Preparation method of food-grade calcium hydroxide

Abstract

The invention discloses a preparation method of food-grade calcium hydroxide, which comprises the following steps: firstly, modifying a raw material calcium oxide by using a method of combining corrosive microorganisms and ball milling, and reducing magnesium, iron, lead and the like in the calcium oxide into soluble low-valence metal ions by using the corrosive action of dehydrococcus and shewanella; microorganisms can be attached to the surface of the calcium oxide powder to generate a layer of hydrophilic and lipophilic biological membrane, so that the calcium oxide powder can be more favorably subjected to a digestion reaction to prepare calcium hydroxide. And finally, carrying out wet digestion and aging to prepare the food-grade calcium hydroxide. According to the method, calcium hydroxide can be generated through complete digestion at a lower water cement ratio, the cost is reduced, and the purity of the prepared calcium hydroxide is higher.

Description

Technical Field

[0001] The invention belongs to the technical field of calcium hydroxide preparation, and particularly relates to a method for preparing food-grade calcium hydroxide. Background Art

[0002] Food grade calcium hydroxide is an inorganic compound, commonly known as slaked lime or hydrated lime. Calcium hydroxide is a strong alkali with bactericidal and antiseptic capabilities, and is corrosive to skin and fabrics. Calcium hydroxide is widely used in industry. It is a commonly used building material, and is also used as a bactericide and chemical raw material. Calcium hydroxide can be divided into food grade, pharmaceutical grade and industrial grade calcium hydroxide, and the alkalinity is almost the same. Food grade calcium hydroxide is widely used in the synthesis of food additives, the synthesis of VC phosphate esters of feed additives, the synthesis of high-tech biomaterials HA, food konjac, calcium preparation synthesis, and calcium cyclohexane acid, calcium citrate, calcium lactate sugar industry additives and water treatment and other high-end organic chemical synthesis. With the rapid and sustained development of my country's national economy, the demand for food grade calcium hydroxide in the market continues to increase.

[0003] Invention patent CN201310415042.7 discloses a method for preparing food-grade calcium hydroxide, including: 1. Screening bluestone raw materials, and then crushing the bluestone raw materials to form bluestone fragments with a particle size of 2 to 4 cm; 2. Adding the bluestone fragments to an electric-burning rotary furnace for calcination to obtain quicklime, the calcination temperature is 800°C to 1100°C, the calcination time is 1h to 3h, and the speed of the electric-burning rotary furnace is 10 to 20 revolutions / h; 3. Adding quicklime to a digester, adding 35 to 50% of the weight of quicklime water for digestion reaction, and obtaining a digestion reaction product; 4. Screening the digestion reaction product to obtain calcium hydroxide. The beneficial effects of the invention are: the inventive method uses an electric-burning rotary furnace for calcination, avoiding coal ash residue, and no exhaust gas is discharged, protecting the air. In addition, the calcium hydroxide produced has ① high whiteness; ② high content; ③ few impurities, and can meet the food-grade calcium hydroxide required by GB25572-2010.

[0004] However, the existing production methods of food-grade calcium hydroxide still have defects such as failure to remove impurities such as magnesium, iron, and lead in the raw material lime, the produced calcium hydroxide has low purity and cannot meet the production requirements of food additive calcium hydroxide, or a large amount of ammonia water needs to be added to the reaction, resulting in high cost. Summary of the invention

[0005] Aiming at the problems of low product purity and large raw material consumption in the existing preparation of food-grade calcium hydroxide, the present invention provides a preparation method of food-grade calcium hydroxide, which has a simple process and greatly improves the product purity.

[0006] The present invention is achieved through the following technical solutions: A method for preparing food-grade calcium hydroxide comprises the following steps: (1) preparing a sodium lactate solution with a mass concentration of 3.0-5.0 g / L, a yeast extract with a mass concentration of 0.8-1.2 g / L, an ascorbic acid solution with a mass concentration of 0.08-0.15 g / L, a magnesium sulfate heptahydrate solution with a mass concentration of 0.08-0.12 g / L, and a potassium hydrogen phosphate solution with a mass concentration of 0.01-0.02 g / L, and mixing the above solutions in equal amounts to obtain a mixed solution A; (2) Sodium chloride and ammonium ferrous sulfate were added to the mixed solution A to prepare a culture medium, and then Desulfococcus solution, Shewanella solution and calcium oxide were added. The culture medium was supplemented with distilled water and shaken to mix well. After sealing, the mixture was cultured at 37°C for 14 days to obtain a culture solution. (3) After filtering the culture medium in the culture solution, the culture medium is dried at 60° C. to obtain biological calcium oxide powder; the biological calcium oxide powder is then placed in a planetary ball mill and ball-milled at a speed of 250 r / min for 15-30 min to obtain micro-powdered calcium oxide; (4) adding powdered calcium oxide to water at 40-60° C. at a water-cement ratio of (6-10):1 for digestion reaction, with a stirring speed of 700 rpm. After the digestion reaction, the calcium hydroxide is passed through a 200-mesh sieve and dehydrated to prepare a calcium hydroxide emulsion with a concentration of 1.90-2.4 mol / L; (5) The calcium hydroxide emulsion is placed in a sealed device and aged at 45-60° C. for 20-30 days to obtain food-grade calcium hydroxide.

