Influence of GO, MXene, and MoS₂ on sodium alginate–polyacrylic acid hydrogels for forward osmosis groundwater treatment

Hydrogels have emerged as promising draw agents for forward osmosis due to their high-water uptake capacity and their polymeric structure which may reduce reverse solute transport compared with conventional dissolved draw solutes. While graphene oxide (GO) has previously demonstrated potential for enhancing hydrogel performance, the effects of other emerging 2D materials such as Ti₃C₂Tₓ MXene and MoS₂ on hydrogel-based draw agents remain largely unexplored. Therefore, this work investigates the influence of incorporating different 2D materials into sodium alginate–polyacrylic acid hydrogels dedicated to forward osmosis groundwater treatment. Eight hydrogels were prepared, where one was used as a control hydrogel (HG-1) that did not contain any 2D materials, while the other seven hydrogels (HG-2 to HG-8) contained either one, two, or all the 2D materials synthesized in this work. All the 8 hydrogels were characterized using scanning electron microscopy, energy dispersive X-ray elemental mapping, swelling ratio tests, and compressive strength tests. Moreover, the water tests of the hydrogels were implemented using two feeds: deionized water (DI water) and groundwater. The GO-containing hydrogel HG-2 had the best performance among all the other hydrogels, drawing water at 0.581 ± 0.012 LMH when the DI water feed was used and 0.451 ± 0.029 LMH when the groundwater feed was used. The collected water products were analyzed to inspect the removal of the salinity and hardness of the ions from the groundwater feed, and the FO-membrane–hydrogel system produced water with high reductions in salinity and hardness. Lastly, a partial gate-to-gate life cycle assessment was conducted for the best-performing HG-2 formulation to evaluate the environmental impacts associated with the hydrogel synthesis stage, excluding the synthesis of the 2D materials.