Europium extraction into D2EHPA: Kinetics of mass transfer in a stirred cell

The kinetics of europium extraction into D2EHPA is studied in a stirred cel l. For the range of concentrations investigated (10(-6)kmol/m(3) less than or equal to [Eu3+] less than or equal to 10(-4) kmol/m(3); 0.01 kmol/m(3) l ess than or equal to [H+] less than or equal to 0.15 kmol/m(3); 0.001 kmol/ m(3) less than or equal to [(HX)(2)] less than or equal to 0.05 kmol/m(3)) extraction rate increases linearly with stirring speed, i.e. mass transfer is limited by diffusion. An increase in proton concentration or a decrease of complexant concentration reduces fluxes but does not change the extracti on regime. Based on the found equilibrium constant and individual mass tran sfer coefficients, extraction rates are calculated showing good agreement w ith experimental data. The influence of concentrations on extraction rate i s explained by the gradient between bulk concentration and interfacial conc entration as the driving force for mass transfer in an extraction system co ntrolled by diffusion.