Nanoporous Polyethersulfone Substrates Improved by Hydrophilic Additives for Composite Membranes in Gas Separation
Methods to improve morphology of nanoporous polyethersulfone (PES) substrate by incorporating a small amount of hydrophilic additives, such as polyvinylpyrrolidone (PVP), hydroxylated polyethersulfone (PES-OH), and sulfonated polysulfone (SPSf)
Nanoporous polymer substrates are commonly used to provide the mechanical strength for composite membranes in gas separation. The surface property and morphology of the substrate are critical for improving the transport performance of composite membranes. The present invention discloses an effective method of fabricating polymer (e.g., polyethersulfone (PES)) substrates in pilot scale for composite membrane preparation that can be used for gas separation, such as CO2 separation from flue gas. The resultant improved PES substrates are effective support for the fabrication of composite membranes for gas separations including the removal and capture of CO2 from N2-containing streams, e.g., flue gas.
Researchers at The Ohio State University, led by W.S. Winston Ho, have shown that the hydrophilicity and morpholoy of nanoporous polyethersulfone (PES) substrate can be improved by incorporating a small amount of hydrophilic additives, such as polyvinylpyrrolidone (PVP), hydroxylated polyethersulfone (PES-OH), and sulfonated polysulfone (SPSf). The surface and bulk morphologies of PES substrate were affected by providing less gas permeation resistance by the incorporation of the hydrophilic additives. Moreover, a thinner selective layer can be coated on top of the improved PES substrates due to the enhanced hydrophilicity. Both the morphological and hydrophilic modifications can improve the separation performance of the composite membrane. The developed PES substrates have a porous surface possessing an average pore size of 28.5 – 70 nm and a surface porosity of 11.4 – 18.5% with different preparation conditions.