CN110980781A

CN110980781A - Method for preparing high-purity magnesium sulfate

Info

Publication number: CN110980781A
Application number: CN201911278071.7A
Authority: CN
Inventors: 任业明; 牟英迪; 赵思太; 马新成; 邓玉晓; 张宁; 张宗磊; 冯光玲; 孔祥雨; 杨利; 崔新强; 龚艳艳; 樊志萍; 孙晋瑞; 段崇刚
Original assignee: Shandong Academy of Pharmaceutical Sciences
Current assignee: Shandong Academy of Pharmaceutical Sciences
Priority date: 2019-12-12
Filing date: 2019-12-12
Publication date: 2020-04-10

Abstract

The invention discloses a method for preparing high-purity magnesium sulfate. The method takes magnesium oxide and sulfuric acid as raw materials, takes phosphoric acid as an impurity removal reagent, and prepares high-purity magnesium sulfate through one-step reaction, thereby omitting a refining link. The preparation method provided by the invention has the advantages of cheap and easily-obtained raw materials, simple operation, mild reaction conditions, no harsh reaction conditions, high product yield and purity, and suitability for industrial production.

Description

Method for preparing high-purity magnesium sulfate

Technical Field

The invention belongs to the field of food and medicine, and particularly relates to application of high-purity magnesium sulfate in the field of food and medicine.

Background

Magnesium sulfate is commonly referred to as magnesium sulfate heptahydrate, also known as thiopicrin, bitter salt, epsomite. It can be widely applied to the fields of food, medicine and the like. In the food field, magnesium sulfate is used for producing products such as monosodium glutamate, yeast, salt and the like; can also be used as food additive as nutritional supplement. In clinical application, magnesium sulfate can be used for catharsis, detoxification, cholagogue, and treatment of cholecystitis and biliary colic. When used as magnesium ion supplement in vivo, it can be used for preventing and treating toxic arrhythmia and other arrhythmia of digitalis; can be used for treating hyperlipidemia, congestive heart failure, angina pectoris, and myocardial infarction; can be used for sedation, anticonvulsant and lowering blood pressure; intravenous injection or intravenous drip can be used for treating biliary ascariasis, tetanus, preterm pregnancy, etc.

The quality index of the industrial grade magnesium sulfate is that the magnesium sulfate is more than or equal to 99.5 percent, the pH (5w/v percent solution) is between 5 and 9, and the content of iron is not more than 0.0015 percent; the chlorine content (Cl) is not more than 0.015 percent; heavy metal (Pb) no more than 0.0008%; the arsenic content (As) is not more than 0.0002%; the calcium content (Ca) is not more than 0.05%; the water-insoluble matter is not more than 0.01%. The high-purity magnesium sulfate is a substance with the content of the magnesium sulfate of more than 99.9 percent, the quality index is far higher than that of industrial-grade magnesium sulfate, the application range is wider than that of the industrial-grade magnesium sulfate, and the magnesium sulfate used in the field of food and medicine is often the high-purity magnesium sulfate. In the process of preparing the high-purity magnesium sulfate, metal substances such as iron ions, lead ions, arsenic ions and the like are relatively easy to remove, and calcium and magnesium are homologous elements and have very similar chemical properties, so that in the purification process, impurity calcium salt is difficult to remove from a finished product, and the content of calcium in the product exceeds the standard. Especially, the calcium ion content of magnesium sulfate used in medicine is not more than 0.02%.

