**Abstract**

The adsorption of Ni(II) onto blue green marine algae (BGMA) in batch conditions is being investigated. The highest adsorption capacity of BGMA was found to be 42.056 mg/g under ideal testing conditions, where the initial Ni(II) metal ion concentration was adjusted from 25 ppm to 250 ppm. The optimal pH, biomass loading, and agitation rate for maximum Cu(II) ion removal have been determined to be 6, 2 g and 120 rpm, respectively. For the equilibrium condition, 24 hours of contact time is allowed. At room temperature, all of the experiments are conducted. The isotherm has a L shape, based on the equilibrium experimental data. It indicates that there is no considerable competition for active sites between the solvent and Ni(II). There is no strong competition between the solvent and Ni(II) for the active sites of BGMA, indicating that there is no strong competition between the two. It also suggests that the BGMA's Ni sorption ability is restricted (II). The experimental data is validated using multiple isotherm models, and the mechanism of adsorption is then discovered, as well as the process design parameters. The Fritz-Schlunder-V isotherm model is particularly relevant in defining the mechanism of Ni(II) adsorption under the conditions used in this study, according to modelling studies. This model's qmax of 41.89 mg/g shows that it matches experimental data more closely.

**Keywords:** divalent nickel, adsorption, isotherm models, blue green marine algae, modelling
