Kinetics and mechanism of Am(III) extraction with TODGA

In the present paper, N,N,N’,N’-tetraoctyl diglycolamide (TODGA) as the extractant and n-dodecane as the diluent, the extraction kinetics behavior of Am(III) in TODGA/n-dodecane–HNO₃ system were studied, including stirring speed, the interfacial area, extractant concentration in n-dodecane, extracted ions concentration, acidity of aqueous phase and temperature. The results show that: the extraction process is controlled by diffusion mode under 130 rpm of stirring speed and by chemical reaction mode above 150 rpm. The extraction rate equation and the apparent extraction rate constant of Am(III) by TODGA/n-dodecane in 170 rpm and at 25 °C are followed as: $$ \begin{aligned} r_{0} = \left. {\frac{{{\text{d}}{\text{M}}]_{{{\text{org}} .}} }}{{{\text{d}}{{t}}}}} \right|_{t = 0} & = k\,\frac{S}{V}\left {\text{Am}} \right]_{{{\text{aq}} . ,0}}^{0.94} \left {{\text{HNO}}_{3} } \right]_{{{\text{aq}} . ,0}}^{1.05} \left {\text{TODGA}} \right]_{{{\text{org}} . ,0}}^{1.19} \\ & \quad k = \left( {24.17 \pm 3.43} \right) \times 10^{ - 3} \,{\text{mol}}^{ - 2.18} \,L^{2.18} \,{ \hbox{min} }^{ - 1} \,{\text{cm}},E_{\text{a}} \left( {{\text{Am}}\left( {\text{III}} \right)} \right) = 25.94 \pm 0.98{\text{kJ/mol}} .\\ \end{aligned} $$