Svetlana V. Smirnova

Task-specific ionic liquid trioctylmethylammonium salicylate as extraction solvent for transition metal ions

A quaternary ammonium-based room temperature ionic liquid trioctylmethylammonium salicylate (TOMAS) has been studied as an extractant of transition metal ions (Fe(3+), Cu(2+), Ni(2+), Mn(2+)) in aqueous solutions. The effect of pH value on the recovery of metal ions has been investigated. The mechanism of extraction into the ionic liquid has been proposed. The possibility of stripping voltammetric determination of transition metals in aqueous solutions using TOMAS-modified electrodes has been demonstrated.

18-Crown-6 and dibenzo-18-crown-6 assisted extraction of cesium from water into room temperature ionic liquids and its correlation with stability constants for cesium complexes.

The pH-profiles of the extraction of Cs+ into four conventional (1-butyl-3- methylimidazolium hexafluorophosphate and bis[trifluoromethyl)sulphonyl]imides of 1- butyl-3-methylimidazolium, 1-hexyl-3-methylimidazolium, and 1-(2-ethylhexyl)-3-methylimidazolium) and two novel (trioctylmethylammonium salicylate and tetrahexyl-ammonium dihexylsulfosuccinate) room temperature ionic liquids have been determined both in the absence and in the presence of crown ether (18-crown-6 or dibenzo-18-crown-6). The pH-profiles of distribution ratio of crown ethers have been established in the same conditions. The relationship of cesium extraction efficiency both with the stability of its complexes with crown ethers and crown ethers’ distribution ratio has been clarified.

Hydrophobic–hydrophilic ionic liquids for the extraction and determination of metal ions with water-soluble reagents

Tetraoctylammonium N-lauroyl sarcosinate and trioctylmethylammonium salicylate are water-immiscible solvents which contain a large amount of dissolved water and may be called “hydrophobic–hydrophilic” ionic liquids (HHILs). We found that several representative water-soluble reagents – Arsenazo I, Arsenazo III, Alizarin Red S, Nitroso-R salt, and Xylenol Orange – are strongly partitioned into the HHIL phase from aqueous solutions over a wide pH range. Metal ions that form complexes with these reagents are extracted efficiently from aqueous solutions. We studied the details of extraction in two representative systems, Sc(III) with Arsenazo III and Co(II) with Nitroso-R salt. A sensitive, selective, and rapid procedure for the extraction-photometric determination of cobalt with HHILs and Nitroso-R salt has been developed.

Extraction of Nitrates of Alkali and Alkaline Earth Metals with Crown Ether into Hydrophilic Ionic Liquid in the Presence of Salting out Agent

We show that the hydrophilic liquid N-butyl-4-methylpyridinium tetrafluoroborate is suitable for the extraction of metal ions with dicyclohexyl-18-crown-6. We used magnesium sulfate as salting-out agent, resulting in the formation of two immiscible phases in the ionic liquid-water system. The pH profiles of the extraction of alkali and alkaline earth metals have been determined; the influence of the concentration of the salting-out agent on recovery has been investigated.

Extraction of amino acids with di(2-ethylhexyl)phosphoric acid in the presence of dicyclohexyl-18-crown-6

Extraction of amino acids from aqueous solutions into chloroform with di(2-ethyl-hexyl)phosphoric acid was studied. The extraction efficiency decreases in the sequence Trp>Phe>Leu>Arg>Lys>He>Ala>Gly. The addition of dicyclohexyl-18-crown-6 improves the efficiency and kinetics of extraction of most amino acids. The extraction degree depends on the concentration of the crown ether.

Multielement Determination of Trace Heavy Metals in Water by Microwave-Induced Plasma Atomic Emission Spectrometry after Extraction in Unconventional Single-Salt Aqueous Biphasic System

For the first time liquid-liquid extraction was used for the preconcentration of heavy metals prior to their determination in water by microwave-induced plasma atomic emission spectrometry (MP-AES). Extraction of Pb(II), Cd(II), Co(II), Ni(II), Zn(II), and Cu(II) was performed in unconventional aqueous biphasic system (ABS) formed by addition of hydrophobic solid salt, namely, tetrahexylammonium bromide, to aqueous sample, with neither organic solvents nor salting-out agents being used. The metal ions were quantitatively recovered with 4-(2-pyridylazo)-resorcinol (PAR). The extract was diluted with ethanol/HCl and introduced directly into an MP-AES instrument. The factors influencing extraction (pH, reagent concentration, phase contact time, etc.) and MP-AES detection parameters were studied and optimized. For the developed method, limits of detection of 1.3, 4.9, 0.06, 1.2, 4.2, and 3.2 μg L-1 were obtained for cadmium, cobalt, copper, nickel, lead, and zinc, respectively, providing from 60- to 500-fold improvement as compared with the analysis without preconcentration. The method was applied for the analysis of two certified reference materials (CRM) of wastewater and surface water as well as the samples of well and seawater. Coupling MP-AES with ABS extraction significantly extends the capabilities of the method, especially for the analysis of high salinity waters.

Extraction of cadmium, lead, cobalt, copper, and zinc ions from aqueous solutions into hydrophilic–hydrophobic ionic liquids

Extraction of cadmium(II), lead(II), cobalt(II), copper(II), and zinc(II) into ionic liquids tetraoctylammonium N-lauroyl sarcosinate and trioctylmethylammonium salicylate is studied. Cadmium(II), lead(II), copper(II) in tetraoctylammonium N-lauroyl sarcosinate and copper(II) in trioctylmethylammonium salicylate are quantitatively extracted from neutral and weakly alkaline solutions in the absence of additional reagents. The effect of the composition of aqueous and organic phases, as well as the contact time, on metal extraction is investigated.

The method of appearing solvent: Extraction of metal ions from aqueous solutions into in situ forming ionic liquid

The simultaneous dissolution of tetraoctylammonium bromide and sodium N-lauroyl sarcosinate in water leads to the in situ formation of a water-immiscible ionic liquid, tetraoctylammonium N-lauroyl sarcosinate. The new phase formed can extract cadmium, cobalt, copper, nickel, lead, and zinc ions from aqueous solution in the presence of 4-(2-pyridylazo)resorcinol (PAR), while it can extract cadmium ions in the absence of PAR.

Solubilization of 4-(2-Pyridylazo)resorcinol in hydrophobic–hydrophilic ionic liquids and extraction of heavy metal ions from aqueous solutions

The distribution of 4-(2-pyridylazo)resorcinol, PAR (5 × 10–4–1 × 10–2 M) in the systems tetraoctylammonium N-lauroylsarcosinate (TOALS)–water and trioctylmethylammonium salicylate (TOMAS)–water is studied. It is shown that the distribution coefficient of PAR does not depend on the ionic state of the reagent in aqueous solution at pH 2.3–11.8; the logD values are 3.5 and 3.7 (Vo: Vw = 1: 20) for TOALS and TOMAS, respectively. The conditions for quantitative extraction of the ions of cadmium(II), lead(II), cobalt(II), copper(II), and zinc(II) in TOALS and TOMAS in the presence of 4-(2-pyridylazo)resorcinol are determined.