Preparation process of high-purity active magnesium oxide

Abstract

The invention discloses a preparation process of high-purity active magnesium oxide, which comprises the following steps: calcining magnesite to obtain light calcined magnesium oxide; adding a hydrating agent into the light calcined magnesia for hydration treatment, and filtering after hydration treatment to obtain a filter cake; and carrying out secondary calcination on the filter cake to obtain the active magnesium oxide. A sodium alpha-olefin sulfonate-acetic acid solution is used as a hydrating agent, the concentration of components in the hydrating agent and the adding time of organic acid are controlled, and the hydrating agent is matched with the organic acid, so that on one hand, calcium oxide is converted into soluble calcium salt calcium acetate by acetic acid; on the other hand, the hydration of magnesium oxide or magnesium hydroxide is inhibited by using the specific organic acid, so that the active magnesium oxide with high purity and high yield is obtained.

Description

Technical Field

[0001] The invention relates to the technical field of magnesium oxide purification and preparation, and more specifically to a process for preparing high-purity active magnesium oxide. Background Art

[0002] Activated magnesium oxide is one of the important basic raw materials for producing various high-tech fine products. It has important applications in the fields of electronics, superconductivity, optics, catalysis, hydrometallurgy, etc., especially as an adsorption material in the field of environmental protection and water purification. With the rapid development of industry, the types and quantities of wastewater have increased rapidly, and the pollution of water bodies has become increasingly serious. Among them, lead-containing wastewater is one of the wastewaters with the largest discharge volume, which seriously threatens human health and safety.

[0003] At present, there are two problems in the production of activated magnesium oxide. One is that the purity is not high enough, which greatly reduces the performance during use; the other is that the activity is not high enough and the stability is not high enough, which causes the performance to decay during use.

[0004] The existing method for preparing magnesium oxide on a large scale is to obtain high-grade light-burned magnesium oxide by calcining magnesite. However, the light-burned magnesium oxide contains calcium oxide impurities, which seriously affects the purity of the magnesium oxide.

[0005] In the early research of the applicant (CN 115124264 A), acetic acid solution was used as a hydrating agent to convert calcium oxide or calcium hydroxide into soluble calcium salt calcium acetate, so that calcium ions are present in the solution, reducing the interference of calcium oxide and improving the quality of magnesium oxide. However, as the hydration reaction time is prolonged and the concentration of the acetic acid solution is increased (the concentration of the acetic acid solution is increased to speed up the hydration reaction and improve the reaction efficiency during mass production), a part of the magnesium oxide will react with water to form magnesium hydroxide, and the reaction of magnesium hydroxide with acetic acid will result in a decrease in the yield of magnesium oxide. Summary of the invention

[0006] Therefore, the technical problem to be solved by the present invention is to provide a process for preparing high-purity active magnesium oxide to solve the problem of reduced magnesium oxide yield due to increased hydration reaction time and increased hydration agent concentration.

[0007] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0008] A process for preparing high-purity active magnesium oxide comprises the following steps:

[0009] (1) calcining magnesite to obtain light-burned magnesium oxide;

[0010] (2) adding a hydrating agent to the light-burned magnesium oxide for hydration treatment, adding an organic acid after a period of reaction, and filtering after the hydration treatment is completed to obtain a filter cake;

[0011] (3) The filter cake is subjected to secondary calcination to obtain active magnesium oxide.

[0012] In the above-mentioned process for preparing high-purity active magnesium oxide, in step (1), magnesite is crushed to a particle size of 10-100 mesh, the calcination temperature of magnesite is 800-1200° C., and the calcination time is 2-3 hours. The light-burned magnesium oxide is crushed and passed through a 100-mesh sieve for standby use.

[0013] In the above-mentioned process for preparing high-purity active magnesium oxide, in step (2), the hydrating agent is sodium α-olefin sulfonate-acetic acid solution.

[0014] In the above-mentioned high-purity active magnesium oxide preparation process, the preparation method of the hydrating agent sodium α-olefin sulfonate-acetic acid solution is: adding sodium α-olefin sulfonate to the acetic acid solution and stirring evenly so that the concentration of sodium α-olefin sulfonate in the hydrating agent is 0.5-5wt.%.

[0015] In the above-mentioned process for preparing high-purity active magnesium oxide, the mass ratio of light-burned magnesium oxide to hydrating agent is 1:1-10; the mass ratio of acetic acid in the hydrating agent to calcium oxide in the light-burned magnesium oxide is 2-4:1.

