Spectroscopic study on the role of TiO2 in the adsorption of Eu(III) and U(VI) on silica surfaces in aqueous solutions

• Enhanced adsorption of Eu(III) and U(VI) onto TiO2-coated silica.
• Enhanced Eu(III) luminescence and lifetime on TiO2-coated silica.
• Energy transfer from TiO2 of TiO2-coated silica to Eu(III) in solutions.

To determine the effects of TiO2 on the adsorption of actinides onto mineral surfaces in groundwater, silica was partially coated with TiO2, and Eu(III) and U(VI) were individually adsorbed from separate 0.1 mM concentration solutions. The TiO2-coated silica showed higher Eu(III) and U(VI) adsorption capacities for increasing amounts of TiO2 coated on the silica surfaces, and thus the existence of TiO2 can decrease the mobility of Eu(III) and U(VI) contaminants.In luminescence studies, it was found that TiO2 considerably enhanced the luminescence of the adsorbed Eu(III) indicating that TiO2–Eu(III) forms surface complexes which may decrease the number of water molecules at the inner sphere of Eu(III), but this was not observed for U(VI). An energy transfer from the TiO2 to the Eu(III) was confirmed in this case of amorphous TiO2-coated silica in Eu(III) solutions, and an increase of the luminescence lifetime of Eu(III) for increasing concentrations of coated TiO2 was also observed.

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