Method for simultaneously preparing calcium citrate and magnesium citrate from natural dolomite

Abstract

The invention discloses a method for simultaneously preparing calcium citrate and magnesium citrate from natural dolomite, which comprises the following steps: adding dolomite powder into an acetic acid aqueous solution, and stirring at 10-50 DEG C for 0.5-3.5 hours to obtain a mixed solution; adding citric acid into the obtained mixed solution, stirring at 40-100 DEG C for 1-6 hours, filtering while the solution is hot, and respectively collecting precipitates and filtrate; drying the precipitate to obtain calcium citrate, and drying the filtrate at low temperature to obtain magnesium citrate; the natural dolomite is directly acidified through acetic acid, then calcium citrate and magnesium citrate are replaced, the cost of raw materials is lower, the natural dolomite does not need to be calcined, the energy consumption is low, and the preparation conditions are green and mild; meanwhile, the preparation and post-treatment process and operation are simple, the reaction process can be controlled without adjusting the pH value of the system, and the method has industrial application prospects.

Description

Technical Field

[0001] The invention relates to a method for simultaneously preparing calcium citrate and magnesium citrate from natural dolomite. Background Art

[0002] Calcium is the mineral element with the highest proportion in the human body (1.5-2%). It is an important component of bones and teeth and is involved in the transmembrane transport of inorganic salt ions, the transmission of hormones and nerve signals, etc. Magnesium is one of the important elements for maintaining normal human metabolism. It participates in the synthesis of more than 300 enzymes in cells and is closely related to the physiological metabolic cycles of carbohydrates, fats, proteins, etc.

[0003] Common calcium / magnesium supplements include inorganic calcium / magnesium, organic acid calcium / magnesium, chelated calcium / magnesium, etc. Inorganic calcium / magnesium generally has a high calcium / magnesium content. Due to the low water solubility of calcium / magnesium, it needs to be decomposed by gastric acid to be absorbed, which has a greater irritation to the gastrointestinal tract and a low absorption rate; common inorganic calcium / magnesium supplements include calcium carbonate, calcium bicarbonate, magnesium carbonate, and magnesium chloride. Organic acid calcium / magnesium supplements are relatively water-soluble and easier to absorb, but usually contain less calcium, such as calcium gluconate, calcium lactate, calcium citrate, magnesium gluconate, magnesium lactate, and magnesium citrate (Fan Liqun. Reasonable selection of commonly used calcium supplements for children [J]. Clinical Rational Drug Use, 2023, 16(06): 179-181.). The digestive organs have better tolerance and bioavailability for calcium citrate and magnesium citrate, which are more easily absorbed by the digestive system and will not affect the absorption of other trace elements. Therefore, calcium citrate / magnesium has a broader market space, and its large-scale food industry production has also attracted more and more people's interest.

[0004] At present, calcium citrate is generally prepared in the following ways: First, calcium citrate is directly prepared from natural calcium sources, such as eggshells and shells, which are acidified, pH adjusted, calcined, and then reacted with citric acid to obtain calcium citrate. Second, calcium citrate is prepared by the natural calcium source replacement method, which uses an organic acid with an acidity between carbonic acid and citric acid to react with eggshells, and then replaces citric acid with organic calcium to obtain calcium citrate. These two methods are complicated and require eggshell processing, and the eggshell raw materials are inconvenient to recycle, and the calcination process consumes a lot of energy. The third is to use a soluble calcium source, such as calcium chloride, calcium hydroxide, etc., to react with citric acid to obtain calcium citrate, and then heat or add ethanol to precipitate calcium citrate. This method needs to adjust the reaction temperature and pH value during the reaction, and the production time is long, which is not suitable for mass production.

[0005] The preparation technology of current magnesium citrate mostly exists and needs high temperature heating and process complexity, resulting in excessive energy consumption, generation of a large amount of wastewater, environmental pollution and other problems. The process of synthesizing magnesium citrate crystals or powders (Lu Shengjie. A method for producing magnesium citrate: Chinese patent, CN102285877A, 2011.) is relatively simple, but there is a need to adjust the pH operation, which is relatively complicated in actual production. The synthesis operation of anhydrous magnesium citrate (Shi Zhiyong. Production method of anhydrous magnesium citrate: Chinese patent, CN104447272A, 2015.) is simple, requires a long heating time, and has high energy consumption.

[0006] Dolomite (CaMg(CO3)2) is a carbonate mineral. Dolomite is abundant in my country and its production areas are spread across provinces. Current researchers mainly focus on the preparation of inorganic magnesium chemical products from dolomite, and there is less research on the preparation of organic magnesium compounds and organic calcium compounds from dolomite. The process of preparing calcium and magnesium chemical products from dolomite has the disadvantages of incomplete separation of calcium and magnesium and complicated process, which results in a waste of dolomite resources. Therefore, it is necessary to develop a method for preparing calcium citrate and magnesium citrate products from dolomite. The present invention uses dolomite to simultaneously prepare calcium citrate and magnesium citrate high value-added products, and the production process is green and low in energy consumption. Summary of the invention

[0007] In view of the problems that the current production of calcium citrate and magnesium citrate has complex process, cumbersome steps, need for specific equipment, high energy consumption, wastewater pollution, high production cost and low added value of dolomite products, the present invention provides a method for simultaneously preparing calcium citrate and magnesium citrate from natural dolomite.

