Kinetics and Mechanism of Sr(Ⅱ) 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 behaviors of Sr(Ⅱ) in TODGA/n-dodecane HNO₃ system were studied, including stirring speed, specific interface, extractant concentration in n-dodecane, Sr²⁺ concentration of aqueous phase, HNO₃ concentration of aqueous phase and temperature. The results show that the extraction process is controlled by diffusion mode under 130 r/min of stirring speed and by chemical reaction mode above 150 r/min. The extraction rate equation and the apparent extraction rate constant of Sr(Ⅱ) by TODGA/n-dodecane in (170±2) r/min and (25±0.1)℃ are as follows: 
r₀= ((dc_org(M)/dt) |_t=0)=k• (S/V)c^0.91_aq,0(Sr)c^0.73_aq,0(HNO₃)c^0.87_org,0 (TODGA)
k=(22.5±2.5)×10^-3mol^-1.51•L^1.51•min^-1•cm；E_a(Sr(Ⅱ))=(24.3±0.7)kJ/mol.