System for mercury preconcentration in natural waters based on a polymer inclusion membrane incorporating an ionic liquid

In this study, we have evaluated two different ionic liquids (IL) as extractants based on the same cation (trioctylmethylammonium) but bearing the anion thiosalicylate (TOMATS) or salicylate (TOMAS). Both IL have been incorporated as carriers in polymer inclusion membranes (PIMs), and mercury (Hg) has been pre-concentrated using a special device. Results show that among the tested IL, TOMATS has given better results. A PIM made of 50% cellulose triacetate, 30% TOMATS and 20% nitrophenyl octyl ether as a plasticizer enabled the effective transport of Hg to a 10(-3)M cysteine solution used as a stripping phase. This novel and simple PIM-device system allows the transport of Hg at low concentration levels in different types of natural waters such as rivers, groundwater and seawater without any previous treatment. Since no matrix effect was observed on Hg transport efficiency with different waters, this newly developed PIM-system could be used as a global detection system for this metal. The effect of biofilm growth on the surface of PIMs has been investigated for the first time, and no significant differences on Hg transport have been found when using a fresh PIM and a PIM deployed for 7 days in a pond.