[0016] In the above-mentioned process for preparing high-purity active magnesium oxide, organic acid is added after reacting for 0.5-5 minutes, and the concentration of organic acid in the hydrating agent is calculated to be 0.01-0.5wt.% based on the initial mass of the hydrating agent.

[0017] In the above-mentioned process for preparing high-purity active magnesium oxide, the organic acid is oxalic acid.

[0018] In the above-mentioned process for preparing high-purity active magnesium oxide, the organic acids are oxalic acid and aminosulfonic acid, and the concentrations of oxalic acid and aminosulfonic acid are 0.01-0.5wt.%, respectively.

[0019] In the above-mentioned high-purity active magnesium oxide preparation process, the hydration treatment temperature is 10-40° C. and the hydration treatment time is 30-60 min.

[0020] In the above-mentioned process for preparing high-purity active magnesium oxide, in step (3), the secondary calcination temperature is 600-1000° C., and the calcination time is 3-6 hours.

[0021] The technical solution of the present invention achieves the following beneficial technical effects:

[0022] 1. The present invention uses sodium α-olefin sulfonate-acetic acid solution as a hydrating agent, controls the concentration of sodium α-olefin sulfonate in the hydrating agent, and the timing of adding the organic acid, utilizes the mutual cooperation between the hydrating agent and the organic acid, on the one hand, utilizes acetic acid to convert calcium oxide into soluble calcium salt calcium acetate, and on the other hand, utilizes a specific organic acid to inhibit the hydration of magnesium oxide or magnesium hydroxide, thereby obtaining high-purity and high-yield active magnesium oxide.

[0023] 2. The reaction of magnesium oxide and water to generate magnesium hydroxide is relatively slow, while calcium oxide and water react quickly to generate calcium hydroxide. In the initial stage of adding sodium α-olefin sulfonate-acetic acid solution, acetic acid and calcium hydroxide react rapidly to generate soluble calcium acetate. This process can remove most of the calcium oxide in light-burned magnesium oxide and improve the purity of magnesium oxide.

[0024] In order to prevent magnesium oxide from hydrating to generate magnesium hydroxide when the hydration time is prolonged, it gradually reacts with acetic acid to generate soluble magnesium acetate, thereby reducing the yield of magnesium oxide. The present invention adds oxalic acid after hydration reaction for 0.5-5min, and the addition of oxalic acid can inhibit the hydration of magnesium oxide, and the hydrating agent of the present application also contains sodium α-olefin sulfonate, which can avoid the addition of oxalic acid to generate calcium oxalate precipitation. This is because: as the reaction proceeds and the soluble calcium ions in the hydration solution increase, the ionic strength of the hydration solution increases, and the presence of sodium α-olefin sulfonate increases the viscosity of the solution, which is not conducive to the nucleation of calcium oxalate and the formation of calcium oxalate precipitation, and within the concentration range of the acetic acid solution of the present application, the viscosity of the solution increases with the increase of the concentration of calcium acetate, and sodium α-olefin sulfonate will not have the phenomenon that the viscosity of the solution suddenly decreases due to salting out, so that the solution can adapt to the difference in the content of calcium oxide in the light-burned magnesium oxide without or very little calcium oxalate precipitation.

[0025] Therefore, after adding acetic acid solution containing sodium α-olefin sulfonate and reacting for 0.5-5 minutes, adding oxalic acid can effectively inhibit the hydration of magnesium oxide and avoid the formation of calcium oxalate precipitation, which affects the decalcification effect.

[0026] 3. In addition, in order to deal with light-burned magnesium oxide with a high calcium oxide content, it was found that adding aminosulfonic acid to the acetic acid solution can better inhibit the formation of calcium oxalate precipitation, which is suitable for the hydration of light-burned magnesium oxide with a high calcium oxide content, and the ability of aminosulfonic acid to complex calcium ions is less affected by the pH of the solution. DETAILED DESCRIPTION

[0027] Example 1

[0028] The preparation process of active magnesium oxide in this embodiment comprises the following steps:

[0029] 1. Place magnesite with a particle size of 10-100 mesh in a calcining furnace and calcine at 900° C. for 3 hours to obtain light-burned magnesium oxide (the mass fraction of CaO in the light-burned magnesium oxide is 3.0wt%); crush the obtained light-burned magnesium oxide, and the crushed light-burned magnesium oxide is sieved through a 100-mesh sieve for standby use.

[0030] 2. Mix 1 kg of light-burned magnesium oxide with a hydrating agent for hydration treatment. After adding the hydrating agent for 5 minutes, add oxalic acid. The concentration of oxalic acid in the hydrating agent is calculated to be 0.5 wt.% based on the initial mass of the hydrating agent. The hydration temperature is 30°C and the hydration time is 40 minutes. After hydration treatment, filter and obtain a filter cake.

