Preparo de membranas de separação compostas por Poli (Ácido Lático) pelo método de inversão de fases para permeação de gases

Abstract

The main objective of carrying out a membrane separation process is the separation of components in solution, due to the ability of the membrane to transport some substances present in the feed phase, as well as blocking the passage of others. Despite many studies and implemented strategies to extend the useful life, fouling is still the main cause for the disposal of separation membranes, a factor that generates tons of this technology disposed in landfills, due to the fossil origin of the polymers used in its manufacture. Thus, in this work poly(lactic acid) (PLA) membranes were prepared by the phase inversion method and characterized to verify their possible application in gas separation processes using synthetic air. PLA membranes were prepared using dichloromethane (DCM) as solvent and distilled water as non-solvent. The produced membranes, at concentrations of 8% and 12% by mass of polymer, were characterized by Scanning Electron Microscopy and Infrared Spectroscopy by Fourier Transform. Their specificities regarding permeability were also evaluated. The results showed that the properties on the morphology and chemical structure of PLA were not altered by the use of the chosen solvent. The membranes showed an asymmetrical structure, with the formation of a porous layer at the top followed by a porous substructure of spherical pores. The observed pore diameter range was 0.43 µm to 0.85 µm for the 8% concentration membrane and 0.55 µm to 1.34 µm for the 12% concentration membrane. The thickness of the dense layer for the 8% membrane was approximately 17.21 µm, less than that of the 12%, which presented a dense layer of approximately 25.55 µm. The transmembrane gas flow was lower for the 8% membrane, as it suffered greater compaction due to the lower percentage of polymer (m/m) than the 12% membrane. The observed transmembrane flux for the 8% membrane was 50.90 L m-2 h-1 while for the 12% membrane a flux of 312.89 L m-2 h-1 was observed. In the degradability tests, it was possible to observe the biodegradation of the membrane in a relatively short period – 12 days – by by placing it in different types of soil prepared in a similar way, showing that the solvent used did not have a great influence on the biodegradation properties of the polymer. It was possible to observe a great potential for degradability of the samples. [resumo fornecido pelo autor]