The development of composite membranes via polymer coatings for organic solvent nanofiltration
File(s)
Author(s)
Cook, Marcus
Type
Thesis
Abstract
This thesis offers a comprehensive study into the development of composite membranes for Organic Solvent Nanofiltration via solvent-free coating of epoxysilicones, and dip coating of polymers of intrinsic microporosity. Firstly, two different ultrafiltration membranes are fabricated from polyacrylonitrile
and a polyetherimide and optimised to similar nominal pore sizes. These are both then employed as support membranes for the formation of Thin Film Composite membranes from coating epoxysilicones
or PIMs. Minor changes in the coating solvent mixture for the PIMs enabled the formation of uniform coatings of <500 nm thickness. The separation performance of three PIM variants was found to be fairly similar, with each displaying a Molecular Weight Cut Off of 500-800 g mol-1 in various test solvents. In parallel, a solvent free coating approach was developed to fabricate epoxysilicone TFC membranes. In this case, the support membrane was found to be a key factor in the separation performance of the composite membrane. Since the PDMS based TFC membranes were formed from cationically curable epoxysilicones, residual pendant amines in the support membrane were found to be inhibitory to the crosslinking of the cycloaliphatic epoxy. Intrusion of the epoxysilicone into the support membrane was also verified by SEM/EDS. Epoxysilicone TFC membranes were then used in a three stage membrane cascade to mimic a light/heavy key separation, whereby attention is drawn to the engineering analysis of the membrane cascade. Finally, nanofiltration of azeotropic mixtures of toluene/alcohol was conducted using the epoxysilicone composite membranes. For a system of toluene/n-butanol, the separation was observed to go through a maximum at the azeotropic composition, suggesting an integrated distillation and membrane process may be feasible for this mixture. The
Flory-Huggins ternary equations were integrated into the solution diffusion transport model to enable estimations of how these types of mixtures may separate through dense, non porous membranes.
and a polyetherimide and optimised to similar nominal pore sizes. These are both then employed as support membranes for the formation of Thin Film Composite membranes from coating epoxysilicones
or PIMs. Minor changes in the coating solvent mixture for the PIMs enabled the formation of uniform coatings of <500 nm thickness. The separation performance of three PIM variants was found to be fairly similar, with each displaying a Molecular Weight Cut Off of 500-800 g mol-1 in various test solvents. In parallel, a solvent free coating approach was developed to fabricate epoxysilicone TFC membranes. In this case, the support membrane was found to be a key factor in the separation performance of the composite membrane. Since the PDMS based TFC membranes were formed from cationically curable epoxysilicones, residual pendant amines in the support membrane were found to be inhibitory to the crosslinking of the cycloaliphatic epoxy. Intrusion of the epoxysilicone into the support membrane was also verified by SEM/EDS. Epoxysilicone TFC membranes were then used in a three stage membrane cascade to mimic a light/heavy key separation, whereby attention is drawn to the engineering analysis of the membrane cascade. Finally, nanofiltration of azeotropic mixtures of toluene/alcohol was conducted using the epoxysilicone composite membranes. For a system of toluene/n-butanol, the separation was observed to go through a maximum at the azeotropic composition, suggesting an integrated distillation and membrane process may be feasible for this mixture. The
Flory-Huggins ternary equations were integrated into the solution diffusion transport model to enable estimations of how these types of mixtures may separate through dense, non porous membranes.
Version
Open Access
Date Issued
2018-07
Date Awarded
2018-12
Copyright Statement
Creative Commons Attribution NonCommercial Licence
Advisor
Livingston, Andrew
Sponsor
Engineering and Physical Sciences Research Council
Grant Number
EP/L50547X/1
Publisher Department
Chemical Engineering
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)