Comparison of single-phase and two-phase measurements in extraction, separation and back-extraction of Cd, Zn and Co from a multi-element matrix using Aliquat 336

Cd and Zn were separated from Co, from chloride solutions containing 16 different metal ions. The separation method used was liquid–liquid extraction. Two different chloride concentrations, 0.5 and 5 mol/kg, were tested. Aliquat 336 in toluene was used as extractant. It is shown that Li2SO4 can back-extract the metals. Distribution ratios were determined using radiotracers or inductively coupled plasma mass spectrometry. The results of these methods are compared. In particular, we demonstrate that the determination of low distribution ratios are limited by the uncertainty of the measured concentration of the feed solution.