[0031] The hydrating agent is sodium α-olefin sulfonate-acetic acid solution, and the preparation method of the sodium α-olefin sulfonate-acetic acid solution is as follows: the acetic acid solution is prepared from 3.0 kg of water and 0.090 kg of acetic acid (the mass ratio of acetic acid in the hydrating agent to calcium oxide in light-burned magnesium oxide is 3:1), and then sodium α-olefin sulfonate is added, and the concentration of sodium α-olefin sulfonate in the hydrating agent is 1wt.%.

[0032] 3. The filter cake is placed in a multi-layer furnace and calcined at 800°C for 6 hours.

[0033] In the high-purity active magnesium oxide prepared in this embodiment, the mass fraction of magnesium oxide is 99.6wt%, the mass fraction of calcium oxide is 0.06wt%, the citric acid activity is 16s, and the yield of magnesium oxide is 99.2%.

[0034] Example 2

[0035] 1. Place magnesite with a particle size of 10-100 mesh in a calcining furnace and calcine at 900° C. for 3 hours to obtain light-burned magnesium oxide (the mass fraction of CaO in the light-burned magnesium oxide is 8.0wt%); crush the obtained light-burned magnesium oxide, and the crushed light-burned magnesium oxide is sieved through a 100-mesh sieve for standby use.

[0036] 2. Mix 1 kg of light-burned magnesium oxide with a hydrating agent for hydration treatment. After adding the hydrating agent for 5 minutes, add oxalic acid and aminosulfonic acid. The concentrations of oxalic acid and aminosulfonic acid in the hydrating agent are calculated to be 0.5wt.% based on the initial mass of the hydrating agent. The hydration temperature is 30°C and the hydration time is 40 minutes. After hydration treatment, filter and obtain a filter cake.

[0037] The hydrating agent is sodium α-olefin sulfonate-acetic acid solution, and the preparation method of the sodium α-olefin sulfonate-acetic acid solution is as follows: the acetic acid solution is prepared from 3 kg of water and 0.32 kg of acetic acid (the mass ratio of acetic acid in the hydrating agent to calcium oxide in light-burned magnesium oxide is 4:1), and then sodium α-olefin sulfonate is added, and the concentration of sodium α-olefin sulfonate in the hydrating agent is 1wt.%.

[0038] 3. The filter cake is calcined twice. The filter cake is directly put into a multi-layer furnace and calcined at 700°C for 3 hours.

[0039] The mass fraction of magnesium oxide in the high-purity magnesium oxide prepared in this embodiment is 99.8wt%, the mass fraction of calcium oxide is 0.03wt%, the citric acid activity is 9s, and the yield of magnesium oxide is 99.5%.

[0040] Example 3

[0041] 1. Place magnesite with a particle size of 10-100 mesh in a calcining furnace and calcine at 1000° C. for 2.5 hours to obtain light-burned magnesium oxide (the mass fraction of CaO in the light-burned magnesium oxide is 4.0wt%); crush the obtained light-burned magnesium oxide, and the crushed light-burned magnesium oxide is sieved through a 100-mesh sieve for standby use.

[0042] 2. Mix 1 kg of light-burned magnesium oxide with a hydrating agent for hydration treatment. After adding the hydrating agent for 5 minutes, add oxalic acid. The concentration of oxalic acid in the hydrating agent is calculated to be 0.2 wt.% based on the initial mass of the hydrating agent. The hydration temperature is 30°C and the hydration time is 40 minutes. After hydration treatment, filter and obtain a filter cake.

[0043] The hydrating agent is sodium α-olefin sulfonate-acetic acid solution, and the preparation method of the sodium α-olefin sulfonate-acetic acid solution is as follows: the acetic acid solution is prepared from 3.5 kg of water and 0.08 kg of acetic acid (the mass ratio of acetic acid in the hydrating agent to calcium oxide in light-burned magnesium oxide is 2:1), and then sodium α-olefin sulfonate is added, and the concentration of sodium α-olefin sulfonate in the hydrating agent is 0.8wt.%.

[0044] 3. The filter cake is calcined twice. The filter cake is directly put into a multi-layer furnace and calcined at 900°C for 5 hours.

[0045] The mass fraction of magnesium oxide in the high-purity magnesium oxide prepared in this embodiment is 99.6wt%, the mass fraction of calcium oxide is 0.07wt%, the citric acid activity is 19s, and the yield of magnesium oxide is 99.3%.

