Feasibility of Poly (Vinyl Alcohol)/Poly (Diallyldimethylammonium Chloride) Polymeric Network Hydrogel as Draw Solute for Forward Osmosis Process

Ananya Bardhan; Senthilmurugan Subbiah; Kaustubha Mohanty; Ibrar Ibrar; Ali Altaee

doi:10.3390/membranes12111097

Feasibility of Poly (Vinyl Alcohol)/Poly (Diallyldimethylammonium Chloride) Polymeric Network Hydrogel as Draw Solute for Forward Osmosis Process

Membranes (Basel). 2022 Nov 3;12(11):1097. doi: 10.3390/membranes12111097.

Authors

Ananya Bardhan¹, Senthilmurugan Subbiah¹, Kaustubha Mohanty¹, Ibrar Ibrar², Ali Altaee²

Affiliations

¹ Department of Chemical Engineering, Indian Institute of Technology Guwahati, Guwahati 781039, India.
² Centre for Green Technology, School of Civil and Environmental Engineering, University of Technology Sydney, 15 Broadway, Sydney, NSW 2007, Australia.

Abstract

Forward osmosis (FO) has been identified as an emerging technology for the concentration and crystallization of aqueous solutions at low temperatures. However, the application of the FO process has been limited due to the unavailability of a suitable draw solute. An ideal draw solute should be able to generate high osmotic pressure and must be easily regenerated with less reverse solute flux (RSF). Recently, hydrogels have attracted attention as a draw solution due to their high capacity to absorb water and low RSF. This study explores a poly (vinyl alcohol)/poly (diallyldimethylammonium chloride) (PVA-polyDADMAC) polymeric network hydrogel as a draw solute in forward osmosis. A low-pressure reverse osmosis (RO) membrane was used in the FO process to study the performance of the hydrogel prepared in this study as a draw solution. The robust and straightforward gel synthesis method provides an extensive-scale application. The results indicate that incorporating cationic polyelectrolyte poly (diallyldimethylammonium chloride) into the polymeric network increases swelling capacity and osmotic pressure, thereby resulting in an average water flux of the PVA-polyDADMAC hydrogel (0.97 L m−2 h−1) that was 7.47 times higher than the PVA hydrogel during a 6 h FO process against a 5000 mg L−1 NaCl solution (as a feed solution). The effect of polymer and cross-linker composition on swelling capacity was studied to optimize the synthesized hydrogel composition. At 50 °C, the hydrogel releases nearly >70% of the water absorbed during the FO process at room temperatures, and water flux can be recovered by up to 86.6% of the initial flux after 12 hydrogel (draw solute) regenerations. Furthermore, this study suggests that incorporating cationic polyelectrolytes into the polymeric network enhances FO performances and lowers the actual energy requirements for (draw solute) regeneration. This study represents a significant step toward the commercial implementation of a hydrogel-driven FO system for the concentration of liquid-food extract.

Keywords: SWRO-FO hybrid process; draw solute; forward osmosis; hydrogel; liquid-food concentrate.

Grants and funding

This research was funded by the Department of Science and Technology, Ministry of Science and Technology, Government of India, Project Number No. DST/TM/WTI/2K16/73 (G).