Preparation method of high-purity magnesium sulfate

Abstract

The invention relates to a method for purifying magnesium sulfate, in particular to a method for preparing high-purity magnesium sulfate, which comprises the following steps: preparing industrial-grade magnesium sulfate heptahydrate with MgSO4 purity greater than or equal to 97.0% into a magnesium sulfate saturated aqueous solution, and / or introducing an oxidizing agent into the magnesium sulfate aqueous solution to prepare magnesium sulfate slurry, adding high-purity high-activity magnesium oxide fiber into semi-concentrate, and filtering after full reaction to obtain magnesium sulfate powder; and preparing the filtrate into MgSO4 mother liquor with the purity of refined MgSO4 being greater than or equal to 99.8 percent or dehydrating the filtrate into high-purity MgSO4. 7H2O solid. The production process is simple, the problem of high impurity content in the crude magnesium sulfate is effectively solved, the refined MgSO4. 7H2O mother liquor and the high-end MgSO4. 7H2O product can be prepared, the application field of magnesium sulfate is expanded, valuable elements in the crude magnesium sulfate are extracted, and huge economic benefits and social benefits are brought.

Description

Technical Field

[0001] The invention relates to a method for purifying magnesium sulfate, in particular to a method for preparing high-purity magnesium sulfate. Background Art

[0002] my country processes industrial waste sulfuric acid and magnesium-containing solid waste. At present, we make crude magnesium sulfate by mixing industrial waste sulfuric acid with a concentration greater than 40% with an excess of light-burned magnesium oxide. However, the crude magnesium sulfate contains a high level of impurities, and the product is limited to agricultural fertilizers and building materials. Some of the products even contain highly hazardous impurities such as hexavalent chromium ions and cadmium, which limits the application of magnesium sulfate. It is urgently needed to purify it to prepare various food-grade and pharmaceutical-grade magnesium sulfates. Summary of the invention

[0003] The object of the present invention is to provide a method for preparing high-purity magnesium sulfate, which produces refined magnesium sulfate with less impurities and extracts valuable metals in crude magnesium sulfate, but the present application is not suitable for purifying magnesium sulfate with high potassium, high sodium content and high chlorine content.

[0004] The objective of the present invention is achieved through the following technical solutions: A method for preparing high-purity magnesium sulfate comprises the following steps: preparing an industrial-grade magnesium sulfate heptahydrate with a MgSO4 purity of ≥97.0% into a saturated magnesium sulfate aqueous solution, and then introducing an oxidant into the magnesium sulfate aqueous solution to prepare magnesium sulfate slurry (semi-refined material for short), adding an appropriate amount of high-purity and high-activity magnesium oxide fiber into the semi-refined material, filtering after sufficient reaction, and preparing the filtrate into a refined MgSO4 mother liquor with a purity of ≥99.8% or dehydrating the filtrate to prepare a high-purity MgSO4·7H2O solid.

[0005] A method for preparing high-purity magnesium sulfate, wherein the industrial-grade magnesium sulfate heptahydrate with a MgSO4 purity of ≥97.0% is selected as magnesium sulfate with low K, low Na and low Cl. - ≤0.03%,Na + +K + ≤0.03%.

[0006] The method for preparing high-purity magnesium sulfate comprises adding an appropriate amount of high-purity and high-activity magnesium oxide fiber to semi-refined material, wherein the MgO of the high-purity and high-activity magnesium oxide fiber is ≥99.0wt%, the MgO active content is ≥90.0%, the MgO activity is less than 25s, and the fiber length is greater than 50 microns.

[0007] Advantages and positive effects of the present invention: The invention has a simple production process, effectively solves the problem of high impurities in crude magnesium sulfate, can also prepare refined MgSO4·7H2O mother liquor and high-end MgSO4·7H2O products, expands the application field of magnesium sulfate, extracts valuable elements in crude magnesium sulfate, and brings huge economic and social benefits. DETAILED DESCRIPTION

[0008] Example 1 Take 100g, MgSO4≥97.0%, Cl - ≤0.03%, Na + +K + ≤0.03% industrial grade magnesium sulfate heptahydrate is prepared into a saturated magnesium sulfate aqueous solution, and then hydrogen peroxide is introduced into the magnesium sulfate aqueous solution to prepare magnesium sulfate slurry (referred to as semi-fine material), and high-purity and high-activity magnesium oxide fiber accounting for 1% of the mass of magnesium sulfate heptahydrate is added into the semi-fine material, and the technical indicators of the magnesium oxide fiber are: MgO content ≥99.0%, MgO activity content ≥90.0%, MgO activity less than 22s, and MgO fiber length greater than 50 microns. After sufficient reaction, the filtrate is filtered, and the filtrate is prepared into a refined MgSO4 with a purity of ≥99.8% MgSO4 mother liquor or dehydrated to prepare a high-purity MgSO4·7H2O solid.

