Solubility Of DES-based ATPS And Its Application In Separation Of O-xylene And P-xylene

Deep Eutectic Solvent（DES）is a new generation of ionic liquid analogues with high biocompatibility,high solute solubilisation capacity,low toxicity and simple preparation,which can be used in many fields such as analysis and detection,separation and synthesis,catalysis and ionisation.Aqueous Two-Phase Systems（ATPS）are widely used for purification and separation in various fields due to their low energy consumption and low cost,low contamination and easy scale-up,and high recovery rates.Aqueous two-phase systems based on low eutectic solvents overcome the disadvantages of traditional solvent separation systems,such as poor stability,poor biocompatibility and difficulty in reuse,and are also characterised by adjustable structure and polarity,easy continuous scale-up and high recoveries,which can be used for the fine separation of difficult systems.The separation of xylenes has been recognised as a difficult problem due to their structural similarity and physical and chemical properties,so it is important to explore low-cost and efficient methods for the separation of xylenes.In this thesis,different molar ratios of DES-based ATPS were prepared with choline chloride（Ch Cl）,Polyethylene glycol（PEG）400,PEG 600 and Glycerin as the main components of DES.The solubility and polarity of DES-based ATPS with different compositions were studied by using the difference of the solubility of DES-based ATPS relative to naphthalene.In the separation process,a system with high solubility and wide polar range was selected to separate the mixture of o-xylene and p-xylene,the separation ability of o-xylene and p-xylene in different systems was analyzed.The experimental results show that DES with PEG 400 as hydrogen bond donor has strong solubility.The ratio of K₂HPO₄ mass fraction to DES mass fraction affects the separation of o-xylene and p-xylene,the maximum selectivity of 27.5%DES（Ch Cl:PEG 400:Glycerin=1:1:1）-11.25%K₂HPO₄ ATPS for xylene separation was 1.77.The distribution and selectivity of Tetrabutylphosphnium Bromide（TBPB）DES-（NH₄）₂SO₄ were higher than those of DES（Ch Cl:PEG 400:Glycerin）-K₂HPO₄ ATPS,the selectivity was 2.32 in 40%DES-25%（NH₄）₂SO₄ATPS.A liquid-liquid-liquid three-phase ATPS was prepared on the basis of liquid-liquid two-phase system.The separation of o-xylene and p-xylene was carried out by using 50%DES（Ch Cl:PEG 400:Glycerin=1:1:1）-15%K₂HPO₄ three-phase ATPS,the selectivity of o-xylene and p-xylene in top phase and middle phase,middle phase and bottom phase were 1.80 and 1.57,respectively.The three-phase ATPS increases the separation dimension,and has great potential applications in some fields,such as biomass treatment,biocatalysis,enrichment and separation of environmental pollutants,etc.