In this work, the nanoadsorbent efficiency of nickel oxide nanoparticles (NiONPs) for the degradation of rhodamine B (RhA-B) dye was examined. The NiONPs were synthesized by green technique using NiCl<inf>2</inf>·H<inf>2</inf>O and Phyllanthus emblica fruit extract. The NiO nanoparticles were characterized using UV, FTIR, FESEM, HRTEM and TGA/DTA analysis to study the decomposition pattern, functional groups, crystalline size and elemental composition of nanoparticles. TEM analysis showed that the nanoparticles were spherical, highly crystalline, highly agglomerated and appeared as clusters of nanoparticles in the size range converted into tubular shape. The prepaed NiONPs were used for batch experiments to evaluate the adsorption capacities of the dye. The influence of various key parameters, i.e. adsorbent dosage and initial dye concentration were investigated. The extent of adsorption of RhA-B was found to be 88% at pH 6. Langmuir isotherm showed maximum monolayer adsorption with qm values from 328-465 mg/L. The kinetic investigation of RhA-B degradation followed a pseudo-second-order rate kinetics with a rate constant of 2.0495 × 10-2mg-1min-1. ΔGo° = - 79.00 kJ/mol indicates that the adsorption is chemisorption and spontaneous. © 2023 Elsevier B.V., All rights reserved.