CA2142663A1 - Process for preparing calcium salts of low aluminum content - Google Patents
Process for preparing calcium salts of low aluminum contentInfo
- Publication number
- CA2142663A1 CA2142663A1 CA 2142663 CA2142663A CA2142663A1 CA 2142663 A1 CA2142663 A1 CA 2142663A1 CA 2142663 CA2142663 CA 2142663 CA 2142663 A CA2142663 A CA 2142663A CA 2142663 A1 CA2142663 A1 CA 2142663A1
- Authority
- CA
- Canada
- Prior art keywords
- calcium
- aluminum
- starting material
- hydroxide
- chloride
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
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Classifications
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
- C01F11/00—Compounds of calcium, strontium, or barium
- C01F11/18—Carbonates
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B25/00—Phosphorus; Compounds thereof
- C01B25/16—Oxyacids of phosphorus; Salts thereof
- C01B25/26—Phosphates
- C01B25/32—Phosphates of magnesium, calcium, strontium, or barium
- C01B25/322—Preparation by neutralisation of orthophosphoric acid
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2006/00—Physical properties of inorganic compounds
- C01P2006/80—Compositional purity
Abstract
ABSTRACT OF THE INVENTION
A process is provided for manufacturing a calcium salt, e.g., tricalcium phosphate, dicalcium phosphate or calcium carbonate, of low aluminum content starting with a calcium oxide (lime) containing a relatively high level of aluminum as an impurity. The calcium oxide is reacted with hydrochloric acid in aqueous medium to provide dissolved calcium chloride and a solid residue containing the impurities, including aluminum, originally present in the calcium oxide. The low-aluminum content calcium chloride which is recovered from the reaction medium is thereafter converted to another correspondingly low-aluminum content calcium salt employing known chemical procedures.
A process is provided for manufacturing a calcium salt, e.g., tricalcium phosphate, dicalcium phosphate or calcium carbonate, of low aluminum content starting with a calcium oxide (lime) containing a relatively high level of aluminum as an impurity. The calcium oxide is reacted with hydrochloric acid in aqueous medium to provide dissolved calcium chloride and a solid residue containing the impurities, including aluminum, originally present in the calcium oxide. The low-aluminum content calcium chloride which is recovered from the reaction medium is thereafter converted to another correspondingly low-aluminum content calcium salt employing known chemical procedures.
Description
PROCESS FOR PREPARING CALCIUM SALTS
OF LOW ALUMINUM CONTENT
BACKGROUND OF THE INVENTION
This invention relates to a process for preparing calcium salts of low aluminum content. In particular, this invention relates to the manufacture of such calcium salts as the calcium phosphates, e.g., tricalcium phosphate and dicalcium phosphate, and calcium carbonate containing not more than about 100 parts per million (ppm) aluminum.
Concern about the role of aluminum in foods as it relates to Alzheimer's disease has created a market for foods and food additives which contain minimal amounts of aluminum. In particular, manufacturers of liquid foods for geriatric care and of infant formulas, both of which contain hydroxyapatite (known commercially as tricalcium phosphate or TCP), are concerned with the aluminum levels in their products.
The tricalcium phosphate present in these products contains relatively large amounts of aluminum, e.g., 400 ppm or more, due to its being manufactured from quicklime or hydrated lime typically containing more than 0.1 weight percent aluminum. Physical treatment of slaked lime slurry does not completely free it of the aluminum impurity. A
commercial tricalcium phosphate containing 400 ppm of aluminum would contain about half the aluminum present in the quicklime from which it was manufactured.
U.S. Patent No. 3,872,219 discloses that commercial limes may contain impurities such as iron compounds, silica, aluminum salts, magnesium salts, magnesia, unburned limestone (calcium carbonate and magnesium carbonate) and other compounds in trace quantities. This patent further discloses that the chlorination of an aqueous slurry of lime with a chlorinating agent such as chlorine gas forms a chlorinated lime solution containing calcium hypochlorite and calcium chloride. During the chlorination, most of the foregoing impurities remain insoluble and can be removed from the chlorinated lime solution, e.g., by filtering or centrifuging. While calcium chloride is a co-product of this chlorination reaction, there is no suggestion of its recovery per se much less its recovery and conversion to some other calcium salt. The chlorination procedure of U.S.
