Thermodynamics and mechanism of Th(IV) extraction from nitrate medium with cyanex 272 in kerosene

Batch extraction investigation was carried out to elucidate the stochiometry of the extracted Th(IV) species. The effects of nitric acid concentration, extractant concentration and temperature were studied. The results showed that the extraction of thorium follows solvation mechanism in the low  (0.001 mol L-1) and high (8 mol L-1) nitric acid concentration, while the cation exchange mechanism dominates the middle acidic area (1 mol L-1). The extracted species was found to be Th(OH)2(NO3)A.HA on the basis of the slope analysis method. The results of the thermodynamic investigations indicated that the extraction process is spontaneous (DG<0), exothermic (DH<0), and less random in nature (DS<0). The value of activation energy of the extraction reaction was calculated to be 17.46 kJ mol-1 which indicates that the extraction reaction is controlled  by the diffusion process.