The potential to remove Ni (II) from aqueous solutions through adsorption using Delonix regia (Gulmohar) tree bark was investigated. The effects of pH, contact time, initial concentration and adsorbent dosage on the adsorption of Ni (II) were studied. The different experimental conditions were investigated in this study. It was observed that the amount of Ni (II) adsorbed increases rapidly initially, then system approaches equilibrium within 90 minutes. The extent of Ni (II) removal increased with increase in time and adsorbent dosage. The reaction kinetics was studied using different models. Langmuir and Freundlich adsorption model is used for the mathematical description of the adsorption equilibrium and isotherm constants are evaluated. Equilibrium data fitted very well to the Langmuir and Freundlich model. The Langmuir adsorption capacity was found to be 4.81 mg/g. The Freundlich constants Kf and n were 0.4315 and 1.5715, respectively. The pseudo first- and second-order kinetic models were also applied to the experimental data. The data agreed very well with the pseudo second-order kinetic model.
