Coprecipitaton of uranium and thorium macroquantities in UO22+-Th4+-NO3--CO32-(OH-)-H2O system and investigation of solid phases

Solid phases formed under coprecipitation of uranium (6) and thorium from carbonate-containing and alkaline solutions are studied using chemical analysis, IR spectroscopic, DTA and thermogravimetric methods. It is ascertained, that solid phases of the system investigated are of variable chemical composition depending on coprecipitation conditions and contain certain quantities of water and carbonate-ions. Practically compute uranium and thorium coprecipitation is observed at pH=8.0 from alkaline solution. In systems with sodium carbonate the maximum of relative coprecipitation of uranium with thorium is typical to a system with final value pH=5.0. At pH=8.0 in carbonate medium thorium coprecipitates uranium in a lower degree than at other pH value. Coprecipitation degree correlates with water and carbonate-ion content in precipitates: the higher the atomic-molecular ratio of uranium to H2O and CO2 the lower the precipitation degree is