In this study a non-competitive adsorption of NO₂^- ions to alumina surface was studied in an aqueous system. To express the magnitude of the process, we used Langmuir and Freundlich adsorption models and it was seen that the equilibrium data fitted well to both models in the concentration range studied. Different volumes (20 to 100 cm3) of NaNO₂ solution of 10^-3 to 10^-1 M were used in experiments. Also, we used activated alumina (0.2 to 1.0 g) and a pH values around 4, mentioned with drops of either HCl or NaOH 0.1 N. The values of the constants obtained from graphical forms of the equations were used in the assessment of the adsorption intensity of the process. The results show that the maximum adsorption appears in the case of the more concentrated solution of NaNO₂ (10^-1 M) and to small quantities of adsorbant material, both for Langmuir and for Freundlich isotherms (with some exceptions). The value of k constant from Langmuir equation shows a better affinity of mineral substratum for NO₂^- in diluted solutions comparable with the concentrated solutions of analyzed anion. In the same time, the value of n constant from Freundlich equation shows (with one exception) a better affinity for medium concentration of analyzed anion, comparable with the other solutions.