Hydrodynamics And Mass Transfer Characteristics Of Molybdenum In L35 Aqueous Two-Phase System With A Packed Column

The phase equilibrium properties,physical property parameters,the hydrodynamic andmasstransfercharacteristicsofmolybdenuminthepoly?ethylene oxide?-poly?propylene oxide?-poly?ethylene oxide??PEO-PPO-PEO?triblock copolymer surfactant?L35?+sodium sulfate+H₂O aqueous two-phase system were investigated.Firstly,phase equilibrium properties of L35+sodium sulfate aqueous two-phase systems were studied.The experimental results indicate that with increasing temperature,the single-phase area of aqueous two-phase system decreases and the two-phase area increases,which is contribute to enhancing phase separation ability of aqueous two-phase systems.With the increase of the system composition,the tie line length?TLL?of aqueous two-phase system increases and the phase difference becomes more obviously.The Othmer-Tobias and Bancroft empirical equations were used to fit the tie-line data of L35-sodium sulfate aqueous two-phase systems and the correlation results proved very successful.The density and viscosity of the salt-rich bottom phase and L35-rich top phase decrease with the increase of temperature,and increase with the increase of the tie-line length.The difference of interfacial tension between two phases is very low,showing that the used aqueous two-phase system belongs to a low interfacial tension system.Secondly,the hydrodynamic characterization in the packed column using L35-sodium sulfate aqueous two-phase system were researched and the effects of flow rate of dispersed phase,tie line length,different kinds of packing?metal?rings,glass springs,and ceramic rasching rings?on the hold up of dispersed phase and the residence time distribution were also explored.The experimental results indicate that the hold up of dispersed phase increases with increasing the flow rate of the dispersed phase,and decreases with the increase of the tie line length?TLL?,and increases as increasing the void fraction of the packing according to the sequence from strong to weak is metal?rings>glass springs>ceramic rasching rings.The mean residence time of the dispersed phase decrease,showing that the axial diffusion extent of the dispersed phase become more serious with increasing the rate of dispersed phase and the TLL,and increase with the increase of the void fraction of packing bed.Finally,the mass transfer characteristics of molybdenum in the packed extraction column using L35-sodium sulfate aqueous two-phase system was studied and the effect of flow rate of dispersed phase and continuous phase,tie line length,different kinds of packing?metal?rings,glass springs,and ceramic rasching rings?on the overall volumetric mass transfer coefficient of the dispersed phase was discussed.The experimental results demonstrated that the overall volumetric mass transfer coefficient of dispersed phase increases with the increase of the flow rate of dispersed phase and continuous phase,and decreases with increasing the TLL.For three different kinds of packing,the sequence of overall volumetric mass transfer coefficient from strong to weak is glass springs>metal?rings>ceramic rasching rings.In addition,the height of mass transfer unit and needed packing layer under specific separation demand of molybdenum and different operating conditions were also calculated.