Phoenix dactylifera mediated green synthesis of Mn doped ZnO nanoparticles and its adsorption performance for methyl orange dye removal: A comparative study

A comprehensive study on Phoenix dactylifera mediated green synthesis of ZnO, and different content (2%, 4%, 6%, 10%) of Mn doped ZnO nanoparticles (Mn@ZnO-NPs) were performed to evaluate the elimination of dispersing acid dye methyl orange (MO) from aqueous solutions. The as-synthesized ZnO and Mn@ZnO-NPs adsorbents were characterized by XRD, FT-IR, UV-VIS spectrophotometer, TEM, and point of zero charges (pHpzc). In accordance with the sorption capacity of the adsorbents, the 10% Mn@ZnO-NPs shows the optimal adsorption of MO dye. The adsorption results perfectly matched the pseudo-2nd order kinetic model and Freundlich adsorption isotherm. The maximum monolayer adsorption capacity were recorded to be 87.72, 90.09, 91.74, 92.59, 96.15 mg/g for ZnO and 2%, 4%, 6%, and 10% Mn@ZnO-NPs, respectively at the pH 5, adsorbent dose 1.5 g/L, and 303 K. The thermodynamic data of all the systems confirms that the adsorption of MO was feasible and endothermic in nature. Regeneration study showed that after four successive ad-/de-sorption cycles, the absorption potential of ZnO and 10% Mn@ ZnO was not reduced more than 15%. The collective benefits of easy preparation, non-toxic and good removal efficiency towards anionic dye make Mn@ZnO-NPs as a novel adsorbent.