Nanocellulose-based membranes for CO2 capture

A new type of hydrophilic polymeric membrane based on microfibrillated cellulose (MFC) has been investigated to determine its potential in the field of gas separation, with special reference to carbon capture and natural gas sweetening. In particular, pure MFC films and MFC/Lupamin® (a commercial polyvinylamine produced by BASF) nanocomposite membrane have been synthesized and characterized. The effect of relative humidity on gas permeability was considered and independent water vapor sorption experiments were also carried out in order to correlate the permeation results to the actual water content in the materials. The experimental results showed that very good CO2/N2 and CO2/CH4 selectivity (in the order of 500 and 350 respectively) could be reached by using pure MFC films, which however showed limited CO2 permeability, never exceeding 25 Barrer, even at the highest relative humidity investigated. To increase the transmembrane flux, a hydrophilic polyvinylamine (Lupamin®) has been added to the pure MFC: the addition caused a marked increase in permeability of up to one order of magnitude but decreased the selectivity to about the same extent, thus decreasing the overall membrane performance. The reason of such behavior seems to be related to the amount of water absorbed by the membrane as the MFC/Lupamin nanocomposite resulted to be highly swollen by water vapor. Nonetheless, both the investigated materials showed separation performances that are above the 2008 Robeson's upper bound for CO2/N2 and CO2/CH4 systems, disclosing an attractive potential for the production of advanced gas separation membranes.