[0007] Preferably, the amount of sodium chloride added is 0.2 g / mL of mixed solution A.

[0008] Preferably, the added amount of ferrous sulfate is 0.04 g / L mixed solution A.

[0009] Preferably, the amount of Desulfurococcus liquid added is 4 times that of mixed liquid A, and the number of bacteria is 0.4×10 8 cfu / mL.

[0010] Preferably, the amount of Shewanella solution added is 0.2 times that of mixed solution A, and the number of bacteria is 0.8×10 8 cfu / mL.

[0011] Preferably, the amount of calcium oxide added is 1 g / mL of mixed solution A.

[0012] The present invention utilizes a method combining corrosive microorganisms with ball milling to modify the raw material calcium oxide, and utilizes the corrosion of sulfate-reducing bacteria (Desulfococcus genus) and dissimilatory iron-reducing bacteria (Shewanella genus) to reduce magnesium, iron, lead, etc. in the calcium oxide to soluble low-valent metal ions, so that the calcium oxide has holes in its structure due to the lack of elements, thereby obtaining calcium oxide with a porous structure. Subsequently, the porous calcium oxide is further ground by a short ball milling to prepare fine-grained calcium oxide powder. In addition, microorganisms will adhere to the surface of the calcium oxide powder to form a hydrophilic and lipophilic biofilm, which is more conducive to the digestion reaction of the calcium oxide powder to prepare calcium hydroxide.

[0013] After ball milling, calcium oxide powder is subjected to wet digestion reaction. The fine powder digestion reaction is not easy to agglomerate, and the reaction is more complete. At the same time, the calcium oxide powder after biological corrosion has fewer impurities, so the prepared calcium hydroxide has higher purity. Because the biofilm covering the surface of calcium oxide makes it highly hydrophilic, the digestion reaction can be completed at a very small water-cement ratio. With a small water-cement ratio, the heat released by the digestion reaction can be better transferred in the reaction system, which is conducive to the growth of calcium hydroxide crystals. At the same time, the digestion reaction of porous calcium oxide helps to increase the specific surface area of ​​the prepared calcium hydroxide, thereby improving the product quality.

[0014] The higher the aging temperature of calcium hydroxide, the faster the system reaches stability and the narrower the particle size distribution of calcium hydroxide. The aging time is an important factor affecting the changes in calcium hydroxide, causing changes in viscosity and specific surface area. The specific surface area first increases and then decreases with the increase of aging time. It gradually tends to be stable after aging for 20-30 days, and the same is true for viscosity.

[0015] The beneficial effects of the present invention are as follows: 1. The present invention pre-treats the raw materials, uses corrosive microorganisms to remove impurities in calcium oxide, and then grinds the raw materials into powder. The microorganisms form a biofilm on the surface of the calcium oxide powder to increase the hydrophilicity of the calcium oxide, so that the calcium oxide can be completely digested to generate calcium hydroxide at a lower water-cement ratio, thereby reducing costs.

[0016] 2. The present invention performs microbial corrosion treatment on the raw material calcium oxide to remove impurities therein, so that the calcium oxide has a porous structure, which can better react with water for digestion, and the prepared calcium hydroxide has a higher purity. DETAILED DESCRIPTION

[0017] The present invention will be further described below in conjunction with the embodiments.

[0018] Embodiment 1: A method for preparing food-grade calcium hydroxide comprises the following steps: (1) Prepare a sodium lactate solution with a mass concentration of 3.0 g / L, a yeast extract with a mass concentration of 0.8 g / L, an ascorbic acid solution with a mass concentration of 0.08 g / L, a magnesium sulfate heptahydrate solution with a mass concentration of 0.08 g / L, and a potassium hydrogen phosphate solution with a mass concentration of 0.01-0.02 g / L, and mix the above solutions in equal amounts to obtain a mixed solution A.

