Apricot stones, obtained from Boumerdes region (50 km east
Algiers), are air-dried, crushed and screened to obtain two
fractions with geometrical mean sizes of 63 and 2.5mm. 100 g
of the selected fraction are impregnated with concentrated
H3PO4 (85%), dried in air and activated in a muffle furnace at 250 ◦C (4h)