Process for producing a calcium sulfate product containing low amounts of radium

A process for producing a calcium sulfate product having low amounts of radium comprising the steps of:

• (a) adding at least one sequestering agent to a substantially homogeneous radium-containing monocalcium phosphate solution, the amount of said sequestering agent added being at least the stoichiometric amount necessary to complex with said radium in said solution;
• (b) then reacting said solution with sufficient sulfuric acid to form a monocalcium phosphate/phosphoric acid solution, to precipitate a first calcium sulfate product and to precipitate at least a portion of said radium, the amount of said sulfuric acid added being from about 5% up to about 50% of the stoichiometric amount necessary to react with the total Ca.sup.++ present in said monocalcium phosphate solution in forming calcium sulfate;
• (c) separating said resulting monocalcium phosphate/phosphoric acid solution from said first radium-containing calcium sulfate precipitate;
• (d) then reacting the monocalcium phosphate/phosphoric acid solution with sufficient sulfuric acid to form a phosphoric acid solution and to precipitate a second calcium sulfate product, the amount of sulfuric acid being at least sufficient to react with substantially all of the Ca.sup.++ present in said monocalcium phosphate/phosphoric acid solution in forming calcium sulfate;
• and
• (e) separating the phosphoric acid solution from the second calcium sulfate product, said second calcium sulfate product having a lower radium concentration than said first calcium sulfate product.