Design, Synthesis Of CO₂-Philic Compound And Sodium Ions Extraction In Supercritical Carbon Dioxide

With the increasing concerns on environmental protection and sustainabledevelopment, developing a faster and more efficient chemical separations and processesis becoming an urgent affair. Supercritical CO₂（scCO₂） with the unique solventproperties of （moderate critical constants, nonflammable nature, low cost andno-toxicity） has elicited significant interest. Using scCO₂as a medium for separationtechnology is potentially important for solving many environmental and energy relatedproblems. To date, processes with scCO₂have been put to use in a variety of industrialbranches, such as agriculture and food, cosmetics, pharmaceuticals, medicine, coatings,textiles, electronics and semiconductors, and waste treatment.Unfortunately, CO₂is a non-polar molecule with a low dielectric constant, whichprevents it from dissolving hydrophilic compounds with high polarity, metal ions andhigh-molecular-mass compounds. One solution to enhance the solubility is to introducesome CO₂-philic compounds into the scCO₂system. Up to now, it has been found thatmost efficient CO₂-philic compounds are fluorides or silicones. However, fluorides arequite expensive and toxic, and silicone-functioned amphiphiles require relatively highpressure to generate a single-phase solution in scCO₂. Thus, design and synthesis ofnew nonfluorous CO₂-philic compounds became an interesting challenge.Based on theoretical analysis and study of the relation between ligand structure andchelating behavior, a series of new CO₂-philic compounds, which contained thecarbonyl group and ether group, were desigined and synthesized as chelating ligandsand their structure were determined. The solubility evaluation of these compounds inscCO₂were carried out at different temperatures and pressures. To confirm the accuracy,two density-based models proposed by Bartle and Chrastil were investigated.Furthermore, the solubility data were also employed for the estimation of partial molarvolumes of these compounds in the scCO₂according to the theory developed by Kumarand Johnston.Meanwhile, alkali metal ion （Na+） was extracted from aqueous with ether-oxideester compounds by scCO₂. The effects of pressure, temperature, extraction time, pHand the amount of ligands on the extraction efficiency of Na+were systematicallyinvestigated. The optimum conditions obtained were313K, pH=7, and the extraction efficiency was improved by increasing the CO₂pressure. While the extraction efficiencyincreased steeply with increasing time, and remained stable after the peaking.