Extraction And Separation Of Gold(?)and Platinum(?)from Acidic Chloride Media By Nitrogen Containing Ionic Liquids

Recently,the liquid-liquid extraction system involved ionic liquids has played an extremely important role in the extraction of precious metals,and has also attracted much attention.Nitrogen-containing ionic liquids are the main members of ionic liquids,but more researches are still limited to imidazoles and quaternary ammonium ionic liquids,so the nitrogen-containing ionic liquids have not been fully explored.Therefore,a variety of novel nitrogen-containing ionic liquids were synthesized in this paper,and various extraction systems including homogeneous liquid-liquid extraction were constructed,which were used for the extraction and separation of Au(III)and Pt(IV)from acidic chloride media.The main contents are as follows:1.Extraction and stripping of Pt(IV)from acidic chloride media using guanidinium ionic liquidIn this work,the guanidinium ionic liquid[diHTMG]Br was successfully designed and synthesized,and[diHTMG]Br/chloroform system was constructed for the extraction of Pt(IV)in acidic chloride media.Under the optimized extraction conditions,the extraction efficiency could achieve 99.5%,and the distribution ratio could reach up to 356.67.The extraction efficiency of Pt(IV)could still achieve 98.2%in a multi-metal solution,which means the system has excellent selectivity to Pt(IV).The extraction mechanism of anion exchange was confirmed by combining Electrostatic potential(ESP)map with spectra analysis.Using 0.5 M CS(NH2)2/0.5 M HCl solution as the stripping agent,the[diHTMG]Br could be recycled for 4 times.Finally,the extraction isotherm and McCabe-Thiele diagram were used to predict the theoretical counter-current extraction/stripping stages under selected phase ratio and simulation experiments were carried out to verify the prediction.2.Recovery of Au(III)from acidic chloride media by homogenous liquid-liquid extraction with UCST-Type gemini imidazole ionic liquidsTwo gemini ionic liquids[C4OMIM2][Tf2N]2 and[C6O2MIM2][Tf2N]2 were synthesized.The binary mixtures of the two ionic liquids with pure water showed thermodynamic property.Two homogenous liquid-liquid systems were used to extract Au(III)from acidic chloride media based on the thermodynamic property.First,the UCST of ionic liquid/water binary mixtures at different mass ratios were measured and phase diagrams were drawn.Extraction behaviors of Au(III)to[C4OMIM2][Tf2N]2 and[C6O2MIM2][Tf2N]2 were investigated at room temperature,UCST and above UCST,respectively.The extraction kinetics and performance of Au(III)were improved a lot owing to the forming of homogenous region at UCST and above UCST.The extraction mechanism was confirmed to be anion exchange through 13C NMR,UV-vis spectra and determination vf woordinatiun nuubei of the extracted species.Finally,the loaded phase was stripped with oxalic acid as the stripping agent to obtain simple substance of gold.3.Recovery of Au(III)from acidic chloride media by homogenous liquid-liquid extraction with UCST-Type morpholinium ionic liquidUCST-type ionic liquid[EtbetmMor][Tf2N]was designed.Firstly,we predicted the ability of the three ionic liquids([EtbetmMor][Tf2N],[C4OMIM2][Tf2N]2 and[C602MIM2][Tf2N]2)to form solvated hydrogen bonding to estimate the UCST ordering of their binary mixture with water and experimental verification was carried out.Based on the global minima order of+20.69<+95.11<+119.26 kcal/mol,which is consistent with the average ESP order of 85.61<144.01<153.58 kcal/mol,it was inferred that the ability to form solvated hydrogen bonding and the value of UCST of the three ionic liquids could be ordered as[EtbetmMor][Tf2N]<[C6O2MIM2][Tf2N]2<[C4OMIM2][Tf2N]2.Furthermore,a homogeneous liquid-liquid extraction system involving[EtbetmMor][Tf2N]was constructed,and the extraction behavior of Au(III)at different temperatures was investigated.Under the optimum conditions,the[EtbetmMor][Tf2N]showed outstanding selective extractability for Au(III)over base metals and other precious metals.The[EtbetmMor][Tf2N]could be regenerated simply by mixing the raffinate containing[Tf2N]-with the[EtbetmMor]Cl phase separated with gold after stripping.