Extraction of radium from phosphogypsum

Abstract

Systems and methods are provided for separation / extraction of radium from phosphogypsum. A series of extractants to remove radium from phosphogypsum, thereby producing clean phosphogypsum that can be used in many applications, such as for roads, building foundations, and drywall. The extracted radium can be used in applications, such as for the production of radiopharmaceuticals.

Description

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit of U.S. Provisional Application Serial No. 63 / 770,690, filed Mar. 12, 2025, the disclosure of which is hereby incorporated by reference in its entirety, including all figures, tables, and drawings.BACKGROUND

[0002] Phosphogypsum is a solid waste byproduct from processing phosphate ore to make phosphoric acid that is later used in fertilizer. Phosphogypsum contains radium, which decays to form radon gas, both of which are radioactive and harmful to humans. Phosphogypsum is typically stored in large stacks that pose physical and chemical hazards to the surrounding communities.BRIEF SUMMARY

[0003] Embodiments of the subject invention provide novel and advantageous systems and methods for separation / extraction of radium from phosphogypsum. A series of extractants to remove radium from phosphogypsum, thereby producing clean phosphogypsum that can be used in many applications, such as roads, building foundations, and drywall. The extracted radium can be used in applications, such as for the production of radiopharmaceuticals.

[0004] In an embodiment, a method for extraction of radium from phosphogypsum can comprise: i) mixing the phosphogypsum with a first solution to give the phosphogypsum and a first supernatant; ii) removing the phosphogypsum from the first supernatant; iii) after step ii), mixing the phosphogypsum with a second solution to give the phosphogypsum and a second supernatant; iv) removing the phosphogypsum from the second supernatant; v) after step iv), mixing the phosphogypsum with a third solution to give the phosphogypsum and a third supernatant; and vi) removing the phosphogypsum from the third supernatant. After step vi), the phosphogypsum can have a radium activity of, for example, 10 picocuries per gram (pCi / g) or less (e.g., 5 pCi / g or less, or 1 pCi / g or less). The method can further comprise, before step i), rinsing the phosphogypsum with a liquid (e.g., water). The rinsing of the phosphogypsum can give a rinse comprising water and radium. The method can further comprise: vii) after step iv), combining the first supernatant, the second supernatant, the third supernatant, and / or the rinse to give a radium-containing solution; and viii) performing a separation step on the radium-containing solution to separate out radium from the radium-containing solution. The separation step can be or can comprise, for example, chromatography (e.g., cation chromatography). The radium separated out from the radium-containing solution can be in an amount sufficient for commercial applications. The first solution, the second solution, or the third solution can be ethylenediaminetetraacetic acid (EDTA). The first solution, the second solution, or the third solution can be diethylenetriamine pentaacetic acid (DTPA). The first solution, the second solution, or the third solution can be 3,4-diaminobenzoic acid. For example, the first solution can be EDTA, the second solution can be DTPA, and the third solution can be 3,4-diaminobenzoic acid.BRIEF DESCRIPTION OF DRAWINGS

[0005] FIG. 1 shows a flow chart for extraction of radium from phosphogypsum, according to an embodiment of the subject inventionDETAILED DESCRIPTION

[0006] Embodiments of the subject invention provide novel and advantageous systems and methods for separation / extraction of radium from phosphogypsum. A series of extractants to remove radium from phosphogypsum, thereby producing clean phosphogypsum that can be used in many applications, such as for roads, building foundations, and drywall. The extracted radium can be used in applications, such as for the production of radiopharmaceuticals.

[0007] FIG. 1 shows a flow chart for extraction of radium from phosphogypsum, according to an embodiment of the subject invention. Referring to FIG. 1, the phosphogypsum can first be rinsed S1 (e.g., with water, such as deionized water). The rinse (e.g., the liquid that was used for rinsing the phosphogypsum) can be retained as it can contain radium. Next, the phosphogypsum can be mixed S2 with a first solution (e.g., a basic solution, such as a basic solution of ethylenediaminetetraacetic acid (EDTA)), after which the supernatant is removed S3 from the phosphogypsum. The supernatant from this step can be retained. Next, the phosphogypsum can be mixed S4 with a second solution (e.g., a basic solution, such as a basic solution of diethylenetriamine pentaacetic acid (DTPA)), after which the supernatant is removed S5 from the phosphogypsum. The supernatant from this step can be retained. Then, the phosphogypsum can be mixed S6 with a third solution (e.g., a solution of 3,4-diaminobenzoic acid (C7H8N2O2)), after which the supernatant can be removed S7 from the phosphogypsum. The supernatant from this step can be retained. Each step of mixing with a solution can extract some radium from the phosphogypsum, and the sequential mixing with extractants can have a cumulative effect of removing a large amount of radium from the phosphogypsum. In particular, the mixing with the third solution of 3,4-diaminobenzoic acid can advantageously remove a large amount of radium remaining after the first two mixing / extraction steps. In some embodiments, the rinsing step S1 can be omitted.

