Quantification of anions and cations from ternary phosphate based glasses with fixed 50 and 55 mol percent P_2O_5 using ion chromatography

摘要

The aim of this paper was to characterise the dissolution and release profiles for a range of compositions based on the formula 50P_2O_5-50(xCaO-Na_2O), and 55P_2O_5-45(xCaO-Na_2O) where x=30, 35 and40mol percent , in particular to fully investigate the phosphate anions released from these glasses using ion chromatography analysis. A decrease in dissolution rates with increasing CaO content was observed from these glasses. This de-crease was attributed to the Ca~(2+) ions acting as chelates, cross/inking the phosphate chains, and also to an increase in the ionic strength of the solution. An inhibition of the dissolution rates was also caused by the solution becom-ing saturated with insoluble species (i.e. higher polyphosphate rings/chains). The sodium ion release data correlated with that seen for the dissolution rates for glasses with fixed 50 mol percent P_2O_5 content, whereas for compositions with fixed 55 mol percent P_2O_5, increasing Ca~(2+) ion release was seen with an increase in CaO con-tent. The proposed mode of dissolution for the glasses investigated was the hydration model suggested by Bun-ker et al. Higher phosphate species were observed in the chromatograms obtained, and according to a method proposed by Stover et al they were quantified using a response factor. Initial analysis using the response fac-tor also showed a decrease in their rates of release, with increasing CaO content.