MXPA97003753A - Method for the purification of calbonate carbonate - Google Patents
Method for the purification of calbonate carbonateInfo
- Publication number
- MXPA97003753A MXPA97003753A MXPA/A/1997/003753A MX9703753A MXPA97003753A MX PA97003753 A MXPA97003753 A MX PA97003753A MX 9703753 A MX9703753 A MX 9703753A MX PA97003753 A MXPA97003753 A MX PA97003753A
- Authority
- MX
- Mexico
- Prior art keywords
- calcium carbonate
- suspension
- weight
- process according
- chelating agent
- Prior art date
Links
- 238000000034 method Methods 0.000 title claims abstract description 43
- BVKZGUZCCUSVTD-UHFFFAOYSA-L Carbonate Chemical compound [O-]C([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-L 0.000 title claims description 4
- 238000000746 purification Methods 0.000 title description 6
- VTYYLEPIZMXCLO-UHFFFAOYSA-L Calcium carbonate Chemical compound [Ca+2].[O-]C([O-])=O VTYYLEPIZMXCLO-UHFFFAOYSA-L 0.000 claims abstract description 153
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims abstract description 85
- 229910000019 calcium carbonate Inorganic materials 0.000 claims abstract description 74
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 claims abstract description 44
- 239000000725 suspension Substances 0.000 claims abstract description 44
- 229910052742 iron Inorganic materials 0.000 claims abstract description 42
- 229910002092 carbon dioxide Inorganic materials 0.000 claims abstract description 22
- 239000002738 chelating agent Substances 0.000 claims abstract description 19
- 239000007900 aqueous suspension Substances 0.000 claims abstract description 12
- 239000001569 carbon dioxide Substances 0.000 claims abstract description 10
- 238000010438 heat treatment Methods 0.000 claims abstract description 6
- 238000003756 stirring Methods 0.000 claims abstract description 5
- 239000002253 acid Substances 0.000 claims description 8
- 235000013305 food Nutrition 0.000 claims description 7
- 239000004033 plastic Substances 0.000 claims description 6
- 229920003023 plastic Polymers 0.000 claims description 6
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 claims description 4
- 239000011575 calcium Substances 0.000 claims description 4
- 229910052791 calcium Inorganic materials 0.000 claims description 4
- 230000007423 decrease Effects 0.000 claims description 3
- KCXVZYZYPLLWCC-UHFFFAOYSA-N EDTA Chemical compound OC(=O)CN(CC(O)=O)CCN(CC(O)=O)CC(O)=O KCXVZYZYPLLWCC-UHFFFAOYSA-N 0.000 claims description 2
- CYDQOEWLBCCFJZ-UHFFFAOYSA-N 4-(4-fluorophenyl)oxane-4-carboxylic acid Chemical compound C=1C=C(F)C=CC=1C1(C(=O)O)CCOCC1 CYDQOEWLBCCFJZ-UHFFFAOYSA-N 0.000 claims 1
- 238000006243 chemical reaction Methods 0.000 claims 1
- 230000037213 diet Effects 0.000 claims 1
- 235000005911 diet Nutrition 0.000 claims 1
- 229940079593 drug Drugs 0.000 claims 1
- 150000002825 nitriles Chemical class 0.000 claims 1
- 229940005581 sodium lactate Drugs 0.000 claims 1
- 239000001540 sodium lactate Substances 0.000 claims 1
- 235000011088 sodium lactate Nutrition 0.000 claims 1
- 239000003795 chemical substances by application Substances 0.000 abstract description 3
- 235000010216 calcium carbonate Nutrition 0.000 description 53
- 239000000047 product Substances 0.000 description 22
- 235000019738 Limestone Nutrition 0.000 description 7
- 239000006028 limestone Substances 0.000 description 7
- 238000001914 filtration Methods 0.000 description 6
- 239000000126 substance Substances 0.000 description 4
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 4
- 239000008367 deionised water Substances 0.000 description 3
- 229910021641 deionized water Inorganic materials 0.000 description 3
- 238000000227 grinding Methods 0.000 description 3
- 239000000797 iron chelating agent Substances 0.000 description 3
- 229940075525 iron chelating agent Drugs 0.000 description 3
- 239000000123 paper Substances 0.000 description 3
- 229940088417 precipitated calcium carbonate Drugs 0.000 description 3
- OVBJJZOQPCKUOR-UHFFFAOYSA-L EDTA disodium salt dihydrate Chemical compound O.O.[Na+].[Na+].[O-]C(=O)C[NH+](CC([O-])=O)CC[NH+](CC([O-])=O)CC([O-])=O OVBJJZOQPCKUOR-UHFFFAOYSA-L 0.000 description 2
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N Iron oxide Chemical compound [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 description 2
