Method for producing calcium salt

Abstract

Provided is a novel method for producing a calcium salt. A method for producing a calcium salt according to one embodiment of the present disclosure has the following steps. Step S20: A step for acid-treating a raw material containing calcium phosphate to obtain an acid extract. Step S30: A step for mixing the resulting acid extract with a base to obtain a calcium phosphate precipitate. Step S40: A step for mixing the resulting calcium phosphate precipitate with an acid and / or a salt thereof and forming a calcium salt.

Description

Calcium salt manufacturing method

[0001] The present invention relates to a method for producing a calcium salt.

[0002] Calcium salts are used in a wide range of applications, including construction, agriculture, medicine, and food. For example, gypsum, which is made primarily from calcium sulfate, is generally produced by mining natural gypsum or by chemical synthesis, but methods for producing gypsum using waste as a raw material have also been developed. For example, Patent Document 1 discloses a method for producing α-type gypsum hemihydrate using gypsum produced as a by-product in a flue gas desulfurization system as a raw material. Calcium sulfite can also be produced from flue gas dust collected from thermal power plants and the like.

[0003] Japanese Patent Application Publication No. 52-048594

[0004] Calcium phosphate is one of the most readily available forms of calcium. For example, bone tissue, which is primarily composed of calcium phosphate, is said to contain approximately 30% calcium by weight before drying. Therefore, if calcium salts could be produced using calcium phosphate as a raw material, waste bones and other materials could be effectively utilized. Therefore, there is considerable interest in developing methods for producing calcium salts from calcium phosphate.

[0005] An object of one aspect of the present invention is to provide a novel method for producing a calcium salt.

[0006] In order to solve the above-mentioned problems, one embodiment of the present invention provides a method for producing a calcium salt, which comprises the following steps: Step S20: treating a raw material containing calcium phosphate with an acid to obtain an acid extract; Step S30: mixing the obtained acid extract with a base to obtain a calcium phosphate precipitate; Step S40: mixing the obtained calcium phosphate precipitate with an acid and / or a salt thereof to form a calcium salt.

[0007] According to one aspect of the present invention, a novel method for producing calcium salts is provided.

[0008] 1 is a flowchart showing an overview of a method for producing a calcium salt according to one embodiment of the present invention. FIG. 2 is a partial flowchart showing a first embodiment of step S40. FIG. 3 is a partial flowchart showing a second embodiment of step S40. FIG. 4 is a microscopic image of calcium sulfate obtained by a production method according to one embodiment of the present invention. FIG. 5 is a microscopic image of calcium sulfate obtained by a production method according to one embodiment of the present invention. FIG. 6 is a polarized light microscope image of calcium sulfate obtained by a production method according to one embodiment of the present invention. FIG. 7 is a polarized light microscope image of calcium sulfate obtained by a production method according to one embodiment of the present invention. FIG. 8 is a polarized light microscope image of calcium sulfate obtained by a production method according to one embodiment of the present invention. FIG. 9 is a polarized light microscope image of calcium sulfite and calcium tartrate obtained by a production method according to one embodiment of the present invention. FIG. 10 is a polarized light microscope image of calcium metasilicate and calcium orthosilicate obtained by a production method according to one embodiment of the present invention. FIG. 11 is a diagram showing the effect of pretreatment of raw materials on the amount of phosphate contained in an acid extract. FIG. 12 is a diagram showing the effect of pH on the efficiency of separation of phosphate and calcium salt from calcium phosphate precipitate. FIG. 13 is a diagram showing the use of a calcium salt obtained by a production method according to one embodiment of the present invention as an abrasive. FIG. 14 is a spectrum of transmitted light of a calcium salt obtained by a production method according to one embodiment of the present invention. FIG. 15 is a diagram showing the use of a calcium salt obtained by a production method according to one embodiment of the present invention as an abrasive for toothpaste.

[0009] Hereinafter, an example of an embodiment of the present invention will be described in detail, but the present invention is not limited to this.

[0010] Unless otherwise specified in this specification, "A to B" representing a numerical range means "greater than or equal to A and less than or equal to B."

[0011] As used herein, "calcium phosphate" refers to a substance that may contain phosphate ions, calcium ions, and optionally other ions. The specific composition of calcium phosphate is not particularly limited. Examples of calcium phosphate include calcium monohydrogen phosphate, calcium dihydrogen phosphate, tricalcium phosphate, β-tricalcium phosphate, octacalcium phosphate, hydroxyapatite, fluoroapatite, chloroapatite, and carbonate apatite. Specific examples of raw materials containing calcium phosphate include bone tissue (usually composed primarily of carbonate apatite), apatite (usually composed primarily of chloroapatite), chicken manure ash, incineration ash, sewage sludge, dried sludge, and dephosphorized slag (usually composed primarily of fluoroapatite). In one embodiment, the raw material containing calcium phosphate is bone tissue.

[0012] In this specification, solids that become acidic when dissolved are also generally referred to as "acids." Examples of such acids include some organic acids, specifically tartaric acid and citric acid.

[0013] Calcium salts used industrially are often produced using minerals or waste as raw materials. However, these production methods are accompanied by issues of impurities and non-homogeneity. Minerals and waste contain different impurity compositions depending on their origin (such as the place of production or collection). It is difficult to ensure the homogeneity of the composition of calcium salts obtained from such raw materials. Furthermore, minerals and waste may contain heavy metals or radioactive elements as impurities. From a safety perspective, the range of uses for calcium salts obtained from such raw materials is extremely limited. Furthermore, if a carbon credit system is introduced in the future, calcium salts, which emit large amounts of carbon dioxide during quarrying, will incur additional costs.

[0014] In contrast, calcium phosphate-containing raw materials (especially bone tissue) are tissues with extremely high compositional homogeneity. In particular, because the rearing conditions of livestock or farmed fish are nearly identical regardless of their origin, their waste bones are highly homogeneous raw materials. Furthermore, if livestock or farmed fish are raised on normal feed, it is unlikely that heavy metals or radioactive elements will be present in the bone tissue. For example, in the case of livestock raised for meat production, the period from birth to slaughter is short, so even if there is a possibility of absorbing heavy metals or radioactive elements from the environment, that period is extremely short. Therefore, bone tissue contains almost no components such as aluminum, arsenic, lead, nickel, chromium, or manganese. Thus, the method for producing a calcium salt according to one embodiment of the present invention can solve the problems of impurities and non-uniformity. However, solving this problem is not essential to the present invention. Furthermore, one embodiment of the present invention also anticipates using bone tissue from natural animals or fish or calcium phosphate-containing materials other than bone tissue as raw materials.