[0008] After the third mixing with a third solution, the phosphogypsum can have low enough radium levels to be safe, viable, and useful in many applications (e.g., for roads, building foundations, and drywall). The resulting phosphogypsum can have a radium activity level of, for example, 10 picocuries per gram (pCi / g) or less, 9 pCi / g or less, 8 pCi / g or less, 7 pCi / g or less, 6 pCi / g or less, 5 pCi / g or less, 4 pCi / g or less, 3 pCi / g or less, 2 pCi / g or less, 1 pCi / g or less, or 0.5 pCi / g or less (e.g., in a range of from 0.01 pCi / g to 10 pCi / g).

[0009] The supernatants from any or all of the three extraction / mixing steps, as well as optionally the rinse from the initial rinse step, can be combined S8 to give a radium-containing solution, and a separation step S9 can be performed on the radium-containing solution to separate some or all of the radium (e.g., pure radium) out from other species present therein. The separation step can be or can include, for example, chromatography (e.g., cation chromatography). The separated radium can be in an amount sufficient for commercial applications (e.g., for use in the production of radiopharmaceuticals).

[0010] No related art method exists that uses sequential extraction / mixing steps with solutions to attempt to remove radium from phosphogypsum. Use of a single extractant on phosphogypsum does not extract enough radium for the phosphogypsum to be safe, viable, or useful in practical applications, nor does it extract enough radium to be particularly useful in commercial applications. Embodiments of the subject invention give phosphogypsum with radium levels low enough for the phosphogypsum to be sold and for pure radium to be extracted at levels high enough to be sold. Also, the use of 3,4-diaminobenzoic acid as an extractant for phosphogypsum is novel, and it is able to remove from phosphogypsum not only radium but also trace levels of radionuclides that are not radium. The extraction sequence of embodiments of the subject invention can be applied to phosphogypsum mining waste throughout the world, and can be used to clean up phosphogypsum stacks everywhere.

[0011] When ranges are used herein, combinations and subcombinations of ranges (e.g., subranges within the disclosed range) and specific embodiments therein are intended to be explicitly included. When the term “about” is used herein, in conjunction with a numerical value, it is understood that the value can be in a range of 95% of the value to 105% of the value, i.e., the value can be + / - 5% of the stated value. For example, “about 1 kg” means from 0.95 kg to 1.05 kg.

[0012] A greater understanding of the embodiments of the subject invention and of their many advantages may be had from the following examples, given by way of illustration. The following examples are illustrative of some of the methods, applications, embodiments, and variants of the present invention. They are, of course, not to be considered as limiting the invention. Numerous changes and modifications can be made with respect to embodiments of the invention.Example 1

[0013] Phosphogypsum was first rinsed with water, and the rinse was retained. Next, the phosphogypsum after rinsing was mixed with a basic solution of EDTA. After mixing (for a sufficient amount of time for the solution to extract radium from the phosphogypsum), the phosphogypsum was removed from the supernatant, and this first supernatant was retained. The phosphogypsum was then mixed with a basic solution of DTPA. After mixing (for a sufficient amount of time for the solution to extract radium from the phosphogypsum), the phosphogypsum was removed from the supernatant, and this second supernatant was retained. The phosphogypsum was then mixed with 3,4-diaminobenzoic acid. After mixing (for a sufficient amount of time for the 3,4-diaminobenzoic acid to extract radium from the phosphogypsum), the phosphogypsum was removed from the supernatant, and this third supernatant was retained. The radium level in the phosphogypsum was then below 10 pCi / g (i.e., low enough for the phosphogypsum to be safely deployed in practical applications). The rinse, the first supernatant, the second supernatant, and the third supernatant were then combined into a radium-containing solution. Cation chromatography was performed on the radium-containing solution to separate radium from other species. The pure radium was retained for use in practical applications.

[0014] It should be understood that the examples and embodiments described herein are for illustrative purposes only and that various modifications or changes in light thereof will be suggested to persons skilled in the art and are to be included within the spirit and purview of this application.

[0015] All patents, patent applications, provisional applications, and publications referred to or cited herein are incorporated by reference in their entirety, including all figures and tables, to the extent they are not inconsistent with the explicit teachings of this specification.

