Hydrolytic Behavior of Th⁴⁺, UO₂²⁺, and Ce³⁺ Ions at Various Temperatures

The hydrolytic behavior of Th4+, UO22+, and Ce3+ was investigated using the potentiometric method at elevated temperatures in KCl medium. For each metal ion, stability constants were obtained from the pH-metric data using the program HYPERQUAD2006. The formation of [Th(OH)]3+, [Th(OH)2]2+, [Th(OH)3]+, Th(OH)4, [Th4(OH)8]8+, and [Th6(OH)15]9+ for the thorium ion, [UO2(OH)]+, [(UO2)2(OH)2]2+, [(UO2)3(OH)4]2+, and [(UO2)3(OH)5]+ for the uranyl ion, and [Ce2(OH)]5+, [Ce2(OH)2]4+, Ce(OH)3, and [Ce2(OH)5]+ for the cerium ion was taken into consideration. In addition, the effect of temperature on the stability constants was studied, and thermodynamic parameters were derived and discussed.