[0015] 1. Overview of the Method for Producing Calcium Salt An overview of the method for producing a calcium salt according to one embodiment of the present invention is illustrated in the flowchart of FIG. 1. Most of the calcium contained in raw materials such as bone tissue is in the form of calcium phosphate. Furthermore, the raw materials may contain organic components such as collagen in addition to calcium phosphate. In the method illustrated in FIG. 1, calcium is dissolved in steps S10 and S20, and components other than phosphate and calcium are removed in step S30. Thereafter, calcium salt (typically a calcium salt precipitate) is obtained in step S40. Each step is described in detail below.

[0016] [1.1. Step S10] In step S10, a raw material containing calcium phosphate is pretreated. Step S10 is an optional step and may not be performed. It has been suggested that pretreating the raw material increases the amount of calcium contained in the acid extract (see Example 7).

[0017] The raw material to be subjected to step S10 may be of any type. When the raw material contains bone tissue, the bone tissue may be derived from any organism. Examples of organisms include mammals, birds, amphibians, and fish. For mass production, it is preferable that the raw material be available in large quantities, and for example, bone tissue from livestock (such as cattle, pigs, sheep, and chickens) or whales or farmed fish is preferably used. The raw material may be shredded or crushed before or after step S10. This may allow the raw material to be decomposed more efficiently, thereby shortening the production time.

[0018] In one embodiment, in step S10, the raw material is heated. The heating temperature at this time may be 30° C. or higher or 40° C. or higher; or 100° C. or lower or 80° C. or lower. The raw material may be heated while immersed in acid.

[0019] In one embodiment, in step S10, the raw material is heated under pressure. The pressure at this time may be 200 kPa or more or 1 MPa or more; 500 MPa or less or 800 MPa or less. The heating temperature at this time may be 10°C or more or 50°C or more; 120°C or less or 200°C or less. The raw material may be heated under pressure while immersed in acid.

[0020] In one embodiment, in step S10, the raw material is irradiated with microwaves. Heating, heating under pressure, and microwave irradiation may be performed in any combination. Among these, microwave irradiation is more preferable as step S10 because it can achieve its effect in a short time. The microwave irradiation time can be appropriately determined depending on the volume of the raw material. For example, when the volume of the raw material is 1 cm ３ When the microwave irradiation time is about 5 seconds or more, 10 seconds or more, or 15 seconds or more; or 10 minutes or less, 7 minutes or less, or 5 minutes or less. Of course, when the volume of the raw material is large, the irradiation time may be longer. When the microwave irradiation time is within an appropriate range, inorganic components including phosphoric acid can be efficiently extracted from the raw material.

[0021] [1.2. Step S20] In step S20, a raw material containing calcium phosphate is treated with an acid to obtain an acid extract. In step S20, inorganic components containing calcium are separated from the raw material and eluted into the acid extract.

[0022] The acid used to treat the raw material in step S20 is not particularly limited. Examples of acids include hydrochloric acid, nitric acid, formic acid, sulfuric acid, and trichloroacetic acid. An acidic decalcifying solution such as Planck-Lycros solution may also be used. From the viewpoint of availability, one or more acids selected from the group consisting of nitric acid, hydrochloric acid, formic acid, and sulfuric acid are preferred. From the viewpoint of calcium recovery efficiency, one or more acids selected from the group consisting of nitric acid, hydrochloric acid, and formic acid are preferred, and one or more acids selected from the group consisting of hydrochloric acid and formic acid are more preferred. Two or more acids may be mixed in an appropriate ratio and used.

[0023] In step S20, the raw material may be acid-treated with a solution prepared by diluting an acid in a solvent. Examples of the solvent include water, lower alcohols, glycerol, propane-1,2-diol, and 1,3-propanediol. Two or more types of solutions may be mixed in an appropriate ratio.

[0024] The acid concentration can be appropriately determined depending on the volume of the raw material to be acid-treated. When the volume of the raw material is small, it can be treated with a low-concentration acid. When the volume of the raw material is large, it is preferable to use a high-concentration acid. When performing acid treatment with a low-concentration acid, it is preferable to treat a finely powdered raw material. However, even when the volume of the raw material is large, inorganic components can be sufficiently extracted by increasing the acid concentration and immersing for a long period of time. For example, when the volume of the raw material is several cm ３ When the following crushed bone material is used as the raw material, the lower limit of the acid concentration in step S20 can be 0.3 mol / L or more, 0.4 mol / L or more, 0.5 mol / L or more, 0.6 mol / L or more, 0.7 mol / L or more, 0.8 mol / L or more, or 0.9 mol / L or more. The upper limit of the acid concentration in step S20 can be 2.0 mol / L or less, 1.5 mol / L or less, 1.0 mol / L or less, or 0.9 mol / L or less. When the acid concentration is within the above range, inorganic components including phosphoric acid can be efficiently extracted, and the cost of neutralizing the acid extract can be reduced because the acid concentration is not too high.

[0025] Examples of suitable acid concentrations when treating the pulverized raw material with an acid are as follows: When the acid is nitric acid, the lower limit of the nitric acid concentration is preferably 0.6 mol / L or more, more preferably 0.7 mol / L or more; The upper limit of the nitric acid concentration is preferably 1.0 mol / L or less, more preferably 0.9 mol / L or less; When the acid is hydrochloric acid, the lower limit of the hydrochloric acid concentration is preferably 0.8 mol / L or more, more preferably 0.9 mol / L or more; The upper limit of the hydrochloric acid concentration is preferably 1.2 mol / L or less, more preferably 1.1 mol / L or less; When the acid is formic acid, the lower limit of the formic acid concentration is preferably 0.8 mol / L or more, more preferably 0.9 mol / L or more; The upper limit of the formic .... When the acid is sulfuric acid, the lower limit of the sulfuric acid concentration is preferably 0.8 mol / L or more, more preferably 0.9 mol / L or more. The upper limit of the sulfuric acid concentration is preferably 1.2 mol / L or less, more preferably 1.1 mol / L or less. However, the above concentrations are examples of suitable concentrations when the raw material is pulverized, and the acid concentration may be higher when the raw material has a larger volume.

