Liquid Separation through Polymeric Membranes

Abstract

The project aimed to investigate the use of polymeric membranes, mainly based upon the polymer of intrinsic microporosity PIM-1, in the membrane-based liquid separation technique perstraction. In the first part of the project, PIM-1 polymer was synthesized and used to cast the polymeric membranes. Due to the instability of PIM-1 polymer in harsh organic solvents, its cross-linking by blending with polyethyleneimine (PEI) followed by thermal treatment, was carried out. Thermally cross-linked PIM-1-PEI were then used for the separation of a mixture of dyes (Oil Red O and Remazol) from their ethanolic and aqueous ethanolic (70 wt% ethanol) solutions, both by sorption and perstraction experiments. Comparison of sorption analyses on PIM-1 and PIM-1-PEI cross-linked membrane tells that cross-linking due to the introduction of PEI although stabilized PIM-1 yet it reduced the membrane selectivity from neutral organic component towards anionic ones. Comparison of rate of sorption and perstraction experiments was found to be almost same at the end. PIM-1-PEI cross-linked membranes were then used for the perstraction of phenol from its aqueous solution into methyl isobutyl ketone (MIBK). Phenol has previously been separated by a pervaporation process, at higher temperature (50-80 °C). Perstraction process was found to be advantageous in terms of high membrane flux of 0.3 kg m-2 h-1 and separation factor of 588 as compared to the pervaporation flux of 0.003 kg m-2 h-1 and separation factor of 0.9 at 20°C, measured after running both the separation processes for 2 h. Another method to stabilize PIM-1 in organic solvents was carried out by incorporating metal salt, palladium acetate (Pd(OAc)2), into PIM-1 and used for the perstraction of phenol from its aqueous solution into MIBK. The metal salt blended membranes (PIM-1-Pd(OAc)2) were further compared with PIM-1-PEI cross-linked membranes. Comparison showed that PIM-1- Pd(OAc)2 displayed a higher steady state normalized flux 4.8-5.2 × 10-6 kg m m-2 h-1 as compared to steady state normalized flux for PIM-1-PEI cross-linked membrane, 3.3-4.0 × 10-6 kg m m-2 h-1. Both of these polymeric membranes were further compared with the polymer based upon rubbery polymer, polydimethylsiloxane (PDMS). The comparison showed that PDMS displayed 10 times higher normalized flux, 3.0 × 10-5 kg m m-2 h-1 as compared to membranes based upon PIM-1. However, comparison of sorption analyses showed that PIM-1 possessed much higher sorption capacity as compared to PDMS

Date of Award	1 Aug 2021
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Peter Budd (Supervisor) & Patricia Gorgojo (Supervisor)