfuric acid is 1:4, the stirring time is 4 h, the stirring speed is 400 r / min, and the stirring temperature is 80°C.

[0036] 3) Add sodium hydroxide with a concentration of 15% to the crude magnesium sulfate solution, adjust the pH value of the solution to 6, and then filter.

[0037] 4) Concentrate the solution filtered in step 3) to a concentration of magnesium sulfate of 30%.

[0038] 5) Cool the concentrated solution to 4°C at a cooling rate of 2.5°C / h to fully precipitate magnesium sulfate heptahydrate. The stirring speed during concentration is 350 r / min.

[0039] 6) Filter the crystallized mixture to separate the magnesium sulfate heptahydrate crystals.

[0040] 7) Finally, dry the filtered magnesium sulfate heptahydrate crystals to obtain the finished product of magnesium sulfate heptahydrate. The drying temperature is 60°C and the drying time is 3 h.

[0041] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, and these simple modifications all fall within the protection scope of the present invention. In addition, it should be noted that, among the various specific technical features described in the above specific embodiments, they can be combined in any suitable manner without conflict. To avoid unnecessary repetition, the present invention will not separately describe various possible combination methods. In addition, any combination can be made between various different embodiments of the present invention, as long as it does not violate the idea of the present invention, it should also be regarded as the content disclosed by the present invention.

Claims

1. A method for preparing magnesium sulfate heptahydrate from flotation tailings of magnesite, characterized in that It includes the following steps: 1) Crush the magnesite flotation tailings to a particle size of ≤ 0.074 mm to obtain tailings powder; 2) Mix the tailings powder with sulfuric acid and stir, then filter to obtain a crude magnesium sulfate solution; wherein, the concentration of sulfuric acid is 35% - 45%; 3) Add sodium hydroxide to the crude magnesium sulfate solution to adjust the pH value of the solution to 6, and then filter; 4) Concentrate the solution filtered in step 3) to concentrate the concentration of magnesium sulfate to 30% - 40%; 5) Cool the concentrated solution to 0 - 10 °C, and control the cooling rate at 1 - 5 °C / h to fully crystallize magnesium sulfate heptahydrate; 6) Filter the crystallized mixture to separate out magnesium sulfate heptahydrate crystals; 7) Finally, dry the filtered magnesium sulfate heptahydrate crystals to obtain the finished product of magnesium sulfate heptahydrate.

2. A method for preparing magnesium sulfate heptahydrate from magnesite flotation tailings according to claim 1, characterized in that, In step 2), the mass ratio of the tailings powder to sulfuric acid is 1:(1 - 5); the stirring time is 2 - 4 h, and the stirring speed is 300 - 600 r / min; the stirring temperature is 60 - 80 °C.

3. A method for preparing magnesium sulfate heptahydrate from magnesite flotation tailings according to claim 1, characterized in that, In step 3), the concentration of sodium hydroxide is 10% - 20%.

4. A method for preparing magnesium sulfate heptahydrate from magnesite flotation tailings according to claim 1, characterized in that, In step 5), the stirring speed during the concentration process is 200 - 400 r / min.

5. A method for preparing magnesium sulfate heptahydrate from magnesite flotation tailings according to claim 1, characterized in that, In step 7), the drying temperature is 40 - 60 °C, and the drying time is 0.5 - 3 h.