The effect of ionic strength on the extraction of Thorium(IV) from nitrate solution by didodecylphosphoric acid (HDDPA)

Abstract

Extraction of Th(IV) ion from nitrate media at high ionic strength (I = 1.00, 3.00, 5.00 and 7.00 M) using didodecylphosphoric acid was studied. The effect of HDDPA concentration, ionic strength, pcH and temperature on the extraction processes have been studied in nitrate media. From the equation of the extraction process, (Kex) extraction constant can be calculated from the distribution ratio Dc values at different temperatures. Enthalpy, free energy and entropy changes were determined. The composition of the complex formed were established to correspond to [Th(X)4(HR2)Y]org, where X=NO3- and Y = 1 or 2, HR2 = HDDPA molecule and R2 = deprotonated HDDPA molecule.