USE OF D2EHPA-MEDIATED LIQUID MEMBRANES FOR HEAVY METAL IONS SEPARATION: A REVIEW

The removal and recovery of heavy metal ions by various types of liquid membranes (LMs), coupled with the commercial extractant di-2-ethylhexyl phosphoric acid (D2EHPA) as carrier, have been extensively studied by many researchers. In this paper, the D2EHPA-mediated LM systems used for transport of heavy metal ions are classified, briefly summarized, and reviewed. The effects of the system chemical compositions and the LM configurations on the separation selectivity and the transport efficiency are evaluated. It seems that depending on the way of choosing the chemical composition of the D2EHPA system, the formed LMs can separate selectively one or a mixture of heavy metal ions. Practically, D2EHPA-mediated LMs can be applied in a laboratory-scale as separation and preconcentration step for a heavy metal ion over the detection limits of routine analytical instruments. For large-scale applications on the removal and recovery of the heavy metal ions from waste water or industrial effluents, further modifications and improvements to the existing LM configurations should be developed in order to surmount certain problems such as slow transport rate or reduced stability of some LMs.