NAMS 2002 Workshop - ICOM 2008

Membrane Fouling - General Topics – 3
Monday July 14, 10:45 AM-11:15 AM, O’ahu
Impact of Diluate Solution Composition in Protein and Magnesium on
Membrane Fouling During Conventional ED
G. Pourcelly (Speaker), Institut Europeen des Membranes, France,
gerald.pourcelly@iemm.univ-montp2.fr
C. Casademont, University Laval, Québec, Canada
E. Ayala Bribiesca, Institut Nutraceutiques et Aliments Fonctionnels, Québec, Canada
M. Araya Farias, Institut Nutraceutiques et Aliments Fonctionnels, Québec, Canada
L. Bazinet, Institut Nutraceutiques et Aliments Fonctionnels, Québec, Canada
Fouling formation is among the most important limitations in electrodialysis (ED)
processes. Build- up of fouling film causes an increase in resistance, which
deteriorates the performance of process and can eventually lead to membrane
integrity alteration [1] . Numerous studies have been done on the identification of
species causing fouling [2-3] , but most of these works are directly related to anion-
exchange membrane (AEM), since their fouling susceptibility is higher than that
of cation- exchange membrane (CEM). But recently, the formation of a mineral
fouling on CEM and AEM has been reported during conventional ED of different
solutions of CaCl2 and Na2CO3 [2] . Furthermore, during the production of high
purity bovine milk casein isolates from skim milk by bipolar membrane
electroacidification (BMEA), a further step in the ED process evolution, where
bipolar membranes allow the dissociation of water molecules in protons and
hydroxyl ions under an electric field, two types of fouling were observed. A
mineral fouling identified as a mixture of CaCO3 and Ca(OH)2 was observed on
both sides and inside the CEM as well as a slight protein fouling on the CEM. For
the CaCO3 mineral fouling, it was suggested that nucleation would be the
controlling step, since crystallization occurred when the nuclei were formed and
the solution was supersaturated [4] and that Mg, present in milk at an average
concentration of 105 mg/kg would initiate and structure the formation of CaCO3 [5-
6] . However the impact of Mg on the formation of a CaCO3 fouling at the interface
of a CEM has never been studied. In addition, not much work characterizing
protein-caused fouling of ED membranes has been found.
The aim was to study the effect of the concentrate solution pH, the composition
in calcium, carbonate, magnesium (at different ratios of Mg/Ca) and protein of the
diluate solution to be treated by conventional ED on the fouling of ion- exchange
membranes. Conductivity, system resistance, pH of the diluate and cation
migration were monitored to follow the evolution of the demineralization. Acidic
and neutral conditions led to protein film formation over the diluate side of the
AEM, but basic conditions prevented its formation. Protein fouling on CEM was
not visually apparent. CEM presented mineral fouling only in basic concentrate
conditions when calcium was present, which would precipitate as calcium