| 摘要 |
Disclosed is a process for producing a calcium sulfate product containing low amounts of radium comprising the steps of: (a) adding at least one sequestering agent to a substantially homogeneous radium-containing monocalcium phosphate (MCP) solution, the amount of the sequestering agent added being at least the stoichiometric amount necessary to complex with the radium in the MCP solution; (b) reacting the treated MCP solution with H2SO4 to form a monocalcium phosphate/phosphoric acid solution, to precipitate a first calcium sulfate product, and to precipitate at least a portion of the radium, the amount of said H2SO4 being up to about 50% of the stoichiometric amount necessary to react with the total CA++ present in the MCP solution; (c) separating the monocalcium phosphate/phosphoric acid solution from the radium-containing calcium sulfate precipitate; (d) then reacting the monocalcium phosphate/phosphoric acid solution with H2SO4 to form a phosphoric acid solution and to precipitate a second calcium sulfate product, the amount of the H2SO4 added being at least sufficient to react with substantially all of the CA++ present in the monocalcium phosphate/phosphoric acid solution; and (e) separating the phosphoric acid from the second calcium sulfate product.
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