Influence of pH and salt concentration on the cross-flow microfiltration of BSA through a ceramic membrane

In this paper, the influence of pH in the 4–8 interval and NaCl concentration up to 25 mM on the cross-flow microfiltration of BSA was investigated. A tubular ceramic membrane with a pore size of 0.14 μm was employed and its point of zero charge was calculated. The evolution of permeate flow and BSA transmission with time was determined at 45 °C, a cross-flow velocity of 3.5 m/s and a transmembrane pressure of 100 kPa. The curves of permeate flow were explained according to the resistances in series model. Maximum protein transmission was obtained at the isoelectric point of BSA (4.9), with significant transmission also at the point of zero charge of the membrane and null transmission at pH 4 and 8. The highest permeate flow was observed at pH 7 and the lowest at 4.9. Finally, the addition of salt resulted to some extent in an improvement of both protein transmission and permeate flow.