[0008] The technical solution of the present invention is as follows:

[0009] A method for simultaneously preparing calcium citrate and magnesium citrate from natural dolomite, comprising:

[0010] Add dolomite powder to acetic acid aqueous solution, stir at 10-50°C (preferably 25-45°C) for 0.5-3.5h (preferably 0.5-1.5h) to obtain a mixed solution; add citric acid to the obtained mixed solution, stir at 40-100°C (preferably 60-90°C) for 1-6h (preferably 3-6h), filter while hot, and collect the precipitate and the filtrate respectively; dry the precipitate to obtain calcium citrate, and dry the filtrate at low temperature to obtain magnesium citrate;

[0011] in,

[0012] Dolomite powder is obtained by crushing, grinding, sieving and drying natural dolomite;

[0013] Preferably, the molar ratio of acetic acid to dolomite powder is 1:1 to 3:1;

[0014] Preferably, the volume fraction of the acetic acid aqueous solution is 5 to 10%;

[0015] The liquid-to-solid ratio of the acetic acid aqueous solution to the dolomite powder is preferably 10:1 to 30:1, mL / g;

[0016] Preferably, the molar ratio of citric acid to dolomite powder is 1:1 to 5:3;

[0017] Specifically, the drying conditions for the precipitate are 95° C. for 12 h; and the low-temperature drying conditions for the filtrate are -60° C. for 24 h.

[0018] The beneficial effects of the present invention are:

[0019] The invention provides a method for simultaneously preparing calcium citrate and magnesium citrate from natural dolomite. The method comprises the following steps: directly acidifying the natural dolomite with acetic acid and then replacing the calcium citrate and magnesium citrate. The raw material cost is lower, and there is no need to calcine the natural dolomite or adjust the pH value of the system to control the reaction process. The method has the advantages of simple process, low energy consumption, green and mild preparation conditions, and industrial application prospects. DETAILED DESCRIPTION

[0020] The present invention will be further described below in conjunction with specific embodiments, and the advantages and features of the present invention will become clearer as the description proceeds. However, these embodiments are exemplary only and do not constitute any limitation to the scope of the present invention. It should be understood by those skilled in the art that the details and forms of the technical solution of the present invention may be modified or replaced without departing from the subject matter and scope of the present invention, but these modifications and replacements all fall within the scope of protection of the present invention.

[0021] In the following embodiments,

[0022] The natural dolomite comes from Qingyang County, Anhui Province;

[0023] Acetic acid was from Sinopharm Chemical Reagent Co., Ltd., ≥99.8%;

[0024] Citric acid was from Sinopharm Chemical Reagent Co., Ltd., ≥99.5%.

[0025] Example 1

[0026] Use an agate mortar to grind natural dolomite into powder, grind it thoroughly, and pass it through a 100-mesh sieve to obtain dolomite powder. Weigh 3.00g of dolomite powder, 5.84g of citric acid powder, 6ml of acetic acid, and 84ml of deionized water. Add acetic acid to deionized water and mix evenly. Add the weighed dolomite powder to the acetic acid aqueous solution, and then stir with a constant temperature magnetic stirrer. Control the temperature to 25°C. After reacting for 1h, add the weighed citric acid powder, control the temperature to 80°C, and filter while hot after reacting for 3h to obtain magnesium citrate solution and calcium citrate precipitate. The magnesium citrate solution is dried at -60°C for 24h to obtain magnesium citrate solid, and the calcium citrate precipitate is dried at 95°C for 12h to obtain calcium citrate solid. 3.16g of calcium citrate is obtained. 1.84g of magnesium citrate is obtained.

[0027] Example 2

[0028] Use an agate mortar to grind natural dolomite into powder, grind it thoroughly, and pass it through a 100-mesh sieve to obtain dolomite powder. Weigh 3.00g of dolomite powder, 5.84g of citric acid powder, 4ml of acetic acid, and 56ml of deionized water. Add acetic acid to deionized water and mix evenly. Add the weighed dolomite powder to the acetic acid aqueous solution, and then stir with a constant temperature magnetic stirrer. Control the temperature to 25°C. After reacting for 1h, add the weighed citric acid powder, control the temperature to 60°C, and filter while hot after reacting for 6h to obtain magnesium citrate solution and calcium citrate precipitate. The magnesium citrate solution is dried at minus 60°C for 24h to obtain magnesium citrate solid, and the calcium citrate precipitate is dried at 95°C for 12h to obtain calcium citrate solid. 3.06g of calcium citrate is obtained. 1.9g of magnesium citrate is obtained.

Claims

1. A method for simultaneously preparing calcium citrate and magnesium citrate from natural dolomite, characterized in that: The method comprises: Add dolomite powder to acetic acid aqueous solution, stir at 10-50°C for 0.5-3.5h to obtain a mixed solution; add citric acid to the obtained mixed solution, stir at 40-100°C for 1-6h, filter while hot, and collect the precipitate and filtrate respectively; dry the precipitate to obtain calcium citrate, and dry the filtrate at low temperature to obtain magnesium citrate.

2. The method for simultaneously preparing calcium citrate and magnesium citrate from natural dolomite as claimed in claim 1, characterized in that: The molar ratio of acetic acid to dolomite powder is 1:1 to 3:

1.

3. The method for simultaneously preparing calcium citrate and magnesium citrate from natural dolomite as claimed in claim 1, characterized in that: The volume fraction of the acetic acid aqueous solution is 5 to 10%.

4. The method for simultaneously preparing calcium citrate and magnesium citrate from natural dolomite as claimed in claim 1, characterized in that: The liquid-to-solid ratio of the acetic acid aqueous solution to the dolomite powder is 10:1 to 30:1, mL / g.

5. The method for simultaneously preparing calcium citrate and magnesium citrate from natural dolomite as claimed in claim 1, characterized in that: The molar ratio of citric acid to dolomite powder is 1:1 to 5:

3.

6. The method for simultaneously preparing calcium citrate and magnesium citrate from natural dolomite as claimed in claim 1, characterized in that: The conditions for drying the precipitate are 95°C for 12 h; the conditions for low-temperature drying of the filtrate are -60°C for 24 h.