Examples

example 1

[0013]Phosphogypsum was first rinsed with water, and the rinse was retained. Next, the phosphogypsum after rinsing was mixed with a basic solution of EDTA. After mixing (for a sufficient amount of time for the solution to extract radium from the phosphogypsum), the phosphogypsum was removed from the supernatant, and this first supernatant was retained. The phosphogypsum was then mixed with a basic solution of DTPA. After mixing (for a sufficient amount of time for the solution to extract radium from the phosphogypsum), the phosphogypsum was removed from the supernatant, and this second supernatant was retained. The phosphogypsum was then mixed with 3,4-diaminobenzoic acid. After mixing (for a sufficient amount of time for the 3,4-diaminobenzoic acid to extract radium from the phosphogypsum), the phosphogypsum was removed from the supernatant, and this third supernatant was retained. The radium level in the phosphogypsum was then below 10 pCi / g (i.e., low enough for the phosphogypsum...

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit of U.S. Provisional Application Serial No. 63 / 770,690, filed Mar. 12, 2025, the disclosure of which is hereby incorporated by reference in its entirety, including all figures, tables, and drawings.BACKGROUND

[0002] Phosphogypsum is a solid waste byproduct from processing phosphate ore to make phosphoric acid that is later used in fertilizer. Phosphogypsum contains radium, which decays to form radon gas, both of which are radioactive and harmful to humans. Phosphogypsum is typically stored in large stacks that pose physical and chemical hazards to the surrounding communities.BRIEF SUMMARY

[0003] Embodiments of the subject invention provide novel and advantageous systems and methods for separation / extraction of radium from phosphogypsum. A series of extractants to remove radium from phosphogypsum, thereby producing clean phosphogypsum that can be used in many applications, such as roads, building foundations, and drywall. The extracted radium can be used in applications, such as for the production of radiopharmaceuticals.

[0004] In an embodiment, a method for extraction of radium from phosphogypsum can comprise: i) mixing the phosphogypsum with a first solution to give the phosphogypsum and a first supernatant; ii) removing the phosphogypsum from the first supernatant; iii) after step ii), mixing the phosphogypsum with a second solution to give the phosphogypsum and a second supernatant; iv) removing the phosphogypsum from the second supernatant; v) after step iv), mixing the phosphogypsum with a third solution to give the phosphogypsum and a third supernatant; and vi) removing the phosphogypsum from the third supernatant. After step vi), the phosphogypsum can have a radium activity of, for example, 10 picocuries per gram (pCi / g) or less (e.g., 5 pCi / g or less, or 1 pCi / g or less). The method can further comprise, before step i), rinsing the phosphogypsum with a liquid (e.g., water). The rinsing of the phosphogypsum can give a rinse comprising water and radium. The method can further comprise: vii) after step iv), combining the first supernatant, the second supernatant, the third supernatant, and / or the rinse to give a radium-containing solution; and viii) performing a separation step on the radium-containing solution to separate out radium from the radium-containing solution. The separation step can be or can comprise, for example, chromatography (e.g., cation chromatography). The radium separated out from the radium-containing solution can be in an amount sufficient for commercial applications. The first solution, the second solution, or the third solution can be ethylenediaminetetraacetic acid (EDTA). The first solution, the second solution, or the third solution can be diethylenetriamine pentaacetic acid (DTPA). The first solution, the second solution, or the third solution can be 3,4-diaminobenzoic acid. For example, the first solution can be EDTA, the second solution can be DTPA, and the third solution can be 3,4-diaminobenzoic acid.BRIEF DESCRIPTION OF DRAWINGS

[0005] FIG. 1 shows a flow chart for extraction of radium from phosphogypsum, according to an embodiment of the subject inventionDETAILED DESCRIPTION

[0006] Embodiments of the subject invention provide novel and advantageous systems and methods for separation / extraction of radium from phosphogypsum. A series of extractants to remove radium from phosphogypsum, thereby producing clean phosphogypsum that can be used in many applications, such as for roads, building foundations, and drywall. The extracted radium can be used in applications, such as for the production of radiopharmaceuticals.

