Stabilities and thermodynamics of uranyl(II) and thorium(IV) complexes of 2-mercaptoethanol

摘要

The complexation of UO2+2and Th+4ions with 2-mercaptoethanol has been studied by potentiometric and conductometric titration techniques. Uranyl ion forms 1∶1 and 1∶2 complexes in the pH-range 3.3–6.5 and thorium ion forms 1∶2, 1∶3, and 1∶4 complexes in the pH-range 3.2–4.8 with considerable overlapping. Their logkstab.values are determined at 10, 20, and 30°C at ionic strength μ=0.1M(NaClO4) by applyingCalvin-Melchior'sextension of theBjerrummethod. The overall changes in thermodynamic functions ΔG, ΔH, and ΔSaccompanying complexation determined at 20°C are −19.48 kcal/mole, −22.77 kcal/mole, −11.23 cal/deg·mole for uranyl complexes and −33.94 kcal/mole, −4.93 kcal/mole, 99.00 kcal/deg·m