Extraction And Separation Of Au(?),Pd(?),Pt(?)from Hydrochloric Acid Medium By Phosphorus And Nitrogen Containing Hydrophobic Deep Eutectic Solvents

In recent years,hydrophobic deep eutectic solvent(HDES)as a new type of green solvent and extracting agent,has been widely applied in the process of material separation,making it more in line with the concept of green chemical technology.HDES.a eutectic mixture formed by hydrogen bonding interaction between the donor and the acceptor,possessing the merits of convenient preparation,low cost,excellent biocompatibility and adjustable physical and chemical properties,gradually becoming the ideal substitute of ionic liquid organic reagents.Although in the field of precious metals extraction,liquid-liquid extraction technologies have strong operational continuity,high degree of automation and good extraction selectivity,problems of toxic reagent consumption and waste pollution seriously restrict the development of liquid-liquid extraction technology.Therefore,developing a green precious metals extraction method to improve the extraction process of efficient clean environmental protection and reduce the production cost is of great urgency.On this basis,this article combined hydrophobic deep eutectic solvent with liquid-liquid extraction technology,and then designed three systems of precious metal extraction containing hydrophobic deep eutectic solvent,applying into the extraction and separation research of precious metals such as platinum,palladium and gold.At first,trioctylphosphine oxide(TOPO)was combined with some environmental-friendly molecules to form HDESs for Pt extraction from secondary resources.Due to the formation of HDESs,the loss of TOPO content in the aqueous solution obviously decreased.Then,the extraction behaviors under different vibrating time,acidity and salinity were investigated.Among all the constructed HDESs,the TOPO/1-butanol showed the best Pt(IV)extraction performance(98.90%)in 5.60 mmol·L-1 Pt(?)solution.Ion-association mechanism in the extraction process was proposed through the analysis of UV-vis and FT-IR spectra.In addition,the HDESs exhibited excellent selectivity to Pt(?)in the experiments of multi-metal selective extraction.The extracted Pt(?)could be easily and completely stripped by adding 3 mL 0.50 mol·L-1 NaOH solution,and the extraction ability of recovered extractants remained constant after 4 cycles of extraction tests.Furthermore,by using RSM-CCD optimization,the operating concentration of acidity and salinity was obtained:1.27 mol L-1 HCl and 2.65 mol·L-1 NaCl.Under optimal experimental conditions,the designed processes of Pt(IV)extraction further improved recycling efficiency.Next,using HDES made of tetrabutyl alkyl amide and fatty acid to selectively extract Au(?)from HCl medium,further achieving the green and efficient Au(?)extraction process.At first,under the factors of different molecular ratio,time,concentration of hydrochloric acid,sodium chloride and metal,we explored the HDES behavior to Au(?)extraction effect,using the response surface optimization method to get the best experimental conditions of Au(?)extraction,namely 0.56 mol/L HCl,2.19 mol/L NaCl,5.83 mmol/L Au(?);On this basis,HDES of Au(?)maximum loaded experiment was carried to study the extraction capacity;Finally,with the help of FTIR,the extraction mechanism based on ion association was obtained.Additionally,0.10 mol/L thiourea solution as extraction agent can easily extract Au(?)out of the HDES phase,after 4 cycles extract experiments,the HDES extraction ability still remained stable.At last,HDES based on two natural molecules(lidocaine and thymol)was applied to the extraction and separation of Au(?)/Pd(?)/Pt(?)from HCl media.At first,its properties were characterized by radial distribution function(RDF)analysis,1HNMR,DSC and TGA.Extraction behaviors under different molecular ratio,vibrating time,the concentration of HCl,NaCl and H+were investigated.In addition,the maximum extraction capacities of Au(?)/Pd(?)/Pt(?)were measured as 76.65 mg/g,9.89 mg/g and 30.15 mg/g under the optimal conditions.Ion-association mechanism in the extraction process was proposed through the analysis of FT-IR spectra.Finally,based on the competitive extraction experiment among Au(?)/Pd(?)/Pt(?),the separation routine was proposed:The HDES showed the ability to selectively extract 98%Au(?)under higher acidity(2 mol/L)from secondary resource solution.Afterward,the acidity of above solution was adjusted to 0.25 mol/L.Through a secondary extraction process,the extraction efficiency of Pd(?)/Pt(?)reached 99%and 90%.Then,0.20 mol/L KSCN was used to transfer Pt(?)to aqueous solution and separated from Pd(?).Striping of Au(?)or Pd(?)from HDES phase was done using 0.20 mol/L thiourea as stripping solution.After collecting and regenerating the used HDES,it can still maintain the extraction performance of Au(?)/Pd(?)/Pt(?).