Patent Number: 
Section: claims

1. A method of synthesizing a mixed-layered bismuth oxy-iodine material, comprising:a) forming a mixture by combining and mixing the following ingredients:a bismuth salt,deionized water,XI or XIO3, where X is selected from the group consisting of alkali and alkali earth cations, H, and ammonium; anda sufficient amount of a base to adjust the pH of the mixture to an optimal range for forming precipitates with a maximum iodine update;b) heating the mixture, thereby precipitating solids and leaving a supernate; andc) separating the precipitated solids from the supernate;whereby the precipitated solids comprise the mixed-layered bismuth oxy-iodine material; andwherein the mixed-layered bismuth oxy-iodine material has between has between 15 mole % and 20 mole % Bi5O7I with a remainder corresponding amount of between and 80 mole % and 85 mole % BiOI. 2. The method of claim 1, wherein the mixed-layered bismuth oxy-iodine material has between 17 wt % and 22 wt % iodine. 3. The method of claim 1, wherein X=potassium. 4. The method of claim 1, wherein the mixture is heated to a temperature less than 100° C. for at least 12 hours. 5. The method of claim 1, wherein the bismuth salt is bismuth nitrate or bismuth trichloride. 6. The method of claim 5, wherein the bismuth salt is bismuth nitrate. 7. A method of synthesizing a mixed-layered bismuth oxy-iodine material, comprising:a) forming a mixture by combining the following components:bismuth nitrate, Bi(NO3)3.5H2O;deionized water;potassium iodide;NaOH;b) heating the mixture, thereby precipitating solids and leaving a supernate;c) separating the precipitated solids from the supernate;and d) drying the separated solids to produce the mixed-layered bismuth oxy-iodine material; wherein the mixed-layered bismuth oxy-iodine material has between has between 15 mole % and 20 mole % Bi5O7I with a remainder corresponding amount of between and 80 mole % and 85 mole % BiOI. 8. The method of claim 7, wherein the mixture is heated at 90° C. for at least 12 hours. 9. The method of claim 7, wherein the potassium iodide contains 129I. 10. A method of capturing and immobilizing radioactive isotopes of iodine, the method comprising:a) providing a caustic waste stream comprising XOH and the radioactive isotopes of iodine in the form of YI or YIO3, where X and Y are selected from the group consisting of alkali and alkali earth cations, H, and ammonium, and where X can be the same, or different, than Y;b) adding a bismuth salt and an acid to the caustic waste stream, then mixing;c) heating the stream of step b), whereby a precipitate forms and leaves a supernate;d) separating the precipitated solids from the supernate; andwherein the precipitated solids comprise a mixed-layered bismuth oxy-radioiodine material containing the radioactive isotopes of iodine; andwherein the mixed-layered bismuth oxy-iodine material has between has between 15 mole % and 20 mole % Bi5O7I with a remainder corresponding amount of between and 80 mole % and 85 mole % BiOI. 11. The method of claim 10, wherein the radioactive isotopes of iodine are one or both 129I and 131I. 12. The method of claim 10, wherein X and Y are both potassium. 13. The method of claim 10, wherein X is sodium and Y is potassium. 14. The method of claim 10, wherein the bismuth salt comprises bismuth nitrate or bismuth trichloride. 15. The method of claim 10, wherein the acid comprises nitric acid. 16. The method of claim 10, further comprising adjusting the pH of the caustic waste stream so that the supernate has a pH from 4.7 to 6.5 after heating. 17. The method of claim 10, wherein the mixed-layered bismuth oxy-radioiodine material has an elemental composition comprising 17-22 wt % iodine, with the balance comprising bismuth and oxygen. 18. The method of claim 10, wherein the mixed-layered bismuth oxy-radioiodine material has a bismuth-to-iodine molar ratio between 1.64 and 2.13. 19. A mixed-layered bismuth oxy-iodine material, made by performing the process of claim 10.