Pressure-Dependent Permeate Flux in Ultra- and Microfiltration

The effect of applied pressure on the permeate flux in cross-flow ultrafiltration (UF) and microfiltration (MF) was investigated both theoretically and experimentally. In UF and MF processes, the permeate fluxes are controlled by concentration polarization and cake formation over the membrane surface. As a better understanding of concentration polarization and cake formation becomes available, the permeate flux under any pressure can be theoretically predicted. Experiments were conducted in a ceramic tubular cross-flow filter with silica colloids of a narrow size distribution (model colloids). The pressure-dependent flux of the model colloidal suspension in cross-flow filtration was investigated under various experimental conditions. The experimental measurements were compared with the theoretical predictions, and the results showed that the pressure-dependent permeate flux in cross-flow filtration can be adequately predicted. Furthermore, theory and experiments demonstrated that the performance and operating state of UF and MF could be well characterized by the so-called "characteristic pressure" of the process.