Dissolution of polyphosphate glass: Impact of pH on diffusion coefficients of modifying cations at low temperatures

Abstract

This paper shows the dissolution behavior of polyphosphate glass in demineralized water and 2% citric acid solution at temperatures: 15, 20, 30, 37 and 50 °C. The influence of the solvent type on the diffusion coefficients of the modifying cations, under static conditions, is also presented. The diffusion coefficients, determined from concentration profiles of the modifying cations, are calculated to be in the range of 0.27 to 350x10-14 m2/h for dissolution in demineralized water, and in the range of 3.6 to 148x10-12 m2/h for the dissolution in 2% citric acid solution. The values of activation energy of cations diffusion in demineralized water are in the range from 68.32 to 105.41 kJ/mol, while for 2% citric acid solution they are in the range from 39.28 to 55.34 kJ/mol.