[0046] Example 4

[0047] 1. Place magnesite with a particle size of 10-100 mesh in a calcining furnace and calcine at 800° C. for 3 hours to obtain light-burned magnesium oxide (the mass fraction of CaO in the light-burned magnesium oxide is 9.0wt%); crush the obtained light-burned magnesium oxide, and the crushed light-burned magnesium oxide is sieved through a 100-mesh sieve for standby use.

[0048] 2. Mix 1 kg of light-burned magnesium oxide with a hydrating agent for hydration treatment. After adding the hydrating agent for 5 minutes, add oxalic acid and aminosulfonic acid. The concentrations of oxalic acid and aminosulfonic acid in the hydrating agent are calculated to be 0.4 wt.% and 0.4 wt.% g, respectively, based on the initial mass of the hydrating agent. The hydration temperature is 35°C and the hydration time is 30 minutes. After hydration treatment, filter and obtain a filter cake.

[0049] The hydrating agent is sodium α-olefin sulfonate-acetic acid solution, and the preparation method of the sodium α-olefin sulfonate-acetic acid solution is as follows: the acetic acid solution is prepared from 3.2 kg of water and 0.27 kg of acetic acid (the mass ratio of acetic acid in the hydrating agent to calcium oxide in light-burned magnesium oxide is 3:1), and then sodium α-olefin sulfonate is added, and the concentration of sodium α-olefin sulfonate in the hydrating agent is 0.9wt.%.

[0050] 3. The filter cake is calcined twice. The filter cake is directly put into a multi-layer furnace and calcined at 900°C for 3 hours.

[0051] The mass fraction of magnesium oxide in the high-purity magnesium oxide prepared in this embodiment is 99.4wt%, the mass fraction of calcium oxide is 0.04wt%, the citric acid activity is 17s, and the yield of magnesium oxide is 99.5%.

[0052] Example 5

[0053] 1. Place magnesite with a particle size of 10-100 mesh in a calcining furnace and calcine at 1100° C. for 2 hours to obtain light-burned magnesium oxide (the mass fraction of CaO in the light-burned magnesium oxide is 3.0wt%); crush the obtained light-burned magnesium oxide, and the crushed light-burned magnesium oxide is sieved through a 100-mesh sieve for standby use.

[0054] 2. Mix 1 kg of light-burned magnesium oxide with a hydrating agent for hydration treatment. After adding the hydrating agent for 5 minutes, add oxalic acid. The concentration of oxalic acid in the hydrating agent is calculated to be 0.4 wt.% based on the initial mass of the hydrating agent. The hydration temperature is 35°C and the hydration time is 30 minutes. After hydration treatment, filter and obtain a filter cake.

[0055] The hydrating agent is sodium α-olefin sulfonate-acetic acid solution, and the preparation method of the sodium α-olefin sulfonate-acetic acid solution is as follows: the acetic acid solution is prepared from 3.0 kg of water and 0.12 kg of acetic acid (the mass ratio of acetic acid in the hydrating agent to calcium oxide in light-burned magnesium oxide is 4:1), and then sodium α-olefin sulfonate is added, and the concentration of sodium α-olefin sulfonate in the hydrating agent is 0.6wt.%.

[0056] 3. The filter cake is calcined twice. The filter cake is directly put into a multi-layer furnace and calcined at 800°C for 3 hours.

[0057] The high-purity magnesium oxide prepared in this embodiment has a mass fraction of 99.5wt% of magnesium oxide, a mass fraction of 0.06wt% of calcium oxide, a citric acid activity of 13s, and a magnesium oxide yield of 99.3%.

[0058] Example 6

[0059] 1. Place magnesite with a particle size of 10-100 mesh in a calcining furnace and calcine at 1100° C. for 2 hours to obtain light-burned magnesium oxide (the mass fraction of CaO in the light-burned magnesium oxide is 5.0wt%); crush the obtained light-burned magnesium oxide, and the crushed light-burned magnesium oxide is sieved through a 100-mesh sieve for standby use.

[0060] 2. Mix 1 kg of light-burned magnesium oxide with a hydrating agent for hydration treatment. After adding the hydrating agent for 5 minutes, add oxalic acid and aminosulfonic acid. The concentrations of oxalic acid and aminosulfonic acid in the hydrating agent are calculated to be 0.4%wt.% and 0.3wt.% respectively based on the initial mass of the hydrating agent. The hydration temperature is 35°C and the hydration time is 30 minutes. After hydration treatment, filter and obtain a filter cake.

