Nanocellulose based facilitated transport membranes for CO2 separation

In the present work the performance of a new membrane material, based on Microfibrillated Cellulose (MFC), was investigated in view of its use in CO2 separation applications. In particular the membranes were obtained by casting, from a solution of carboxymethylated MFC and Lupamin (a Polyvinylamine produced by BASF), followed by a thermal treatment at 105 °C. Permeability of CO2 and CH4 were measured at 35 °C as a function of relative humidity and water sorption experiments were performed as well to relate the previous results to the actual water content in the membrane. As a reference, pure MFC films have been also prepared and their gas permeability tested in the same conditions. The overall results suggest that both MFC and MFC-Lupamin films have really interesting performance for the CO2/CH4 separation showing very high selectivity values (higher than 400) which place both materials well above the trade-off curve of 2008 Robeson's plot. In particular MFC films showed higher maximum selectivity but lower average CO2 permeability with respect to the MFC-lupamin blends probably because of the different level of water absorbed by the two materials. Pure MFC indeed never exceeded 10% water uptake, while the Polyvinylamine blend showed water sorption very similar to the previous material up to 60% RH; it then definitely increased, reaching a mass uptake higher than 50% at the maximum water activity inspected.