Patent No. 3,872,219 is not a practical way of obtaining a low-aluminum content calcium chloride product where such product is specifically intended for use as a reactant in other syntheses. Production of calcium chloride in U.S.
Patent No. 3,872,219 is accompanied by another soluble calcium product, i.e., calcium hypochlorite, from which the calcium chloride would have to be separated for the latter to serve as a reactant in a subsequent chemical conversion operation. Separating one solute (calcium chloride) from the other (calcium hypochlorite) could be expected to be a fairly complex and expensive task.
U.S. Patent No. 4,324,772 discloses a continuous process for preparing tricalcium phosphate in which lime slurry is reacted with phosphoric acid solution to form the desired product. All or most of the impurities originally present in the lime slurry including, of course, the aluminum, are passed on to the tricalcium phosphate product which is precisely what the process of the present invention seeks to avoid.
SUMMARY OF THE INVENTION
In accordance with the present invention, calcium salts such as calcium phosphates and calcium carbonate possessing low concentrations, e.g., preferably not more than about 100 ppm, more preferably not more than about 10 ppm and most preferably not more than about 2 ppm, of aluminum are provided. The low-aluminum content calcium salts are produced by a process which involves the preliminary step of reacting calcium oxide (via a calcium hydroxide slurry) with aqueous hydrochloric acid. In this reaction, an aqueous solution of low-aluminum content calcium chloride and an insoluble residue containing various impurities including aluminum originally associated with the starting calcium oxide are produced. Most of the aluminum is tied up or bound in this insoluble residue which can be readily removed by any suitable method, e.g., by filtration.
OF LOW ALUMINUM CONTENT
BACKGROUND OF THE INVENTION
This invention relates to a process for preparing calcium salts of low aluminum content. In particular, this invention relates to the manufacture of such calcium salts as the calcium phosphates, e.g., tricalcium phosphate and dicalcium phosphate, and calcium carbonate containing not more than about 100 parts per million (ppm) aluminum.
Concern about the role of aluminum in foods as it relates to Alzheimer's disease has created a market for foods and food additives which contain minimal amounts of aluminum. In particular, manufacturers of liquid foods for geriatric care and of infant formulas, both of which contain hydroxyapatite (known commercially as tricalcium phosphate or TCP), are concerned with the aluminum levels in their products.
The tricalcium phosphate present in these products contains relatively large amounts of aluminum, e.g., 400 ppm or more, due to its being manufactured from quicklime or hydrated lime typically containing more than 0.1 weight percent aluminum. Physical treatment of slaked lime slurry does not completely free it of the aluminum impurity. A
commercial tricalcium phosphate containing 400 ppm of aluminum would contain about half the aluminum present in the quicklime from which it was manufactured.
U.S. Patent No. 3,872,219 discloses that commercial limes may contain impurities such as iron compounds, silica, aluminum salts, magnesium salts, magnesia, unburned limestone (calcium carbonate and magnesium carbonate) and other compounds in trace quantities. This patent further discloses that the chlorination of an aqueous slurry of lime with a chlorinating agent such as chlorine gas forms a chlorinated lime solution containing calcium hypochlorite and calcium chloride. During the chlorination, most of the foregoing impurities remain insoluble and can be removed from the chlorinated lime solution, e.g., by filtering or centrifuging. While calcium chloride is a co-product of this chlorination reaction, there is no suggestion of its recovery per se much less its recovery and conversion to some other calcium salt. The chlorination procedure of U.S.
Patent No. 3,872,219 is not a practical way of obtaining a low-aluminum content calcium chloride product where such product is specifically intended for use as a reactant in other syntheses. Production of calcium chloride in U.S.
Patent No. 3,872,219 is accompanied by another soluble calcium product, i.e., calcium hypochlorite, from which the calcium chloride would have to be separated for the latter to serve as a reactant in a subsequent chemical conversion operation. Separating one solute (calcium chloride) from the other (calcium hypochlorite) could be expected to be a fairly complex and expensive task.
U.S. Patent No. 4,324,772 discloses a continuous process for preparing tricalcium phosphate in which lime slurry is reacted with phosphoric acid solution to form the desired product. All or most of the impurities originally present in the lime slurry including, of course, the aluminum, are passed on to the tricalcium phosphate product which is precisely what the process of the present invention seeks to avoid.
