| The extraction process is an old and active separation technology. Since1891the distribution theory was published by Nerst, which was a theoretical foundation for the extraction chemistry, the extraction chemistry started to be a blooming research area in inorganic chemistry and organic chemistry. The industrial applications of extraction shows that compares to the other separation methods, the extraction does a better job at selective separation, capacity, metal recovery, reagent consumption, and the production process is easy to achieve automatic and continuous because it only needs simple equipment. Therefore, the research and application of extraction in hydrometallurgical continue to be expanded. Recently, a lot of researchers used microemulsion and ionic liquids in extraction because of their unique properties. In this paper, Winson Ⅱ microemulsion was used to recovery gold from e-waste and its industrial application was discussed, four hydrophobic ionic liquids were used for the extraction of gold and a easily synthesized ionic liquid-based thione was used as extractant for mercury.The detailed information of the paper is listed as follows:1. Extraction of gold(Ⅲ) from hydrochloric acid solutions by CTAB/n-heptane/iso-amyl alcohol/Na2SO3microemulsionThe extraction of Au(Ⅲ) from hydrochloric acid solutions by microemulsion was studied. The extraction experiments were carried out using cetyltrimethylammonium bromide (CTAB) as surfactant and iso-amyl alcohol as co-surfactant. Au(Ⅲ) was found to be extracted into the microemulsion phase due to ion pair formation such as AuCV CTAB+. The influence of temperature on the extraction of Au(Ⅲ) has been investigated at temperatures ranging from288to313K. Temperature was found to decrease the distribution of Au(Ⅲ). Thermodynamic parameters like enthalpy and entropy of the extraction, calculated by applying Van’t Hoff equation, were-36.76kJ mol-1and-84.87J mol-1K-1, respectively. Furthermore, the influence of the concentrations of hydrogen ion and chloride anion on the extraction efficiency (E%) were verified. Au(Ⅲ) was extracted quantitatively (E%>99%) and selectively at the whole range of HC1concentrations (0.2- 5M). Recovery of gold from electrical waste and treatment of CTAB wastewater generated from the extraction were also discussed. Thus, the extraction of Au(III) from hydrochloric acid solutions by microemulsion is an effective approach.2. Extraction of gold(III) by four hydrophobic ionic liquidsUsing ionic liquids (ILs) instead of volatile organic compounds (VOCs) in solvent extraction process has attracted increasing interest. In our paper, four hydrophobic ionic liquids,1-hexyl-3-methylimidazolium hexafluorophosphate ([C6mim][PF6]),1-butyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide ([C4mim][NTf2]),1-hexyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide ([C6mim][NTf2]) and1-octyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide ([C8mim][NTf2]) were used as both solvent and extractant for gold extraction from hydrochloric acid solutions. Investigations of the influence of temperature (T=288to313K) on the extraction and enthalpy of the extraction process calculated by applying Van’t Hoff equation are reported, ΔH[C6mim][PF6]=5.554kJ-mol-1, ΔH[C4mim][NTf2]=-13.078kJ-mol-1, ΔH[C6mim][NTf2]=-12.862kJ·mol-1, ΔH[C8mim][NTf2]=-12.504kJ-mol-1. The anion-exchange extraction mechanism was investigated by extraction efficiency (E%) studies as a function of aqueous ionic concentrations and crystallographic analysis of the extracted species.3. Coordination and extraction of mercury(II) with an ionic liquid-based thione extractantA neutral thione extractant derived from an ionic liquid,1,3-diethylimidazole-2-thione (C2C2ImT), was used to extract Hg(II) from aqueous solutions of HgCl2or Hg(OAc)2into a hydrophobic ionic liquid (IL),1-ethyl-3-methylimidazolium bis(trifluoromethane)sulfonamide ([C2mim][NTf2]). Investigations of the extraction mechanism, spectroscopic analyses of the extracted species, and crystallographic studies of the interactions of C2C2ImT with Hg(II) are reported, including the first structurally characterized Hg-NTf2coordination compound, Hg(C2C2ImT)2(NTf2)2. Coordination complexes of the thione ligand with Hg(II) show variability in coordination numbers and geometries with stoichiometry, suggesting that the extraction mechanism is dependent on the speciation of mercury in aqueous solution. HgCl2can form neutral, extractable complexes with the thione in aqueous solution. Hg(OAc)2dissociates on dissolution in water and Hg(II) is extracted through a cation exchange mechanism involving [Hg(C2C2ImT)2]2+ions. The precipitation of neutral mercury complexes from the IL following the extraction of excess mercury suggests a simple and unusual way to recycle the IL. |
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