[0009] The physical and chemical data of MgSO4·7H2O solid detected are: MgSO4≥99.8%; heavy metal (in terms of Pb)≤8mg / kg; Se≤20mg / kg; Cl - ≤0.03; As≤2mg / kg; Fe≤10mg / kg; pH=6.3.

[0010] Example 2 Take 100g, MgSO4≥97.5.0%, Cl - ≤0.03%, Na + +K + ≤0.03% industrial grade magnesium sulfate heptahydrate is prepared into a saturated magnesium sulfate aqueous solution, and then compressed air is introduced into the magnesium sulfate aqueous solution to prepare magnesium sulfate slurry (referred to as semi-fine material), and high-purity and high-activity magnesium oxide fiber accounting for 1% of the mass of magnesium sulfate heptahydrate is added to the semi-fine material, and the technical indicators of the magnesium oxide fiber are: MgO content ≥99.0%, MgO activity content ≥90.0%, MgO activity less than 25s, and MgO fiber length greater than 50 microns. After sufficient reaction, the filtrate is filtered, and the filtrate is prepared into a refined MgSO4 with a purity of ≥99.8% MgSO4 mother liquor or dehydrated to prepare a high-purity MgSO4·7H2O solid.

[0011] The physical and chemical indicators of MgSO4·7H2O solid were detected as follows: MgSO4 ≥ 99.8%; heavy metal (in terms of Pb) ≤ 10 mg / kg; Se ≤ 20 mg / kg; Cl- ≤0.03; As≤3mg / kg; Fe≤10mg / kg; pH=6.4.

[0012] Example 3 Take 100g, MgSO4≥98.0%, Cl - ≤0.03%, Na + +K + ≤0.03% industrial grade magnesium sulfate heptahydrate is prepared into a saturated aqueous solution of magnesium sulfate, which is fully stirred to form a magnesium sulfate slurry (referred to as semi-fine material), and high-purity and high-activity magnesium oxide fiber accounting for 1% of the mass of magnesium sulfate heptahydrate is added to the semi-fine material. The technical indicators of the magnesium oxide fiber are: MgO content ≥99.0%, MgO activity content ≥90.0%, MgO activity less than 25s, and MgO fiber length greater than 50 microns. After sufficient reaction, the filtrate is filtered, and the filtrate is prepared into a refined MgSO4 with a purity of ≥99.8% MgSO4 mother liquor or dehydrated to form a high-purity MgSO4·7H2O solid.

[0013] The physical and chemical data of MgSO4·7H2O solid detected are: MgSO4≥99.5%; heavy metal (in terms of Pb)≤10mg / kg; Se≤25mg / kg; Cl - ≤0.03; As≤3mg / kg; Fe≤10mg / kg; pH=6.4.

Claims

1. A method for preparing high-purity magnesium sulfate, characterized in that: The method comprises preparing an industrial-grade magnesium sulfate heptahydrate with a MgSO4 purity of ≥97.0% into a saturated magnesium sulfate aqueous solution, and then introducing an oxidant into the magnesium sulfate aqueous solution to prepare a magnesium sulfate slurry, adding high-purity and high-activity magnesium oxide fiber into the semi-refined material, filtering after sufficient reaction, and preparing the filtrate into a refined MgSO4 mother liquor with a purity of ≥99.8% or dehydrating the filtrate to prepare a high-purity MgSO4·7H2O solid.

2. A method for preparing high-purity magnesium sulfate as claimed in claim 1, characterized in that: The industrial grade magnesium sulfate heptahydrate with MgSO4 purity ≥97.0% is low in K, Na and Cl. - ≤0.03%,Na + +K + ≤0.03%.

3. A method for preparing high-purity magnesium sulfate as claimed in claim 1, characterized in that: High-purity and high-activity magnesium oxide fiber is added to the semi-refined material, wherein the MgO of the high-purity and high-activity magnesium oxide fiber is ≥99.0wt%, the MgO activity content is ≥90.0%, the MgO activity is less than 25s, and the fiber length is greater than 50 microns.