Mineral Phase Transformation of Fly Ash with Alkali Carbonates

The mineral phase transformation for FA was conducted in muffle furnace. FA was dried first and then mixed with Na₂CO₃ and/or K₂CO₃ respectively via a planetary ball mill for 2 h. The sample was calcined in the muffle furnace at the designed temperature for 2 h and cooled to room temperature to obtain activated fly ash. To study the effect of alkali metal cations on the mineral phase transformation for fly ash, three systems including fly ash–sodium carbonate (FN), fly ash–potassium carbonate (FK) and fly ash–sodium carbonate–potassium carbonate (FNK) were carried out. The addition of Na₂CO₃ in FN was 40% and the calcination temperatures was varied from 600 °C to 1200 °C. The addition of K₂CO₃ in FK was 50% and the calcination temperatures was from 600 °C to 1100 °C. The experimental conditions of FNK are shown in Table S1.†