posted on 2009-09-02, 10:19authored byJ.P. Robinson, Steve Tarleton, C.R. Millington, Arian Nijmeijer
Transport mechanisms and process limitations are relatively well understood for aqueous nanofiltration systems. Much work has also been done on the use of membranes for the removal
of suspended matter from organic solvents. The removal of organic solute compounds from
organic solvents using membrane technology has been addressed by very few workers, and little is
known of the fundamental transport and separation mechanisms.
The work aims to enhance the understanding of non-aqueous nanofiltration by focusing on the flux
performance of organic solvents through a dense 2 μm polydimethylsiloxane composite
membrane. The flux of alcohols, n-alkanes, i-alkanes and cyclic compounds were studied in deadend
mode, at pressures of 10–900 kPa. Fluxes of 10–80 l/m2 h were obtained for alkanes and
cyclic compounds, whereas alcohol flux was around two orders of magnitude lower. The results
suggest that the solvent flux through polydimethylsiloxane takes place via two distinct mechanisms
– namely hydraulic and chemical transport. Hydraulic transport appears to dominate at pressures
above 300 kPa, whereas chemical transport becomes more apparent at lower pressures.
Comparison of the hydraulic transport data with a Hagen-Poisuelle model gives good agreement
for similar solvents. Swelling effects caused by solvent-membrane interactions are identified as
playing a major role in solvent flux behaviour, and compressibility effects are also thought to
account for deviations from the Hagen-Poisuelle model. Viscous flow was verified by a nonseparation
of mixtures of n-alkane and cyclic compounds, which suggests that the
polydimethylsiloxane layer cannot sustain a dense structure when used in organic solvent
nanofiltration applications.
History
School
Aeronautical, Automotive, Chemical and Materials Engineering
Department
Chemical Engineering
Citation
ROBINSON, J.P. ... et al, 2004. Nanofiltration of organic solvents. Membrane technology, 2004(7), pp. 5-12.