Acidity measurement
For potentiometric titration, 0.05 g of solid was suspended in acetonitrile (90 mL) and stirred for 3 h. The suspension was titrated with a 0.05-M solution of n-butylamine in acetonitrile. The potential variation was measured using a double-junction electrode.
Lime reactivity
The reactivity of the ash was determined according to a given chemical method [23]. Lime reactivity of the various ashes was determined by suspending a small quantity (approximately 0.3 g) of the ash in 50 mL of saturated lime solution at room temperature and by stirring after 18 h. The unused Ca was estimated by titration with a 0.001-M EDTA solution.