Study On Inner-Coupled Liquid Membrane Separation Based On Ionic Liquid

Traditional chemical reactions and correlated chemical industry are the main source of pollution and most of the wastes are volatile organic compounds(VOC).Therefore,it is very essential to find green solvents to replace the organic solvents.Ionic liquids are liquid salts at or close to room temperature,which entirely consist of cations and anions.They have the unique advantages of no-toxicity,no-volatility,no-flammability,high thermal stability,wide liquid range(-100℃～200℃)and facility in recycling etc..Ionic liquids have attracted more and more attention as green solvent because of these advantages.Synthesises of intermediate 1-butyl-3-methylimidazolium bromide([BMIM]Br),hydrophilic ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate([BMIM]BF₄)and hydrophobic ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate([BMIM]PF₆)under microwave irradiation have been studied in this paper.Effects of raw material ratio,temperature, reaction time on the yield have been discussed.Subsequently,structures of the products have been identified by IR and physical properties also have been analyzed.[BMIM]PF₆ synthesized has been applied in the system of inner-coupled liquid membrane to transport phenol, p-nitrophenol and salicylic acid in the second part of the experiment.Effects of pH of the feed solution phase,initial solute concentration in the feed solution phase,sodium hydroxide concentration in the strip solution phase on transport of phenol,p-nitrophenol and salicylic acid have been studied.The optimum transport conditions have been obtained.The conclusions are as follows:(1)Optimum synthesis condition of 1-butyl-3-methylimidazolium bromide are:raw material ratio 1.1:1(n-bromobutane:n-methylimidazole),T=85℃,t=4 min;Optimum synthesis condition of 1-butyl-3-methylimidazolium tetrafluoroborate are:raw material ratio 1.2:1(NaBF₄: [BMIM]Br),T=60℃,t=6 min;Optimum synthesis condition of 1-butyl-3-methylimidazolium hexafluorophosphate are:raw material ratio 1.1:1(NH₄PF₆:[BMIM]Br,T=80℃,t=9 min.(2)Viscosities of both ionic liquids decrease as temperature increases,while conductivities are on the contrary;there is certain hydrophilicity in[BMIM]BF₄,while hydrophilicity is very weak in[BMIM]PF₆;solubilities of ionic liquids have great relationship with types of anions.(3)The optimum transport conditions of phenol:temperature 300 K,stirring speed 350 r/min,pH in the feed solution phase 3.65,sodium hydroxide concentration in the strip solution phase 0.8 mol/L;The optimum transport conditions of p-nitrophenol:pH in the feed solution phase 3.21,sodium hydroxide concentration in the strip solution phase 0.1 mol/L,ionic strength 0.4;The optimum transport conditions of salicylic acid:pH in the feed solution phase 1.0, sodium hydroxide concentration in the strip solution phase 0.3 mol/L,ionic strength 0.5.(4)There are retention phenomena in the system of inner-coupled liquid membrane;ionic liquids can be reused after treatment.