[0026] For example, a volume of several cm ３ When the following crushed bone material is used as the raw material, the lower limit of the extraction time in step S20 is preferably 6 hours or more, more preferably 8 hours or more, and even more preferably 10 hours or more. The upper limit of the extraction time in step S20 is preferably 48 hours or less, more preferably 24 hours or less, and even more preferably 14 hours or less. If the extraction time is within the above range, inorganic components including phosphate contained in the raw material can be sufficiently extracted.

[0027] For example, a volume of several cm ３ When using crushed bone material as the raw material, the temperature of the acid treatment in step S20 is preferably 5 to 60°C. Carrying out the acid treatment within the above temperature range can reduce the generation of unpleasant odors associated with the acid treatment. This also mitigates the location requirements for the manufacturing plant. Furthermore, adjusting the temperature to 60°C or below does not require expensive special equipment; a constant temperature can be maintained using a water bath or incubator.

[0028] [1.3. Step S30] In step S30, the acid extract and a base are mixed. In step S30, calcium ions contained in the acid extract are precipitated as calcium phosphate, and other components (such as components derived from bone impurities) are contained in the supernatant. Therefore, calcium can be extracted by recovering the precipitate. Examples of bases that can be used include sodium hydroxide and potassium hydroxide.

[0029] [1.4. Step S40] In step S40, calcium phosphate is mixed with an acid, and a calcium salt is further formed. In a first embodiment, calcium phosphate is mixed with an acid and / or its salt that forms a calcium salt. In a second embodiment, calcium phosphate is mixed with an acid to obtain a solution of phosphate ions and calcium ions. Thereafter, another acid or its salt is mixed to form a calcium salt.

[0030] 2. First Aspect of Step S40 Fig. 2 is a partial flowchart showing a first aspect of step S40. Step S40 of the first aspect includes step S42.

[0031] [2.1. Step S42] In step S42, calcium phosphate is mixed with an acid and / or its salt that forms a calcium salt. In step S42, the pH of the system is lowered by adding the acid, so that the calcium phosphate precipitate dissolves. At the same time, anions contained in the acid and calcium ions form a calcium salt.

[0032] Examples of the acid and / or its salt to be mixed in step S42 include condensed phosphoric acid, tartaric acid, oxalic acid, citric acid, sulfuric acid, and salts thereof. These acids and / or salts are strong enough to dissolve calcium phosphate and contain anions that form poorly soluble calcium salts. Examples of salts to be mixed in step S42 are described below in Section [3.2].

[0033] In step S42, the lower limit of the pH of the system after mixing the poorly soluble calcium salt-forming acid and / or its salt may be 1.0 or more, 1.1 or more, 1.2 or more, 1.3 or more, 1.4 or more, 1.5 or more, 1.6 or more, 1.7 or more, 1.8 or more, 1.9 or more, 2.0 or more, 2.1 or more, 2.2 or more, 2.3 or more, 2.4 or more, 2.5 or more, 2.6 or more, 2.7 or more, 2.8 or more, 2.9 or more, 3.0 or more, 3.1 or more, 3.2 or more, 3.3 or more, 3.4 or more, 3.5 or more, 3.6 or more, 3.7 or more, 3.8 or more, 3.9 or more, or 4.0 or more. In step S42, the upper limit of the pH of the system after mixing the poorly soluble calcium salt-forming acid and / or its salt may be 6.0 or less, 5.9 or less, 5.8 or less, 5.7 or less, 5.6 or less, 5.5 or less, 5.4 or less, 5.3 or less, 5.2 or less, 5.1 or less, 5.0 or less, 4.9 or less, 4.8 or less, 4.7 or less, 4.6 or less, 4.5 or less, 4.4 or less, 4.3 or less, 4.2 or less, 4.1 or less, 4.0 or less, 3.9 or less, 3.8 or less, 3.7 or less, 3.6 or less, 3.5 or less, 3.4 or less, 3.3 or less, 3.2 or less, 3.1 or less, 3.0 or less, 2.9 or less, 2.8 or less, 2.7 or less, 2.6 or less, or 2.5 or less.

[0034] 3 is a partial flowchart showing a second aspect of step S40. Step S40 of the second aspect includes steps S46 and S48. Each step will be described in detail below.

[0035] [3.1. Step S46] In step S46, the calcium phosphate precipitate is mixed with an acid. This redissolves the calcium phosphate that was precipitated. Examples of acids that can be used include hydrochloric acid, nitric acid, formic acid, and phosphoric acid.

[0036] In the second embodiment, steps S30 and S46 may be repeated. Repeating these steps increases the purity of the calcium phosphate. Steps S30 and S46 may be repeated, for example, two or more times, three or more times, four or more times, or five or more times. From an economical standpoint, steps S30 and S46 may be repeated, for example, ten or fewer times. After repeating steps S30 and S46, a washing treatment may be performed as many times as necessary to wash away unnecessary components contained in the calcium phosphate precipitate with pure water before proceeding to step S15.

[0037] [3.2. Step S48] In step S48, the solution of phosphate ions and calcium ions is mixed with an acid and / or a salt thereof, and the resulting calcium salt is collected by centrifugation, filtration, or the like.

[0038] In one embodiment, the calcium salt produced in step S48 is a poorly soluble calcium salt. The solubility of the poorly soluble calcium salt at 25°C (maximum amount dissolved per 100 mL of water) is preferably 0.3 g or less, more preferably 0.1 g or less, even more preferably 0.05 g or less, and even more preferably 0.01 g or less. The poorly soluble calcium salt forms a precipitate and is therefore easy to recover. Furthermore, the poorly soluble calcium salt can capture a large amount of calcium ions in a solution of phosphate ions and calcium ions, resulting in a good yield of the produced calcium salt.

