Kinetics of extraction and stripping of Ti(IV) in HCl–D2EHPA–kerosene system using the single drop technique

• Published in: Hydrometallurgy Vol. 55; no. 1; pp. 57 - 77
• Main Authors: Biswas, R.K., Begum, D.A.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.02.2000; Elsevier
• Subjects: Applied sciences; Backward; Exact sciences and technology; Extraction; Forward; HCl–D2EHPA–kerosene system; Hydrometallurgy; Kinetics; Metals. Metallurgy; Production of metals; Production of non ferrous metals. Process materials; Ti(IV); Forward; Extraction; Kinetics; Ti(IV); Backward; HCl–D2EHPA–kerosene system; Stripping; Titanium IV; Chemical engineering; Data processing; Experimental study; Kerosine; Hydrometallurgy
• ISSN: 0304-386X; 1879-1158
• DOI: 10.1016/S0304-386X(99)00074-2

Kinetics of the forward extraction of Ti(IV) and stripping of Ti-D2EHP chelate in HCl–di-2-ethylhexylphosphoric acid (D2EHPA, H 2A 2) kerosene system have been investigated using the single drop falling technique. In the lower concentration region of Ti(IV), the rate of forward extraction at 303 K can be represented by: J f (kmol m −2 s −1)=10 −4.02[Ti 4+][H 2A 2] (0)[H +] −1 and this suggests that the rate-determining step is: TiO (i) 2++HA 2(i) −→[TiO(HA 2)] (i) +. In the higher concentration region of Ti(IV), the rate of forward extraction expression at 303 K is represented by: J f (kmol m −2 s −1)=10 −6.06[H 2A 2] (0)[H +] −1; and this suggests that the diffusions of H 2A 2 to and of H + from the interface are rate-determining. The activation energy ( E a) of 98±3 kJ/mol is decreased to 18±4 kJ/mol on increasing Ti(IV) concentration from 2.08 to 41.6 mM. The Δ H ± and Δ S ± values in forward extraction have been evaluated. The rate of stripping of Ti(IV) at 303 K is governed by: J b (kmol m −2 s −1)=10 −8.67[Ti–D2EHP] 3(0) 1/3(1+22.4[H 2A 2] (0)) −1[H +]. The rate-determining steps have been assigned in both lower and higher concentration regions of H 2A 2. In the higher concentration regime of D2EHPA, the values of E a, Δ H ± and Δ S ± have been estimated to be 94 kJ/mol, 92 kJ/mol, and −108 J/K mol respectively. The equilibrium constant obtained from the rate study seems comparable with that obtained from the rate studies.