The effect of nanosheets on polymer hydrogels performance in Rhodamine B dye removal by forward osmosis process

Abstract

This study provides a novel and straightforward method for preparing nanocomposite polymer hydrogels (NPHs) as high-performance forward osmosis (FO) draw agents. Pure polymer hydrogel was synthesized via in-situ free-radical copolymerization of acrylic acid (AA) and N-vinyl pyrrolidone (NVP) monomers. Precisely, NPHs were fabricated through the same procedures except for the use of different nanosheets (clay and graphene oxide, GO). The successful incorporation of clay and GO into the hydrogel matrix was confirmed by different analyses. Then, the effect of nanofiller type on the microstructure characteristics (surface porosity), swelling ratio, and FO-performance (FO water flux and water recovery) of the modified NPHs were systemically studied. Compared to the pure hydrogel, clay and the GO-modified NPHs (with 0.5 wt% nanofiller) presented higher FO water flux due to improved swelling ratio, osmotic pressure gradient, and hydrogel surface porosity. In addition, the NPHs were recovered and reused four times without any significant reduction in FO water flux. Finally, the best performing clay and GO-modified NPHs were used as proper draw agents to treat the water-soluble Rhodamine B dye from an aqueous solution (200 ppm). Therefore, this study provides a simple method for preparing highly porous and hydrophilic NPHs, which can probably have potential applications in the FO process.