Reusability, optimization, and adsorption studies of modified graphene oxide in the removal of Direct Red 81 using response surface methodology

In the present study, graphene oxide (GO) was synthesized by the oxidation of graphite powder using the Hummers method. The GO was polymerized with poly methyl vinyl ketone (PMVK) and aniline (GO-MVK-ANI). It was utilized as the effective adsorbent towards the removal of Direct Red 81 (DR 81) in aqueous solutions. Response surface methodology (RSM) was applied for optimization and adsorption studies of Direct Red 81 removal using GO-MVK-ANI. According to the RSM results, the effects of the main parameters (the adsorbent dose, contact time, and pH) in dye removal efficiency were investigated. The R2 value of 99.99% indicated that the predictions of the RSM model were acceptable for Direct Red 81 adsorption onto the adsorbent. The regeneration of GO-MVK-ANI for the dye adsorption showed fine efficacy in up to seven times of recyclability. The RSM model was used to evaluate the respective minimum and maximum values of 56.52% and 99.90% for the removal efficiencies of Direct Red 81.