Selective liquid phase micro-extraction of metal chloro-complexes from saline waters using ionic liquids

Existing methods for the extraction of priority metallic pollutants as Ag, Cd, Cu, Ni and Zn from saline waters present limited efficacy due to the high complexity of the water matrix, which affects metals speciation. There is a lack of reagents for the efficient extraction of the metal chlorocomplexes formed at the natural pH of saline waters, requiring tedious and reagent consuming processes. To develop a simple method for the efficient micro-extraction of metallic chlorocomplexes in saline waters, two task specific ionic liquids (TSILs) are proposed. The TSILs methyltrioctilammonium hexylsulfanyl acetate ([N-1888] [C6SAc]) and methyltrioctilphosphonium hexylsulfanyl acetate ([P-1888][C6SAc]) have been supported on a solvent bar micro-extraction (SBME) device and applied to the micro-extraction of Ag, Cd, Cu, Ni and Zn from seawater, as well as inland and marshland salt-pan waters. The extraction efficacy was related with the formation of negatively charged chlorocomplexes, being higher for Cd, Ag and Zn than for Cu and Ni. Concluding, the proposed methodology can be considered as a valuable and simple tool for the selective extraction of metals from saline and hypersaline natural waters. (C) 2020 Elsevier Ltd. All rights reserved.