SUMMARY OF THE INVENTION
In accordance with the present invention, calcium salts such as calcium phosphates and calcium carbonate possessing low concentrations, e.g., preferably not more than about 100 ppm, more preferably not more than about 10 ppm and most preferably not more than about 2 ppm, of aluminum are provided. The low-aluminum content calcium salts are produced by a process which involves the preliminary step of reacting calcium oxide (via a calcium hydroxide slurry) with aqueous hydrochloric acid. In this reaction, an aqueous solution of low-aluminum content calcium chloride and an insoluble residue containing various impurities including aluminum originally associated with the starting calcium oxide are produced. Most of the aluminum is tied up or bound in this insoluble residue which can be readily removed by any suitable method, e.g., by filtration.
The calcium chloride which is substantially free of the aluminum-containing insoluble residue can then be employed in the manufacture of other calcium salts in accordance with this invention.
To produce tricalcium phosphate, the low-aluminum content calcium chloride is converted into calcium hydroxide by reaction with alkali metal hydroxide in an aqueous medium. The resulting low-aluminum calcium hydroxide is thereafter recovered and reacted with phosphoric acid to produce the low-aluminum content tricalcium phosphate.
To produce dicalcium phosphate, the low-aluminum content calcium chloride is reacted with diammonium phosphate in aqueous medium to provide an aqueous solution of ammonium chloride and a precipitate of dicalcium phosphate, the latter being recovered employing any one of several known methods.
To produce calcium carbonate, the low-aluminum content calcium chloride is reacted with ammonia, carbon dioxide and water to provide an aqueous solution of ammonium chloride and a precipitate of calcium carbonate. The low aluminum content calcium carbonate is then recovered by any suitable method.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The process of this invention employs as a starting material calcium oxide ("quicklime" or simply "lime") which, in addition to other impurities, contains generally from about 600 to about 2000 ppm aluminum.
Reaction of the calcium oxide starting material with hydrochloric acid produces dissolved calcium chloride and an insoluble gelatinous residue containing a complex aluminosilicate and other impurities such as SiO2, etc. The residue ties up most of the silica, iron, aluminum and zinc impurities together with some of the fluoride originally present in the calcium oxide. It is preferred to use a slight molar excess of acid to insure total conversion of the calcium oxide to calcium chloride. This gelatinous residue can be separated by any suitable method, e.g., by filtration. Since the pH of calcium chloride is neutral, the separation of aluminum, which is amphoteric and exhibits minimum solubility at this point, is facilitated. Employing the foregoing procedure, commercial calcium oxide, which typically contains from about 600 to about 2000 ppm aluminum, can be converted to dissolved calcium chloride which on recovery contains less than about 5 weight percent, and preferably less than about 1 weight percent, of the aluminum originally present in the calcium oxide starting material. The calcium chloride, once separated from the insoluble residue, can then be employed in the production of other low residual aluminum-containing calcium compounds in one or more subsequent chemical conversion operations, e.g., any of the aforementioned calcium phosphates and carbonate, calcium hydroxide (which can be converted to either of the aforementioned salts), etc.
To produce tricalcium phosphate, the low-aluminum content calcium chloride is converted into calcium hydroxide by reaction with alkali metal hydroxide in an aqueous medium. The resulting low-aluminum calcium hydroxide is thereafter recovered and reacted with phosphoric acid to produce the low-aluminum content tricalcium phosphate.
To produce dicalcium phosphate, the low-aluminum content calcium chloride is reacted with diammonium phosphate in aqueous medium to provide an aqueous solution of ammonium chloride and a precipitate of dicalcium phosphate, the latter being recovered employing any one of several known methods.
To produce calcium carbonate, the low-aluminum content calcium chloride is reacted with ammonia, carbon dioxide and water to provide an aqueous solution of ammonium chloride and a precipitate of calcium carbonate. The low aluminum content calcium carbonate is then recovered by any suitable method.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The process of this invention employs as a starting material calcium oxide ("quicklime" or simply "lime") which, in addition to other impurities, contains generally from about 600 to about 2000 ppm aluminum.
