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. St able operation with low fouling could be achieved at low fluxes, e.g. 50 1/ m(2) h. However, as flux was increased, severe fouling occurred, e.g. at 20 0 1/m(2) h, probably because lactoferrin formed a concentration-induced sur face layer. The presence of sodium dodecyl sulphate in the feed caused dram atic decreases in fouling resistance but had a complex effect on protein tr ansmission. Increased cross-flow velocity usually decreased fouling resista nce 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. (C) 2001 Elsevier Science B.V. All rights reserved.