A new method was developed for group separation of some heavy metals (HM) from rare earth elements (REEs) followed by online individual separation of REEs. Various chelating agents were used as mobile phases such as DTPA, PDCA, NTA, HIBA and oxalic acid. These chelating agents were selected with different number of carboxylic acid groups and various geometrical structures which control the elution capability and the separation efficiency. The results showed that selective group separation of HM from REEs could be achieved by different options including 0.0005 M PDCA at pH 1, 0.005 M DTPA at pH 2, 0.1 M AHIBA at pH 2 or 0.0007 M NTA at pH 2. The selective elution of HM is attributed to the stronger complex formation between the carboxylic acid groups of the chelating agent with divalent HM ions than with trivalent REE ions especially at relatively low pH values. NTA chelating agent was selected for further investigation to test the individual separation of REEs. Finally, the optimum chromatographic conditions showed that HREEs and IREEs could be efficiently separated by 0.001 M NTA at pH 3 while LREEs were separated by 0.005M AHIBA at pH 4 followed by 0.001M PDCA at pH 2.
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