- 230000003466 anti-cipated effect Effects 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 238000004061 bleaching Methods 0.000 description 2
- 238000000576 coating method Methods 0.000 description 2
- 230000003247 decreasing effect Effects 0.000 description 2
- 239000002270 dispersing agent Substances 0.000 description 2
- 238000001035 drying Methods 0.000 description 2
- 238000000605 extraction Methods 0.000 description 2
- 239000000945 filler Substances 0.000 description 2
- 150000003839 salts Chemical class 0.000 description 2
- 239000007787 solid Substances 0.000 description 2
- 239000000654 additive Substances 0.000 description 1
- 230000000996 additive effect Effects 0.000 description 1
- 238000013019 agitation Methods 0.000 description 1
- 239000007844 bleaching agent Substances 0.000 description 1
- ZHBYMYNWPFDUAN-UHFFFAOYSA-J calcium iron(2+) dicarbonate Chemical compound [Ca+2].[Fe+2].[O-]C([O-])=O.[O-]C([O-])=O ZHBYMYNWPFDUAN-UHFFFAOYSA-J 0.000 description 1
- -1 chalk Substances 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 230000000536 complexating effect Effects 0.000 description 1
- 239000000356 contaminant Substances 0.000 description 1
- 238000004090 dissolution Methods 0.000 description 1
- 239000010459 dolomite Substances 0.000 description 1
- 229910000514 dolomite Inorganic materials 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000005530 etching Methods 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 238000011049 filling Methods 0.000 description 1
- 239000000706 filtrate Substances 0.000 description 1
- 238000005188 flotation Methods 0.000 description 1
- 239000002778 food additive Substances 0.000 description 1
- 229910052500 inorganic mineral Inorganic materials 0.000 description 1
- 238000002386 leaching Methods 0.000 description 1
- 235000012204 lemonade/lime carbonate Nutrition 0.000 description 1
- 238000007885 magnetic separation Methods 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 235000010755 mineral Nutrition 0.000 description 1
- 239000011707 mineral Substances 0.000 description 1
- MGFYIUFZLHCRTH-UHFFFAOYSA-N nitrilotriacetic acid Chemical compound OC(=O)CN(CC(O)=O)CC(O)=O MGFYIUFZLHCRTH-UHFFFAOYSA-N 0.000 description 1
- 238000010979 pH adjustment Methods 0.000 description 1
- 239000000546 pharmaceutical excipient Substances 0.000 description 1
- 239000000825 pharmaceutical preparation Substances 0.000 description 1
- 229940127557 pharmaceutical product Drugs 0.000 description 1
- 238000007873 sieving Methods 0.000 description 1
- 239000002002 slurry Substances 0.000 description 1
- JVBXVOWTABLYPX-UHFFFAOYSA-L sodium dithionite Chemical compound [Na+].[Na+].[O-]S(=O)S([O-])=O JVBXVOWTABLYPX-UHFFFAOYSA-L 0.000 description 1
- 238000005063 solubilization Methods 0.000 description 1
- 230000007928 solubilization Effects 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
- 238000005406 washing Methods 0.000 description 1
Abstract
The present invention relates to a method for reducing the iron content of calcium carbonate containing iron, characterized in that it comprises treating an aqueous suspension of said calcium carbonate with a chelating agent, heating said calcium carbonate aqueous suspension containing agent chelating and treating said aqueous calcium carbonate suspension containing chelating agent with carbon dioxide gas, wherein said treatment with said chelating agent is carried out while heating and stirring said suspension and said carbon dioxide gas is introduced to maintain a pH of said suspension on the scale of about 5.5 to no more than 7
Description
METHOD FOR PURIFICATION OF CALCIUM CARBONATE
FIELD OF THE INVENTION
The present invention relates to a method for reducing the iron content of calcium carbonate. More particularly, the present invention relates to a method for purifying calcium carbonate. Still more particularly, the present invention relates to a method for decreasing the iron content in calcium carbonate suspensions by treating the calcium carbonate suspension with a chelating agent such as, for example, ethylenediaetetraacetic acid (EDTA). The calcium carbonate produced according to the method of this invention is particularly suitable for use with food or pharmaceutical additives and may also be useful as a filler in paper or co-process processes or an additive in plastic products.
