Extraction kinetics of Uranium(VI) and Thorium(IV) with Tri-iso-amyl phosphate from nitric acid using a Lewis Cell

The extraction kinetics of uranium(VI) and thorium(IV) with Tri-iso-amyl phosphate (TiAP) from nitric acid medium has been investigated using a Lewis Cell. Especially, dependences of the extraction rate on stirring speed, temperature, interfacial area were firstly measured to elucidate the extraction kinetics regimes. The experimental results demonstrated that extraction kinetic of U(VI) is governed by chemical reactions at interface with an activation energy, E_a, of 43.41 kJ/mol, while the rate of Th(IV) extraction is proved to be intermediate controlled, of which the E_a is 23.20 kJ/mol. Reaction orders with respect to the influencing parameters of the extraction rate are determined, and the rate equations of U(VI) and Th(IV) at 293 K have been proposed as $$ {text{r}} = - {text{dcUO}}_{ 2} left( {{text{NO}}_{ 3} } right)_{ 2} /{text{dt}} = 1. 80 times 10^{ - 3} left[ {{text{UO}}_{ 2} left( {{text{NO}}_{ 3} } right)_{ 2} } right]^{ 1.0 1} left[ {text{TiAP}} right]^{0. 5 5} , $$ $$ {text{r}} = - {text{dcTh }}left( {{text{NO}}_{ 3} } right)_{ 4} /{text{dt}} = 1. 8 8times 10^{ - 3} left[ {{text{Th }}left( {{text{NO}}_{ 3} } right)_{ 4} } right]^{ 1.0 4} left[ {text{TiAP}} right]^{ 1. 7 7} left[ {{text{HNO}}_{ 3} } right]^{0. 3 8} , $$ respectively.