Novel bio-polymer based membranes for CO2/CH4 separation

This work deals with the utilization of the poly(lactic acid) (PLA) to fabricate biopolymer membranes by phase inversion technique for the treatment of gaseous streams rich in CO2 and CH4. PLA is an excellent biopolymer constituting a viable option to most of the traditional fossil-based polymers, possessing zero environmental impact once exhausted and interesting gas separation properties as membranes. Several parameters of the phase inversion process were studied in order to identify the optimal PLA membrane preparation, as a function of the best performance in terms of ideal CO2/CH4 selectivity, CO2 permeability and membrane degradability. The PLA membranes were fully characterized in terms of morphology, thickness, differential scanning calorimetry, Scanning Electron Microscopy and Fourier Transform Infrared Spectroscopy analyses. Afterwards, single gas permeation tests were performed in order to prove the relevance of PLA membranes in CO2/CH4 separation, and membrane degradation tests under water as well. The results of the wide experimental campaign on PLA membranes preparation evidenced how specific membrane samples (thickness > 25 mu m) possess quite high CO2/CH4 ideal selectivity (between 220 and 230) and CO2 permeability similar to 11 Barrer at ambient temperature, which allowed to collocate this biopolymer based membrane material above the correspondent Robeson's upper bound.