Study On New Solvent Extraction System Of Au(?) In Hydrochloric Acid Medium

In this paper,the two of novel imidazolium ionic liquids were synthesized.Three kinds extraction systems,which diethlyeneglycol ether,phosphonium salt,and pyrrolinidium salt were established to extract and separate Au?III?.The mechanisms of the extraction were studied preliminarily.The results showed that Au?III?can be quantitatively extracted by diethlyeneglycol ether?DEGE?in hydrochloric acid medium.The optimum extraction parameters:Au?III?concentration in aqueous phase,0.1g/L;DEGE concentration in the organic phase,20%?v/v?;phase ratio?O/A?,1.0;hydrochloric acid concentration,5.0 mol/L,and equilibrium time,2 min.The percentages of extraction of Au?III?were>99.0%under the optimum extraction conditions.Au?III?was stripped using a mixed solution of0.1%Na₂SO₃ and 4%ammonia,or the thiourea of 0.02 mol/L CS?NH₂?₂ in 0.5M HCI,the stripping ratios of the two methods were above 99.0%.The extraction reaction can be carried out at room temperature.A total of seven sequential extraction and stripping cycles,the recovery ratios for Au?III?were always above 94.0%.The separation factors of?_Au/M(M:Pd?II?,Pt???,Rh???,Fe³⁺,Cu²⁺,Co²⁺and Ni²⁺)were all greater than 1.0×10⁴.DEGE concentration of 20%?v/v?was found to be sufficient to effectively separate Au?III?from the multi-metal mixed solution.FT-IR and UV-visible spectroscopy revealed that the mechanism for the extraction of Au?III?from hydrochloric acid solution with DEGE follows an ion-association mechanism.The novel phosphonium-based ionic liquids,trihexyl?tetradecyl?phosphonium bromide?TTPB?,trihexyl?tetradecyl?phosphonium decanoate?TTPD?,and trihexyl?tetradecyl?phosphonium hexafluorophosphate?TTPHP?,were used for the construction of novel systems for the extraction and separation of Au?III?.The key extraction parameters such as hydrochloric acid concentration,extractant concentration,extraction time etc.,were investigated.Three new systems of the phosphonium-based ionic liquid extraction of Au?III?from hydrochloric acid medium were established.Under the optimum conditions,the percentages of extraction of Au?III?were all more than 99.0%.The thermodynamic data showed that the extraction process were all the exothermal reactions.The separation factors of?_Au/M(M:Pd?II?,Pt???,Rh???,Fe³⁺,Cu²⁺,Co²⁺and Ni²⁺)were all greater than 2.4×10².Au?III?can be efficiently stripped from the organic phase with 0.02 mol/L CS?NH₂?₂/HCI solution.The ion-exchange mechanisms were confirmed for those systems by the method of equimolar continuous transformation method,infrared spectrum and ultraviolet spectrum.The saturated loading capacities of the system for Au?III?followed the order TTPB>TTPD>TTPHP.The experiment results showed that Au?III?can be quantitatively extracted by1-?Chloro-1-pyrrolidinylmethylene?pyrrolidinium hexafluorophosphate?PyCIU?in hydrochloric acid medium.The optimum extraction parameters:Au?III?concentration in aqueous phase,0.1g/L;PyCIU concentration in the organic phase,3.6 mmol/L;phase ratio?O/A?,1.0;hydrochloric acid concentration,0.1mol L^-1,and equilibrium time,10min.The percentages of extraction of Au?III?were>99.0%under the optimum extraction conditions.Au?III?can be efficiently stripped from the organic phase with0.02 mol/L CS?NH₂?₂/HCI solution.The stripping percentage of Au?III?was>98.0.The separation factors of?_Au/M(M:Pd?II?,Pt???,Rh???,Fe³⁺,Cu²⁺,Co²⁺and Ni²⁺)were all greater than 6.2×10².The mechanism of extraction reaction was deduced to be both coordination and ion exchange mechanism.Two new ionic liquids,1-vinyl-3-?2-amyl?imidazolium bromide,1-vinyl-3-?3-methylbutyl?imidazolium bromide,were synthesized,and their structures were characterized by IR,NMR and HRMS.