Protein fractionation by membrane filtration has been investigated through
the selective adsorption on clay particles. The micro-filtration of bovine
serum albumin, haemoglobin and montmorillonite mixtures was carried out. Bo
th proteins have similar molecular weights, bovine serum albumin (BSA) has
an isoelectric point at pH 4.8 while haemoglobin (Hb) is positively charged
up to pH 7.0. The aim was to improve the selectivity of the separation by
exploiting the different electrostatic interactions and in the meantime to
reduce membrane fouling by proteins, thanks to the formation of a secondary
membrane by the clay particles on top of the original membrane. We have st
udied the effects of suspension characteristics (pH, ionic strength, protei
n and clay concentrations) on adsorption isotherms of protein on clay parti
cles and on separation performances such as micro-filtration limiting flux,
protein transmission and separation factor. The optimum results were obtai
ned with an ionic strength of 10(-3) M and a pH value around 7.0. In these
conditions, only Hb was adsorbed on clay particles while BSA stayed free in
solution. (C) 2001 Elsevier Science B.V. All rights reserved.