Reaction of the calcium oxide starting material with hydrochloric acid produces dissolved calcium chloride and an insoluble gelatinous residue containing a complex aluminosilicate and other impurities such as SiO2, etc. The residue ties up most of the silica, iron, aluminum and zinc impurities together with some of the fluoride originally present in the calcium oxide. It is preferred to use a slight molar excess of acid to insure total conversion of the calcium oxide to calcium chloride. This gelatinous residue can be separated by any suitable method, e.g., by filtration. Since the pH of calcium chloride is neutral, the separation of aluminum, which is amphoteric and exhibits minimum solubility at this point, is facilitated. Employing the foregoing procedure, commercial calcium oxide, which typically contains from about 600 to about 2000 ppm aluminum, can be converted to dissolved calcium chloride which on recovery contains less than about 5 weight percent, and preferably less than about 1 weight percent, of the aluminum originally present in the calcium oxide starting material. The calcium chloride, once separated from the insoluble residue, can then be employed in the production of other low residual aluminum-containing calcium compounds in one or more subsequent chemical conversion operations, e.g., any of the aforementioned calcium phosphates and carbonate, calcium hydroxide (which can be converted to either of the aforementioned salts), etc.
For example, to produce tricalcium phosphate, (hydroxyapatite), the calcium chloride solution which is substantially free of the aluminum-containing insoluble residue is converted to calcium hydroxide by reaction with alkali metal hydroxide. Alkali metal hydroxides suitable for use in the process of this invention include those of sodium, potassium or lithium with sodium hydroxide being preferred. A slight molar excess of alkali metal hydroxide is preferred.
The precipitate of calcium hydroxide can be recovered by filtration or other suitable method and preferably washed free of any adhered sodium chloride. The recovered calcium hydroxide is then repulped to a slurry and reacted with dilute phosphoric acid, preferably a slight molar excess thereof, to yield a tricalcium phosphate slurry containing, e.g., approximately 10 to 15 weight percent solids. The tricalcium phosphate is then recovered by filtration, washed, dried and deagglomerated or milled to yield the final product containing less aluminum than that present in the calcium oxide starting material. Thus, by the process of this invention, a tricalcium phosphate product preferably containing not more than about 100 ppm, more preferably not more than about 10 ppm and most preferably not more than about 2 ppm aluminum can be produced.
Dicalcium phosphate can be obtained in accordance with the invention by reacting the calcium chloride which is substantially free of the aluminum-containing insoluble residue with diammonium phosphate, preferably a molar excess thereof, in an aqueous medium to provide an aqueous solution of ammonium chloride and a precipitate of dicalcium phosphate product. The dicalcium phosphate product is recovered by any suitable method, e.g., filtration, and thereafter washed, dried and milled to yield the final product containing less aluminum than that present in the calcium oxide starting material. The dicalcium phosphate thus produced can preferably contain not more than about 100 ppm, more preferably not more than about 10 ppm and most preferably not more than about 2 ppm aluminum.
Further in accordance with this invention, low aluminum content calcium carbonate can be formed by reacting the calcium chloride which is substantially free of the aluminum-containing insoluble residue with molar excesses of ammonia, carbon dioxide and water. The resulting calcium carbonate precipitate can be recovered by any suitable method, e.g., filtration. If desired, the recovered calcium carbonate can be washed free of residual ammonium chloride and then dried and milled to yield a final product containing less aluminum than that present in the calcium oxide starting material. Thus, the calcium carbonate product resulting from the process of this invention preferably contains not more than about 100 ppm, more preferably not more than about 10 ppm and most preferably not more than about 2 ppm aluminum. The low aluminum content calcium carbonate can be incorporated in a wide variety of foods, food additives and other consumer products which typically contain amounts of calcium carbonate.
The calcium salts of this invention possess significantly lower fluoride concentrations than those present in products obtained by conventional processes.
Specifically, the compounds herein contain not more than about 20 ppm fluoride whereas products obtained by conventional processes normally contain not less than 45 ppm fluoride. Thus, the process of this invention affords an additional benefit by obviating problems encountered by commercial lime suppliers in supplying lime containing fluoride that is low enough in concentration to meet the Food Chemicals Codex specifications for calcium phosphates.
The calcium salts of this invention also possess significantly lower silicon, iron, manganese, and zinc concentrations than those present in products obtained by conventional processes.
The following examples illustrate the practice of the present invention:
The precipitate of calcium hydroxide can be recovered by filtration or other suitable method and preferably washed free of any adhered sodium chloride. The recovered calcium hydroxide is then repulped to a slurry and reacted with dilute phosphoric acid, preferably a slight molar excess thereof, to yield a tricalcium phosphate slurry containing, e.g., approximately 10 to 15 weight percent solids. The tricalcium phosphate is then recovered by filtration, washed, dried and deagglomerated or milled to yield the final product containing less aluminum than that present in the calcium oxide starting material. Thus, by the process of this invention, a tricalcium phosphate product preferably containing not more than about 100 ppm, more preferably not more than about 10 ppm and most preferably not more than about 2 ppm aluminum can be produced.