The literature search shows that the high-purity magnesium sulfate is generally prepared by reacting industrial magnesium oxide or high-purity magnesium oxide with sulfuric acid and then removing impurities by different methods; or the industrial-grade magnesium sulfate is purified to obtain the high-purity magnesium sulfate. For example, the Chinese patent publication CN101885498A controls the purity of magnesium sulfate by reacting high-purity magnesium oxide with sulfuric acid, adjusting pH, and concentrating the filtrate to a certain relative density. Chinese patent publication CN107935003A provides a method for preparing high purity magnesium sulfate from magnesium sulfate waste. The method mainly comprises the steps of roasting magnesium sulfate waste at high temperature, hydrating, and then concentrating and crystallizing twice to prepare the high-purity magnesium sulfate. Chinese patent publication CN103058235A uses hydrofluoric acid to precipitate calcium ions in magnesium sulfate as impurities, and obtains high-purity magnesium sulfate. In addition, the high-purity magnesium sulfate is prepared by adopting multi-stage series equipment such as a majun and the like through multi-step recrystallization, decoloration and washing; the method is characterized in that the high-purity magnesium sulfate is produced by using industrial magnesium sulfate heptahydrate, and the high-purity magnesium sulfate is obtained by adding an alkaline auxiliary agent, activated carbon and the like to remove impurities and decolor.

The method related to the patent literature has a complex preparation process, and the problem of calcium salt impurities in the prepared magnesium sulfate is not effectively solved. Chinese patent publication CN103058235A uses hydrofluoric acid to precipitate calcium ions in magnesium sulfate as impurities to obtain high-purity magnesium sulfate, but hydrofluoric acid belongs to a highly corrosive liquid and has great danger in the processes of production, storage and use.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provides the method for preparing the high-purity magnesium sulfate, which has the advantages of simple process and mild reaction conditions, and can effectively reduce the content of calcium ions in the magnesium sulfate product.

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

adding a certain proportion of magnesium oxide and distilled water into a reactor, stirring, and slowly dropwise adding concentrated sulfuric acid to obtain a magnesium sulfate solution with the pH value of 5-6; then heating to 70-80 ℃; adding phosphoric acid and active carbon in proportion, keeping the temperature, stirring and reacting for 0.5-2 hours; filtering; and cooling the filtrate, crystallizing, and filtering to obtain the high-purity magnesium sulfate.

In the technical scheme, the mass ratio of the magnesium oxide to the distilled water is 1: 4-6; the mass ratio of the magnesium oxide to the phosphoric acid is 20-30: 1. Compared with the prior art, the invention has the following advantages:

1) the solubility of calcium phosphate in water is very low, the pKsp value is 28.68, and the solubility product Ksp is 2.07 x 10-²⁹In the technical scheme of the invention, a proper amount of phosphoric acid is added into the reaction system, which is beneficial to forming precipitate and separating out calcium ions from the reaction system. The finished magnesium sulfate prepared by the technical scheme meets the quality standard of magnesium sulfate collected in the 2015 edition of Chinese pharmacopoeia, and particularly, the content of calcium ions is lower than the limit of the quality standard.

2) The invention relates to a method for preparing high-purity magnesium sulfate, wherein the used raw material magnesium oxide does not need to have high-purity grade, and the content of the magnesium oxide in the raw material is higher than 92.0%.

3) The invention relates to a method for preparing high-purity magnesium sulfate, which has simple reaction impurity removal steps and mild reaction conditions and is particularly suitable for industrial scale production. And meanwhile, nontoxic carbon dioxide is released in the reaction process, and the waste liquid is mother liquid containing magnesium sulfate, so that the waste liquid can be repeatedly used, and the requirements of energy conservation and emission reduction are met.

Detailed Description

The present invention is further illustrated by the following specific examples, which are intended to be illustrative, not limiting and are not intended to limit the scope of the invention.

Example 1

Adding 2 kg of raw material magnesium oxide into a reactor, adding 10 liters of distilled water, starting stirring, slowly dripping concentrated sulfuric acid after the materials are dispersed into paste, and controlling the adding speed to avoid foam overflow. And when the pH value of the reaction system is 5, stopping adding sulfuric acid, heating to 80 ℃, adding 67 g of phosphoric acid and 60 g of activated carbon, stirring for reacting for 0.5 hour, filtering while hot, naturally cooling the filtrate for crystallization, filtering for crystallization, washing with water, and drying to obtain the high-purity magnesium sulfate.

