The Extraction Of Platinum By Imidazolethione And The Application Of Quantum Chemistry In The Extraction Of Platinum Group Metals

Imidazole-2-thiones have attracted considerable attention due to its wide applications in vulcanization accelerators,complexing agents,rubber antioxidants,and high-speed photothermographic materials,etc..However,few researches on the removal of metals from aqueous solutions have been reported by 1,3-disubstituted imidazole-2-thiones,which are a kind of versatile catalysts.1-octyl-3-methylimidazole-2-thione and 1-butyl-3-methylimidazole-2-thione are promising neutral sulfur-bearing extractants for noble metal due to its bad solubility in water,low melting point and negligible vapor pressure.In the sense of green chemistry and green engineering,quantum chemistry is a potential tool,as it can be utilized to prescreen large numbers of possible multisite extractants at low cost without the difficulties of laboratory synthesis.In recent years,a series of computational investigations on solvent extraction have appeared.However,little attention has been paid to the computational research studies on platinum group metal extraction,especially for those taking environmentally benign ionic liquids as solvents.Based on the above research background,the main research contents of this paper are mainly divided into two parts,namely,the research on the extraction of platinum by imidazolithione and the research on the application of quantum chemistry in platinum group metals extraction.The specific content is as follows1.Removal of platinum(Ⅳ)from hydrochloric acid medium with OMImTIn this section,1-octyl-3-methylimidazole-2-thione(OMImT),a neutral sulfur-bearing extractant with low melting point and negligible vapor pressure,was synthesized and first utilized for the removal of Pt(Ⅳ)from hydrochloric acid medium by disperser-free precipitation owing to its excellent hydrophobicity and low viscosity.Estimation for the removal performance of Pt(Ⅳ)by disperser-free precipitation,in comparison with that by liquid-liquid extraction with disperser cyclohexane,as conducted on the effects of the dosage of OMImT and vibration time Subsequently,variable influence factors on the removal of Pt(Ⅳ)(e.g.phase ratio,HCl concentration,H+concentration and Cl-concentration)were also explored Afterwards,the removal mechanismof Pt(Ⅳ)with OMImT was first proposed and evidenced to be a special neutral complexing mechanism via a combination of quantum-chemical calculations and experimental measurements.At last,kinetic datawere analyzed by kinetics fitting methods2.Extraction of platinum(Ⅳ)from hydrochloric acid medium with OMImTIn this section,1-butyl-3-methyl imidazole-2-thione(BMImT),a neutral sulfur-bearing extractant with low melting point and negligible vapor pressure,was synthesized and first utilized for the extraction of Pt(Ⅳ)from hydrochloric acid medium by liquid-liquid extraction with disperser chloroform.Subsequently,variable influence factors on the removal of Pt(Ⅳ)(e.g.BMImT concentration,phase ratio,HCl concentration and Cl-concentration)were also explored.Afterwards,the removal mechanismof Pt(Ⅳ)with OMImT was first proposed and evidenced to be a special neutral complexing mechanism via a combination of quantum-chemical calculations and experimental measurements.At last,kinetic datawere analyzed by kinetics fitting methods.3.ESP-ALIE analysis as a theoretical tool for identifying the coordination atoms of possible multi-site extractantsIn this section,we assessed the performances of five functionals(B3LYP,CAMB3LYP,M06,M06-2X,and ωB97X-D)and two solvation models(the SMD and SMD-GIL models)for identifying the coordination atoms of possible multisite extractants by ESP-ALIE analysis(i.e.,a combination of electrostatic potential analysis and average local ionization energy analysis).First,for the test sets consisting of two neutral extractants and two ionic liquid extractants in ionic liquid solvents for Pd(II)extraction,the reliability of ESP-ALIE analysis for complexation site identification was validated by the crystal evidences.Subsequently,to provide data for the predictive ability of ESP-ALIE analysis,variable influence factors(e.g.,extractant concentration,HCl concentration,and Cl-concentration)and mechanism on the Pt(Ⅳ)extraction with a neutral extractant in ionic liquid diluents were explored.The extracted complex Pt(BMImT)2Cl4,whose single-crystal data were first reported herein,validated the theoretical forecast from the ESP-ALIE point of view.4.Theoretical study on the relationship between the ESP of UCST-type ionic liquid cations with[NTF2]-and theupper critical solution temperatureIn this section,we investigated the relationship between ESP and upper critical temperature of 13 UCST ionic liquids cations with[NTF2]-,and systematically evaluated the performances of four functional(B3LYP,M06-2X,ωB97X-D and B3PW91).