Synthesis and Characterization of Magnetic Nanoparticles as a Candidate Draw Solution for Forward Osmosis

Abstract

Synthesis of magnetic nanoparticles (MNPs) attracted the interest of many researchers for many applications. Among the applications of interest is their potential use as a draw solution in forward osmosis owing to their ease of recovery and surface-area-to-volume ratio. Such a draw solution is expected to generate high osmotic pressure. However, for such an application, the choice of coating material is a crucial parameter which is still poorly understood. In this paper, we tested three different coating materials with different properties (molecular weight and hydrophobicity) to better understand their effect on the properties (ability to generate flux, dispersion, magnetic properties, recovery, etc.) of coated MNPs. Magnetic nanoparticles were prepared using co-precipitation method. Various coating materials were used in this study, namely dextran 40,000, oleic acid and polyethylene glycol 2,000 and 4,000. Magnetite co-precipitation and nanoparticle coating were carried out simultaneously. The coated nanoparticles were characterized using scanning electron microscope, X-ray Powder Diffraction, coating ratio, and osmotic pressure and flux generation. Findings indicate that in order to suppress aggregation and generate osmotic pressure, coating material should have low molecular weight and feature a hydrophilic property.

Optimization of Magnetic Nanoparticles Draw Solution for High Water Flux in Forward Osmosis

“…The water flux measured in the experiment was 1.98 LMH which is close to the predicted value of 2.06 LMH. The water flux of the synthesized bare iron oxide nanoparticles was low compared to the water flux obtained when using stabilized iron oxide nanoparticles [33][34][35]. Therefore, it is expected to obtain high water flux when stabilizing the optimized bare iron oxide nanoparticles that were synthesized in this study.…”

Highly stable superparamagnetic iron oxide nanoparticles as functional draw solutes for osmotically driven water transport

“…Among these, a relatively small number of studies were evaluated for long operation times (>4 h), all of which observed significant flux decline (up to 50%) due to membrane blocking (from the draw side) 10,13 . For the regeneration/recovery of IONPs, most studies also observed aggregation, which also contributes to flux decline 8,12,[16][17][18] . For all, IONPs aggregation and deposition on the surface of membrane (blocking) remains a critical challenge for effective, long term operation.…”