Synthesis of graphene oxide–magnesium oxide composites and cationic dyes removal from water

Abstract

Herein, graphene oxide (GO)–magnesium oxide (MgO) nanocomposites (GO-MgO) (GO1.5MgO, GO3MgO, GO4.5MgO, and GO6MgO) were synthesized and characterized. Methylene blue (MB) and crystal violet (CV) as cationic dyes were used as contaminants. The results showed that MB and CV adsorption followed pseudo-second-order kinetics. The isotherm data indicated that MB and CV removal obeyed the Langmuir isotherm model. It means that the adsorption process was carried out in specific homogeneous sites on the adsorbent surface. The adsorption thermodynamic data presented that the negative Δ G of CV and MB removal by the synthesized adsorbents presented physical and spontaneous adsorption. Also, the positive values of Δ H and Δ S showed the endothermic properties of adsorption and the increase of dye irregularity on the adsorbent surface. The amount of dye adsorbed on the synthesized adsorbents increases by increasing the contaminant concentration. The results indicated that contaminant adsorption capacity enhances by enhancing the adsor-bent dose and then decreases to some extent. As the adsorbent dose increases, the active sites will be more accessible. The adsorbent particles are agglomerated at values higher than the optimal value of the adsorbent dose. Thus dye removal is reduced. It can be concluded that the synthesized GO-MgO nanocomposites could be used as alternative adsorbents to remove cationic dyes.