| In recent years,the comprehensive green transformation of economic development has prompted various industries to move towards a green development path with low energy consumption,less pollution and high quality,which has caused great challenges to the traditional hydrometallurgical technology with high energy consumption and heavy pollution,especially in the field of precious metal recycling.However,with the increasing demand for precious metals and the increasing scarcity of natural mineral resources,this makes it increasingly crucial to develop green and efficient precious metal recovery process routes from secondary resources.As a kind of organic salt that melts at room temperature and has good physical and chemical properties,ionic liquid has gradually become a focus in the field of precious metal separation due to its strengths of green and pollution-free.At present,in view of the problems of high toxicity,low efficiency and poor selectivity of the current extraction system,this paper designed and synthesized four nitrogen-containing and phosphorus-containing ionic liquids,and constructed a series of new green extraction systems,for efficient extraction separation of Au(Ⅲ)from hydrochloric acid medium,which provides new ideas and new methods for secondary resource recovery of precious metals.The concrete reasearch contents are as follows:First,extraction of Au(Ⅲ)from hydrochloric acid medium with novel gemini benzimidazole-based ionic liquid[C6BIM2][NTf2]2.Firstly,the elements such as extractant concentration,acidity and salinity were optimized,the comprehensive effect of[C6BIM2][NTf2]2 dosage and acidity on the extraction of Au(Ⅲ)were further studied by response surface methodology(RSM).Then,the anion exchange mechanism between[C6BIM2][NTf2]2 and Au(Ⅲ)was verified by the Job’s method and combined with UV-vis,FT-IR and NMR.The thermodynamic data indicated that the extraction process was exothermic and spontaneous.The CS(NH2)2/HCl solution was used as the stripping agent,and the Au(Ⅲ)could be efficiently and rapidly separated from the chloroform phase,after 5 times performance verrfication experiments,the ability of[C6BIM2][NTf2]2 to extract Au(Ⅲ)did not change significantly.Additionly,under the interference of various base metal and precious metal ions with similar properties,the extractant can still maintain high extraction capacity for Au(Ⅲ),exhibited satisfactory Au(Ⅲ)extraction selectivity.Second,extraction of Au(Ⅲ)from hydrochloric acid medium by P44414Cl/HCl novel aqueous biphasic system.A novel type aqueous biphasic system constructed by P44414Cl/HCI can extract Au(Ⅲ)into the separated water phase at the phase transition temperature,thus achieve the green and efficient separation of Au(Ⅲ).Firstly,by drawing the phase diagram of the aqueous biphasic system at different temperatures,the best experiment temperature,the mass percentage of ionic liquids and hydrochloric acid in the aqueous biphasic system were determined.On the basis of the above optimal conditions,a series of experimental parameters such as time,gold(Ⅲ)concentration were optimized,and the extraction mechanism of anion exchange was explained in detail by means of UV-vis,FT-IR and NMR.Meanwhile,hydrazine hydrate solution was selected as the stripping agent,the successfully separation of Au(Ⅲ)from ionic liquid phase,and the X-ray diffractometer and scanning electron microscone were used to analyzed the structure and morphology of the simple substance gold obtained after stripping.In addition,the selectivity of the P44414Cl/HCl aqueous biphasic system for Au(Ⅲ)in multi-metal solutions was evaluated.Th e results showed that the novel aqueous aqueous biphasic system constructed by P44414Cl/HCl has great potential in the field of selective separation of Au(Ⅲ).Third,extraction of Au(Ⅲ)in hydrochloric acid by UCST type gemini ethanolamine ionic liquid constructed homogeneous system.Two UCST-type ionic liquids[C6(N112OH)2][NTf2]2,[C4(N112OH)2][NTf2]2 were designed and synthesized,binary homogeneous extraction system of[C6(N112OH)2][NTf2]2-H2O,[C4(N112OH)2][NTf2]2-H2O was constructed,the homogeneous phase extraction of Au(Ⅲ)was realized by the temperaturecontrolled characteristic of ionic liquid.Firstly,the phase diagrams of the[C6(N112OH)2][NTf2]2-H2O,[C4(N112OH)2][NTf2]2-H2O systems were drawn,meanwhile,the phase behavior of the binary system was further studied by nanoparticle size and 1H NMR spectroscopy at different temperatures.The extraction ability of the two extractants for Au(Ⅲ)at different temperatures was compared and the suitable salinity and acidity environment of the extractant also were explored.And using the maximum loading method,combined with UV-vis and 13C NMR,it was determined that the extractant was bound to Au(Ⅲ)in the form of anion exchange.Then,[C6(N112OH)2][NTf2]2 with the best extraction ability was selected to explore the extraction performance of Au(Ⅲ)in multi-metal solution,the extractant exhibited highly selectivity for separation of Au(Ⅲ).Finally,ionic liquid phase loaded with Au(Ⅲ)was stripped by oxalic acid solution.After 5 rounds of extraction-stripping experiments,the extraction ablity of the extractant to Au(Ⅲ)remained basically unchanged.The homogeneous liquid-liquid extraction system constructed by[C6(N112OH)2][NTf2]2 and[C4(N112OH)2][NTf2]2 provided a green and environmentally friendly separation idea for the selective separation of Au(Ⅲ). |