BACKGROUND; OF THE INVENTION
The calcium carbonate in most limestone quarries contains a certain level of iron, usually in the form of iron oxide. However, the presence of iron in any form is sometimes considered a contaminant in calcium carbonate. The presence of iron specifically prevents the use of this calcium carbonate in many specialized markets, such as food products and pharmaceutical applications. Moreover, the presence of iron in calcium carbonate decreases the economic value of final products, either in papermaking processes or in the production of plastic. Various physical and chemical procedures have been suggested to remove iron from calcium carbonate. Physical removal first requires the grinding of calcium carbonate to such a fineness that the iron can be subsequently removed by sieving, sorting, magnetic separation or flotation. The chemical leaching or bleaching of calcium carbonate grinded with solvents followed by filtration has also been suggested as a method to remove iron from calcium carbonate. However, these physical and chemical procedures for the removal of iron from calcium carbonate are complex and difficult to administer. Of equal importance are the erratic results, the unpredictable efficiencies of the procedures, the amounts of iron removed, and the expenses associated with many of the chemical and physical processes for removing iron from calcium carbonate. What has been discovered as novel and not anticipated by the prior art is a process for the purification of calcium carbonate containing iron and the subsequent use of such purified calcium carbonate in applications and markets, such as, specialized grade products. , for example, in foods, plastics and pharmaceutical products where a higher purity of calcium carbonate is required. It is therefore an object of the present invention to provide a simple, predictable and inexpensive process for the purification of calcium carbonate containing iron. Another object of the present invention is to provide a purified calcium carbonate product containing less than 500 parts per million of iron. A further object of the present invention is to provide a product that is particularly useful in food grade and pharmaceutical applications where the purity of calcium carbonate is a requirement. These and other objects of the present invention will become apparent from the detailed description that continues.
RELATED PREVIOUS TECHNIQUE
The patent of E.U.A. No. 4,824,653 discloses a process for bleaching limestone by first grinding limestone into small sizes by conventional grinding methods, either wet or dry. The milled limestone is then mixed with water to form a suspension having a solids content of about 15 percent to 50 percent. An etching agent, such as ethylenedianinotetraacetic acid (EDTA) and a bleaching agent, such as sodium hydrosulfite, are added to the suspension and mixed at an elevated temperature before filtering and drying. The limestone product produced in accordance with the process of this invention exhibits improved whiteness.
BRIEF DESCRIPTION OF THE INVENTION
What was discovered as novel and not anticipated by the prior art is a method for the purification of calcium carbonate containing iron. The iron content of calcium carbonate is substantially decreased by treating an aqueous suspension of calcium carbonate with an iron chelating agent, while heating the suspension and treating the suspension with carbon dioxide. The extracted iron is subsequently separated from the calcium carbonate by filtration. The purified calcium carbonate product produced according to the method of the present invention is particularly useful in food grade products, paper products, coatings and plastic products, where a reduced iron content is required.
DETAILED DESCRIPTION OF THE INVENTION
The present invention includes a process for reducing the iron content of calcium carbonate. The iron in the calcium carbonate is extracted by treating an aqueous suspension of calcium carbonate with an iron-containing agent, heating and stirring the suspension at the same time and introducing a gas containing carbon dioxide to control the pH during the process. Mien-o of extraction. The extracted iron is subsequently separated from the calcium carbonate by filtration. The purification process of the present invention can be used to reduce the iron content of any limestone product. This includes U5P and food grade products, fillers and paper and product coating *; of plastic filling. Calcium carbonates that are useful in the present invention include, but are not limited to, any calcium carbonate that con + mineral, eg, limestone, chalk, dolomite, and precipitated calcium carbonate produced synthetically. The calcium carbonate is processed as an aqueous suspension of about 1 weight percent to about 70 weight calcium carbonate, based on the total weight of the suspension. The preferred weight concentration of calcium carbonate is from about 10 percent to about 30 percent by weight of calcium carbonate, based on the total weight of the suspension. Suspension concentrations of less than about 10 weight percent based on the total weight of the suspension tend not to be practical based on economic considerations. More than 30 percent by weight of calcium carbonate based on the