Physicochemical properties of Fe₂TiO₅ (pseudobrookite structure) surface was studied and basic properties of electrical double layer of the Fe₂TiO₅/NaCl+Ni²⁺ solution system were described. The adsorption of Ni (II) at the pseudobrookite/aqueous solutions interface was studied over the pH range of 3 to 11. The influence of ionic strength, pH, and presence of ions was researched. ζ potential, surface charge density, adsorption density, pH_50% and ∆pH_10-90% parameters for different concentrations of background electrolyte were presented. The adsorption constants of surface hydroxyl groups’ reactions were determined using numerical optimization.