Separation Of Au(?),Pd(?)and Pt(?) By Ion Liquid Extraction

In this paper,we synthesized a series of ionic liquid,and studied their extraction performance for noble metal Au???,Pd???and Pt???.The extraction performance of hydrophilic ionic liquid?1-alkyl-3-methylimidazo bromine?[Cnmim]Br,n = 4,6,8??for Au???from alkaline cyanide solution were studied.The results show that hydrophilic ionic liquid mixed with the salting-out agent K2HPO4 formed a two-phase system,Upper phase is ionic liquid-rich phase and the lower phase is salt-enriched phase.Then,we studied the effects of equilibrium time,concentration of inorganic salt,concentration of Au???and pH on the extraction behavior at room temperature.The results show that the extraction capacity of the ionic liquid aqueous two-phase system is[C6mim]Br>[C8mim]Br>[C4mim]Br.The bright yellow substance on the copper plate was obtained from the Au???phase by electrolytic deposition,and the EDS and XRD analysis proved that this substance is Au???with high purity.The phase of the ionic liquid was analyzed by FTIR and MS,It show that the Au?CN?₂^-was extracted into the upper phase of ionic liquid aqueous two-phase system followed the ion exchange principle.We synthesized three hydrophobic quaternary ammonium salt ionic liquids,including[A336][SCN],[A336][MTBA]and[A336][Mal].The extraction and separ-ation of Au???from alkaline cyanide solution were studied using the organic phase composed of ionic liquid as extractant,TBP as modifier and 260 solvent oil as diluent.The extraction rate of the three ionic liquids could reach up to 99.75%,99.92%,99.94%under the optimum conditions including extraction time of 10 minutes,the phase ratio of 1:1,25? and pH?10.5.Then used KSCN,2-methylthio-benzoic acid?MTBA?and methyl maltol?Mal?solution were used to reverse extract Au???from organic phase,and the extraction rate was above 90%.The transfer mechanism of Au?CN?₂^-into the ionic liquid was proved to be an anion exchange reaction.The compound of extraction complex was obtained by logarithmic method.The structure of[A336][SCN]is[(C₈H₁₇)₃?CH₃?N⁺·2TBP][Au?CN?₂^-],The structure of[A336][MTBA]and[A336][Mal]is:[(C₈H₁₇)₃?CH₃?N⁺]·[Au?CN?₂^-].The extraction of palladium???from hydrochloric acid solutions of various concentrations were investigated using ionic liquid[A336][SCN],[A336][MTBA]and[A336][Mal]as the extractant,TBP as the modifier,260 solvent oil as the diluent The extraction of Pd???is very effective under the optimum conditions including extraction time,concentration of extractant,concentration of HCl,concentration of NaCl and pH on the extraction rate.The results show that[A336][SCN]can extract Pd???only at high acidity.But the[A336][MTBA]/[A336][Mal]system can extract Pd???under low acidity.The acid thiourea concentration of 200 mg L-1 achieved the high back extraction rate,and had the good reprocessing performance.The organic phase before and after extraction were analyzed by IR and UV.The results show that the ionic liquid extract palladium followed the anion exchange mechanism.The extraction equation was determined by logarithmic method.the extraction complex of[A336][SCN],[A336][MTBA]and[A336][Mal]is[(C₈H₁₇)₃?CH₃?N⁺]2·[PdCl42-]·TBP,[(C₈H₁₇)₃?CH₃?N⁺]2·PdCl2-],[(C₈H₁₇)₃?CH₃?N⁺]2 ·[PdCl42-]·TBP.In this study,selective extraction and recovery of Pd?II?and Pt?IV?from acidic solution were investigated using ionic liquid[A336][Mal].The extraction rates of Pd?II?and Pt?IV?reached 99.94%,99.67%after 10 min under the conditions,25?,the phase rate of 1:1,and 0.1 mol L-1 HCl in acidic solution.The results show that PdCl42-extraction is stronger than PtCl62-.The organic phase of Pd???and Pt???were separated by two-steps.Pt???was back extracted using KSCN at first,The reverse extraction rate was 98.35%,then the reverse extraction rate of Pd???was 82.42%using the Thiourea as extraction.The effectively extraction and separation of Pd???and Pt???were realized.