Forward osmosis desalination using pectin-coated magnetic nanoparticles as a draw solution

Abstract

In this study, magnetic Fe3O4 nanoparticles and pectin-coated magnetic Fe3O4 nanoparticles were used as a potential draw solution in forward osmosis (FO) water desalination applications due to enhanced water flux and easy recovery of the nanoparticles using magnetic separation. The effect of the pectin coating and the operating conditions on the FO performance were studied. The results showed that the fabricated nanoparticles have spherical and rod-like shapes of magnetite Fe3O4 crystal phase and superparamagnetic properties, which allow for facile recovery of the magnetic nanoparticles using a simple magnet. Water flux of 35.7 LMH was obtained using uncoated magnetic Fe3O4 nanoparticles as draw solution against deionized water as the feed solution. The effect of increasing water salinities in the feed side was studied, and water flux decrease of 14%, 58%, and 76% was observed for 0.25, 0.50, and 1.00 g% NaCl solution, respectively. Furthermore, the effect of the pectin coating (0.5 and 1.0 g%) on the use of magnetic nanoparticles as draw solution proved to have a significant effect on the pure water flux. The water flux of 2.6 LMH was obtained against 5.5 g%, 55,000 ppm, NaCl solution as the feed solution showing the potential use of magnetic nanoparticles as draw solution for brine management. The salt rejection exceeded 95% for all experiments. Therefore, this study demonstrates the superiority of magnetic nanoparticles as draw solution and provides new insights in using FO directly for desalination applications. Full economic analysis of the use of magnetic nanoparticles as draw solution for FO processes is still needed and is recommended for future research.