Lead metallic-lead dioxide glasses as alternative of immobilization of the radioactive Wasters
Mioara Zagrai, Loredana Rus, Simona Rada, Simina Stan, Mihai Rada, Elena Maria Pica, Eugen Culea
In this work, we report structural, optical and electrochemical investigations on the gadolinium–lead glass system with the xGd2O3·(100 − x)[4PbO2·Pb] composition where x = 0, 1, 5, 10, 15 mol% Gd2O3 obtained by the melt quenching method. The studied homogeneous glass system was characterized by X-ray diffraction (XRD), infrared (IR) spectroscopy, ultraviolet–visible (UV–VIS) spectroscopy, electron paramagnetic resonance (EPR) spectroscopy, and cyclic voltammetry (CV) measurements. The purpose of this paper was i) to immobilize the gadolinium ions in the lead–lead dioxide glasses and ii) to investigate the structural, optical and electrochemical properties of the obtained glasses for possible applications in the radioactive waste recycling.
IR data show that the [PbO6] octahedral structural units do not accommodate with the excess of non-bridging oxygen, [PbO3] pyramidal units are suitable neighbors for the gadolinium ions and [GdOn] entities will be intercalated in the host matrix. The EPR spectra of Gd+ 3 ions in lead–lead dioxide glasses exhibit four resonance lines situated at about g ≈ 2.0; 2.8; 4.8 and 6. The EPR signals located at about g ~ 2; 2.8 and 6 are known as the U-spectrum of Gd+ 3 ions situated in higher symmetry which can be readily accommodated in a vitreous system whereas the sharpness of the signal situated at about g ~ 4.8 is associated with Gd+ 3 ions having low coordination numbers.
These structural modifications are supported by the increase in the intensity of the UV–VIS absorption bands associated to the electronic transitions of the Pb+ 2 and Gd+ 3 ions and the formation of non-bridging oxygen centers. Electrochemical performances of electrode glasses show the pronounced mobility of the lead ions comparative with the gadolinium ions.