Design Of Hydrophobic Deep Eutectic Solvent And Its Application In Valuable Metal

Hydrophobic deep eutectic solvent is a new type of green solvent proposed,which is a low melting point mixture formed by hydrogen bonding between hydrogen bond donors and hydrogen bond acceptors.Due to their simple preparation,low price,high atom utilization,biodegradability and adjustable structural properties,hydrophobic deep eutectic solvents have gradually become ideal substitutes for organic solvents and ionic liquids,so they are widely used in the field of material separation.In order to more effectively apply the hydrophobic deep eutectic solvent to industrial production,It is particularly important to explore the relationship between the interaction force between components and the structural properties.Based on this,this paper combined the hydrophobic deep eutectic solvent with liquid-liquid extraction technology to design a valuable metal extraction system constructed by three types of hydrophobic deep eutectic solvents,which were used for the green extraction and separation of valuable metals.The main research contents and conclusions are as follows:(1)Hydrophobic deep eutectic solvent(HDES)was formed by using lidocaine as a hydrogen bond acceptor and carboxylic acids with different carbon chain lengths as hydrogen bond donors.The interaction force between HDES components was analyzed by the excess molar properties of HDES and FT-IR characterization.The results showed that there was a strong interaction between lidocaine and carboxylic acid,and the hydrogen bonding between lidocaine and carboxylic acid was weakened as the carbon chain length of carboxylic acid increased.With the increase of the carboxylic acid content in the mixture,the ability of lidocaine to weaken the hydrogen bond of the carboxylic acid itself was reduced,resulting in the weakening of the hydrogen bond between the components.Then,the effect of the interaction force between HDES components on the extraction of cobalt and nickel in aqueous phase was investigated.In the extraction of cobalt and nickel,lidocaine/capric acid(molar ratio 1:1)with the strongest interaction force between the components in the HDES system showed the best extraction performance in cobalt-nickel solution and the extraction efficiency was much higher than the traditional extraction system.Subsequently,after adding oxalic acid solution,cobalt and nickel can be stripped from the organic phase.In addition,the recovery and regeneration of HDES to the cobalt and nickel extraction ability basically remained unchanged.(2)HDES were prepared by trioctylphosphorus oxide(TOPO),Carboxylic acids with different structures,menthol and 2-thiopheneformyl trifluoroacetone(HTTA)for the extraction of gallium in hydrochloric acid medium.The excess molar properties of HDES were determined and calculated.Moreover,the interaction between TOPO and different hydrogen bond donors was analyzed combined with FT-IR.Then,the extraction performance of HDES in hydrochloric acid medium under different molar ratios of hydrogen bond donor and acceptor-donor was investigated under different acidity.The results showed that the excess molar properties of HDES deviated less from the ideal solution behavior,indicating that the HDES components had weaker interactions.In the extraction experiment of gallium,TOPO/HTTA(molar ratio 1:1)with weak interaction between components showed the best gallium extraction performance.Finally,0.1 M acidic thiourea solution can be used to extract gallium from HDES.After five cycles of experiments,the HDES extraction system can still achieve an extraction rate of more than 90 % for gallium in the aqueous phase,which proved that the system had excellent reuse performance.(3)Natural HDES were prepared using two natural molecules menthol and long-chain organic acids for copper extraction from hydrochloric acid medium.First,the density and viscosity of this type of HDES were measured.The excess molar volume,viscosity deviation and interaction force parameters of HDES were calculated.The hydrogen bonding between HDES components was investigated by FT-IR on HDES.The results showed that the structure was relatively stable only when the acceptor-donor molar ratio was 2:1.In the copper extraction experiment,The HDES formed by menthol and capric acid in a molar ratio of 2:1 were found to be the most effective for copper extraction.HDES was used for 5 cycles and the activity did not decrease significantly.Finally,the extraction mechanism of copper was discussed through the relationship between the structural properties of the menthol-capric acid deep eutectic solvent and the hydrogen bonding between the components.The idea of optimizing the extraction performance was given,which was helpful for the design of the deep eutectic solvent.