Specific Adsorption of Aspartic Acid on Iron (III) and Nickel (II) Oxides

The dependences of zeta - potential and adsorption of aspartic acid on NiO and Fe2O3 oxideswere investigated as a function of aspartic acid concentration, pH and adsorption time using microelectrophoresis and potentiometric titration methods. Shifting of pHIEP (the isoelectric point or IEP) towards the acid zone for Fe2O3 and towards the base zone for NiO in the solutions of aspartic acid in comparison with HCl shows the presence of specific adsorption of aspartic acid anion and cation forms on the surfaces of Fe2O3 and NiO oxides, respectively. The complexation process of Fe(III) ions with aspartic acid in the bulk solution and on the oxide surface was examined by spectrophotometer. It was determined that Fe(III) ions form complexes with aspartic acid in the bulk solution