Patent Number: 052231810
Section: claims

1. In a process for separating magnesium from a magnesium slag using water and carbon dioxide, the improvement comprises: a) forming an aqueous magnesium slurry from the magnesium slag, which slag contains radioactive thorium and its daughters, and water;  b) solubilizing magnesium from the magnesium slurry by reacting the aqueous magnesium slurry with carbon dioxide;  c) selectively concentrating by filtering the radioactive thorium and its daughters such that the radioactive thorium and its daughters are separated from the solubilized magnesium filtrate; and  d) reducing volume and/or weight of radioactive solids for disposal as radioactive waste.  a) forming an aqueous magnesium slurry from the magnesium slag, which slag contains radioactive thorium and its daughters, and water;  b) solubilizing magnesium from the magnesium slurry by reacting the aqueous magnesium slurry with carbon dioxide wherein the carbon dioxide is at a pressure from greater than ambient to about 1,000 psig (about 7,000 kPa);  c) selectively concentrating by filtering the radioactive thorium and its daughters such that the radioactive thorium and its daughters are separated from the solubilized magnesium filtrate; and  d) reducing volume and/or weight of radioactive solids for disposal as radioactive waste. 2. The process of claim 1 wherein the volume and/or weight of radioactive solids for disposal as radioactive waste has been reduced by at least about 50%. 3. The process of claim 2 wherein the volume and/or weight of radioactive solids for disposal as radioactive waste has been reduced from about 50% to about 90%. 4. The process of claim 1(d) wherein an increased concentration of radioactivity from radioactive thorium and its daughters has occurred by at least about 200% from that present in the magnesium slag. 5. The process of claim 4 wherein the concentration of radioactivity has increased from at least about 200% to about 1,000% from that present in the magnesium slag. 6. The process of claim 1 wherein a ratio of water to magnesium slag used is at least about 1:1. 7. The process of claim 6 wherein the ratio of water to magnesium slag is from about 1:1 to about 10:1. 8. The process of claim 6 wherein the ratio of water to magnesium slag is from about 1:1 to about 5:1. 9. The process of claim 6 wherein the ratio of water to magnesium slag is about 3:1. 10. The process of claim 1 wherein the carbon dioxide is at a pressure from greater than ambient to about 1,000 psig (about 7,000 kPa). 11. The process of claim 10 wherein the carbon dioxide is at a pressure from about 50 to about 500 psig (about 450 to about 3,500 kPa). 12. The process of claim 1 wherein the volume of radioactive solids is further reduced after Step (d) by compacting the solids. 13. The process of claim 1 wherein after Step (d) the volume and/or weight of radioactive solids is further reduced by heating the solids. 14. The process of claim 1 wherein after Step (d) the volume and/or weight of radioactive solids is further reduced by compacting and heating the solids. 15. The process of claim 1 wherein the magnesium slag is heated prior to addition of the water and carbon dioxide. 16. The process of claim 1 wherein the steps are repeated at from 1 to 20 times. 17. The process of claim 1 wherein the carbon dioxide is added at a temperature of from about -10.degree. to about 70.degree. C. 18. The process of claim 17 wherein the carbon dioxide is added at a temperature of from about 4.degree. to about 35.degree. C. 19. The process of claim 1(c) wherein the solubilized magnesium is essentially void of radioactivity from radioactive thorium and its daughters. 20. The process of claim 1 wherein barium sulfate is added to the magnesium slurry after Step (a) prior to reacting with carbon dioxide. 21. The process of claim 1 wherein after Step (c) the filtrate has barium sulfate added. 22. The process of claim 21 wherein an insoluble barium sulfate-thorium daughter coprecipitate is separated from the filtrate. 23. The process of claim 1 wherein in Step (c) the radioactive thorium and its daughter solids are filtered and then barium sulfate is prepared in situ in the filtrate after either removal of excess carbon dioxide from the filtrate or after acidifying the filtrate. 24. The process of claim 23 wherein an insoluble barium sulfate-thorium daughter coprecipitate is separated from the filtrate. 25. In a process for separating magnesium from a magnesium slag using water and carbon dioxide, the improvement comprises: 26. The process of claim 25 wherein the carbon dioxide is at a pressure from about 50 to about 500 psig (about 450 to about 3,500 kPa). 27. The process of claim 25 wherein the magnesium slag is heated prior to addition of the water and carbon dioxide. 28. The process of claim 25 wherein barium sulfate is added to the magnesium slurry after Step (a) prior to reacting with carbon dioxide. 29. The process of claim 25 wherein after Step (c) the filtrate has barium sulfate added.