Abstract
The extraction of sulfuric acid has been investigated by tri-n-dodecylamine (\overline TDA ) in kerosene in the presence of octanol-1 as modifier. The effect of octanol-1 has been studied on the equilibrium constant of (TDAH)2SO4 and TDAHHSO4 formation in the concentration range from 5 to 25% v/v and within the temperature range from 25 to 50 o C. The equilibrium constants (K1 and K2, at 25 o C), the enthalpy (&Delta ;Ho1, Δ Ho2) and the entropy (Δ So 1, Δ S o2) changes were calculated for two extraction reactions of sulfuric acid by tri-n-dodecylamine containing 10% octanol-1 and they were found to be 109.642 l4/mol4, 10-0.899 l/mol, -99.11, -22.17 kJ/mol, -0.149, -0.063 kJ/mol.K, respectively. The two reactions are: 2 \overline TDA + 2 H++SO42- \rightleftarrows K1 \overline (TDAH)2 SO4 and \overline (TDAH)2 SO4 H^+ + HSO4^- \rightleftarrows K2 2 \overline TDAHHSO4 .
Highlights
Tertiary amines dissolved in aliphatic diluents such as kerosene have been widely and satisfactorily used in the extraction of numerous metal ions such as uranium(VI), molybdenum(VI), tungsten(VI), chromium(III, VI), and vanadium(V) from sulfate and sulfuric acid solutions, due to their reasonable cost, and high yield, as a result of solubility or degradation properties [1,2,3,4,5,6]
This means that one mole of TDA reacts with one mole of H2SO4 and TDAHSO4 is the only species present in the organic phase when the concentration of sulfuric acid in the aqueous phase ≥ 2.5 M
Knowing the initial concentration of TDA and the concentration of H2SO4 in the aqueous and organic phases, the equilibrium concentration of TDA, (TDAH)2SO4 and TDAHSO4can be calculated from equations 30, 27 and 28, respectively, and the equilibrium constant K2 may be obtained from Eq 24
Summary
Tertiary amines dissolved in aliphatic diluents such as kerosene have been widely and satisfactorily used in the extraction of numerous metal ions such as uranium(VI), molybdenum(VI), tungsten(VI), chromium(III, VI), and vanadium(V) from sulfate and sulfuric acid solutions, due to their reasonable cost, and high yield, as a result of solubility or degradation properties [1,2,3,4,5,6]. The extraction of 0.49 M sulfuric acid by various concentrations of tridodecylamine/kerosene containing 10 % octanol-1 was studied at 25 ̊C and at an organic to aqueous phase ratio (Vorg/Vaq=1).
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