Liquid-liquid extraction of chromium (VI) from sulfuric acid solutions using tri-n-dodecylamine/kerosene

Abstract

Extraction of chromium(VI) from sulfuric acid solutions with tri-n-dodecylamine containing octanol-1 as a modifier in kerosene was investigated. All parameters influencing the extraction of chromium(VI) (time of agitation, concentrations of chromium(VI), sulfuric acid, tri-n-dodecylamine and temperature) were studied. The mathematical treatment of the obtained data enabled us to propose a mechanism of chromium(VI) extraction by tri-n-dodecylamine as follows: 2‾ TDAHHSO₄ + Cr₂ O₇^2- ↔ ‾ (TDAH)_2 Cr₂ O₇ + 2 HSO₄^- The logarithm of the equilibrium constant of the extraction reaction was found to be 10.6. Stripping of more than 99% of chromium(VI) from the organic phase of tri-n-dodecylamine/kerosene can be easily achieved in two stages using 0.05 M sodium carbonate solution. The synergistic effect of tri-n-butylphosphate and tri-n-octylphosphine oxide on the extraction of chromium(VI) were also studied.