total weight of the suspension may require the use of a dispersant, which could interfere with the extraction process, although not necessarily. Routine experimentation would determine what dispersant could be used in the present inventive process. The iron chelating agents useful in the method of the present invention may be any material capable of iron complexing, more specifically the chelating agent must have a much higher formation constant with iron than with calcium. The chelating agents especially useful in the method of the present invention are selected from the group consisting of nitrilotriacetic acid (H3NTA), ethylenediaminetetraacetic acid (H4EDTA), diethylenetria inopentaacetic acid (H5DPTA) and hydroxyethylenediaminetriacetic acid (H3HEDTA) and salts thereof. The preferred chelating agent is ethylenediaetetraacetic acid (EDTA) and any salt thereof. The calcium carbonate containing iron is treated with from about 0.01 percent to about 10 percent chelating agent. When the chelating agent is EDTA the preferred treatment level is from about 0.1 weight percent to about 1.0 weight percent, based on the weight of the calcium carbonate present, depending on the amount of iron present in the calcium carbonate. The gas containing carbon dioxide useful in the process of the present invention contains between about 1 percent to about 100 percent CO2 on a volume basis. Typical concentrations of CO2 range from approximately 10 percent to approximately 30 percent CO2 on a volume basis. In view of the fact that the gas containing carbon dioxide described above is used to control the pH of the calcium carbonate suspension, the rate of addition of said gas containing CO2 is adjusted to maintain the pH of the suspension in the range of about 5.5 to about 7.0, preferably about 6.0 to about 6.5. The calcium carbonate suspension and the chelating agent are heated to a high temperature scale of from about 20 degrees to about 100 degrees centigrade. The preferred temperature scale is from about 40 degrees to about 60 degrees centigrade. The suspension is stirred, filtered, washed and dried. It is believed that by employing an iron chelating agent, controlling both the temperature and the pH, it promotes the dissolution of the iron in calcium carbonate. The dissolved iron is conpleted by the chelating agent. When the iron is dissolved by lowering the pH and raising the temperature, the iron is complexed by the chelating agent and diverts the equilibrium to solubilize more iron. Additionally, the lower pH provides a higher formation constant between the iron and the chelating agent, thus improving the overall equilibrium towards the solubilization of the iron. The calcium carbonate and the iron are subsequently separated by filtration, containing the filtrate to the complexed iron. However, what is being suggested here is a theory about why the method of the present invention decreases iron calcium carbonate. This should be accepted only as a theory as to why the invention works and should not be used under any conditions or whatever to limit the scope of the present invention, which is illustrated in more detail by means of the examples below and it is defined more specifically by means of the claims.
EXAMPLES 1 TO 6
In Examples 1 to 6, calcium carbonate (untreated) with an iron content of 715 ppm of Fß2? 3 was treated as a suspension with 0.33 weight percent of
EDTA during variable treatment times, at different treatment temperatures and at different suspension pH values. The resulting treated calcium carbonate suspensions were filtered, the treated products thus obtained were washed, dried and analyzed to verify the F 2? 3 content. The experiments were carried out as follows:
EXAMPLE 1
To 81 rnl of deionized water, 9 ml of a 0.01 molar solution of Na2H2 EDTA.2H2O was added. To the above stirred solution were added 10 grams of precipitated calcium carbonate. The suspension was then heated to 60 ° C and stirred at 60 ° C for 24 hours. The pH of the suspension was 8.0 and remained 8.0 since no pH control (no CO2) was used in this treatment. The suspension was filtered, the collected solids were washed with deionized water and subsequently dried.
EXAMPLE 2
In the same manner described in example 1, to 90 ml of deionized water containing 9 ml of 0.02 molar Na2H2 EDTA.2H2O solution, 10 grams of precipitated calcium carbonate was added. While stirring, CO2 was introduced into the suspension to adjust the pH of the suspension to 6.0 and the suspension was heated to 60 ° C. The suspension was stirred for 24 hours at 60 ° C, maintaining the pH at 6.0 introducing CO2 as necessary, the resulting treated calcium carbonate slurry was further processed as in Example 1. 5 EXAMPLE 3
In the same manner as in example 2, the calcium carbonate product was treated with 0.33 weight percent of O EDTA as a suspension at a temperature of 60 ° C and a pH of 6.0, using CO2 to con + roll the pH, only for 2 hours. The resulting suspension was processed as in Example 1.
EXAMPLE 4
In the same manner as in example 2, the calcium carbonate product was treated with 0.33 weight percent EDTñ in the form of a suspension at a temperature of 60 ° C and a pH 0 of 6.0, using CO2 to con + roll the pH only for 1 hour. The resulting suspension was processed as in Example 1.
