Green-synthesized NiO NPs using celery extracts for brilliant green dye adsorption: Kinetic, thermodynamic, and isotherm studies

This study focuses on the environmentally friendly preparation of nickel oxide nanoparticles using an aqueous extract of using celery (Apium graveolens) extract as a reducing medium for nickel ions. This oxide was used to adsorb Brilliant Green (BG) dye from its aqueous solutions using the batch adsorption method. Various techniques were employed to characterize and study its surface. XRD analysis spectrum revealed that the particle size obtained was around 16.5 nm of green-synthesized NiO using celery extracts. The value of Zeta potential was -34.9 mV suggesting the stability of the colloidal suspension. While the hydrodynamic diameter value of DLS was189.1 nm indicated the presence the layer of a bio-organic celery extract capping. The mean pore diameter of 28.198 nm, a specific surface area of 16.567 m²/g, and the type of isotherm was IV demonstrated in BET analysis suggesting mesoporous architecture of green-synthesized NiO. Pseudo- 1 st and pseudo- 2 nd kinetic models and Langmuir and Freundlich isotherm models have been utilized to examine the adsorption mechanism. The pseudo- 2 nd kinetic and Freundlich isotherm models were properly matched to the BG dye adsorption data. The negative value of ΔG° (-0.826 to -2.726 kJ/mol) and a positive value of ΔS° (56.68 J/mol·K) and ΔH° (15.932 kJ/mol) indicate the endothermic spontaneity of adsorption.