Dicalcium phosphate can be obtained in accordance with the invention by reacting the calcium chloride which is substantially free of the aluminum-containing insoluble residue with diammonium phosphate, preferably a molar excess thereof, in an aqueous medium to provide an aqueous solution of ammonium chloride and a precipitate of dicalcium phosphate product. The dicalcium phosphate product is recovered by any suitable method, e.g., filtration, and thereafter washed, dried and milled to yield the final product containing less aluminum than that present in the calcium oxide starting material. The dicalcium phosphate thus produced can preferably contain not more than about 100 ppm, more preferably not more than about 10 ppm and most preferably not more than about 2 ppm aluminum.
Further in accordance with this invention, low aluminum content calcium carbonate can be formed by reacting the calcium chloride which is substantially free of the aluminum-containing insoluble residue with molar excesses of ammonia, carbon dioxide and water. The resulting calcium carbonate precipitate can be recovered by any suitable method, e.g., filtration. If desired, the recovered calcium carbonate can be washed free of residual ammonium chloride and then dried and milled to yield a final product containing less aluminum than that present in the calcium oxide starting material. Thus, the calcium carbonate product resulting from the process of this invention preferably contains not more than about 100 ppm, more preferably not more than about 10 ppm and most preferably not more than about 2 ppm aluminum. The low aluminum content calcium carbonate can be incorporated in a wide variety of foods, food additives and other consumer products which typically contain amounts of calcium carbonate.
The calcium salts of this invention possess significantly lower fluoride concentrations than those present in products obtained by conventional processes.
Specifically, the compounds herein contain not more than about 20 ppm fluoride whereas products obtained by conventional processes normally contain not less than 45 ppm fluoride. Thus, the process of this invention affords an additional benefit by obviating problems encountered by commercial lime suppliers in supplying lime containing fluoride that is low enough in concentration to meet the Food Chemicals Codex specifications for calcium phosphates.
The calcium salts of this invention also possess significantly lower silicon, iron, manganese, and zinc concentrations than those present in products obtained by conventional processes.
The following examples illustrate the practice of the present invention:
Laboratory Synthesis of High Purity TCP (Hydroxyapatite) Pulverized Food Chemicals Codex (FCC) grade CaO
(vertical process) (614.7 grams) was added to deionized H2O
(4800 ml). The resulting slurry contained 15 weight percent solids (772g as Ca(OH) 2 at 95% conversion). While the slurry was agitated, a 32 weight percent solution of FCC grade HCl was introduced. The acid was added slowly, then drop-wise, until the pH stabilized between 6.8 and 7.2. 2372 grams of a 32 weight percent solution of HCl were required to neutralize the reactant mixture.
The resulting solution of CaCl2 was then vacuum-filtered to remove the residue containing impurities which formed as the result of contaminants present in the CaO.
While agitating, 50 weight percent NaOH (1754 grams) was added slowly to the filtered CaCl2 solution. The resulting Ca(OH)2-in-brine mixture contained 15 weight percent solids. The water content of this slurry was sufficiently high to keep the NaCl in solution. The slurry was then vacuum-filtered to a wet cake. The cake was washed with deionized H2O (approximately 3 liters) to remove most of the NaCl.
The purified Ca(OH)2 cake, which contained approximately 50 weight percent water, was then re-pulped with deionized water (6000 mL) to make a mixture containing about 10 weight percent solids. While agitating, 39.8 weight percent solution of phosphoric acid was introduced to the slurry. The H3PO4 was added slowly, then drop-wise, until the pH decreased to 7Ø In order to prevent contamination with dicalcium phosphate the pH was not allowed to decrease below 6.8 at any time. 1540 grams of 39.8 weight percent H3PO4 were added to neutralize the reactant mixture.
The resulting hydroxyapatite slurry (approximately 12 weight percent solids) was vacuum-filtered and dried in a convection oven at 100°C for 16 hours. The experiment yielded 1047 grams of hydroxyapatite (dry basis) with the following assay:
Calcium, weight percent 37.14 Phosphorus, weight percent 17.92 Aluminum, ppm 1.5 The yield was 95.2 weight percent based on the total weight of CaO used. The typical analysis for this grade of quicklime states that the available CaO is 93.0 to 96.5 weight percent.
