Crossflow microfiltration of a colloidal suspension with the presence of macromolecules

Crossflow microfiltration of a colloidal suspension of bentonite with the presence of macromolecules of BSA, dextran and PEG was studied. The plate and frame tangential flow module with the hydrophilic PVDF membrane of nominal pore size of 0.2 mu m was used in the experiments which were carried out at constant temperature and flow rate. The results presented are the permeation flux, solute rejection and flow resistances. The constant pressure filtration models were also applied to explain the blocking process. The macromolecules decreased the permeation flux of a bentonite suspension while their rejections were enhanced with presence of bentonite. An increase of flow resistance of a bentonite suspension with BSA was due to internal fouling. For dextran and PEG, external fouling resulted from concentration polarisation and deposition on the membrane surface was an important factor for flux decline. The blocking process of a suspension of bentonite followed the cake filtration model (CFM). The presence of macromolecules affected the blocking process of a suspension of bentonite and the experimental data conformed with CFM and/or incomplete blocking model (IBM). (C) 1998 Elsevier Science B.V.