Extrtaction Of Au(?)and Pt(?)from Hydrochloric Acid Medium By Quaternary Phosphonium/quaternary Ammonium-oleic Based Ionic Liquid

With the increasing use of precious metals,efficient mining of precious metals and recovery of precious metals from secondary resources has become a hot topic.Quaternary ammonium and quaternary phosphonium salt are emerging high-efficiency cationic extractant.In this paper,quaternary ammonium/phosphonium based cation were combined with different anions to synthesize various ionic liquids.It was used to construct a high-efficiency liquid-liquid extraction system for the extraction and separation of Au(?)and Pt(?):in hydrochloric acid medium.The work was carried out in detail through three experimental systems.In the first system,we synthesized a quaternary phosphonium-oleate acid based ionic liquid([P4444][OLA])to investigate the extraction behavior and extraction mechanism of the ionic liquid in AuC14-in hydrochloric acid media,including the ILs concentration,cumulative loading of Au,HCl concentration and NaCl concentration.Besides,single crystal of extracted complex,[P4444][AuC14],was cultivated and analyzed by X-ray diffraction.Based on the structure of crystal,we optimized the isosurface map of reduced density gradient(RDG),and revealed weak interaction type in the system.Finally,four reagents were applied for stripping studies,and Au(?)in loaded organic phase could be effectively stripped by either sodium thiosulfate or 0.5 M thiourea/1.0 M HCl.In the second system,we synthesized five quaternary ammonium-oleate based ionic liquids,which are tetrabutyl quaternary ammonium oleate([N4444][OLA]),tetrahexyl quaternary ammonium oleate([N6666][OLA]),tetraoctyl quaternary ammonium oleate([N8888][OLA]),dodecyltrimethyl quaternary ammonium oleate([N12111][OLA]),cetyltrimethyl quaternary ammonium oleate([N16111][OLA]).The[N8888][OLA]with best extraction behavior was used for the extraction and separation of gold and platinum.Various parameters were including HCl concentration,NaCl concentration and temperature were investigated.Furthermore,the extraction mechanism was explained by the combination of the continuous variation method,1H NMR spectrum and the charge density analysis.Finally,in the stripping step,the effective separation of the two was achieved by using thiourea as the stripping agent through the difference in reducibility of the two extraction complex of gold and platinum.In the third system,bis(2-ethylhexyl)phosphate was used as an anion to synthesize bifunctional quaternary phosphonium based ionic liquid[P4444][DEHP]by one-step method to realize extraction of Au(?)and Li(?)under different acidity conditions.Firstly,the effects of ionic liquid concentration,hydrochloric acid and sodium chloride concentration were investigated in detail.The anion exchange mechanism was confirmed by the continuous variation method and FT-IR spectrum of the ionic liquid and extraction complex.Furthermore,we carried out the research of Li(?)extraction,including ionic liquid concentration,cumulative loading of Li,aqueous acidity,phase ratio and temperature were optimized.Under optimum conditions,the ionic liquid could achieve up to 90.36%Li extraction rate.In summary,through the work of the above three systems,we systematically studied the extraction behavior and extraction mechanism of quaternary phosphonium/ammonium based ionic liquids for Au(?)and Pt(?)in hydrochloric acid medium,and realized the effective separation and extraction of Au and Pt.