Forward osmosis by introducing temperature responsive poly(propylene fumarate-co-N-vinyl pyrrolidinone) hydrogel as a new draw solute

Forward osmosis (FO) is an emerging technology for water desalination which requires no external force for its operation. The performance of FO for water desalination is dependent on draw solution (DS) that must provide high osmosis pressure, minimum reverse flux, and efficient separation of water. The purpose of this study was to evaluate and characterize the novel temperature responsive hydrogel of poly(propylene fumarate-co-N-vinyl pyrrolidinone) that can be used as a new draw agent in the forward osmosis process of desalination. These hydrogels were synthesized using the copolymerization method. By considering the initial PPF/NVP mole ratios, copolymers were synthesized to have their own distinctive volume phase transition temperature which was established using differential scanning calorimetry. Also, these hydrogels were systematically investigated by using scanning electron microscopy and Fourier transform infrared spectroscopy. The swelling ratios of the hydrogels at different temperatures were measured. Furthermore, the deswelling kinetics of the hydrogels was also studied by measuring their water retention capacity. The osmotic pressure, relative viscosity, and FO performance of poly(PPF-co-NVP) draw solutions with different concentrations are studied systematically. It is found that the osmotic pressure and water flux of the novel DS are directly dependent on the concentration of hydrogels. This work proposes an innovative temperature responsive material as the draw solution having some functions, that is, high osmotic pressure, low salt leakage, high generated flux, and efficient recovery by temperature difference. So, the excellent performance and available recovery route of the developed poly(PPF-co-NVP) hydrogels as the draw solutions imply their great potential as promising draw solutions for FO applications.