NAMS 2002 Workshop - ICOM 2008

Nanofiltration and Reverse Osmosis I - Membranes – 6
Monday July 14, 5:00 PM-5:30 PM, Maui
Polypyrrole Modified Solvent Resistant Nanofiltration Membranes
X. Li (Speaker), Centre for Surface Chemistry and Catalysis, Faculty of Bioscience Engineering,
Leuven, Belgium
P. Vandezande, Centre for Surface Chemistry and Catalysis, Faculty of Bioscience Engineering,
Leuven, Belgium
I. Vankelecom, Centre for Surface Chemistry and Catalysis, Faculty of Bioscience Engineering,
Leuven, Belgium, ivo.vankelecom@biw.kuleuven.be
Nanofiltration (NF) is a process in which feeds are separated over a membrane
by means of pressures between 5 and 20 bars. Permeation takes place through
the very small pores present in the membranes, or sometimes even through the
available polymer free volume only.1 Large scale applications currently exist in
waste water treatment and drinking water production. A major challenge these
days is to broaden the range of NF- applications to organic feeds (SRNF).2-3 A
more widespread use requires solvent-resistant membranes that preserve their
separation characteristics under more aggressive conditions of strongly swelling
solvents and elevated temperatures. Solvent stable polymers mostly contain
aromatic structures and hardly possess functional groups. Since some affinity
between membrane polymer and permeating solvent is needed, the few
commercial SRNF-membranes currently available are limited to applications in
apolar solvents. Moreover, being uncrosslinked, the existing polymeric
membranes dissolve in aprotic solvents. Polypyrrole (PPy) is a chemically
extremely resistant polymer, being insoluble in any organic solvent. Shaped as
nanoparticles, it has received considerable attention in catalysis,
chromatography, controlled drug release and pigment applications.4-5 Compared
with conventional polymers, PPy has a high surface energy, as well as good
electro-conductive and acid-base properties. In the membrane field, PPy based
membranes have been already mentioned for in the gas separation and
pervaporation but not for nanofiltration (NF) and solvent resistant nanofiltration
(SRNF) applications. Most of PPy based membranes were prepared by
interfacial polymerization. Pyrrole monomer vapour then first goes through the
membranes and reaches the other side of membranes, which was contacted with
oxidant and then polymerizes on the surface of the membranes. In the presented
work, the special properties of PPy will be used to enhance the SRNF
performance of membranes. Due to the poor solubility of PPy, an in-situ
polymerization method was adopted to modify the existing membranes. In this
method, the pyrrole monomer was first introduced on the surface of the
membrane support, which was immersed in an oxidant solution to initiate the
polymerization. The density of PPy can be controlled by the concentration of the
pyrrole solution. To confirm the versatility of this method different membranes