Dissolution kinetics of aluminosilicates from biomass ashes in alkaline solutions

This research explores the influence of fly ash source, alkali concentration and temperature on the dissolution kinetics of Al and Si. The characteristics of the reaction products and the solid residue were evaluated with ICPMS, SEM-EDS, and quantitative XRD. It was found that Al dissolution occurs faster with a higher yield compared to Si for both ash types. The temperature and the NaOH concentration had a similar effect on the dissolution of Al, while the dissolution of Si was influenced more by the NaOH concentration. The simultaneous dissolution of aluminosilicates was achieved by keeping the temperature at 30 degrees C, where the precipitation of Al was prevented, and the concentration of the dissolved Si was close to its maximum value. The Kabai Model was the most suitable to explain the dissolution of Al for both ash sources, while the Si dissolution was described with 1-dimensional diffusion, Jander and Ginstling-Brounsthein models.