Electrophoretic Classification of Ultrafine Silica Particles in Dilute Aqueous Suspension
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This study aims to classify ultrafine silica particles in a dilute aqueous suspension using their electrokinetic properties. Initially, the electrophoretic mobility of three (3) silica particle with mean diameters 2.39 µrn, 3.74 µrn and 5.31 µm are determined from pH 3 to 10 using two (2) electrolyte concentrations (0.01M and 0.001 M KNO3). To evaluate classification, electrophoretic deposition experiments are performed using a modified electrophoretic/ deposition (EPD) cell. The experiments are conducted at pH 10 with an electrolyte concentration of 0.001M KNO3 in four (4) time interval levels (15, 20, 25 and 30 min).
Results show that the electrophoretic mobility (µm.cm/V.s) of ultrafine silica particles in aqueous suspension decreased with increasing particle size. Electrophoretic mobilities also increased with increasing pH, and decreased with a corresponding increase in electrolyte concentration. Furthermore, classification experiments through electrophoretic deposition (EPD) show a gradient in both mean particle diameter and particle size distribution with increasing deposition time. The result are as follows: a) At 15 minutes, the mean particle diameter is 2.24 b) at 20 minutes, the mean particle diameter is 3.01 µm c) at 25 minutes, the mean particle diameter is 3.9 µm for EPD and 4.06 µm for electrophoresis; and, d) at 30 minutes, the mean particle diameter is 4.88 µm.
Based on the observed gradient in particle size and particle size distribution, it shows that the presence of smaller particles in the early stage of migration is probably due to their higher electrophoretic mobility as compared to the larger particles, thus resulting to their classification.
KeywordsEPD stainless steel silica size classification electrophoresis electrophoretic mobility
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