Method for preparing active magnesium oxide from magnesium-containing minerals

Abstract

The invention relates to the technical field of magnesium oxide preparation, in particular to a method for preparing active magnesium oxide from magnesium-containing minerals, which comprises the following specific steps: 1) raw material pretreatment: selecting magnesite and grinding to obtain magnesite powder; 2) acid leaching and oxidation: mixing the magnesite powder with a sulfuric acid solution, and then adding hydrogen peroxide; (3) filtering and separating: filtering the magnesite powder subjected to acid leaching; 4) primary alkali addition: adding a sodium hydroxide solution into the acid leaching solution to enable the pH value of the solution to be neutral, and then filtering; (5) adding alkali for the second time: adding sodium hydroxide into the solution filtered in the step (4) to enable the pH value of the solution to be 10-12, and introducing the carbon dioxide obtained in the step (2) into the solution; and 6) filtering and heat treatment: sequentially filtering, heating and re-filtering the magnesium hydroxide solution, and then carrying out heat treatment to obtain magnesium hydroxide. According to the invention, the acid-base synergistic optimization reaction process is adopted, the reaction efficiency is improved, the production cost is reduced, and the environmental pollution is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of preparing magnesium oxide, in particular to a method for preparing active magnesium oxide from magnesium-containing minerals. Background Art

[0002] The world has huge reserves of magnesium-containing mineral resources, such as magnesite, dolomite, serpentine, etc. my country is also a country with magnesium-containing mineral resources, and its magnesite reserves rank among the top in the world. These magnesium-containing minerals are widely distributed and have mining value, providing sufficient raw material basis for large-scale production of magnesium oxide.

[0003] Traditional methods for producing magnesium oxide include: traditional thermal decomposition method, chemical precipitation method, etc. The traditional thermal decomposition method is to directly calcine magnesium-containing compounds such as magnesium carbonate or magnesium hydroxide. Although the process is simple, it is difficult to accurately control the reaction conditions, which can easily lead to larger product particle size, small specific surface area, limited activity, and relatively high energy consumption. The chemical precipitation method is to add a precipitant to the magnesium salt solution to precipitate magnesium ions, and then calcine to obtain magnesium oxide. However, the selection of precipitants and the control of the amount of addition are difficult, which can easily cause incomplete precipitation or impurities to be mixed in, affecting the purity and activity of magnesium oxide, and there is a lot of wastewater discharge, and the pressure of environmental protection treatment is high.

[0004] In view of the shortcomings of the traditional method, the present invention proposes to use an acid-base synergistic method to prepare active magnesium oxide. Summary of the invention

[0005] In order to overcome the defects of the prior art, the technical problem solved by the present invention is to provide a method for preparing active magnesium oxide from magnesium-containing minerals. The present invention adopts acid-base synergistic optimization of the reaction process, improves reaction efficiency, reduces production costs, and reduces environmental pollution.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A method for preparing active magnesium oxide from magnesium-containing minerals comprises the following steps:

[0008] 1) Raw material pretreatment: magnesite is selected and ground to obtain magnesite powder;

[0009] 2) Acid leaching and oxidation: Mix magnesite powder with sulfuric acid solution, then add hydrogen peroxide and stir thoroughly; wherein the concentration of sulfuric acid is 30% to 40%, and the concentration of hydrogen peroxide is 1% to 5%;

[0010] 3) Filtration and separation: Filter the magnesite powder after acid leaching to obtain the acid leaching solution and residue containing magnesium ions;

[0011] 4) Adding alkali once: adding sodium hydroxide solution to the acid leaching solution to make the pH value of the solution neutral, and then filtering; wherein the concentration of the sodium hydroxide solution is 35% to 40%;

[0012] 5) Secondary alkali addition: Sodium hydroxide is added to the filtered solution in step 4) to make the pH value of the solution 10 - 12, and the carbon dioxide generated in step 2) is introduced into the solution to produce a magnesium bicarbonate solution; wherein, the concentration of the sodium hydroxide solution is 28% - 30%;

[0013] 6) Filtration and heat treatment: The magnesium bicarbonate solution is successively filtered, heated, re-filtered, and then heat-treated to obtain magnesium hydroxide.

[0014] In the said step 1), the particle size of the mixed grinding is less than 200 mesh.

[0015] In the said step 2), the stirring temperature is 60 - 100 °C, the stirring speed is 350 - 650 r / min, and the time is 2 - 6 h.

[0016] In the said step 2), the mass ratio of magnesite powder to sulfuric acid is 1:(3 - 5), and hydrogen peroxide accounts for 10% - 30% of the volume of sulfuric acid;

[0017] In the said step 3), the filtration is carried out using a plate and frame filter press or a centrifuge.

