Fabrication of mixed matrix membranes with zinc ion loaded titanium dioxide for improved CO2 separation

Abstract To date, mixed matrix membranes with nano-filler was considered to be an effective method to enhance the gas permselectivity of membrane separation. In this work, mixed matrix membranes for the facilitated transport of CO2 were prepared. Hexafluoroisopropylidene diphthalic anhydride - based aromatic polyimide was applied as polymeric matrix, while the zinc ion functionalized titanium dioxide spherical nano-particle was selected as nano-filler. The physical property, chemical structure and membranes morphology were characterized by FT-IR, TG, XRD, SEM, CA and XPS. Gas permselectivity was investigated using binary mixture gas of CO2/N2 and CO2/CH4, respectively. The effects of nano-filler content, functional group, operation temperature on gas permselectivity were studied. Results show that the incorporation of spherical nano-filler can effectively restrict the polymer chain packing and lead to low crystallinity. By incorporation of zinc ion modified spherical nano-filler, the CO2 permeability increased about 68.7∼78.7%. PI-TiO2-PDA-Zn2+ mixed matrix membranes with 7.5 wt% nano-filler addition displayed the highest CO2 permeability (145.37 Barrer for CO2/N2 feed gas and 108.36 Barrer for CO2/CH4 feed gas, 1 Barrer = 7.5×10-18 m2 s-1 Pa-1) and satisfied CO2/inert gas selectivity (CO2/N2 selectivity of 49.28 and CO2/ CH4 selectivity of 49.48). CO2 permeability increased and selectivity decreased with the elevated temperature. Besides, the membrane exhibited good stability in the 30 days testing.