RES³T - Rossendorf Expert System for Surface and Sorption Thermodynamics

The effects of pH, initial Eu(III) concentration, ionic strength and fulvic acid (FA) on the adsorption of Eu(III) on TiO₂ are investigated by using batch techniques. The results indicate that the presence of FA strongly enhances the adsorption of Eu(III) on TiO₂ at low pH values. Besides, the adsorption of Eu(III) on TiO₂ is significantly dependent on pH values and independent of ionic strength. The adsorption of Eu(III) on TiO₂ is attributed to inner-sphere surface complexation. The diffuse layer model (DLM) is applied to simulate the adsorption data, and fits the experimental data well with the aid of FITEQL 3.2. X-ray photoelectron spectroscopy (XPS) is performed to study the species of Eu(III) adsorbed on the surfaces of TiO₂/FA–TiO₂ hybrids at a molecular level, which suggest that FA act as “bridge” between Eu(III) and TiO₂ particles to enhance the ability to adsorb Eu(III) in solution.