[0018] In the said step 4), the stirring speed for the first alkali addition is 200 - 400 r / min, the temperature is 20 - 80 °C, and the time is 1 - 3 h.

[0019] In the said step 5), the stirring speed for the second alkali addition is 200 - 400 r / min, the temperature is 20 - 60 °C, and the time is 1 - 3 h.

[0020] In the said step 6), the heating temperature is 80 - 85 °C, heating is accompanied by continuous stirring, the stirring speed is 200 - 650 r / min, and the stirring time is 1.5 - 3 h.

[0021] In the said step 6), the heat treatment temperature is 600 - 700 °C, and the heat preservation time is 2 - 5 h.

[0022] Compared with the prior art, the beneficial effects of the present invention are:

[0023] 1) Through the acid leaching and oxidation steps, using sulfuric acid and hydrogen peroxide to treat magnesite can fully dissolve the magnesium component in magnesite, enabling magnesium to efficiently enter the solution, improving the leaching rate of magnesium in the raw material. Compared with simple acid leaching, the addition of hydrogen peroxide can strengthen the oxidation effect, help to destroy the difficult-to-react impurities on the surface of magnesite or change its structure, making the magnesium element more easily leached and reducing waste. In addition, choosing sulfuric acid and hydrogen peroxide as reaction reagents is relatively mild and environmentally friendly compared to using some reagents with stronger oxidizing or corrosive properties, and is easier to control and handle, generating less waste gas and waste liquid, thus reducing the environmental protection pressure.

[0024] 2) By adding alkali once to adjust the pH of the solution to neutral and then filtering, some acidic impurities and insoluble impurities generated during the acid leaching process can be removed, making the solution purer. Adding alkali a second time to adjust the pH to alkaline and introducing carbon dioxide to generate a magnesium bicarbonate solution can further remove a small amount of impurity ions in the solution, thereby improving the purity of the subsequent product. Detailed Embodiments

[0025] The following further describes the detailed embodiments of the present invention:

[0026] Example 1

[0027] A method for preparing active magnesium oxide from magnesium-containing minerals includes the following steps:

[0028] 1) Raw material pretreatment: Select magnesite and grind it to a particle size less than 200 mesh to obtain magnesite powder;

[0029] 2) Acid leaching and oxidation: Mix the magnesite powder with sulfuric acid solution, and then add hydrogen peroxide and stir thoroughly; among them, the concentration of sulfuric acid is 38%, and the concentration of hydrogen peroxide is 3%. The stirring temperature is 85°C, the stirring speed is 300 r / min, and the time is 4 h. The mass ratio of magnesite powder to the volume of sulfuric acid is 1:3, and hydrogen peroxide accounts for 25% of the volume of sulfuric acid.

[0030] 3) Filtration and separation: Filter the acid-leached magnesite powder to obtain an acid leaching solution containing magnesium ions and residues. Filtration is carried out using a plate and frame filter press or a centrifuge.

[0031] 4) First alkali addition: Add sodium hydroxide solution to the acid leaching solution to make the pH value of the solution neutral, and then filter; among them, the concentration of the sodium hydroxide solution is 40%, the stirring speed for the first alkali addition is 200 r / min, the temperature is 60°C, and the time is 1 h.

[0032] 5) Second alkali addition: Add sodium hydroxide to the solution filtered in step 4) to make the pH value of the solution 10, and introduce the carbon dioxide generated in step 2) into the solution to generate a magnesium bicarbonate solution. Among them, the concentration of the sodium hydroxide solution is 30%, the stirring speed for the second alkali addition is 250 r / min, the temperature is 40°C, and the time is 3 h.

[0033] 6) Filtration and heat treatment: The magnesium bicarbonate solution is filtered, heated, filtered again in sequence, and then heat-treated to obtain magnesium hydroxide. The heating temperature is 80°C, heating is carried out with continuous stirring, the stirring speed is 300 r / min, and the stirring time is 2 h. The heat treatment temperature is 600°C, and the holding time is 3 h.

[0034] Example 2

[0035] A method for preparing active magnesium oxide from magnesium-containing minerals, comprising the following steps:

[0036] 1) Raw material pretreatment: Select magnesite, grind it to a particle size less than 200 mesh to obtain magnesite powder;

[0037] 2) Acid leaching and oxidation: Mix the magnesite powder with sulfuric acid solution, then add hydrogen peroxide and stir well; wherein, the concentration of sulfuric acid is 40%, and the concentration of hydrogen peroxide is 3%. The stirring temperature is 70 °C, the stirring speed is 350 r / min, and the time is 3.5 h. The mass ratio of magnesite powder to the volume of sulfuric acid is 1:5, and hydrogen peroxide accounts for 30% of the volume of sulfuric acid.

