Che-An Ku

Date of Graduation


Document Type



The wetting characteristics of silica microbeads are modified by varying the reaction between the surface silanols with t-butyldimethylchlorosilane. The wicking method is used to obtain the contact angle of the particle systems. Increasing hydrophobicity is observed with increasing silanizing reaction. The surface free energy of particles are calculated from the contact angle data. Nondispersive contribution decreases with increasing hydrophobicity while dispersive component remains unchanged. A mathematical model is developed which considers both the hydrodynamics and the induction times of the system. The transfer rates to and from the water phase are first order with respect to the particle concentrations in the liquid phases. The effect of wetting characteristics of particles is explained by the concept of induction time. The induction time for the particle transfer from the oil to the water phase ((lamda)(,1)) increases while that for the particle transfer from the water to the oil phase ((lamda)(,2)) decreases with increasing water-air contact angle. The model agrees with the experimental data of silanized model particles on the influence of the variables associated with the particle transfer process. The contact angle of particles is constant during the process. The distribution of particles to the water phase decreases with increasing hydrophobicity. The recovery of particles increases with increasing mixing time and higher mixing speed produces more recovery. The transfer of particles at steady state is linearly proportional to the initial particle concentration and decreases slightly with increasing water/oil ratio. Particle size analysis shows that the particle size in the range of 5 to 20 micron has no significant effect on the transfer process. The kinetic model is consistent with the experimental results of mineral particles extracted from coal-derived liquid in the presence of surfactant. The water-air contact angle of the mineral particles increases with increasing mixing time due to partial detergency. As a result, (lamda)(,1) increases while (lamda)(,2) decreases with increasing mixing time. The use of sodium dodecyl sulphate as surfactant in the distribution experiment promotes the transfer of hydrophobic model particles to the aqueous phase. Recovery increases with increasing initial surfactant concentration.