(vertical process) (614.7 grams) was added to deionized H2O
(4800 ml). The resulting slurry contained 15 weight percent solids (772g as Ca(OH) 2 at 95% conversion). While the slurry was agitated, a 32 weight percent solution of FCC grade HCl was introduced. The acid was added slowly, then drop-wise, until the pH stabilized between 6.8 and 7.2. 2372 grams of a 32 weight percent solution of HCl were required to neutralize the reactant mixture.
The resulting solution of CaCl2 was then vacuum-filtered to remove the residue containing impurities which formed as the result of contaminants present in the CaO.
While agitating, 50 weight percent NaOH (1754 grams) was added slowly to the filtered CaCl2 solution. The resulting Ca(OH)2-in-brine mixture contained 15 weight percent solids. The water content of this slurry was sufficiently high to keep the NaCl in solution. The slurry was then vacuum-filtered to a wet cake. The cake was washed with deionized H2O (approximately 3 liters) to remove most of the NaCl.
The purified Ca(OH)2 cake, which contained approximately 50 weight percent water, was then re-pulped with deionized water (6000 mL) to make a mixture containing about 10 weight percent solids. While agitating, 39.8 weight percent solution of phosphoric acid was introduced to the slurry. The H3PO4 was added slowly, then drop-wise, until the pH decreased to 7Ø In order to prevent contamination with dicalcium phosphate the pH was not allowed to decrease below 6.8 at any time. 1540 grams of 39.8 weight percent H3PO4 were added to neutralize the reactant mixture.
The resulting hydroxyapatite slurry (approximately 12 weight percent solids) was vacuum-filtered and dried in a convection oven at 100°C for 16 hours. The experiment yielded 1047 grams of hydroxyapatite (dry basis) with the following assay:
Calcium, weight percent 37.14 Phosphorus, weight percent 17.92 Aluminum, ppm 1.5 The yield was 95.2 weight percent based on the total weight of CaO used. The typical analysis for this grade of quicklime states that the available CaO is 93.0 to 96.5 weight percent.
Example 2 Five batches of hydroxyapatite were prepared by the procedure of Example 1, combined into a single lot in a V-blender, and jet milled. This lot (5.4 kg) had the following analysis:
Assay as calcium, weight percent 37.05 P2O5, weight percent 41.12 Loss on ignition, weight percent 4.68 Heavy metals as Pb, ppm <30 Lead, ppm <0.6 Arsenic, ppm 0.15 Fluoride, ppm 20 Aluminum, ppm 1 Iron, ppm 16 Magnesium, ppm 780 Manganese, ppm none detected Strontium, ppm 17 The procedure of Example 1 was repeated to obtain a quantity of hydroxyapatite product for metals analysis. A sample of this product was dissolved in nitric acid and analyzed via inductively coupled plasma (ICP) spectroscopy for the metals below, as was a sample of commercial tricalcium phosphate produced by the conventional process from a similar lime source by Rhone-Poulenc Basic Chemicals Company. The results of these analyses are tabulated below:
As can be seen, the aluminum levels in the tricalcium phosphate of this invention are significantly reduced by the process of this invention. In addition, the silicon, iron, zinc, and manganese levels are greatly reduced.
Assay as calcium, weight percent 37.05 P2O5, weight percent 41.12 Loss on ignition, weight percent 4.68 Heavy metals as Pb, ppm <30 Lead, ppm <0.6 Arsenic, ppm 0.15 Fluoride, ppm 20 Aluminum, ppm 1 Iron, ppm 16 Magnesium, ppm 780 Manganese, ppm none detected Strontium, ppm 17 The procedure of Example 1 was repeated to obtain a quantity of hydroxyapatite product for metals analysis. A sample of this product was dissolved in nitric acid and analyzed via inductively coupled plasma (ICP) spectroscopy for the metals below, as was a sample of commercial tricalcium phosphate produced by the conventional process from a similar lime source by Rhone-Poulenc Basic Chemicals Company. The results of these analyses are tabulated below:
As can be seen, the aluminum levels in the tricalcium phosphate of this invention are significantly reduced by the process of this invention. In addition, the silicon, iron, zinc, and manganese levels are greatly reduced.
