Polymers for Energy‐efficient Membrane Separations

Abstract

Advanced membrane materials have come under increased scrutiny due to the growing need for environmentally friendly and economically viable gas and organic solvent separation processes. Among them, Polymers of Intrinsic Microporosity (PIMs) are particularly noteworthy because of their high free volume and remarkable permeability, which make them ideal candidates for separation processes. However, despite their outstanding permeability and selectivity, long-term stability issues, particularly under harsh conditions and physical aging, have hindered their widespread adoption. This research seeks to address these challenges by investigating innovative approaches to enhance the performance and durability of membranes based on the prototypical PIM, referred to as PIM-1. A variety of modification options are investigated in this work with the goal of improving PIM-1 membrane stability and overall separation efficiency. These tactics include crosslinking PIM-1 with palladium acetate, functionalising PIM-1 with diethanolamine (DEA), and blending with polyethyleneimine (PEI) to enhance stability in organic solvents. The crosslinking process, in particular, leads to significant improvements in mechanical properties and solvent resistance, making the membranes more suitable for applications such as pervaporation of organic-organic mixtures and phenol removal via perstraction. The use of these modified PIM-1 membranes in pervaporation is exemplified by the separation of toluene from dimethyl sulfoxide mixtures. Crosslinked PIM-1 membranes demonstrated increased flux throughout the separation process, markedly surpassing conventional membranes. Furthermore, the functionalisation of PIM-1 with DEA enhanced selectivity, especially in the separation of methanol from organic solvents. The process of perstraction demonstrates the efficacy of PIM-1 membranes in extracting phenol from aqueous solutions, underscoring the benefits of crosslinking, which result in improved selectivity and stability during prolonged operation. This research not only enhances comprehension of PIM-1-based membrane modifications but also provides practical insights into their industrial applications, thereby facilitating the development of more efficient separation technologies for challenging solvent environments.