| The microstructure of liquid membrane interface was observed combined withvisualization technology, and the thickness of liquid membrane was measured throughbirefringence phenomenon. The shape and movement of micelle in kerosene and wetprocess phosphoric acid were studied from the micro perspective. At the same time, itstrajectory and speed were determined by using particle velocity measurement software.Then the concentration of calcium and magnesium ions in wet process phosphoric acidwhich had been purified by dodecylbenzene sulfonic acid was gained by ionchromatography. The extraction agent concentration, volume ratio of oil and water andthe mass transfer time for purifying wet process phosphoric acid in the influence ofcalcium and magnesium ions were compared. Further more, the movement of theextraction agent dodecylbenzene sulfonic acid with high metal ions in wet phosphoricacid phase and the process of dodecylbenzene sulfonate through oil/water interfacedispersed layer was discussed. Last, RGB color method was used to study ofdodecylbenzene sulfonic acid with calcium ions in the liquid membrane mass transferdynamics, the mass transfer mechanism was formulated by combining with the video.The following conclusions were obtained through the experiment and theoreticalanalysis.1. It was obviously observed liquid membrane microstructure from wet processphosphoric acid-kerosene system, but it was difficult to catch sight of clear scatteredinterface layer from wet process phosphoric acid-hexyl alcohol, wet process phosphoricacid–120℃kerosene fraction and wet process phosphoric acid-130℃kerosenefraction. The result was that the micro droplet of distraction interface layer was so smallthat beyond the scope of the visual instruments. Birefringence phenomenon occurred inthe blurry scattered interface layer. According to the principle of double refractionphenomenon, the interface thickness of wet process phosphoric acid–120℃kerosenefraction system was measured by10.50μm.2. The micelle existing in kerosene and wet process phosphoric phase was spherical.The diameter of micro droplet in oil phase was among5.32~8.46microns. Its averagespeed was32.81μm·s-1. The motion of micelle was random and disordered. Mostlymicro particles were accompanied by vibration. However, the motion of micelle particlesin wet process phosphoric was linear and its average speed was28.59μm·s-1. Itillustrated that solution was not completely homogeneous and transparency in theory.Many ions may exist in the form of micelle.3. The purification rate of calcium and magnesium ions in wet process phosphoricacid was compared under the acid condition of dodecylbenzene sulfonic acid. Theextraction agent concentration, oil/water ratio and mass transfer time were gained. Themolar fraction of extraction agent was6%. The oil/water ratio was1/3. The mass transfertime was100min. The calcium and magnesium ion purification rate can reach60%under the condition.4. Combined with mass transfer dynamics curve of the calcium concentration of wetphosphoric acid near interface and liquid membrane mass transfer diffusion video, the mass transferregularity of dodecylbenzene sulfonic carrying mental calcium ion was gained. At thebeginning, the mass transfer was slow. The middle changed fast. Last, it tended to acertain value. After dodecylbenzene sulfonate absorbed in the liquid membrane, thethickness of liquid membrane got thickening. Under the presence of calcium indicator,the color of liquid membrane changed dark from yellow. The distribution of calciumconcentration in phosphoric acid and interface phase was a driving force of the migrationof dodecyl benzene sulfonate. As long as the concentration of calcium ion in phosphatewas different from the interface phase, the migration process of calcium ion wouldcontinue. |
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