| This thesis describes a cross-flow filtration system containing a mechanically rotated porous membrane. The unique dynamic filtration system combines the concepts of membrane filtration and centrifugation. In principle, the system should concentrate low-density suspended particles or liquid droplets near the center of the membrane lumen and create large shear forces along the membrane inner surface to mitigate fouling. This is particularly relevant to oil-water separations where low-density oil fouls the surface of membranes in conventional cross-flow filtration. Membrane rotation should decrease flux declines during filtration compared to the same experiment with a stationary membrane. Unfortunately, this study did not demonstrate such a result, perhaps because the oil droplets were too small to experience sufficient centripetal force to remove them from the membrane surface. Model experiments with filtration of hollow glass beads (density = 0.46 g/mL), however, provide preliminary data that membrane rotation can reduce fouling. At low cross-flow rates, membrane rotation decreases flux declines during filtration of bead-containing solutions. Additionally, light scattering studies of solutions containing the beads that collected on the membrane during filtration show that rotation leads to smaller beads on the membrane surface. Centripetal force presumably moves most larger beads away from the membrane surface. Future studies should re-exam the performance of this system in oil-water separations with larger oil droplets. |
