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1、iLIQUID-LIQUID EXTRACTION FORMAL REPORT THOMAS SALERNOGROUP MEMBERS: GREGORY ROTHSCHING AN DUiiABSTRACTIn order to determine the correlation of the mass transfer rate, overall mass transfer coefficient, and terminal velocity with diameter during single drop microextraction of acetic acid from toluen
2、e by water, this experiment was designed to educate engineers in this practice. It is also the intention of this paper to reveal the accuracy of predictive equations used to design extraction columns.To achieve these objectives, my fellow teammates and I placed our toluene phase, of .776 M acetic ac
3、id, into a large graduated cylinder. From a syringe suspended above the column, spherical drops of our aqueous phase, made up of .01M NaOH and phenolphthalein, were released at diameters of 3.5, 4.0, and 5.1mm. By recording the time for each drop to traverse .213m of the column, we determined that i
4、ts terminal velocity increased with increasing diameter with values of 9.5, 10.3, 11.9 cm/sec. Furthermore, the time recorded for each drop to turn clear (i.e. the entire concentration of NaOH neutralized), we were able to conclude the mass transfer rate increased with increasing diameters with valu
5、es of 6.0, 7.9, 12.9 e-8 mole/sec. By mixing equal amounts of toluene and water with acetic acid and titrating each phase, we ascertained that the equilibrium distribution coefficient of our solution is 10.631. Thereby, we were able to declare the equilibrium concentration of aqueous acetic acid at
6、the surface of our drop to be 8.25M. This data was inputted into a mass transfer form of Newtons Law of Cooling, , to calculate the overall mass * ,*HAcHAc WatNKACCtransfer coefficient to decrease with our increasing diameters with values of 1.95, 1.92, 1.87 e-7 m/sec.Because the terminal velocities
7、 measured were an average of 22% below those predicted for rigid spheres, and the drops were observed to fall in a helix pattern, we determined that the drops experienced oscillations on its track down the column. By using the model of Handlos and Baron, the overall mass transfer coefficients could
8、be predicted within errors of only 1.5%. with an experimentally determined instability factor of 113.3 as suggested by Henschke and Pfenning.In summary, this report has established that an increase in diameter of a fallen drop will cause an increase in its terminal velocity, a decrease in its overal
9、l mass transfer coefficient (increase in inside mass transfer coefficient but overriding decrease in outside mass transfer coefficient), and an increase in its mass transfer rate. This trend indicates that the toluene (outside) phase is the controlling resistance to mass transfer, and that the surfa
10、ce area of the drop is the controlling factor for the mass transfer rate. We also verified that the trends of our state variables were predicted, but that experimental measurements were required for prediction of absolute numbers. When designing an extraction column, these results are most significa
11、nt for the chemical engineer.iiiTABLE OF CONTENTSABSTRACT.IITABLE OF CONTENTS .IIIINTRODUCTION:.1THEORY: .5EXPERIMENTAL: .5 Introduction:.5 Figure 1: Addition of water phase into column as spherical drops.5 Figure 2: Extraction of HAc from toluene phase by water phase.6 Terminal Velocity:.6 Figure 3: Schematic of forces acting on drop.6 Molar Rate of Transfer:.7 Equilibrium Distribution Coefficient:.9 Overall Mass Transfer Coefficient:.9 THEORETICAL:
