KUCEJOVÁ, Lucia: Adsorption of Ni(II) Ions by Biosorbents [Bachelor thesis]. Constantine the Philosopher University in Nitra. Faculty of Natural Sciences; Department of chemistry. Supervisor: Mgr. Jana Braniša, PhD. Degree of Qualification: Bachelor, teachers of academic subjects biology, chemistry. Nitra: FPV, 2021. 42 p. The bachelor thesis is focused on providing an overview of published research on the adsorption of Ni(II) ions from aqueous solutions by adsorbents of plant and animal origin. The thesis compares chemical modification and various experimental conditions, such as the pH of the solution, the initial metal concentration, the dose of biosorbent, temperature and contact time on the adsorption efficiency. The solution's pH value mainly influences the efficiency of the removal of Ni(II) ions by the biosorbent. Maximum adsorption was observed in the range of pH values 4 – 7. Monitoring of other parameters indicates inconsistent results depending on the type of adsorbent. Two mathematical models, Langmuir and Freundlich, were applied to evaluate the experimental data of adsorption isotherms. A review of these studies shows that the adsorption of heavy metals by biosorbents has the potential to compete with other conventional techniques.