Example 2

Adding 2 kg of raw material magnesium oxide into a reactor, adding 12 liters of distilled water, starting stirring, slowly dripping concentrated sulfuric acid after the materials are dispersed into paste, and controlling the adding speed to avoid foam overflow. And when the pH value of the reaction system is 5, stopping adding sulfuric acid, heating to 70 ℃, adding 77 g of phosphoric acid and 60 g of activated carbon, stirring for reacting for 1 hour, filtering while hot, naturally cooling the filtrate for crystallization, filtering for crystallization, washing with water, and drying to obtain the high-purity magnesium sulfate.

Example 3

Adding 2 kg of raw material magnesium oxide into a reactor, adding 8 liters of distilled water, starting stirring, slowly dripping concentrated sulfuric acid after the materials are dispersed into paste, and controlling the adding speed to avoid foam overflow. And when the pH value of the reaction system is 5, stopping adding sulfuric acid, heating to 80 ℃, adding 87 g of phosphoric acid and 60 g of activated carbon, stirring for reacting for 1.5 hours, filtering while hot, naturally cooling the filtrate for crystallization, filtering for crystallization, washing with water, and drying to obtain the high-purity magnesium sulfate.

Example 4

Adding 2 kg of raw material magnesium oxide into a reactor, adding 12 liters of distilled water, starting stirring, slowly dripping concentrated sulfuric acid after the materials are dispersed into paste, and controlling the adding speed to avoid foam overflow. And when the pH value of the reaction system is 6, stopping adding the sulfuric acid, heating to 70 ℃, adding 100 g of phosphoric acid and 60 g of activated carbon, stirring for reacting for 2 hours, filtering while hot, naturally cooling the filtrate for crystallization, filtering for crystallization, washing with water, and drying to obtain the high-purity magnesium sulfate.

The result of the detection

The magnesium sulfate finished product of the embodiment of the invention is detected according to a detection method of magnesium sulfate in the second part of Chinese pharmacopoeia 2015 edition. The detection results are as follows:

detecting items	Chinese pharmacopoeia 2015 edition	Example 1	Example 2	Example 3	Example 4
						Traits	Colorless crystals	Qualified	Qualified	Qualified	Qualified
Content (wt.)	99.50％	99.60％	99.70％	99.80％	99.70％
						pH value	Should comply with the regulations	Qualified	Qualified	Qualified	Qualified
Clarity test	Should comply with the regulations	Qualified	Qualified	Qualified	Qualified
						Chloride compound	0.01％	0.01％	0.01％	0.01％	0.00％
Iron	0.00％	0.00％	0.00％	0.00％	0.00％
						Calcium carbonate	0.02％	0.01％	0.01％	0.01％	0.01％
Zinc	Should comply with the regulations	Qualified	Qualified	Qualified	Qualified
						Heavy metals	0.00％	0.00％	0.00％	0.00％	0.00％
Arsenic (As)	0.00％	0.00％	0.00％	0.00％	0.00％
						Ignition weightlessness	48.0-52.0％	51.10％	48.90％	49.60％	50.60％

Claims

1. The method for preparing the high-purity magnesium sulfate is characterized in that the method takes phosphoric acid as an auxiliary agent and comprises the following steps:

1) adding a certain proportion of magnesium oxide and distilled water into a reactor, and dropwise adding concentrated sulfuric acid to obtain a magnesium sulfate solution with the pH value of 5-6;

2) heating the magnesium sulfate solution in the step 1) to 70-80 ℃, adding phosphoric acid in proportion, and adding activated carbon;

3) keeping the reaction temperature of the step 2) at 70-80 ℃, and stirring for reaction for 0.5-2 hours;

4) and (3) cooling the filtrate obtained in the step 3), crystallizing, filtering, washing with water, and drying to obtain the high-purity magnesium sulfate.

2. The ratio of magnesium oxide to distilled water as claimed in claim 1, wherein the mass ratio of magnesium oxide to distilled water is 1: 4-6.

3. The proportioned phosphoric acid of claim 1 wherein the mass ratio of magnesium oxide to phosphoric acid is 20-30: 1.