Osmotically driven membrane processes: Exploring the potential of branched polyethyleneimine as draw solute using porous FO membranes with NF separation layers

Abstract Forward osmosis (FO) is a promising membrane process with the potential to offer more efficient separation technologies for various environmental and industrial applications including (i) water reuse, (ii) desalination, and (iii) resource recovery. However, a major and unresolved challenge in FO remains the availability of efficient draw solutions that could be (i) implemented using porous and high flux FO membranes and (ii) reconstituted using a low-energy separation process. This study investigates the potential use of a branched polyethyleneimine (PEI) macromolecule ( M w of 25,000 Da) as osmotic agent to formulate new draw solutions that could be deployed using porous FO membranes with nanofiltration (NF) selective layers. To asses the potential of PEI-based draw solutions, we combine (i) osmotic pressure measurements, (ii) membrane preparation and characterization, (iii) water flux and reverse solute permeation measurements and (iv) draw solution concentration experiments using NF. The overall results of this study suggest that branched PEI macromolecules ( M w of 25,000 Da) are promising building blocks for the development of draw solutions for osmotically-driven membrane processes using a nanofibrous composite (NFC) polyacrylonitrile (PAN) membrane with an NF selective layer and no polyethylene terephthalate (PET) microporous support.