PVA-PEI facilitated transport membranes for separation of CO2 and H2

This thesis aims to prepare thin-film nanocomposite membranes for the separation of CO2 and H2 to improve the efficiency and purity of hydrogen production from conventional fossil fuels. Graphene oxide (GO) was chosen for the nanofiller phase due to its gas barrier properties. Polyvinyl alcohol (PVA) was chosen as a polymer matrix, while GO is modified using Polyethyleneimine (PEI) of low molecular weight (Mw:800) to enhance its compatibility with the polymer matrix. Different types of membranes were fabricated and the effect of different parameters such as concentration of GO, pH of PVA, and concentration of PEI on separation performance were studied. The experiments showed that GO tends to aggregate when its concentration is more than 0.25 wt.% in the polymer matrix. Moreover, the stability of GO was observed to be less than 1 day which prevented the continuation of further analysis using GO. It was also observed that by adjusting the pH of PVA from acidic to basic, the CO2 permeability of the PVA membranes was slightly affected due to compact surface interactions between the polymer chain of PVA. Additionally, variations in thickness resulted in a maximum CO2 permeability at pH 10. The addition of PEI to the PVA improved the separation performance compared with pure PVA due to the presence of reactive amine carriers on PEI. By increasing the PEI concentration from 0 to 20 wt.% in the PVA matrix CO2 permeability increased gradually. However, further increasing the PEI concentration to 40 wt.% resulted in reduced CO2 permeability. Moreover, the selectivity of the developed membranes remained almost constant in both cases. The findings of this study demonstrated that PVA/PEI composite membranes are more effective than pure PVA membranes in the separation of CO2 and Hydrogen.