[0007] FIG. 1 shows a flow chart for extraction of radium from phosphogypsum, according to an embodiment of the subject invention. Referring to FIG. 1, the phosphogypsum can first be rinsed S1 (e.g., with water, such as deionized water). The rinse (e.g., the liquid that was used for rinsing the phosphogypsum) can be retained as it can contain radium. Next, the phosphogypsum can be mixed S2 with a first solution (e.g., a basic solution, such as a basic solution of ethylenediaminetetraacetic acid (EDTA)), after which the supernatant is removed S3 from the phosphogypsum. The supernatant from this step can be retained. Next, the phosphogypsum can be mixed S4 with a second solution (e.g., a basic solution, such as a basic solution of diethylenetriamine pentaacetic acid (DTPA)), after which the supernatant is removed S5 from the phosphogypsum. The supernatant from this step can be retained. Then, the phosphogypsum can be mixed S6 with a third solution (e.g., a solution of 3,4-diaminobenzoic acid (C7H8N2O2)), after which the supernatant can be removed S7 from the phosphogypsum. The supernatant from this step can be retained. Each step of mixing with a solution can extract some radium from the phosphogypsum, and the sequential mixing with extractants can have a cumulative effect of removing a large amount of radium from the phosphogypsum. In particular, the mixing with the third solution of 3,4-diaminobenzoic acid can advantageously remove a large amount of radium remaining after the first two mixing / extraction steps. In some embodiments, the rinsing step S1 can be omitted.

[0008] After the third mixing with a third solution, the phosphogypsum can have low enough radium levels to be safe, viable, and useful in many applications (e.g., for roads, building foundations, and drywall). The resulting phosphogypsum can have a radium activity level of, for example, 10 picocuries per gram (pCi / g) or less, 9 pCi / g or less, 8 pCi / g or less, 7 pCi / g or less, 6 pCi / g or less, 5 pCi / g or less, 4 pCi / g or less, 3 pCi / g or less, 2 pCi / g or less, 1 pCi / g or less, or 0.5 pCi / g or less (e.g., in a range of from 0.01 pCi / g to 10 pCi / g).

[0009] The supernatants from any or all of the three extraction / mixing steps, as well as optionally the rinse from the initial rinse step, can be combined S8 to give a radium-containing solution, and a separation step S9 can be performed on the radium-containing solution to separate some or all of the radium (e.g., pure radium) out from other species present therein. The separation step can be or can include, for example, chromatography (e.g., cation chromatography). The separated radium can be in an amount sufficient for commercial applications (e.g., for use in the production of radiopharmaceuticals).

[0010] No related art method exists that uses sequential extraction / mixing steps with solutions to attempt to remove radium from phosphogypsum. Use of a single extractant on phosphogypsum does not extract enough radium for the phosphogypsum to be safe, viable, or useful in practical applications, nor does it extract enough radium to be particularly useful in commercial applications. Embodiments of the subject invention give phosphogypsum with radium levels low enough for the phosphogypsum to be sold and for pure radium to be extracted at levels high enough to be sold. Also, the use of 3,4-diaminobenzoic acid as an extractant for phosphogypsum is novel, and it is able to remove from phosphogypsum not only radium but also trace levels of radionuclides that are not radium. The extraction sequence of embodiments of the subject invention can be applied to phosphogypsum mining waste throughout the world, and can be used to clean up phosphogypsum stacks everywhere.

[0011] When ranges are used herein, combinations and subcombinations of ranges (e.g., subranges within the disclosed range) and specific embodiments therein are intended to be explicitly included. When the term “about” is used herein, in conjunction with a numerical value, it is understood that the value can be in a range of 95% of the value to 105% of the value, i.e., the value can be + / - 5% of the stated value. For example, “about 1 kg” means from 0.95 kg to 1.05 kg.

[0012] A greater understanding of the embodiments of the subject invention and of their many advantages may be had from the following examples, given by way of illustration. The following examples are illustrative of some of the methods, applications, embodiments, and variants of the present invention. They are, of course, not to be considered as limiting the invention. Numerous changes and modifications can be made with respect to embodiments of the invention.Example 1

[0013] Phosphogypsum was first rinsed with water, and the rinse was retained. Next, the phosphogypsum after rinsing was mixed with a basic solution of EDTA. After mixing (for a sufficient amount of time for the solution to extract radium from the phosphogypsum), the phosphogypsum was removed from the supernatant, and this first supernatant was retained. The phosphogypsum was then mixed with a basic solution of DTPA. After mixing (for a sufficient amount of time for the solution to extract radium from the phosphogypsum), the phosphogypsum was removed from the supernatant, and this second supernatant was retained. The phosphogypsum was then mixed with 3,4-diaminobenzoic acid. After mixing (for a sufficient amount of time for the 3,4-diaminobenzoic acid to extract radium from the phosphogypsum), the phosphogypsum was removed from the supernatant, and this third supernatant was retained. The radium level in the phosphogypsum was then below 10 pCi / g (i.e., low enough for the phosphogypsum to be safely deployed in practical applications). The rinse, the first supernatant, the second supernatant, and the third supernatant were then combined into a radium-containing solution. Cation chromatography was performed on the radium-containing solution to separate radium from other species. The pure radium was retained for use in practical applications.

