Graphene Oxide–Agar–Agar Hydrogel for Efficient Removal of Methyl Orange from Water

We report the preparation of graphene oxide (GO)–agar–agar hydrogel and its utilization toward the removal of methyl orange (MO) dye from water. Graphene oxide–agar–agar composite hydrogel has been prepared from a mixture of chemically synthesized GO and agar–agar powder in hot water followed by cooling at room temperature. To study the dye removal property of the prepared composite hydrogel, we placed the GO–agar hydrogel into an aqueous solution of MO. The dye adsorption was apparent as the color of the solution started disappearing immediately after the addition of the GO–hydrogel. To quantify this effect further, the dye removal efficiency was evaluated and the results suggest that the removal efficiency could reach up to 99% depending on the pH of the medium and the dose of GO used. In an acidic medium (pH ~ 2), the removal efficiency was found to be relatively higher, compared to that of an alkaline medium. The removal efficiency was improved as the dose of GO in the hydrogel was increased. Further, the kinetics of the dye adsorption onto the GO surface has been examined by plotting the experimental data according to Lagergren pseudo-first-order and pseudo-second-order models. The results from these analyses suggest that the pseudo-second-order model gives a better fit for the experimental data, than the first-order model. Our results show that GO–agar gel can be efficiently used for the removal of various toxic dyes from wastewater.