| In this paper,a series of ionic liquid extractants was designed and synthesized.By using the binding capability of gold cyanide with quaternary ammonium cations and KSCN was used as the stripping agent,the extraction performance of noble metal Au?I?on supported liquid membranes and polymer inclusion membranes was researched in the study.By synthesizing several hydrophobic quaternary ammonium salt type ionic liquids,and[A336][SCN]is used as the main extractant.In this article,[A336][SCN]is used as an extractant to form the supported liquid membrane?SLM?,and the extraction performance of Au?I?from alkaline cyanide solution by SLM was studied.The optimum extraction conditions were optimized:under alkaline conditions with the pH value?10.5 and the stirring speed at 1000 rpm,using the ionic liquid[A336][SCN]to extract Au?I?,after the extraction for 24 h when phase ratio was 1:1,the extraction rate can reach more than 99.7%.The Au?I?in organic phase was stripped using KSCN.When the concentration of potassium thiocyanate was 3 mol/L,the stripping rate could reach 98.7%or more,and the supporting liquid membrane system had good reusability on the extraction of Au?I?.The IR spectrum analysis of the ionic liquid organic phase before and after extraction showed that the extraction of Au?I?using quaternary ammonium salt ionic liquid follows the anion exchange theory.The structure of[A336][SCN]extractioncomplexwasobtainedbylogarithmicmethod:[(C8H17)3?CH3?N+]·[Au?CN?2-].Using[A336][SCN]as the main extractant,PVDF as the polymer matrix and NPOE as the plasticizer to form the polymer inclusion membrane?PIM?,the extraction of Au?I?from alkaline solution by polymer inclusion membrane was studied.The effect of membrane concentration,pH value,stirring speed,KSCN concentration,NaCl concentration,anion species of the extractant,polymer species of PIM,plasticizer species of PIM,phase ratio of feed phase and stripping phase on the extraction experiment were investigated.The experimental results showed that at a stirring speed of 400 rpm,when the composition of the polymer inclusion membrane was 0.15g PVDF?50 wt%?-0.12g[A336][SCN]?40 wt%?-0.03g NPOE?10 wt%?,the pH value in the aqueous phase was 10.5,when the concentration of sodium chloride in aqiueous phase was 0.2 mol/L,the extraction rate of Au?I?was 98.5%,when the phase ratio was 1:1,after 24 hours of extraction,the stripping rate can reach 98.0%.The extraction rate of the PIM using[A336][SCN]as the extractant was slightly slower than that with the support liquid membrane,when the KSCN concentration is 3mol/L,the PIM had the highest stripping rate in the stripping phase and the membrane has the good reusability.Electrolysis process can increase the extraction speed and improve the deposition rate of gold.Among several new designed ionic liquids,the extraction performances of[A336]Br and[A336][Mal]are similar to[A336][SCN].The extraction equation of PIM membrane can be obtained by the logarithm method,[R3R'N+][SCN-]org+[Au?CN?2-]aq+2NPOEorg=[[R3R'N+]×[Au?CN?2-]×2NPOE]org+SCN-aqin which R3R?N+=(C8H17)3CH3N+,and the plasticizer also participates in the extraction reaction during the extraction process.Using ionic liquid[A336][SCN]as extractant,the extraction of Au?I?in alkaline system was studied under the condition of electrolytic stripping phase.At the stirring speed of 400 rpm,the composition of the polymer chimeric membrane was 0.15g PVDF?50 wt%?-0.12g[A336][SCN]?40 wt%?-0.03g NPOE?10 wt%?.When the pH value of the aqueous phase was 10.5,the concentration of sodium chloride is 0.2mol/L,the ratio of F:S is 1:1 and the electrolysis voltage is 1.5V.After extraction process for24h,using[A336][SCN]extraction rate of Au?I?is 99.8%.The results show that the extraction capacity is much stronger when the stripping phase is under the electrolysis operation than when the experiment is without the electrolysis operation,and the extraction speed is greatly improved.The deposition rate of stripping phase gold is up to 98.4%,and the extraction of Au?I?can be effectively realized. |
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