[0039] Specific examples of poorly soluble calcium salts include calcium sulfate, calcium sulfite, calcium carbonate, calcium tartrate, calcium oxalate, calcium citrate, calcium silicate, and calcium salts of condensed phosphates (e.g., calcium pyrophosphate). Therefore, examples of acids to be mixed with the phosphate ion and calcium ion solution in step S48 include sulfuric acid, sulfite, carbonic acid, tartaric acid, oxalic acid, citric acid, silicic acid, and condensed phosphates (e.g., pyrophosphoric acid). Examples of salts to be mixed with the phosphate ion and calcium ion solution in step S48 include sulfate, sulfite, carbonate, bicarbonate, tartrate, oxalate, citrate, silicate, and salts of condensed phosphates (e.g., pyrophosphate). These salts may be sodium salts, potassium salts, magnesium salts, ammonium salts, ferric salts, and the like. Tartaric acid and tartrate salts may be in the D- or L-form, or a mixture thereof. Silicic acid is a general term for acids whose main components are silicon, oxygen, and hydrogen, and includes orthosilicic acid, metasilicic acid, etc.

[0040] Anion A produced when a solution of phosphate ions and calcium ions is mixed with an acid (HA) or a salt (MA) ｎ－ In the case of an anion, it is preferable that the solubility of the calcium salt is low and that the acid dissociation constant pKa is far from the third acid dissociation constant of phosphoric acid (12.67). By selecting such an anion, it is possible to form a poorly soluble calcium salt while minimizing the occurrence of calcium phosphate precipitation by appropriately adjusting the pH of the system. For reference, the acid dissociation constants of representative acids and the solubilities of calcium salts (at 25°C, per 100 mL of water) are shown below. For some calcium salts, the solubility product (at 25°C) is also shown. Sulfuric acid (H ２ SO ４ ) ・pK1=-5 ・pK2=1.99 ・CaSO ４ Solubility product: 6.1 × 10 －５ mol / L ・CaSO ４ Solubility: 0.25g Sulfurous acid (H ２ SO ３ ) ・pK1=1.85 ・pK2=7.19 ・CaSO ３Solubility: 0.0043 g Carbonic acid (H ２ CO ３ ) ・pK1=6.35 ・pK2=10.33 ・CaCO ３ Solubility product: 4.7 × 10 －９ mol / L ・CaCO ３ Solubility of tartaric acid (C ４ O ４ (OH) ２ ) ・pK1=2.93 ・pK2=4.20 ・CaC ４ O ４ (OH) ２ Solubility: 0.01 g Pyrophosphate (H ４ P ２ O ７ ) ・pK1=0.2 ・pK2=0.9 ・pK3=6.76 ・pK4=8.95 ・Ca ２ P ２ O ７ Solubility product: 2.0 × 10 －１９ mol / L Ca ２ P ２ O ７ Solubility: Less than 0.01 g Oxalic acid (H ２ C ２ O ４ ) ・pK1=1.27 ・pK2=4.27 ・CaC ２ O ４ Solubility product: 2.0 × 10 －８ mol / L CaC ２ O ４ Solubility: 0.00067g Citric acid (C(OH)(CH ２ COOH) ２ COOH) ・pK1=3.1 ・pK2=4.8 ・pK3=6.4 ・Ca ３ (C(OH)(CH ２ COOH) ２ COOH) 2.4H ２ Solubility of O: 0.085 g Metasilicic acid (H ２ SiO ３ ) CaSiO ３ Solubility: 9.5 x 10 －３ g Orthosilicic acid (H ４ SiO ４ ) Ca ２ SiO ４Solubility: 0.01 g Phosphoric acid (H ３ P.O. ４ (Reference) ・pK1 = 2.12 ・pK2 = 7.21 ・pK3 = 12.67 ・CaHPO ４ Solubility product: 2.6 × 10 －７ mol / L ・CaHPO ４ Solubility: 0.02 g Ca ３ (P.O. ４ ) ２ Solubility product: 2.0 × 10 －２９ mol / L Ca ３ (P.O. ４ ) ２ Solubility: 0.002g

[0041] The acid and / or salt mixed in step S48 is preferably one or more selected from the group consisting of sulfuric acid, sulfates, tartaric acid, tartrates, sulfurous acid, sulfites, citric acid, citrates, silicic acid, and silicates. Examples of sulfates include sodium sulfate, sodium hydrogen sulfate, potassium sulfate, potassium hydrogen sulfate, magnesium sulfate, ammonium sulfate, manganese sulfate (e.g., manganese(II) sulfate), iron sulfate (e.g., iron(II) sulfate), and aluminum potassium sulfate. Examples of tartrates include sodium tartrate, sodium hydrogen tartrate, potassium tartrate, potassium hydrogen tartrate, sodium potassium tartrate, and ammonium tartrate. Examples of sulfites include sodium sulfite, potassium sulfite, and potassium sodium sulfite. Examples of citrates include monosodium citrate, disodium citrate, trisodium citrate, potassium citrate, and ammonium iron citrate. Examples of silicates include sodium metasilicate.

[0042] The amount of acid and / or its salt to be mixed in step S48 can be appropriately determined by those skilled in the art. The amount of acid and / or its salt to be added may be, for example, an amount that results in a concentration of the acid and / or its salt in the mixed system of 0.2 M or more, 0.4 M or more, 0.6 M or more, 0.8 M or more, or 1.0 M or more. The greater the amount of acid and / or its salt to be added, the less residual calcium there will be. The upper limit of the amount of acid and / or its salt to be added may be, for example, an amount that results in a concentration in the mixed system of 3.0 M or less, 2.0 M or less, or 1.0 M or less.

[0043] It may be preferable that the calcium salt crystals obtained in step S48 are not needle-shaped or rod-shaped. For example, when recovering calcium salt crystals by filtration, needle-shaped or rod-shaped crystals may clog the filter material. However, the preferred shape of the calcium salt crystals may vary depending on the recovery method and usage method of the calcium salt.

