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), [Th-4(OH)(8)](8+), and [Th-6(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 [Ce-2(OH)](5+), [Ce-2(OH)(2)](4+), Ce(OH)(3), and [Ce-2(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.