Synthesis and characterization of nanoporous polyethersulfone membrane as support for composite membrane in CO2 separation: From lab to pilot scale

Nanoporous polyethersulfone (PES) membranes were prepared from PES/N-methyl-2-pyrrolidone (NMP)/2-methoxyethanol (2-ME) casting solutions with water as coagulant by both vapor- and non-solvent-induced phase inversion steps successively under various preparation parameters. 2-ME was incorporated into the casting solution as a pore-forming additive because of its high affinity with water, leading to more open membrane morphology. A detailed study of the effects of different parameters, including polymer concentration, 2-ME/NMP ratio, relative humidity, water vapor exposure time, and water coagulation bath temperature, was conducted in lab-scale experiments to determine the operation guidelines for pilot-scale fabrication. 14-in. wide PES membranes were fabricated successfully by using a continuous casting machine. Parametric studies in pilot-scale fabrication were also carried out. Surface morphologies of PES membranes were characterized by scanning electron microscopy (SEM). The morphological differences between both scales by the same preparation conditions were compared. Based on the guidelines established from lab-scale experiments, the casting solution composition and coagulation bath temperature were optimized in a pilot-scale continuous casting machine to fabricate the 14-in. wide PES membrane with a desired morphology suitable for use as the substrate of composite membranes in CO2 separation. The studied fabrication process also showed the potential for the commercial production of the PES membrane in a larger scale by the vapor- and non-solvent-induced phase inversion technique.