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Amira Mohd Nasib
Polyvinylidene Fluoride-co-Polytetrafluoroethylene (PVDF-co-PTFE)/Deep Eutectic Solvent (DES) impregnated membrane for carbon dioxide separtion
2019
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Amira Mohd Nasib
Deep Eutectic Solvent (DES) is a new type of organic slovent that have been considered as an attractive liquid medium to be incorporated in liquid membrane (LM) due to high solubility of carbon dioxide (CO₂). However, DES is still considered as a new and fresh liquid, hence the performance of supported-DES-membrane has not been reported yet. Hence, this study aims to synthesize and characterize polyniylidene fluoride-co-polytetrafluoroethylene (PVDF-co-PTFE) membrane, followed by preparation of supported-DES-membrane and evaluating the prepared LM for carbon dioxide/nitrogen (CO2/N2) separation. Asymmetric PVDF-co-PTFE membrane was prepared via phase inversion method using non-solvent induced phase separation (NIPS). The selection of suitable solvent and polymer concentration were studied first for membrane support preparation. Polymer solution prepared by using N,N-dimethylacetamide (DMAc) showed the lowest viscosity (7800 cP) and hence, produce a membrane with a larger size (115.0 μm) and high quantity of finger-like macrovoids with highest porosity (57.6%) compared with other solvents. Meanwhile, increasing of polymer concentration resulted in lower porosity due to decreasing of macrovoids pore size shown by scanning electron microscope (SEM) micrograph. Furthermore, DES was prepared by the mixing of choline chloride (ChCI) and ethylene glycol (EG), then impregnated into the membrane matrix via vacuum method. In order to increase DES loading,selection and addition of pore additives as well as manipulating the coagulant bath medium were carried out. The CO₂ separation performance of LM was tested using gas permeation at variation of pressure and flow rate. The membrane characterizations as well as gas permeation test results showed that supported-DES-membrane fabricated by using 6 wt.% polyethylene glycol (PEG), 20wt.% polymer and 74 wt.% DMAc in a polymer solution and having a mixture of 25 wt. % of ethanol and 75 wt. % distilled water as a coagulant bath shows the highest porosity with a combination of finger and sponge-like microstructure. From energy dispersive X-ray spectrometer (EDX) and SEM analysis, the respected membrane was able to hold DES at the highest percentage. The optimum CO₂ permeability recorded in this study was 4.41 x 10`6 barrer with CO₂/N2 selectivity at 8.28. Gas separation performance using DES as a solvent in LM demonstrated 99% better as compared to conventional ionic liquid, but a bit lower in terms of CO₂/N2 selectivity. Hence, the promising result obtained in this study demonstrates the potential of DES for gas separation, especially in CO₂ separation.