Gas responsive magnetic nanoparticle as novel draw agent for removal of Rhodamine B via forward osmosis: High water flux and easy regeneration

Abstract

The effective draw agent is vital for developing the forward osmosis (FO) process in water reclamation applications. We have explored the feasibility of using gas-responsive magnetic nanoparticles (NPs) as a novel draw agent for the FO-based separation process. These NPs were fabricated by growing CO2-responsive poly[2-(dimethylamino)ethyl methacrylate] on magnetic Fe3O4 NPs surface (Fe3O4@PDMA). The successful growth of PDMA brushes on the Fe3O4 NPs was confirmed by FTIR, XRD, SEM, VSM, EDS, DLS, Zeta and TGA analysis. Then, the FO water flux, pH and CO2-responsibility, regeneration and dye-removal performance of Fe3O4@PDMA were thoroughly evaluated. The Fe3O4@PDMA NPs were exhibited considerable water flux in acidic conditions. Moreover, the CO2 purging time on water flux was studied. Experimental results revealed that the FO water flux increased with the increase in CO2-purging time. The water flux driven by the Fe3O4@PDMA NPs was found to be a strong function of the net polymer coverage on M NPs, that is, net available hydrophilic groups. The results showed that the water flux of Fe3O4@PDMA-12 h (high content) was much higher than that of Fe3O4@PDMA-4 h (low content). In addition, tunable protonation/deprotonation of PDMA brushes allows us to recycle the draw agent using an external magnetic field with minimum energy consumption. Furthermore, high water flux was achieved for Fe3O4@PDMA in colored wastewater treatment via the FO process.