Continuous Measurement of the Dissolution Rate of Ions from Glasses

A method for measuring the early stage ion release of glasses was developed in order to gain information on leaching kinetics and chemical resistance of glasses in aqueous environments. A continuous flow-through-reactor was designed in which the aqueous solution is fed through a bed of glass particles and the dissolved ions continuously recorded with a sensitive on-line analysis system. Experimental parameters, such as solvent flow rate and temperature, could easily be adjusted according to the needs. The flow-through-reactor system was tested with powdered samples of float and lead glasses, E-glass and bioactive glasses 45S5 and 1-98, all of which showed very different chemical durability in aqueous environments. The reactor was connected to inductively coupled plasma optical emission spectrometry (ICP-OES) and concentrations of the dissolved ions were measured simultaneously on-line every 30-40 seconds. In this work the initial stages of ion release were measured during the first 15 minutes of the leaching experiments at 40 degrees C and 80 degrees C. The results were compared with standard water durability test of the glasses. The dissolution of the glasses according to both methods showed similar behaviour.