Gas-phase conversion of U, Sr, and Mo compounds into water-soluble forms in a nitrating atmosphere

Gas-phase conversion of uranyl molybdates UO2MoO4, UMo1.7O7.2, and UMo0.4O3.4, of strontium molybdate SrMoO4, and of strontium uranate SrUO4 into water-soluble compounds in the NOx–H2O (vapor)–air or HNO3 (vapor)–air atmosphere (hereinafter, nitrating atmosphere) was studied. The conversion of UO2MoO4, UMo1.7O7.2, and UMo0.4O3.4 in nitrating atmosphere results in formation of water-soluble uranium compounds and of the water-insoluble phase MoO3·2H2O. Rapid separation of the solution from the precipitate in reaction of UO2MoO4, UMo1.7O7.2, and UMo0.4O3.4 conversion products with water allows efficient transfer of U into the solution, with Mo remaining in the form of an insoluble precipitate. The conversion of SrMoO4 depends on the composition of the nitrating atmosphere. In the NOx–H2O (vapor)–air atmosphere, there is no SrMoO4 conversion, whereas in the HNO3 (vapor)–air atmosphere it is possible to reach ~85% conversion of SrMoO4 into water-soluble Sr compounds. Complete conversion of SrUO4 into water-soluble U and Sr compounds is reached when performing the gas-phase conversion at 130°С in both nitrating atmospheres. In the case of the HNO3 (vapor)–air atmosphere, increasing the process temperature to 150°С leads to a decrease in the amount of water-soluble U(VI) phases.