[0044] In step S48, the upper and lower limits of the pH of the system after mixing the acid that forms a poorly soluble calcium salt and / or its salt may be the values ​​exemplified in Section [2.1].

[0045] [4. Method for Manufacturing an Article] One aspect of the present invention is a method for manufacturing an article, which includes the above-described manufacturing method. The method for manufacturing an article may include a step of mixing the calcium salt obtained by the above-described manufacturing method with another material, a step of dissolving or dispersing the calcium salt obtained by the above-described manufacturing method, or a step of heating or cooling a material containing the calcium salt obtained by the above-described manufacturing method. Examples of articles obtained by this manufacturing method include building materials, food additives, cosmetic materials, medical materials, filtering media, fertilizers, abrasives, light scattering agents, and dental abrasives.

[0046] 5. Characteristics of the Calcium Salt Obtained The isotopic composition of the calcium salt obtained by the production method according to one embodiment of the present invention reflects the isotopic composition of the elements in the raw materials. Therefore, the isotopic composition of the calcium salt can be strong evidence for inferring the origin of the calcium salt. The stable isotopes of calcium atoms are ４０ Ca, ４２ Ca, ４３Ca, ４４ Ca, ４６ Five types of Ca are known. Recent technology has made it possible to measure stable isotope ratios using high-precision mass spectrometers. According to such research, ４４ The abundance ratio of Ca varies depending on the material.

[0047] Generally, when organisms absorb calcium from water, light isotopes are absorbed preferentially (see Oceanography in Japan, 2 (53), 81-99, 2016). Therefore, calcium in bone tissue is more likely to be absorbed from δ isotopes than calcium in phosphate rock. ４４ The Ca content is low. Therefore, ４４ It is strongly believed that calcium salts with a relatively low Ca content are calcium salts produced from bone tissue. In one embodiment, the calcium salts obtained by one aspect of the present invention contain calcium atoms with a δ ４４ The proportion of Ca may be -0.5 parts per million or more based on a high purity standard material (SRM915a). ４４ The Ca content may be +0.5 parts per million or less based on a high purity standard material (SRM915a).

[0048] [6. Summary] The present invention includes the following aspects. <1> A method for producing a calcium salt, comprising the following steps: Step S20: treating a raw material containing calcium phosphate with an acid to obtain an acid extract; Step S30: mixing the obtained acid extract with a base to obtain a calcium phosphate precipitate; Step S40: mixing the obtained calcium phosphate precipitate with an acid and / or a salt thereof, and forming a calcium salt. <2> The method according to <1>, wherein Step S40 includes the following Step S42: Step S42: mixing the obtained calcium phosphate precipitate with an acid and / or a salt thereof that forms a calcium salt. <3> The method according to <2>, wherein the acid and / or a salt thereof that forms the calcium salt in Step S42 is sulfuric acid and / or tartaric acid. <4> The method according to any one of <1> to <3>, wherein step S40 includes the following steps S46 and S48: step S46: mixing the obtained calcium phosphate precipitate with an acid to obtain a solution of phosphate ions and calcium ions; step S48: mixing the obtained solution of phosphate ions and calcium ions with an acid that forms a calcium salt and / or a salt thereof; wherein the acid in step S46 is different from the acid in step S48. <5> The method according to <4>, wherein the acid in step S48 is one or more selected from the group consisting of sulfuric acid, tartaric acid, sulfurous acid, citric acid, and silicic acid. <6> The method according to <4> or <5>, wherein step S30 and step S46 are repeated two or more times. <7> The manufacturing method according to any one of <1> to <6>, further comprising the following step S10 prior to step S20: S11: a step of pretreating the raw material, the pretreatment being one or more selected from the group consisting of heating the raw material, heating the raw material under pressure, and irradiating the raw material with microwaves. <8> The manufacturing method according to any one of <1> to <7>, wherein in step S20, the raw material is acid-treated with one or more acids selected from the group consisting of nitric acid, hydrochloric acid, and formic acid.<9> The manufacturing method according to any one of <1> to <8>, wherein the calcium phosphate-containing raw material comprises one or more materials selected from the group consisting of bone tissue, apatite, calcium monohydrogen phosphate, calcium dihydrogen phosphate, tricalcium phosphate, and β-tricalcium phosphate. <10> A manufacturing method of an article, including the manufacturing method according to any one of <1> to <9>, wherein the article is a building material, a food additive, a cosmetic material, a medical material, a filtering material, a fertilizer, an abrasive, or an ultraviolet absorber.

[0049] Example 1: Production of Calcium Sulfate (1) Calcium sulfate was obtained from bone tissue using the following procedure. 1. Raw pork bones were crushed into small pieces of 1 to 3 mm. 2. 1.0 g of pork bones were immersed in 10 mL of 1 M hydrochloric acid solution and shaken at 25°C for 48 hours. 3. The mixture was centrifuged at 12,000 x g and 25°C for 5 minutes, and the supernatant was collected. This is the acid extract. Bone impurities were removed as a precipitate. 4. 2 mL of 5 N sodium hydroxide solution was added to 10 mL of the acid extract and mixed. 5. The supernatant was removed to obtain a calcium phosphate precipitate. 6. The calcium phosphate precipitate was washed three times with pure water, and the supernatant was removed. 7. 10 mL of 1 M hydrochloric acid solution was added to the calcium phosphate precipitate to dissolve it. 8. A predetermined concentration of sulfuric acid or sulfate salt was added, and the mixture was mixed overnight at 4°C. This resulted in the precipitation of calcium sulfate. 9. The resulting precipitate was washed with 1.2 mL of water. This procedure was repeated a total of three times.

[0050] [Results] Microscopic images of the obtained calcium sulfate are shown in Figures 2 and 3. As can be seen from these figures, calcium sulfate could be obtained using sulfuric acid, potassium hydrogen sulfate, sodium sulfate, sodium hydrogen sulfate, magnesium sulfate, ammonium sulfate, manganese (II) sulfate, iron (II) sulfate, or aluminum potassium sulfate. As can be seen from these figures, the size and shape of the crystals depend on the type and concentration of the substance added in step 8. The results of this example showed that when sulfuric acid or aluminum potassium sulfate was added, relatively large crystals were likely to form.