Using 307 grams of CaO, the procedure of Example 1 was carried out through preparation of the CaCl2 solution to obtain a sample of the residue containing impurities. The residue was washed thoroughly and dried. 2.7 grams were obtained on a dry basis. The washed-and-dried residue was dissolved and analyzed by inductively-coupled plasma-optical emission spectroscopy. The analytical results are presented below:
These results confirm the reduction of aluminum, silicon, iron, manganese, and zinc seen in the prior examples.
These results confirm the reduction of aluminum, silicon, iron, manganese, and zinc seen in the prior examples.
Claims (16)
1. A process for preparing a calcium salt which comprises:
reacting calcium oxide containing aluminum as an impurity with hydrochloric acid in an aqueous reaction medium to provide an aqueous solution containing calcium chloride and an insoluble residue containing aluminum which was originally present in the calcium oxide starting material;
recovering calcium chloride substantially free of the aluminum-containing insoluble residue; and, converting recovered calcium chloride in at least one chemical conversion operation to the calcium salt product, the calcium salt product containing less aluminum than that present in the calcium oxide starting material.
reacting calcium oxide containing aluminum as an impurity with hydrochloric acid in an aqueous reaction medium to provide an aqueous solution containing calcium chloride and an insoluble residue containing aluminum which was originally present in the calcium oxide starting material;
recovering calcium chloride substantially free of the aluminum-containing insoluble residue; and, converting recovered calcium chloride in at least one chemical conversion operation to the calcium salt product, the calcium salt product containing less aluminum than that present in the calcium oxide starting material.
2. The process of Claim 1 wherein the chemical conversion operation comprises:
reacting recovered calcium chloride with alkali metal hydroxide in an aqueous medium to provide an aqueous solution of alkali metal chloride and a precipitate.
of calcium hydroxide;
recovering calcium hydroxide; and, reacting recovered calcium hydroxide with phosphoric acid to provide a tricalcium phosphate product containing less aluminum than that present in the calcium oxide starting material.
reacting recovered calcium chloride with alkali metal hydroxide in an aqueous medium to provide an aqueous solution of alkali metal chloride and a precipitate.
of calcium hydroxide;
recovering calcium hydroxide; and, reacting recovered calcium hydroxide with phosphoric acid to provide a tricalcium phosphate product containing less aluminum than that present in the calcium oxide starting material.
3. The process of Claim 2 wherein the alkali metal hydroxide is selected from the group consisting of sodium hydroxide, potassium hydroxide and lithium hydroxide.
4. The process of Claim 2 wherein the alkali metal hydroxide is sodium hydroxide.
5. The process of Claim 2 wherein following recovery of calcium hydroxide and before reacting the caicium hydroxide with phosphoric acid, the calcium hydroxide is washed to remove residual alkali metal chloride which may be present.
6. The process of Claim 1 wherein the chemical convercion operation comprises:
reacting recovered calcium chloride with diammonium phosphate in an aqueous medium to provide an aqueous solution of ammonium chloride and a precipitate of dicalcium phosphate product; and, recovering dicalcium phosphate product containing less aluminum than that present in the calcium oxide starting material.
reacting recovered calcium chloride with diammonium phosphate in an aqueous medium to provide an aqueous solution of ammonium chloride and a precipitate of dicalcium phosphate product; and, recovering dicalcium phosphate product containing less aluminum than that present in the calcium oxide starting material.
7. The process of Claim 6 wherein the dicalcium phosphate product is washed to remove residual ammonium chloride which may be present.
8. The process of Claim 1 wherein the chemical conversion operation comprises:
reacting recovered calcium chloride with ammonia, carbon dioxide and water to provide an aqueous solution of ammonium chloride and a precipitate of calcium carbonate product; and, recovering calcium carbonate product containing less aluminum than that present in the calcium oxide starting material.
reacting recovered calcium chloride with ammonia, carbon dioxide and water to provide an aqueous solution of ammonium chloride and a precipitate of calcium carbonate product; and, recovering calcium carbonate product containing less aluminum than that present in the calcium oxide starting material.
9. The process of Claim 8 wherein the calcium carbonate product is washed to remove residual ammonium chloride which may be present.
10. The process of Claim 1 wherein the calcium oxide starting material contains at least about 200 ppm aluminum and the calcium salt product contains not more than about 100 ppm aluminum.
