Osmotically-driven membrane processes for sustainable water reuse and resource recovery

Abstract

Forward osmosis (FO) is a promising membrane process with the potential to offer energy-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 polyethyleninime (PEI) macromolecule [Molecular weights Mn of 10000 Da and Mw of 25000 Da] as osmotic agent to formulate new draw solutions that could be deployed using porous FO membranes with nanofiltration (NF) selective layers. Furthermore, a demonstration of our FO process of branched PEI draw solutes and porous FO membranes was conducted for microalgae harvesting, which is a promising platform to secure the sustainable water-energy-food nexus. To assess the potential of PEI-based draw solutions, we combine (i) physicochemical studies as osmotic agents, (ii) membrane preparation and characterization, (iii) water flux and reverse solute permeation measurements and (iv) draw solution concentration experiments UF and NF. The overall results of this study suggest that branched PEI macromolecules with higher molar mass (Mw of 25000 Da) are promising building blocks for the development of draw solutions of osmotically-driven membrane processes using porous FO membranes with NF selective layers for sustainable water reuse and resource recovery