[0051] Example 2: Production of calcium sulfate (2) In Example 1, calcium sulfate was obtained by varying the concentration of the aqueous hydrochloric acid solution in step 2. The results are shown in Figure 4. As can be seen from the figure, the higher the acid concentration during the acid treatment, the more likely it is that larger crystals will form.

[0052] [Example 3: Production of calcium sulfate (3)] In Example 1, calcium sulfate was obtained by varying the concentration of the hydrochloric acid aqueous solution in step 2 and the substance and its concentration added in step 8. The results are shown in Figures 5 and 6. As can be seen from the figures, the shape of calcium sulfate produced under the following conditions was not needle-like or rod-like: Acid treatment with 2M hydrochloric acid aqueous solution / addition of 1M sulfuric acid; Acid treatment with 3M hydrochloric acid aqueous solution / addition of 1M manganese sulfate.

[0053] Example 4: Production of calcium tartrate and calcium sulfite In Example 1, the substance added in step 8 was changed to tartaric acid or sulfite. The results are shown in Figure 7. As can be seen from the figure, by changing the anion added in step 8, calcium salts other than calcium sulfate (calcium tartrate or calcium sulfite in this example) could be obtained.

[0054] Example 5: Production of calcium metasilicate and calcium orthosilicate In Example 1, the substance added in step 8 was changed to metasilicate or orthosilicate. The results are shown in Figure 8. As can be seen from the figure, by changing the anion added in step 8, calcium salts other than calcium sulfate (calcium metasilicate or calcium orthosilicate in this example) could be obtained.

[0055] Example 6: Calcium concentration in acid extract An acid extract was prepared according to the following procedure, and the calcium ion concentration in the extract was measured. 1. Pork bones obtained from a slaughterhouse were finely ground using a mill (IKA TUBE MILL 100, IKA JAPAN Co., Ltd.). 2. The pork bones were added to acid and soaked at 20°C. The type, concentration, and soaking time of the acid are shown in Table 1. 3. The supernatant was collected and used as the acid extract.

[0056] [Results] The results are shown in Table 1. Table 1 shows the total calcium ion amount (mg) converted per 1 g of wet weight of bone. Component analysis was outsourced to Kurita Analysis Center Co., Ltd. Calcium ions were extracted from the acid extracts obtained using all of the acids. However, acid treatment with sulfuric acid solution resulted in the formation of insoluble calcium sulfate, significantly reducing the amount of calcium ions in the acid extract. Since bone tissue contains organic matter and vitamins in addition to calcium phosphate, it is believed that the calcium sulfate obtained by acid treatment with sulfuric acid solution contains many impurities. In contrast, the production method according to one embodiment of the present invention further includes steps S30 and S40, thereby removing bone impurities and producing a calcium salt with fewer impurities.

[0057] According to the results of the studies using aqueous solutions of nitric acid, hydrochloric acid, and formic acid, an immersion time of about 24 hours recovers almost all of the calcium that can be recovered. Furthermore, an acid concentration of about 1 mol / L recovers sufficient calcium. Among the four acids examined, hydrochloric acid and formic acid had the highest calcium recovery efficiency.

[0058]

[0059] Example 7: Examination of the Effect of Pretreatment We confirmed that pretreating raw materials increases the amount of phosphoric acid contained in the acid extract. Specifically, an acid extract was prepared using the following procedure, and the amount of phosphoric acid contained was quantified. 1. Pork bones obtained from a slaughterhouse were crushed using a mill (IKA TUBE MILL 100, IKA JAPAN Co., Ltd.). 2. 5 g of crushed pork bones were subjected to one of the following pretreatments (1) to (5): (1) No treatment; (2) Soaking in 30 mL of nitric acid (1 mol / L) at 50°C for 1 day; (3) Irradiation with 500 W microwaves for 30 seconds; (4) Irradiation with 500 W microwaves for 60 seconds; (5) Irradiation with 500 W microwaves for 120 seconds. 3. 30 mL of nitric acid (1 mol / L) was added to the pork bones (1) and (3) to (5). The pork bones (1) to (5) were soaked in 30 mL of nitric acid for 48 hours at 20°C with shaking (100 rpm). In this way, the bone tissue was decalcified. 4. The supernatant was collected and used as the acid extract. 5. The phosphate concentration was measured using a Malachite Green Phosphate Assay Kit (BioAssay Systems). The measurement method followed the instructions provided with the product. For the measurement, the supernatant was diluted with distilled water.

[0060] [Results] The results are shown in Figure 8. From bone tissue (2) pretreated by heating at 50°C, 1.18 times more phosphate was extracted than from bone tissue (1) that was not pretreated. Furthermore, from bone tissues (3) to (5) pretreated with microwave irradiation, up to 1.26 times more phosphate was extracted than from bone tissue (1) that was not pretreated. Considering that most of the phosphate contained in bone tissue is in the form of calcium phosphate, this result suggests that pretreatment improves the calcium extraction rate.

[0061] Example 8: pH Dependence of Calcium Salt Formation Efficiency Calcium salt was produced from bone tissue using the following procedure. The calcium salt formation efficiency due to changes in pH was examined by analyzing the components of the supernatant obtained during production. 1. Raw pork bones were crushed into small pieces of 1 to 3 mm. 2. 1.0 g of pork bones was immersed in 10 mL of nitric acid aqueous solution (1N) and shaken at 25°C for 48 hours. 3. The mixture was centrifuged at 12,000 x g and 25°C for 5 minutes, and the supernatant was collected. This is the acid extract. Bone impurities were removed as a precipitate. 4. 2 mL of sodium hydroxide aqueous solution (5N) was added to 10 mL of the acid extract and mixed. 5. 0.3 mL of the mixed solution was placed in a 2 mL microtube and centrifuged at 12,000 x g and 25°C for 5 minutes. The supernatant was discarded, and a calcium phosphate precipitate was obtained. 6. The calcium phosphate precipitate was washed three times with pure water, and the supernatant was removed. 7. The calcium phosphate precipitate was dissolved by adding 0.3 mL of a solution of an acid or salt that forms a poorly soluble calcium salt. The added acid or salt was sulfate (potassium sulfate or ammonium sulfate), citric acid, or tartaric acid. The pH of the mixed solution was adjusted by adding a common acid or base as appropriate. 8. The mixture was centrifuged at 12,000 × g and 25°C for 5 minutes, and the supernatant was collected after removing the poorly soluble calcium salt precipitate (calcium sulfate, calcium citrate, or calcium tartrate). 9. The phosphate ions and calcium ions contained in the supernatant after removing the poorly soluble calcium salt precipitate were quantified using the Malachite Green Phosphate Assay Kit (BioAssay Systems) and the Calcium Assay Kit, QuantiChrom (500 assays), respectively.

