Technology for the Nondestructive Reprocessing of Sodium Iodide Technogenic Solutions into a Charge for Single Crystal Growth

Introduction. The production of NaI-based single crystals results in accumulation of great amount of liquid waste. To bring valuable constituents of this waste back, the NaI technogenic solutions are treated to precipitate iodine that is further used in the synthesis of high-pure NaI. However, the least contaminated part of the waste may be brought back into the main technological process without the intermediary stage of iodine destruction, which allows a considerable cost saving.Problem Statement. There have been no data on the effective purification coefficients for NaI solutions subsequently treated with barium hydroxide, sodium carbonate, and by mass crystallization. Requirements to impurity content, which NaI solutions have to comply with in order to be used in the nondestructive treatment have mot been not formulated.Purpose. The purpose of this research is to develop a technology for reprocessing NaI technogenic solutionsinto sodium iodide of high purity without NaI destruction at the intermediate stage.Material and Methods. The materials that have been used for this research are as follows: aqueous solutions of NaI-based crystal production waste, active coal, barium hydroxide, sodium carbonate. The methods that have been employed are the treatment of NaI solutions with barium hydroxide, sodium carbonate, and by mass crystallization. Results. The technology of NaI solution purification by treatment with barium hydroxide and sodium carbonate with further mass crystallization of the purified salt has been developed. This technology is more environment friendly and cheaper than the conventional one that includes obtaining pure iodine. A series of NaI technogenic solutions has been treated in laboratory conditions and on industrial equipment, and the efficiency of their purification by the chemical treatment and mass crystallization hasbeen estimated. The impurity content in the obtained salt and the scintillation parameters of grown NaI : Tl crystals meet the requirements for these products.Conclusions. The technology has been implemented in the manufacturing process at the pilot plant of the Institute for Scintillation Materials of the NAS of Ukraine. It may be used at other enterprises that deal with alkali metal iodide waste treatment.