[0019] (2) Sodium chloride and ammonium ferrous sulfate are added to mixed solution A to prepare a culture medium. Then, Desulfurococcus solution, Shewanella solution, and calcium oxide are added. The culture medium is supplemented with distilled water and shaken to mix well. After sealing, the mixture is cultured at 37°C for 14 days to obtain a culture medium.

[0020] The amount of sodium chloride added is 0.2 g / mL of mixed solution A.

[0021] The added amount of ferrous sulfate is 0.04 g / L mixed solution A.

[0022] The amount of Desulfurococcus liquid added was 4 times that of mixed liquid A, and the number of bacteria was 0.4×10 8 cfu / mL.

[0023] The amount of Shewanella solution added was 0.2 times that of mixed solution A, and the number of bacteria was 0.8×10 8 cfu / mL.

[0024] The amount of calcium oxide added is 1 g / mL of mixed solution A.

[0025] (3) After filtering the culture medium in the culture solution, the culture medium is dried at 60° C. to obtain biological calcium oxide powder; the biological calcium oxide powder is then placed in a planetary ball mill and ball-milled at a speed of 250 r / min for 15 min to obtain micro-powdered calcium oxide; (4) adding powdered calcium oxide to water at 40° C. at a water-cement ratio of 6:1 for digestion reaction at a stirring speed of 700 rpm. After the digestion reaction, the calcium hydroxide was passed through a 200-mesh sieve and dehydrated to prepare a calcium hydroxide emulsion with a concentration of 1.90 mol / L; (5) The calcium hydroxide emulsion is placed in a sealed device and aged at 45° C. for 30 days to obtain food-grade calcium hydroxide.

[0026] Embodiment 2: A method for preparing food-grade calcium hydroxide, comprising the following steps: (1) Prepare a sodium lactate solution with a mass concentration of 5.0 g / L, a yeast extract with a mass concentration of 1.2 g / L, an ascorbic acid solution with a mass concentration of 0.15 g / L, a magnesium sulfate heptahydrate solution with a mass concentration of 0.12 g / L, and a potassium hydrogen phosphate solution with a mass concentration of 0.02 g / L, and mix the above solutions in equal amounts to obtain a mixed solution A.

[0027] (2) Sodium chloride and ammonium ferrous sulfate are added to mixed solution A to prepare a culture medium. Then, Desulfurococcus solution, Shewanella solution, and calcium oxide are added. The culture medium is supplemented with distilled water and shaken to mix well. After sealing, the mixture is cultured at 37°C for 14 days to obtain a culture medium.

[0028] The amount of sodium chloride added is 0.2 g / mL of mixed solution A.

[0029] The added amount of ferrous sulfate is 0.04 g / L mixed solution A.

[0030] The amount of Desulfurococcus liquid added was 4 times that of mixed liquid A, and the number of bacteria was 0.4×10 8 cfu / mL.

[0031] The amount of Shewanella solution added was 0.2 times that of mixed solution A, and the number of bacteria was 0.8×10 8 cfu / mL.

[0032] The amount of calcium oxide added is 1 g / mL of mixed solution A.

[0033] (3) After filtering the culture medium in the culture solution, the culture medium is dried at 60° C. to obtain biological calcium oxide powder; the biological calcium oxide powder is then placed in a planetary ball mill and ball-milled at a speed of 250 r / min for 30 min to obtain micro-powdered calcium oxide; (4) adding powdered calcium oxide to water at 60° C. at a water-cement ratio of 10:1 for digestion reaction at a stirring speed of 700 rpm. After the digestion reaction, the calcium hydroxide was passed through a 200-mesh sieve and dehydrated to prepare a calcium hydroxide emulsion with a concentration of 2.4 mol / L; (5) The calcium hydroxide emulsion is placed in a sealed device and aged at 60° C. for 20 days to obtain food-grade calcium hydroxide.

[0034] Embodiment 3: A method for preparing food-grade calcium hydroxide, comprising the following steps: (1) preparing a sodium lactate solution with a mass concentration of 4.0 g / L, a yeast extract with a mass concentration of 1.0 g / L, an ascorbic acid solution with a mass concentration of 0.12 g / L, a magnesium sulfate heptahydrate solution with a mass concentration of 0.10 g / L, and a potassium hydrogen phosphate solution with a mass concentration of 0.01 g / L, and mixing the above solutions in equal amounts to obtain a mixed solution A; (2) Sodium chloride and ammonium ferrous sulfate were added to the mixed solution A to prepare a culture medium, and then Desulfococcus solution, Shewanella solution and calcium oxide were added. The culture medium was supplemented with distilled water and shaken to mix well. After sealing, the mixture was cultured at 37°C for 14 days to obtain a culture solution. The amount of sodium chloride added is 0.2 g / mL of mixed solution A.