[0062] [Results] The results are shown in Figure 12. The upper graph shows the pH dependence of calcium ion concentration (g / L), and the lower graph shows the pH dependence of phosphate ion concentration (g / L). As can be seen from the figure, when the pH of the system changes after the addition of an acid or salt, the concentrations of phosphate ions and calcium ions in the supernatant also change. This suggests that the pH suitable for forming calcium salts other than calcium phosphate salts varies depending on the type of acid and / or its salt added in step S42 or step S48. (Note that Figure 12 shows the calcium ion concentration in the supernatant, so a lower value is preferable.) When adding a sulfate salt (potassium sulfate, ammonium sulfate, etc.), the pH after mixing is preferably 1.3 to 5.0. When adding citric acid, the pH after mixing is preferably 3.3 to 4.5. When adding tartaric acid, the pH after mixing is preferably 2.5 to 5.2.

[0063] Example 9: Production of calcium salt from calcium phosphate compound other than bone tissue It was confirmed that calcium salt can be produced from raw materials other than bone tissue by the following procedure. 1. A calcium phosphate reagent and apatite were prepared as raw materials. The calcium phosphate reagent consisted of calcium hydrogen phosphate (CMP, CaHPO ４ ), dihydrogen calcium phosphate (CDP, Ca(H ２ P.O. ４ ) ２ ), tricalcium phosphate (TP, 10CaO·3P ２ O ５ ) and β-tricalcium phosphate (β-TCP, Ca ３ (P.O. ４ ) ２ 2. The raw material was immersed in a 1N hydrochloric acid solution, and the phosphate ion and calcium ion concentrations in the acid extract were measured. Measurements were performed using a Malachite Green Phosphate Assay Kit (BioAssay Systems) and a Calcium Assay Kit, QuantiChrom (500 assays).

[0064] [Results] The results are shown in Table 2.

[0065] The acid extracts obtained from both raw materials contained large amounts of phosphate and calcium ions. The recovery rates of phosphate and calcium ions were over 81% for CMP and CDP, and nearly 100% for TP and β-TCP. In the case of apatite, the calculated recovery rate was low at 32%, due to a discrepancy between the composition and purity of the calcium phosphate (fluoroapatite) used in the calculation and the actual ratio of phosphate and calcium contained. However, by optimizing the soaking time, etc., it is believed that phosphate and calcium can be recovered from apatite at rates similar to those of other raw materials.

[0066] From the acid extract thus obtained, calcium salt can be produced by the same method as in any of the above-mentioned Examples. That is, as shown in this Example, the acid extract obtained in step S20 contains high concentrations of phosphate ions and calcium ions. Therefore, calcium salt can be obtained by going through steps S30 and S40.

[0067] Example 10: Use of calcium salt It was confirmed that the calcium salt obtained by the production method according to one embodiment of the present invention can be used for various purposes.

[0068] [Example 10-1: Abrasive] The effect of calcium salts as abrasives was investigated using the following procedure. 1. Calcium tartrate and calcium sulfate were obtained according to the above example. 2. Calcium tartrate or calcium sulfate was mixed with distilled water to prepare an abrasive. The calcium tartrate or calcium sulfate content was 1 wt%. 3. The abrasive prepared in step 2 was dropped onto the inner bottom surface of an adherent cell culture dish (MS-11350, Sumitomo Bakelite Co., Ltd.) to abrade the plastic surface.

[0069] The results are shown in Figure 14. The top row shows the results of polishing with an abrasive containing calcium tartrate, and the bottom row shows the results of polishing with an abrasive containing calcium sulfate. The left column shows the appearance of the petri dish after polishing, the center column shows images of the surface of the petri dish taken at a magnification of 4x with an objective lens, and the right column shows images of the surface of the petri dish taken at a magnification of 10x with an objective lens. As can be seen from the figure, polishing marks were clearly visible on the surface of the petri dish. This suggests that the calcium salt obtained by the production method according to one embodiment of the present invention can be used as an abrasive. It was also shown that calcium tartrate has a stronger abrasive power than calcium sulfate when the weight concentrations (%) are the same.

[0070] [Example 10-2: UV scattering agent] The effect of calcium salts as UV scattering agents was investigated using the following procedure. 1. Calcium tartrate and calcium sulfate were obtained according to the above-mentioned example. 2. An aqueous solution was prepared from the obtained calcium tartrate or calcium sulfate. This aqueous solution was applied to plastic and dried to prepare a sample. 3. The sample prepared in step 2 was placed in the cell holder of an ultraviolet-visible spectrophotometer (UV-1900i, Shimadzu Corporation), and the wavelength was scanned from 700 nm to 200 nm at room temperature. In this way, the transmittance through the calcium salt was continuously measured. 4. A spectrum of the relative transmittance (%) of light transmitted through the plastic was obtained. The relative transmittance was calculated using the following formula: Relative transmittance (%) = Light transmittance (%) of sample - Light transmittance (%) of control

[0071] The results are shown in Figure 14. In samples coated with calcium tartrate, the relative transmittance increased depending on the calcium tartrate concentration. Spectroscopic observation revealed a positive peak in relative transmittance near 280 nm. This trend was particularly pronounced in the ultraviolet region (210-400 nm). In samples coated with calcium sulfate, the relative transmittance increased depending on the calcium sulfate concentration. Spectroscopic observation revealed two positive peaks in relative transmittance near 220 nm and 280 nm. This trend was particularly pronounced in the ultraviolet region (210-320 nm). It is unusual for the relative transmittance to increase with increasing calcium salt concentration. This phenomenon is thought to be due to the presence of scattered light in the detected output. This suggests that the calcium salt obtained by the production method according to one embodiment of the present invention can be used as a light scattering agent (especially an ultraviolet scattering agent). Light scattering agents can be useful, for example, when incorporated into polymers that are cured by irradiation with light.

