SEPARATION OF HEAVY-METALS BY HIGH-SPEED COUNTERCURRENT CHROMATOGRAPHY

Separation of heavy metal elements such as Co, Cu, Fe(II), Fe(III), Mg, and Ni was performed with a high-speed CCC coil planet centrifuge equipped with a multilayer coil. The two-phase solvent systems used for the separation were composed of n-heptane containing bis(2-ethylhexyl) phosphoric acid (stationary phase) and diluted citric acid (mobile phase), where the distribution ratios of the elements can be optimized by selecting a proper acid concentration. The mobile phase was eluted through the column at a flow rate of 5.0 mL/min while the apparatus was rotated at 800 rpm. Continuous detection of the metal elements was effected by measurement of the emission intensity with direct current plasma atomic emission spectrometry (DCP-AES), where the elution curve was obtained by on-line monitoring of each emission signal. Each metal element was well resolved at high partition efficiencies ranging from 200 to 3600 theoretical plates.