Effect of sodium dodecyl sulphate and cross-flow velocity on membrane fouling during cross-flow microfiltration of lactoferrin solutions

Experiments were performed with 0.2% (w/v) solutions of bovine lactoferrin under constant flux conditions to elucidate fouling mechanisms during cross-flow microfiltration. Fouling resistance curves indicated an initial phase of slow fouling, probably by pore plugging or deposition of aggregates. Stable operation with low fouling could be achieved at low fluxes, e.g. 50 l/m2 h. However, as flux was increased, severe fouling occurred, e.g. at 200 l/m2 h, probably because lactoferrin formed a concentration-induced surface layer. The presence of sodium dodecyl sulphate in the feed caused dramatic decreases in fouling resistance but had a complex effect on protein transmission. Increased cross-flow velocity usually decreased fouling resistance but had no effect on protein transmission. Fouling by protein is highly dependent on the permeate flux and physicochemical properties of the feed. The relationship between permeate flux and surface layer formation and the important role that protein aggregates can play in fouling are highlighted in the discussion.