[0072] [Example 10-3: Toothpaste Abrasive] The effect of calcium salts as toothpaste abrasives was investigated using the following procedure. 1. Calcium tartrate and calcium sulfate were obtained according to the above example. 2. A commercially available toothpaste (Black Grilled Eggplant Salt Toothpaste, Inyan Club Co., Ltd.) that does not contain dental abrasives was prepared. Calcium tartrate or calcium sulfate was mixed with this toothpaste to prepare toothpaste pastes containing abrasives. The calcium tartrate content was 10 mg or 100 mg. The calcium sulfate content was 100 mg. 3. The bottom of an adherent cell culture dish (MS-11350, Sumitomo Bakelite Co., Ltd.) was painted black by drawing in the same direction with a black oil-based marker. This was used as a dental plaque model. 4. A commercially available toothpaste containing no abrasive, a commercially available toothpaste containing abrasive, or one of the three toothpastes prepared in step 2 was applied to a toothbrush, and the toothbrush was brushed back and forth 10 times perpendicular to the direction of application of the black permanent marker. 5. The extent to which the surface of the black permanent marker, which is the dental plaque model, peeled off was observed.

[0073] The results are shown in Figure 15. In this figure, uneven application of the black permanent marker appears as horizontal stripes. Furthermore, peeling of the black permanent marker due to toothpaste appears as vertical white lines. While no vertical lines were observed without treatment, several vertical lines were observed with the commercially available toothpaste that did not contain abrasives. This indicates that vertical lines were caused by brushing. When using a commercially available toothpaste containing abrasives, numerous vertical lines of various thicknesses were observed. On the other hand, the toothpaste prepared in this example produced fewer vertical lines than the commercially available toothpaste containing abrasives. However, as can be seen from the results of the toothpaste containing calcium tartrate, the number of vertical lines produced increased with the amount of calcium salt added. This demonstrates that the polishing effect can be improved by appropriately adjusting the amount of calcium salt used. Furthermore, it was shown that calcium tartrate has a stronger polishing power than calcium sulfate at the same amount.

[0074] In addition, there is a certain demand for toothpastes with less abrasive power than commercially available toothpastes containing abrasives. For example, some consumers who suffer from oral mucosal diseases such as gingivitis or hypersensitive teeth do not like abrasives. For such consumers, the toothpastes prepared in this example may be preferred.

[0075] Calcium salts obtained by the production method according to one embodiment of the present invention can be used in a wide range of industrial fields. For example, calcium sulfate is used in a wide range of industrial fields, including construction and civil engineering, medicine and healthcare, agriculture, and arts and crafts. Calcium tartrate is approved for use as a food additive in Japan and other countries, and is incorporated as a cosmetic ingredient in skin care, hair care, soap, cleansing products, sunscreen, and other products. Calcium sulfite is used as a filter material to remove residual chlorine from water, and its use as a food additive is also approved in some countries and regions. Calcium sulfite is also attracting attention as a gypsum resource due to its excellent thermal stability and insolubility. Calcium citrate is approved for use as a food additive for nutritional enhancement in Japan. Calcium silicate is approved for use as a food additive for anti-caking purposes in Japan, and is also used as a building material and fertilizer. In particular, calcium silicate's water resistance makes it suitable for use in interior walls of kitchens where gypsum board cannot be used, and for exterior building materials near the coast. Calcium silicate can also be used as a substitute for asbestos, and composite materials containing calcium silicate have improved flexural and tensile strength.

Claims

1. A method for producing a calcium salt comprising the following steps: Step S20: treating a raw material containing calcium phosphate with an acid to obtain an acid extract; Step S30: mixing the obtained acid extract with a base to obtain a calcium phosphate precipitate; Step S40: mixing the obtained calcium phosphate precipitate with an acid and / or a salt thereof to form a calcium salt.

2. The method of claim 1, wherein step S40 includes the following step S42: Step S42: mixing the obtained calcium phosphate precipitate with an acid that forms a calcium salt and / or its salt.

3. The method according to claim 2, wherein the acid and / or its salt that forms the calcium salt in step S42 is sulfuric acid and / or tartaric acid.

4. The manufacturing method of claim 1, wherein step S40 includes the following steps S46 and S48: step S46: mixing the obtained calcium phosphate precipitate with an acid to obtain a solution of phosphate ions and calcium ions; step S48: mixing the obtained solution of phosphate ions and calcium ions with an acid that forms a calcium salt and / or its salt; wherein the acid in step S46 and the acid in step S48 are different.

5. The method according to claim 4, wherein the acid in step S48 is one or more selected from the group consisting of sulfuric acid, tartaric acid, sulfurous acid, citric acid and silicic acid.

6. The manufacturing method according to claim 4, wherein steps S30 and S46 are repeated two or more times.

7. The manufacturing method according to any one of claims 1 to 6, further comprising the following step S10 prior to step S20: S11: a step of pretreating the raw material; the pretreatment is one or more selected from the group consisting of heating the raw material, heating the raw material under pressure, and irradiating the raw material with microwaves.

8. The manufacturing method according to any one of claims 1 to 6, wherein in step S20, the raw material is treated with one or more acids selected from the group consisting of nitric acid, hydrochloric acid and formic acid.

9. The method according to any one of claims 1 to 6, wherein the calcium phosphate-containing raw material comprises one or more materials selected from the group consisting of bone tissue, apatite, calcium monohydrogen phosphate, calcium dihydrogen phosphate, tricalcium phosphate, and β-tricalcium phosphate.

10. A method for producing an article, comprising the method according to any one of claims 1 to 6, wherein the article is a building material, a food additive, a cosmetic material, a medical material, a filter medium, a fertilizer, an abrasive, or a light scattering agent.

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