This results in the increase of the surface area of some relatively hydrophobic faces in the material [55]. The mesoporous aluminosilicate synthesized under medium calcination heating rate (5 C/min) is suspected to possess higher surface area of the hydrophobic faces than those under slower and faster calcination heating rates (1 C/min and 10 C/min). This makes it difficult to restore the hydroxyl groups in the subsequent rehydroxylation step, leading to the lowest amount of hydroxyl
groups on the material.