Effective adsorptive removal of azo dyes over spherical ZnO nanoparticles

To minimize the detrimental effects of contaminated water, technology-based smart treatment processes are prerequisite for sustainable supply of drinking water. Nano-sized metal oxides are the best choice futuristic adsorbents for the removal of water toxins as such materials are associated with the characteristics of simplicity, versatility, efficacy and high surface reactivity. In this study, we describe a nanostructured ZnO adsorbent, which displays remarkable efficiency toward the removal of widely used azo dyes, methyl orange (MO) and amaranth (AM), from aqueous systems. The ZnO nanoparticles (ZnO-NPs) were prepared by simple co-precipitation method, and the structural morphology of the as-prepared NPs was revealed by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform IR (FTIR) and Brunauer-Emmett-Teller (BET). After complementary characterization, as-prepared ZnO-NPs were further used as adsorbent for the removal of toxic azo dyes (MO and AM) from water. The results revealed that an amount of 0.3g ZnO-NPs showed maximum removal efficiency of each dye (40 ppm) at pH 6. It was further confirmed that the adsorption of both dyes on ZnO-NPs strongly followed the Langmuir model whereas the kinetics studies revealed that each adsorption process was pseudo second order. Moreover, the findings suggested that R-SO3- groups were active sites and the electrostatic attraction between the dyes (MO-, AM(-)) and ZnO-NPs(+) may be the prime adsorption mechanism of designated removal systems. (C) 2018 Brazilian Metallurgical, Materials and Mining Association. Published by Elsevier Editora Ltda.