[0035] The added amount of ferrous sulfate is 0.04 g / L mixed solution A.

[0036] The amount of Desulfurococcus liquid added was 4 times that of mixed liquid A, and the number of bacteria was 0.4×10 8 cfu / mL.

[0037] The amount of Shewanella solution added was 0.2 times that of mixed solution A, and the number of bacteria was 0.8×10 8 cfu / mL.

[0038] The amount of calcium oxide added is 1 g / mL of mixed solution A.

[0039] (3) After filtering the culture medium in the culture solution, the culture medium is dried at 60° C. to obtain biological calcium oxide powder; the biological calcium oxide powder is then placed in a planetary ball mill and ball-milled at a speed of 250 r / min for 20 min to obtain micro-powdered calcium oxide; (4) adding powdered calcium oxide to water at 50° C. at a water-cement ratio of 7:1 for digestion reaction, with a stirring speed of 700 rpm. After the digestion reaction, the calcium hydroxide was passed through a 200-mesh sieve and dehydrated to prepare a calcium hydroxide emulsion with a concentration of 2.1 mol / L; (5) The calcium hydroxide emulsion is placed in a sealed device and aged at 50° C. for 25 days to obtain food-grade calcium hydroxide.

[0040] The parameters of the calcium hydroxide prepared in Examples 1-3 are shown in Table 1.

[0041] Table 1:

[0042] It can be seen from the data in Table 1 that the calcium hydroxide prepared in the embodiment of the present invention has very good performance.

[0043] The above embodiments are only exemplary embodiments of the present invention and are not intended to limit the present invention. The protection scope of the present invention is defined by the claims. Those skilled in the art may make various modifications or equivalent substitutions to the present invention within the essence and protection scope of the present invention, and such modifications or equivalent substitutions shall also be deemed to fall within the protection scope of the present invention.

Claims

1. A method for preparing food grade calcium hydroxide, characterized in that, The following steps are involved: (1) preparing a sodium lactate solution with a mass concentration of 3.0-5.0 g / L, a yeast extract with a mass concentration of 0.8-1.2 g / L, an ascorbic acid solution with a mass concentration of 0.08-0.15 g / L, a magnesium sulfate heptahydrate solution with a mass concentration of 0.08-0.12 g / L, and a potassium hydrogen phosphate solution with a mass concentration of 0.01-0.02 g / L, and mixing the above solutions in equal amounts to obtain a mixed solution A; (2) Adding sodium chloride and ammonium ferrous sulfate to the mixed solution A to prepare a culture medium, then adding Desulfococcus solution, Shewanella solution and calcium oxide, supplementing the culture medium with distilled water and shaking it to mix well, sealing it and culturing it at 37°C for 12-16 days to obtain a culture solution; (3) After filtering the culture medium in the culture solution, the culture medium is dried at 60° C. to obtain biological calcium oxide powder; the biological calcium oxide powder is then placed in a planetary ball mill and ball-milled at a speed of 250 r / min for 15-30 min to obtain micro-powdered calcium oxide; (4) adding powdered calcium oxide to water at 40-60° C. at a water-cement ratio of (6-10):1 for digestion reaction, with a stirring speed of 700 rpm. After the digestion reaction, the calcium hydroxide is passed through a 200-mesh sieve and dehydrated to prepare a calcium hydroxide emulsion with a concentration of 1.90-2.4 mol / L; (5) The calcium hydroxide emulsion is placed in a sealed device and aged at 45-60° C. for 20-30 days to obtain food-grade calcium hydroxide.

2. The preparation method of food grade calcium hydroxide according to claim 1, wherein: The amount of sodium chloride added is 0.2 g / mL of mixed solution A.

3. The preparation method of food grade calcium hydroxide according to claim 1, wherein: The added amount of ferrous sulfate is 0.04 g / L mixed solution A.

4. The preparation method of food grade calcium hydroxide according to claim 1, wherein: The amount of Desulfurococcus liquid added was 4 times that of mixed liquid A, and the number of bacteria was 0.4×10 8 cfu / mL.

5. The preparation method of food grade calcium hydroxide according to claim 1, wherein: The amount of Shewanella solution added was 0.2 times that of mixed solution A, and the number of bacteria was 0.8×10 8 cfu / mL.

6. The preparation method of food grade calcium hydroxide according to claim 1, wherein: The amount of calcium oxide added is 1 g / mL of mixed solution A.

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