Sustainable manufacture of organic solvent nanofiltration membranes

Abstract

Membranes are a robust, reliable and economical technology. However, polymeric membranes are manufactured from polymeric and organic solvent sources derived from petrochemical sources. The high volatile organic compounds (VOC) emissions of the organic solvents and the non-recyclability of the polymers often question the membrane manufacture sustainability.

The main goal of this dissertation is the preparation of polymeric membranes for liquid separation through more sustainable processes. We report here the green preparations of hollow fibers, thin-film composite and integrally skinned asymmetric membranes.

An important part of the work is represented by the development of cellulose hollow fibers from ionic liquid solutions, avoiding strong alkali or harsh solvents. By tuning the manufacturing process, we prove that the membranes can be used for different applications such as oil-water separation, protein separation via ion-exchange chromatography and solvent purification via organic solvent nanofiltration. The main advantages of using cellulose to prepare hollow fiber membranes are the biodegradability of the polymer and the intrinsic chemical stability.

Another significant milestone of this work is replacing volatile solvents such as hexane during the thin-film composite membrane manufacture. As green alternative solvents, we decided to use naturally extracted oleic acid and decanoic acid. Due to their low costs and volatility, they represent a valid alternative for industrial membrane preparation through the interfacial polymerization process. The membranes prepared with this process were used for solvent resistant nanofiltration.

Finally, by using ionic liquids as solvents, we improved the manufacturing sustainability polytriazole asymmetric membranes synthesized in the lab.