Adsorption studies of Co(II) on ferric oxide particles in aqueous solutions

Three sizes of α-Fe2O3 particles were synthesized and their adsorption properties with Co(II) ions were investigated. Adsorption in aqueous solutions was found to increase with increasing pH, temperature and Co(II) concentration. Adsorption was also found to be more effective by the smaller particles. The results of adsorption are analyzed by the Langmuir adsorption isotherm over a wide range of Co(II) concentration (≅ 10-8 to 10-6 g/ml). The observed heat of adsorption increases with increasing temperature, indicating some chemical reactions have occurred on the oxide particle surfaces, in addition to two possible adsorption mechanisms, ion-exchange and Co(OH)2 precipitation. (orig.)