Polyhydroxyalkanoate (PHA) based microfiltration membranes: Tailoring the structure by the non-solvent induced phase separation (NIPS) process

Abstract

Within the purpose of developing more sustainable membrane systems, it is herein proposed to implement a biobased and biodegradable material, the poly(hydroxybutyrate-co-hydroxyvalerate) (PHBHV), to replace conventional polymers in a commonly used membrane fabrication process. The PHBHV based membranes were made by non-solvent induced phase separation (NIPS) using N-methyl-2-pyrrolidone (NMP) as solvent. The process parameters and dope solution composition were developed in order to give structures suitable for performances characterization. In that sense, the microstructures were characterized in case of non-supported and supported membranes. The addition of hydrophilic additives, ethylene glycol (EG) and polyethylene glycol 300 g mol−1 (PEG300), was linked to the morphology changes. Porous asymmetric membranes were obtained in case of the non-supported membranes or supported membranes with a low amount of additive (1 wt%). Otherwise, symmetric porous membranes, made of interconnected crystal lamellas, were observed. The particularly high crystallinity of this biomaterial involved some different microstructures compared to classic polymers. Both types of structures demonstrated decent rejections of a clay dispersion. Due to the increased pore size, the permeabilities were greatly improved with the additives and values up to 480 L m−2 h−1.bar−1 were achieved.