Synthesis Of New Task-Specific Ionic Liquids And Their Application On Extraction Of Metal Ions

Room temperature ionic liquids as an environmentally friendly solvent with many unique properties such as vapor pressures, low toxicity and "structure can be designed", have aroused increasing interest for their promising role as alternative medium in synthesis, electrochemistry and analytical chemistry. ILs can be used in place of traditional organic solvents in liquid/liquid extraction of metal ions, by adding extractants or attaching a metal ion coordinating group directly to the cation. Experimental results show that ionic liquids bearing coordinating group can significantly increased the distribution ratios of metal ions in IL phase. Task specific ionic liquid can be used in the sample pre-treatment technology to reduce the usage of volatile organic solvents, and to develop "environmentally friendly" green separation technology.In this article, two hydrophobic ionic liquids, 1-(Ethyl-3-oxobutanoate)-3-methylimidazolium hexafluorophosphate, and 1-(2-furanomethylamineethyl)-3-methylimidazolium hexafluorophosphate, were synthesized, their physical and solvent properties were determined, and then proposed a simplicity, rapidity, sensitivity, good antiinterference, less volatile organic solvents and extractants sample preparation technology to determine trace cadmium in water samples.The major contents are described as follows:1. Task-specific ionic liquids bearing 3-oxobutanoate units:synthesis and extraction behavior.A hydrophobic task specific ionic liquid containing (Ethyl-3-oxobutanoate)-functionalized imidazolium cation has been synthesized and characterized by FTIR and 1HNMR, physical and solvent properties were determined. And the extraction of Pb2+, Cd2+, Cu2+, Ni2+, Zn2+, Mn2+, Fe2+ and Cr6+ ions from aqueous solutions were investigated. In the absence of TSIL, the distribution ratios for the metal ions indicate a strong preference for the ionic liquid phase, the recovery for Zn2+, Cu2+ Ni2+ and Fe2+ were 97.0%,84.9%,55.1% and 60.9%, respectively. The metal ion can be quantitatively back-extracted from IL phase by 0.20 mol L-1 of nitric acid, so that TSIL can be reused in the extraction of metal ions as a cycle solvent. 2. Task-specific ionic liquids bearing furanomethylamine units:synthesis and extraction studiesA hydrophobic task specific ionic liquid containing furanomethylamine-functionalized imidazolium cation have been synthesized and characterized by FTIR and ]H NMR. Physical and solvent properties were determined, and studied for the extraction of Pb2+, Cd2+, Cu2+, Ni2+, Zn2+, Mn2+, Fe2+and Cr6+ ions from aqueous solutions. In the absence of TSIL, the distribution ratios for the metal ions indicate a strong preference for the ionic liquid phase, the recovery for Cu2+, Zn2+, Ni2+, Fe2+ and Cd2+ were 97.0%, 93.4%,74.6%,46.0% and 102%, respectively. A method of TSIL-based liquid-liquid microextraction can be developed to determine trace metal ions in water samples.3. Ethyl-3-oxobutanoate functionalized task specific ionic liquid based dispersive liquid-liquid microextraction/micro-volume back extraction procedure combined with electrothermal atomic absorption spectrometry for determination of trace copper in water samplesA new simple and sensitive method for rapid and selective extraction and determination of the trace levels of Cu2+ ion was developed by using task specific ionic liquids dispersive liquid-liquid microextraction preconcentration, micro-volume nitric acid back extraction separation and electrothermal atomic absorption spectrometry detection. Variables affecting the ETAAS signal and DLLME-BE conditions were optimized. The optimum conditions found were:the concentration of TSIL is 0.01 mol L-1; The concentration of nitric acid is 2.0 mol L-1; The volume of extraction solvent (BMIMPF6), disperser solvent (acetonitrile), back-extraction solvent (nitric acid) and sample are 250μL,500μL,50μL and 10 mL, respectively; The extraction time less than 0.5 min; The back-extraction time is 1 min; The enrichment factor of the method is 200; The detection limit is 0.017μg L-1. The relative standard deviation (RSD) for 5 replicates of 0.5μg L-1 Cu is 3.7%. The method was successfully applied for the determination of trace copper in water samples.4. Diethyldithiocarbamatre functionalized task-specific ionic liquid-based single drop microextraction combined with electrothermal atomic absorption spectrometry for the determination of lead in water samplesAnion-specific ionic liquid, 1-butyl-3-methylidazolium diethyldithiocarbamatre (BMIMDDTC) was used as an alternative solvent and extracant in single drop microextraction-electrothermal atomic absorption spectrometry (SDME-ETAAS) for the determation of lead in water samples. Variables affecting the ETAAS signal and SDME conditions were optimized. The optimum conditions found were:microextraction time,30 min; drop volume.5 uL; stirring rate,300 rpm; pH,5-7; the limit of detection (3 s), 0.053μg L-1; precision(RSD, n= 5) is 2.2%. The developed method was applied successfully to the determination of lead in several environment water samples.