Study On Extraction Of Phathalate Esters And Nanosilver Particles Using Ionic Liquids

Ionic liquids are organic salts composed of cations and anions, which exsit asliquid at or near room temperature. As green solvents, ionic liquids have many uniqueadvantages, such as negligible vapor pressure, non-volatility, as well as stabilitynon-falmmable, and good solubility. As “green and designed” solvents with uniquefunctions, ionic liquids are becoming important isures in application separation andconsentration of not only in organic chemicals but also inorganic ions andnanoparticles.In this study, different ionic liquids were used as extraction solvents for phthalateesters and nanosilver particles, respectively. The extraction efficiency and mechanismof phthalate esters were analysed and discussed; In additon, factors impacting on thestability of nanosilver particles during the extraction procedures were investigatedwith DLS, UV-VIS and TEM. The important research contents and results are thefollowing:1. Two kinds of imidazolium-based ionic liquids,1-alkyl-3-alkylimidazoliumbis（trifluoromethanesulfonyl）imide （C_nmimNf₂T, n=4,6,8） and1-alkyl-3-alkyl-imidazolium hexafluorophosphate （C_nmimPF₆, n=6,8）, were used as extractionsolvents in dispersive liquid-liquid microextraction. Coupled with high performanceliquid chromatography （HPLC） determination and UV-vis spectrum, dimethylisophthalate （DMP）, diethyl phthalate （DEP）, butyl benzyl phthalate （BBP）, di-n-butylphthalate （DBP）, dicyclohexyl phthalate （DCHP） and bis（2-ethylhexyl） phthalate（DEHP） in water samples were simultaneously determined. The extraction abilities ofC_nmimNTf₂and C_nmimPF₆for phthalate acid esters were investigated. The effectfactors on extraction efficiency, including the type of ionic liquids, pH values, theamount of ionic liquids, extraction temperature, extraction time, and salting effects,were discussed. The extraction mechanism of ILs for PAEs were also discussedcombined with their physical and chemical properties.（1）The extraction efficiency of C₈mimNf₂T, C₆mimNf₂T and C₈mimPF₆forPAEs is no significant difference. Because the extraction ability of imidazole-basedionic liquids not only depends on the length of akyle of cations, but also depends ontheir anions due to their dissimilar density, solubility, viscosity, and otherthermophysical properties.（2）Ionic liquid C₈mimNf₂T and C₈mimPF₆showed better extraction abilities for the six PAEs at neutral condition, and hydrophobic affinity of PAEs molecule to ILphase and H-bonding of hydroxyl group to Nf₂T-or PF₆-are dominated driving forces.（3）The optimized conditions of C₈mimNf₂T and C₈mimPF₆for PAEs wereobtained in the followings: the amount of ILs were0.07g of C₈mimNf₂T and0.09g ofC₈mimPF₆, respectively; the extraction temperatures were at30℃and50℃, theextraction time were5mins and3mins, respectively; the optimized pH values were inthe range of6-7for both of them.（4）The salt effect on the ILs-PAEs-extraction system was different for six PAEs,the possible reasons were salting in effect to BBP, DBP, DCHP and DEHP in waterphase, on the other hand, for DMP and DEP, it’s salting in effect firstly and graduallychanged to salting out effect. In addition, ion exchange between ILs anions andchloride increased the solubility of ILs in water resulting in the decrease of theextraction efficiency.（5）Under the optimized conditions, the six PAEs were determined in real watersamples, including river water, domestic sewage and effluent after biologicalnitrification and denitrification treatment. The recoveries of the six phthalate esters inreal water samples were in the range of36.4⁸9.4%and RSDs were about in therange of0.21⁵.82%, respectively. DEHP was found both in domestic wastewater andeffluent with the concentration of22.2μg L^-1and12.4μg L^-1, respectively.2. The ionic liquid of1-octyl-3-alkyl-imidazolium hexafluorophosphate（C₈mimPF₆） was used as extraction solvent in dispersive liquid-liquid microextractionfor nanosilver particles in water coupled with UV-vis spectrum, TransmissionElectron Microscope （TEM）, and Dynamic Light Scattering （DLS）. The particle sizesof nanosilver particles were measured and factors impacting on the stability includingthe amount of ionic liquid, extraction temperature, pH values and different anions andcations (including Na⁺, Ca²⁺, Fe³⁺, SO₄^2-) were investigated..（1）Ionic liquid, C₈mimPF₆could extract nanosilver particles in water andmaintain their original size and structures under the following extraction conditions:the amount of C₈mimPF₆was0.10g, extraction temperature was30℃, pH valueswere in the range of5⁸, and without additions of cations and anions.（2）Nanosilver particle size in ionic liquid phase can keep stable during thenormal temperature （20⁴0℃）, but when the temperature increased above50℃, itwas distinctly found the aggregation of nanosilver particles. （3） Because of the stable structure of electric double layer of nanosilverparticles, their sizes can not be changed under pH5⁸.（4） The additions of cations and anions during the extraction proceduresresulted in the aggregation of nanosilver particles. The cations showed stronger abilityof impacting on the aggregation of nanosilver particles than anions under the sameconditions. Among the cations, the ability of impacting on the aggregation is Fe³⁺>Ca²⁺> Na⁺.