[0038] 3) Filtration and separation: Filter the acid-leached magnesite powder to obtain an acid leaching solution containing magnesium ions and residues. Filtration is carried out using a plate and frame filter press or a centrifuge.

[0039] 4) First addition of alkali: Add sodium hydroxide solution to the acid leaching solution to make the pH value of the solution neutral, and then filter; wherein, the concentration of the sodium hydroxide solution is 35%, the stirring speed of the first addition of alkali is 220 r / min, the temperature is 65 °C, and the time is 1.5 h.

[0040] 5) Second addition of alkali: Add sodium hydroxide to the solution filtered in step 4) to make the pH value of the solution 11, and introduce the carbon dioxide generated in step 2) into the solution to form a magnesium bicarbonate solution. Among them, the concentration of the sodium hydroxide solution is 28%, the stirring speed of the second addition of alkali is 280 r / min, the temperature is 45 °C, and the time is 3 h.

[0041] 6) Filtration and heat treatment: The magnesium bicarbonate solution is filtered, heated, filtered again in sequence, and then heat-treated to obtain magnesium hydroxide. The heating temperature is 85 °C, continuous stirring is carried out during heating, the stirring speed is 300 r / min, and the stirring time is 2.5 h. The heat treatment temperature is 600 °C, and the heat preservation time is 2.5 h.

[0042] The preferred embodiments of the present invention are 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 solution of the present invention, and these simple modifications all belong to 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 contradiction. In order 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, and it should also be regarded as the content disclosed by the present invention.

Claims

1. A method for preparing active magnesium oxide from magnesium-containing minerals, characterized in that, It includes the following steps: 1) Pretreatment of raw materials: Select magnesite, mix and grind it to obtain magnesite powder; 2) Acid leaching and oxidation: Mix the magnesite powder with sulfuric acid solution, and then add hydrogen peroxide, and stir well; among them, the concentration of sulfuric acid is 30% - 40%, and the concentration of hydrogen peroxide is 1% - 5%; 3) Filtration and separation: Filter the acid-leached magnesite powder, and filter to obtain an acid leaching solution containing magnesium ions and residues; 4) First addition of alkali: Add sodium hydroxide solution to the acid leaching solution to make the pH value of the solution neutral, and then filter; among them, the concentration of sodium hydroxide solution is 35% - 40%; 5) Second addition of alkali: Add sodium hydroxide to the solution filtered in step 4) to make the pH value of the solution 10 - 12, and introduce the carbon dioxide generated in step 2) into the solution to generate a magnesium bicarbonate solution; among them, the concentration of sodium hydroxide solution is 28% - 30%; 6) Filtration and heat treatment: The magnesium bicarbonate solution is filtered, heated, filtered again in sequence, and then heat treated to obtain magnesium hydroxide.

2. The method for preparing activated magnesium oxide from magnesium-containing minerals according to claim 1, characterized in that, In the said step 1), the particle size of the mixed grinding is less than 200 mesh.

3. A method for preparing active magnesium oxide from magnesium-containing minerals according to claim 1, characterized in that, In the said step 2), the stirring temperature is 60 - 100 °C, the stirring speed is 350 - 650 r / min, and the time is 2 - 6 h.

4. A method for preparing active magnesium oxide from magnesium-containing minerals according to claim 1, characterized in that, In the said step 2), the mass ratio of magnesite powder to sulfuric acid is 1:(3 - 5), and hydrogen peroxide accounts for 10% - 30% of the volume of sulfuric acid.

5. A method for preparing active magnesium oxide from magnesium-containing minerals according to claim 1, characterized in that, In the said step 3), the filtration is carried out by a plate and frame filter press or a centrifuge.

6. The method for preparing active magnesium oxide from magnesium-containing minerals according to claim 1, characterized in that, In the said step 4), the stirring speed of the first addition of alkali is 200 - 400 r / min, the temperature is 20 - 80 °C, and the time is 1 - 3 h.

7. A method for preparing active magnesium oxide from magnesium-containing minerals according to claim 1, characterized in that, In the said step 5), the stirring speed of the second addition of alkali is 200 - 400 r / min, the temperature is 20 - 60 °C, and the time is 1 - 3 h.

8. A method for preparing active magnesium oxide from magnesium-containing minerals according to claim 1, characterized in that, In the said step 6), the heating temperature is 80 - 85 °C, the heating is continuous stirring, the stirring speed is 200 - 650 r / min, and the stirring time is 1.5 - 3 h.

9. A method for preparing active magnesium oxide from magnesium-containing minerals according to claim 1, characterized in that, In the said step 6), the heat treatment temperature is 600 - 700 °C, and the heat preservation time is 2 - 5 h.