The current work deals with the synthesis of ZnO NPs and Mg+2-doped ZnO NPs by a simple coprecipitation method. The structure and morphology of the synthesized nanoparticles were studied by Fourier transform infrared spectroscopy, field emission scanning electron microscopy (FESEM), dynamic light scattering (DLS), and X-ray diffraction. Synthesized nanoparticles are used as an adsorbent for the elimination of toxic dye and they exhibited good efficacy toward the removal of eosin dye. The experimental data were examined with different kinetic models like pseudo-first order, pseudo-second order, and intraparticle diffusion. Isotherm models Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich (D-R) were used to study the equilibrium data. Maximum dye adsorption was obtained at pH = 6, an adsorbent dose of 0.6 g, a temperature of 55 degrees C, an agitation speed of 150 rpm, and a dye concentration of 10 ppm. The maximum dye removal values were found to be 97.9 and 98.4% in ZnO NPs and Mg+2-doped ZnO NPs, respectively. The regeneration efficiencies were 93 and 96% in the first cycle and they were retained up to 71 and 81% after the fifth cycle in ZnO NPs and Mg+2-doped ZnO NPs, respectively. This envisaged that doping with Mg+2 improves the stability and reusability of ZnO NPs. The R-L value of dye adsorption onto Mg+2-doped ZnO NPs is lower than that onto ZnO NPs. The R-2 value of pseudo-second order was <0.99 and was in agreement with the experimental values of adsorption kinetics. The value of Delta G degrees is negative, which indicates that the dye adsorption process is spontaneous.