N-methylimidazolium-based Ionic Liquid:Synthesis,Application,and Mechanism In Au(?) Recovery

In this thesis,a series of N-methylimidazolium-based poly(ionic liquid)modified with Nmethylimidazole were synthesized and using for recovering the trace Au(?)in aqueous solution of complex system.Through the discussion on the recovery process of Au(?),we presented a green,economical and efficient methods to recover the gold in aqueous solution.The mechanism of the Au(?)recovery process was discussed by synthesizing the small molecule ionic liquid which contained the same functional group.The main contents were as follows:1.The physical and chemical properties of precious metals gold and their applications in different fields,as well as the nature of ionic liquids and their application prospects,are discussed in the introduction part.The advantages and disadvantages of traditional methods in precious metal separation are summarized.Based on the excellent properties of ionic liquids,we summarized the application and development of this green material in the recovery of precious metals.In view of the shortcomings of small molecule ionic liquid: water solubility and high production cost,we chose the cheap industrial PVC,benzene ethylene as the skeleton.A series of N-methylimidazolium-based poly(ionic liquid)were designed and synthesized by using the industrial intermediates Nmethylimidazole as the raw materials.The recovery of Au(?)in complex system was investigated.2.[PVC-Nim]Cl polymeric ionic liquid was synthesized by graft-modifying the skeleton of polyvinyl chloride(PVC)with N-methylimidazole.The [PVC-Nim]Cl was characterized by elemental analysis,Fourier transform infrared spectroscopy(FT-IR)and scanning electron microscopy(SEM).The effects of ionic liquid amount,enrichment time,enrichment temperature,solution pH and interfering ions on the recovery efficiency of Au(?)were studied.The results show that it is almost no influence on the gold(?)recovery by [PVC-Nim]Cl under the condition of the interfering ions Ni(?),Zn(?),Cu(?),Cd(?),Co(?)and Fe(?)with the ten times concentration to Au(?)ions.[PVC-Nim]Cl showed an excellent selectivity for Au(?).The gold-loaded [PVCNim]Cl ionic liquid was eluted at 35 ° C using an acid thiourea solution with pH = 4,and the desorption effect was good and its adsorption capacity remained substantially after several adsorption-desorption cycles.3.A series of water-soluble controllable N-methylimidazolium-based poly(ionic liquid)(PIL-MeImCl)were synthesized by polymerizing p-chloromethylstyrene with styrene and modifying with the N-methylimidazole at 100% grafting.The structure of the polymeric ionic liquid was determined by means of 1H Nuclear Magnetic Resonance Spectra(1H NMR),differential scanning calorimetry(XRD),differential scanning calorimetry(DSC)and scanning electron microscopy(SEM).The effects of factors such as the amount of polymeric ionic liquid,the time of enrichment,the reaction temperature,the pH of the system,and the interference ion on the recovery efficiency were studied in the recovery process of AuCl4-.The results show that metal ions such as Ni2+,Zn2+,Cu2+,Cd2+,Co2+ and Fe3+ have no interfere with the recovery of gold(?).The desorption of gold(?)by acid thiourea solution has realized the reproducibility of polymeric ionic liquid.PILMeImCl showed the high activity and efficiency for recovery of gold(?).In addition,in order to study the mechanism of the above reaction,we synthesized a small molecular ionic liquid([Bzmim]Cl)which has the same functional structure.[Bzmim]Cl reacted with chloroauric acid and the corresponding gold-containing ionic liquid([Bzmim][AuCl4])was obtained.The connection methods between N-methylimidazolium and AuCl4-was studied by 1H NMR,X-ray single crystal diffraction and theoretical calculation.The experimental results show that there are supramolecular effects between the N-methylimidazolium and AuCl4-in [Bzmim][AuCl4].The mechanism of reaction of the small molecule ionic liquid and the polymer ionic liquid were compared by nuclear magnetic resonance spectroscopy,Raman spectroscopy and UV-visible spectroscopy.It was reasonable to speculate that the mechanism of the recovery of gold(?)by the PIL-MeImCl was the combination of electrostatic effect and multiple weak forces between molecular.