EXAMPLE 5 F In the same manner as described in Example 2, the lime carbonate product was treated with 0.33 weight percent EDTA as a suspension, the pH of the suspension was adjusted to 6.0 and maintained at 6.0 using CO2. The suspension was heated to 40 ° C with stirring and kept at 40 ° C, pH 6.0 for 3 hours. The resulting treated product was processed dictionally as in Example 1.
EXAMPLE 6
In the same manner as that described in Example 5, the calcium carbonate product was treated with 0.33 weight percent EÜTO as a suspension at a temperature of 40 ° C and a pH of 6.0 only for 1 hour. The resulting product was further processed after filtering, washing and drying as in Example 1.
rü CJ! s L?
PICTURE
Product Resulting time
Example Atmosphere Treatment PH Temp.QC. agitation ppm F? 2? 3 Carbonate of 715 precipitated calcium without treatment 0.J3% by weight Air 8.0 60 24 701 of EDTA 0.33% by weight C0- 6.0 60 24 286 of EDTA 1- '
0. 33% by weight CO 6.0 60 272 of EDTA 0.33% by weight CO. 6.0 60 315 of EDTA 0.33% by weight C0-- 6.0 40 372 of EDTA 0.33% by weight C0-- 6.0 40 415 of EDTA
The treated calcium carbonate products were analyzed to verify the iron content and compared with the calcium carbonate not treated in the table. The data in the table show the pH adjustment value, the value of elevated temperatures and the effect of the present inventive procedure for the removal of iron.
Claims (12)
1. A process to decrease the iron content of calcium carbonate which consists of treating an aqueous suspension of calcium carbonate with a chelating agent, heating the aqueous suspension of calcium carbonate and treating the aqueous suspension of calcium carbonate with 10 carbon dioxide gas.
2. The process according to claim 1, wherein the concentration of calcium carbonate in the aqueous suspension of calcium carbonate is from 1% by weight to 70% by weight, based on the total weight of the suspension 1 r? of calcium carbonate.
3. The process according to claim 1 or 2, wherein the concentration of calcium carbonate in the aqueous calcium carbonate suspension is from JO percent to 30 percent by weight, based on the total weight of ? ü the calcium carbonate suspension.
4. The process of any of the foregoing reactions, in which the chelating agent is selected from the group consisting of nitrile tpacetic acid, ethylenediaminetetraacetic acid, sodium lactate diet, hydroxothylethyldenetriacetic acid and leaves the same.
5. The process according to any of the preceding claims, wherein the amount of chelating agent is 0.01% on weight at 10% by weight, based on the weight of calcium carbonate.
6. The process according to claim 4, wherein the chelating agent is etiiendia inotetraaceti acid and wherein the amount of chelating agent is 0.1% by weight to 1.0% by weight, based on the weight of the carbonate of calcium.
7. The process according to any of the preceding claims, wherein the gas containing carbon dioxide has a concentration of CO2 of 1% to 100% and in which the pH of the carbonate suspension of calcium is from 5.5 to 7.0.
8. The process according to any of the preceding claims, wherein the gas containing carbon dioxide preferred has a concentration of CO2 of 1% at J00% and in which the preferred pH is 6.0 to ñ "5. %:
9. The process according to any of the preceding claims, wherein the temperature scale of the aqueous calcium carbonate suspension is from 20 to 100 degrees centigrade.
10. The process according to claim 9, wherein the preferred temperature scale of the aqueous calcium carbonate suspension is from 40 to 60 degrees centigrade. Ifi
11. - The process according to any of the preceding claims, which further comprises treating an aqueous suspension of calcium carbonate with a chelating agent, heating the aqueous suspension of calcium carbonate, stirring the aqueous suspension of calcium carbonate introducing the same time on said aqueous calcium carbonate suspension a gas containing carbon dioxide.
12. A food product, a pharmaceutical drug, a plastic product or a paper product containing calcium carbonate produced in accordance with the process of any of the preceding claims.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US08/343,002 US5690897A (en) | 1994-11-21 | 1994-11-21 | Method for purification of calcium carbonate |
| US08343002 | 1994-11-21 | ||
| PCT/US1995/014994 WO1996015985A1 (en) | 1994-11-21 | 1995-11-16 | Method for purification of calcium carbonate |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| MX9703753A MX9703753A (en) | 1997-09-30 |
| MXPA97003753A true MXPA97003753A (en) | 1998-07-03 |
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