PROPERTIES OF MICROFILTRATION MEMBRANES - THE SURFACE ELECTROCHEMISTRY OF MIXED-OXIDE CERAMIC MEMBRANES

Citation
Wr. Bowen et H. Mukhtar, PROPERTIES OF MICROFILTRATION MEMBRANES - THE SURFACE ELECTROCHEMISTRY OF MIXED-OXIDE CERAMIC MEMBRANES, Colloids and surfaces. A, Physicochemical and engineering aspects, 81, 1993, pp. 93-101
Citations number
13
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Chemistry Physical
ISSN journal
0927-7757
Volume
81
Year of publication
1993
Pages
93 - 101
Database
ISI
SICI code
0927-7757(1993)81:<93:POMM-T>2.0.ZU;2-Z
Abstract
The surface electrochemical properties of mixed oxide ceramic membrane s (Rappore) have been characterised by means of computerised measureme nts of rates of electro-osmosis as a function of pH (reported as zeta (zeta) potentials) and computerised pH surface titration. The membrane s have modest values of zeta potential and high titratable surface cha rge. Remarkably for an inorganic oxide material, the membranes have a negative zeta potential over the entire pH range 10-3. Both the zeta p otential-pH and surface charge-pH profiles at two ionic strengths coul d be successfully modelled by considering the surface of the membrane to consist of a three-dimensional array (''gel'') of charged groups, b oth protons and counterions being able to penetrate the ''gel'' layer. Counterion penetration was found to be especially important at the lo wer pH values, where the surface charge of the membrane was positive b ut the zeta potential was negative. Such a model allows estimation of the ''gel'' thickness and the relative contribution of the component o xides to the surface chemistry. It was found that aluminium oxide grou ps played the greatest role in determining the surface properties, eve n though zirconium dioxide was by far the largest component of the mem brane based on the bulk composition. The results and analysis show tha t the surface electrochemistry of such membranes is complex, and that in characterising such membranes it is essential to make measurements directly on the membrane rather than on the component oxides.