11. The process ofi Claim l wherein the calcium oxide starting material contains at least about 200 ppm aluminum and the calcium salt product contains not more than about 10 ppm aluminum.
12. The process of Claim 1 wherein the calcium oxide starting material contains at least about 200 ppm aluminum and the calcium salt product contains not more than about 2 ppm aluminum.
13. The process of Claim 1 wherein the calcium salt product contains a lower concentration of fluoride than that of the calcium oxide starting material.
14. The process of Claim 1 wherein the calcium salt product contains not more than about 20 ppm fluoride.
15. The process of Claim 1 wherein the calcium salt product contains a lower concentration of silicon than that present in the calcium oxide starting material.
16. The process of Claim 1 wherein transition elements are present in the calcium salt product in lower concentrations than those of the calcium oxide starting material.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US20333894A | 1994-02-28 | 1994-02-28 | |
| US203,338 | 1994-02-28 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2142663A1 true CA2142663A1 (en) | 1995-08-29 |
Family
ID=22753567
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2142663 Abandoned CA2142663A1 (en) | 1994-02-28 | 1995-02-16 | Process for preparing calcium salts of low aluminum content |
Country Status (5)
| Country | Link |
|---|---|
| EP (1) | EP0673879B1 (en) |
| JP (1) | JPH0848518A (en) |
| AU (1) | AU1349595A (en) |
| CA (1) | CA2142663A1 (en) |
| DE (1) | DE69502326T2 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6193945B1 (en) | 1996-09-27 | 2001-02-27 | Markus Blomquist | Method of recovering calcium from waste material or contaminated natural calcic material |
Families Citing this family (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE19603449C2 (en) * | 1996-01-31 | 1998-03-19 | Papiertechnische Stiftung | Process for the production of calcium carbonate from calcium-containing combustion residues of residues from paper production |
| JP4562512B2 (en) * | 2004-12-20 | 2010-10-13 | 宇部マテリアルズ株式会社 | Method for producing high purity trimagnesium phosphate |
| JP2008214111A (en) * | 2007-02-28 | 2008-09-18 | Tohoku Univ | Manufacturing method of tricalcium phosphate containing silicon and tricalcium phosphate containing silicon |
| WO2012095815A1 (en) * | 2011-01-14 | 2012-07-19 | Csir | Production of calcium carbonate |
| CN103058252B (en) * | 2013-01-30 | 2014-08-27 | 淄博永大化工有限公司 | Method for preparing calcium chloride from high-alkalinity calcium solution and extracted hydrochloric acid in epoxypropane production |
| JP2014177399A (en) * | 2014-04-28 | 2014-09-25 | Asahi Kasei Chemicals Corp | Recovery phosphorus |
| CN110143607B (en) * | 2019-05-08 | 2021-10-22 | 鲁西化工集团股份有限公司 | Technology for preparing calcium chloride by using waste slurry |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3356448A (en) * | 1964-08-18 | 1967-12-05 | Grace W R & Co | Method of preparing dicalcium phosphate substantially free from f, fe, and al impurities |
| US3872219A (en) * | 1973-09-26 | 1975-03-18 | Olin Corp | Process for manufacturing of chlorinated lime solution |
| US4324772A (en) * | 1980-11-19 | 1982-04-13 | Monsanto Company | Process for producing hydroxyapatite |
-
1995
- 1995-02-16 CA CA 2142663 patent/CA2142663A1/en not_active Abandoned
- 1995-02-20 DE DE1995602326 patent/DE69502326T2/en not_active Expired - Fee Related
- 1995-02-20 EP EP19950400349 patent/EP0673879B1/en not_active Expired - Lifetime
- 1995-02-24 JP JP3709095A patent/JPH0848518A/en active Pending
- 1995-02-27 AU AU13495/95A patent/AU1349595A/en not_active Abandoned
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6193945B1 (en) | 1996-09-27 | 2001-02-27 | Markus Blomquist | Method of recovering calcium from waste material or contaminated natural calcic material |
Also Published As
| Publication number | Publication date |
|---|---|
| DE69502326D1 (en) | 1998-06-10 |
| EP0673879B1 (en) | 1998-05-06 |
| DE69502326T2 (en) | 1999-02-11 |
| EP0673879A1 (en) | 1995-09-27 |
| JPH0848518A (en) | 1996-02-20 |
| AU1349595A (en) | 1995-09-07 |
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