The textural properties of the samples were determined by
nitrogen physisorption at liquid nitrogen temperature (196 C)
using a Quadrasorb SI apparatus. The specific surface area was calculated
by using the BET (Brunauer–Emmett–Teller) model. The
pore size distributions were determined by the BJH (Barrett–Joyner–
Halenda) method using the desorption branch of the
isotherms