[0014] It should be understood that the examples and embodiments described herein are for illustrative purposes only and that various modifications or changes in light thereof will be suggested to persons skilled in the art and are to be included within the spirit and purview of this application.

[0015] All patents, patent applications, provisional applications, and publications referred to or cited herein are incorporated by reference in their entirety, including all figures and tables, to the extent they are not inconsistent with the explicit teachings of this specification.

Examples

example 1

[0013]Phosphogypsum was first rinsed with water, and the rinse was retained. Next, the phosphogypsum after rinsing was mixed with a basic solution of EDTA. After mixing (for a sufficient amount of time for the solution to extract radium from the phosphogypsum), the phosphogypsum was removed from the supernatant, and this first supernatant was retained. The phosphogypsum was then mixed with a basic solution of DTPA. After mixing (for a sufficient amount of time for the solution to extract radium from the phosphogypsum), the phosphogypsum was removed from the supernatant, and this second supernatant was retained. The phosphogypsum was then mixed with 3,4-diaminobenzoic acid. After mixing (for a sufficient amount of time for the 3,4-diaminobenzoic acid to extract radium from the phosphogypsum), the phosphogypsum was removed from the supernatant, and this third supernatant was retained. The radium level in the phosphogypsum was then below 10 pCi / g (i.e., low enough for the phosphogypsum...

Claims

1. A method for extraction of radium from phosphogypsum, the method comprising:i) mixing the phosphogypsum with a first solution to give the phosphogypsum and a first supernatant;ii) removing the phosphogypsum from the first supernatant;iii) after step ii), mixing the phosphogypsum with a second solution to give the phosphogypsum and a second supernatant;iv) removing the phosphogypsum from the second supernatant;v) after step iv), mixing the phosphogypsum with a third solution to give the phosphogypsum and a third supernatant;vi) removing the phosphogypsum from the third supernatant,wherein, after step vi), the phosphogypsum has a radium activity of 10 picocuries per gram (pCi / g) or less.

2. The method according to claim 1, wherein after step vi), the phosphogypsum has a radium activity of 5 pCi / g or less.

3. The method according to claim 1, wherein after step vi), the phosphogypsum has a radium activity of 1 pCi / g or less.

4. The method according to claim 1, further comprising:vii) after step iv), combining the first supernatant, the second supernatant, and the third supernatant to give a radium-containing solution; andviii) performing a separation step on the radium-containing solution to separate out radium from the radium-containing solution.

5. The method according to claim 4, wherein the radium separated out from the radium-containing solution is in an amount sufficient for commercial applications.

6. The method according to claim 4, wherein the separation step comprises cation chromatography.

7. The method according to claim 6, wherein the radium separated out from the radium-containing solution is in an amount sufficient for commercial applications.

8. The method according to claim 1, wherein the first solution, the second solution, or the third solution is ethylenediaminetetraacetic acid (EDTA).

9. The method according to claim 8, wherein the first solution is EDTA.

10. The method according to claim 1, wherein the first solution, the second solution, or the third solution is diethylenetriamine pentaacetic acid (DTPA).

11. The method according to claim 10, wherein the second solution is EDTA.

12. The method according to claim 1, wherein the first solution, the second solution, or the third solution is 3,4-diaminobenzoic acid.

13. The method according to claim 12, wherein the second solution is 3,4-diaminobenzoic acid.

14. The method according claim 1, wherein the first solution is EDTA, the second solution is DTPA, and the third solution is 3,4-diaminobenzoic acid.

15. The method according to claim 1, further comprising, before step i), rinsing the phosphogypsum with a liquid.

16. The method according to claim 15, wherein the liquid is water.

17. The method according to claim 15, wherein the rinsing of the phosphogypsum gives a rinse comprising water and radium, andwherein the method further comprises:vii) after step iv), combining the first supernatant, the second supernatant, the third supernatant, and the rinse to give a radium-containing solution; andviii) performing a separation step on the radium-containing solution to separate out radium from the radium-containing solution.

18. The method according to claim 17, wherein the radium separated out from the radium-containing solution is in an amount sufficient for commercial applications.

19. The method according to claim 17, wherein the separation step comprises cation chromatography.

20. The method according to claim 19, wherein the radium separated out from the radium-containing solution is in an amount sufficient for commercial applications.

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