Salomov Firdavs Dzhabborovich, Islomova Mukaddam Sadulloevna,  Badalova Mamlakat Abdukhayrovna, Ruzmatova Gulnoz Kamolovna

Annotation:

Using derivative thermogravimetry (DTG) and tensimetry with a membrane zero-manometer, it was established that the dehydration process of thorium(IV) and uranyl hydrates proceeds in stages: Th(NO3)45H2O ΔТ= 300-325K→Th(NO3)44H2O ΔТ= 330- 350 K→ Th(NO3)43H2O ΔТ= 350-390K→ Th(NO3)4H2O ΔТ= 400-425K→ Th(NO3)4 → ThO2 + NO +3NO2 + 3/2О2; UО2SО43,5H2О ΔТ= 325-370K→ UО2SО42,5H2О ΔТ= 380-420K→ UО2SО4 and the thermal decomposition of UО2SО4 ΔТ= 480-710K→ UО3 + SО3; UO2(CH3COO)22H2O ΔТ= 320-350K→ UO2(CH3COO)21.5H2O ΔТ= 350-380 K→ UO2(CH3COO)2. The subsequent step, occurring in the temperature range (370–392) corresponds to the decomposition of uranyl acetate. The onset temperatures of the process stages, determined under equilibrium conditions (by tensimetry), are shifted toward lower temperatures (by 50–70 degrees) compared to DTA data. A comparative analysis of thermal stability and the characteristics of the dehydration stages of thorium(IV) and uranyl crystallohydrates and salts was conducted.

Keywords: thorium(IV) nitrate, uranyl sulfate, and uranyl acetate crystallohydrates; dehydration; thermal decomposition; equilibria.