[0061] The hydrating agent is sodium α-olefin sulfonate-acetic acid solution, and the preparation method of sodium α-olefin sulfonate-acetic acid solution is as follows: the acetic acid solution is prepared from 3.5 kg of water and 0.20 kg of acetic acid (the mass ratio of acetic acid in the hydrating agent to calcium oxide in light-burned magnesium oxide is 4:1), and then sodium α-olefin sulfonate is added. The concentration of sodium α-olefin sulfonate in the hydrating agent is 0.8wt.%.

[0062] 3. The filter cake is calcined for the second time. The filter cake is directly put into a multi-layer furnace and calcined at 800°C for 5 hours.

[0063] The high-purity magnesium oxide prepared in this embodiment has a mass fraction of 99.7wt% of magnesium oxide, a mass fraction of 0.04wt% of calcium oxide, a citric acid activity of 15s, and a magnesium oxide yield of 99.5%.

[0064] Comparative Example 1

[0065] The difference between Comparative Example 1 and Example 1 is that sodium α-olefin sulfonate is not added as the hydrating agent in step (2), and oxalic acid is not added after the reaction for 5 minutes.

[0066] In the active magnesium oxide prepared in Comparative Example 1, the mass fraction of magnesium oxide was 99.5wt%, the mass fraction of calcium oxide was 0.08wt%, and the yield of magnesium oxide was 91.2%.

[0067] Comparative Example 2

[0068] The difference between Comparative Example 2 and Example 1 is that sodium α-olefin sulfonate is added as the hydrating agent in step (2), but oxalic acid is not added after the reaction for 5 minutes.

[0069] The mass fraction of magnesium oxide in the active magnesium oxide prepared in Comparative Example 2 is 99.6wt%, the mass fraction of calcium oxide is 0.07wt%, and the yield of magnesium oxide is 91.4%. Although sodium α-olefin sulfonate is added, oxalic acid is not added, and it cannot cooperate with sodium α-olefin sulfonate to inhibit the hydration of magnesium oxide, so the yield of magnesium oxide in Comparative Example 2 is equivalent to that in Comparative Example 1.

[0070] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the claims of this patent application.

Claims

1. A process for preparing high-purity active magnesium oxide, characterized in that: The steps include: (1) calcining magnesite to obtain light-burned magnesium oxide; (2) adding a hydrating agent to the light-burned magnesium oxide for hydration treatment, adding an organic acid after a period of reaction, and filtering after the hydration treatment is completed to obtain a filter cake; (3) The filter cake is subjected to secondary calcination to obtain active magnesium oxide.

2. A process for preparing high-purity active magnesium oxide according to claim 1, characterized in that: In step (1), the magnesite is crushed to a particle size of 10-100 mesh, the calcination temperature of the magnesite is 800-1200° C., and the calcination time is 2-3 hours. The light-burned magnesium oxide is crushed and passed through a 100-mesh sieve for later use.

3. A process for preparing high-purity active magnesium oxide according to claim 1, characterized in that: In step (2), the hydrating agent is sodium α-olefin sulfonate-acetic acid solution.

4. A process for preparing high-purity active magnesium oxide according to claim 3, characterized in that: The preparation method of the hydrating agent sodium α-olefin sulfonate-acetic acid solution is as follows: add sodium α-olefin sulfonate to the acetic acid solution and stir evenly, so that the concentration of sodium α-olefin sulfonate in the hydrating agent is 0.5-5wt.%.

5. A process for preparing high-purity active magnesium oxide according to claim 1, characterized in that: The mass ratio of the light-burned magnesium oxide to the hydrating agent is 1:1-10; the mass ratio of the acetic acid in the hydrating agent to the calcium oxide in the light-burned magnesium oxide is 2-4:

1.

6. A process for preparing high-purity active magnesium oxide according to claim 1, characterized in that: After reacting for 0.5-5 minutes, the organic acid is added so that the concentration of the organic acid in the hydrating agent is 0.01-0.5 wt. % calculated based on the initial mass of the hydrating agent.

7. A process for preparing high-purity active magnesium oxide according to claim 6, characterized in that: The organic acid is oxalic acid.

8. A process for preparing high-purity active magnesium oxide according to claim 6, characterized in that: The organic acids are oxalic acid and aminosulfonic acid, and the concentrations of oxalic acid and aminosulfonic acid are 0.01-0.5 wt. % respectively.

9. A process for preparing high-purity active magnesium oxide according to claim 1, characterized in that: The hydration treatment temperature is 10-40°C, and the hydration treatment time is 30-60 minutes.

10. A process for preparing high-purity active magnesium oxide according to claim 1, characterized in that: In step (3), the secondary calcination temperature is 600-1000° C., and the calcination time is 3-6 hours.