Dissolution of Cl in alkaline earth (Ca, Sr, Ba) aluminosilicate glasses

Abstract Some particular hazardous and nuclear wastes containing a large amount of chlorine would cause the problematic processing during the waste vitrification, because of the low solubility of Cl in silicate glasses. Although a few works reported the chlorine behavior in aluminosilicate glasses, the results do not always show the consistency and a small variation of glass compositions may cause the significant changes. The present work studied the dissolution of Cl in the range of alkaline earth aluminosilicate glasses with the nominal mole composition of 50SiO2-10Al2O3-40AeO (Ae = Ca, Sr or Ba). The solubility of Cl in the glasses with different alkaline earth species followed the order of Ca (~8.1 wt%) > Sr (~6.0 wt%) > Ba (~3.5 wt%). The glass density and glass transition temperature decreased with the addition of Cl in three types of glasses, and AeCl2 salts, identified with X-ray diffraction, segregated from the glasses, when Cl addition exceeds its solubility. Raman spectra indicate the dissolution of Cl leads to the increase of bridged oxygen bonds in glasses, supposing that Ca2+ ions are attracted by Cl− ions, leaving the non-bridging oxygens that initially associated with Ca2+ ions are bonded to Si4+ (Al3+) to become bridging oxygens.