The focus of this dissertation was the development, synthesis and modification of
polymers for the preparation of membranes for organic solvent nanofiltration. High
chemical stability in a wide range of solvents was a key requirement. Membranes
prepared from synthesized polymers as well as from commercial polymers were designed
and chemically modified to reach OSN requirements.
A solvent stable thin-film composite (TFC) membrane is reported, which is fabricated on
crosslinked polythiosemicarbazide (PTSC) as substrate. The membranes exhibited high
fluxes towards solvents like THF, DMF and DMSO ranging around 20 L/m2 h at 5 bar
with a MWCO of around 1000 g/mol.
Ultrafiltration PTSC membranes were prepared by non-solvent induced phase separation
and crosslinked with GPTMS. The crosslinking reaction was responsible for the
formation of an inorganic-type-network that tuned the membrane pore size. The
crosslinked membranes acquired high solvent stability in DMSO, DMF and THF with a
MWCO above 1300 g/mol.
Reaction Induced Phase Separation (RIPS) was introduced as a new method for the
preparation of skinned asymmetric membranes. These membranes have two distinctive
layers with different morphologies both from the same polymer. The top dense layer is
composed of chemically crosslinked polymer chains while the bottom layer is a porous
structure formed by non-crosslinked polymer chains. Such membranes were tested for
vitamin B12 in solvents after either crosslinking the support or dissolving the support and
fixing the freestanding membrane on alumina.
Pebax® 1657 was utilized for the preparation of composite membranes by simple coating.
Porous PAN membranes were coated with Pebax® 1657 which was then crosslinked
using TDI. Crosslinked Pebax® membranes show high stability towards ethanol, propanol
and acetone. The membranes were also stable in DMF once crosslinked PAN supports
Sodium alginate polymer was investigated for the preparation of thin film composite
membranes. Composite membranes were prepared using PAN and crosslinked PAN
supports; these membranes were tested for methanol and DMF. Freestanding nanofilms
fixed on alumina were also tested for methanol and DMF as well as many other harsh
solvents. The alginate composite membranes showed excellent solvent stability and good
permeances and a MWCO of around 1300 g/mol.
|Date of Award||May 2017|
|Original language||English (US)|
- Physical Science and Engineering
|Supervisor||Klaus-Victor Peinemann (Supervisor)|
- Organic solvent nanofiltration
- solvent resistant nanofiltration