The Brunauer–Emmett–Teller (BET) method [34] is used for the
determination of the surface area values of samples. In thismethod,
moisture and atmospheric gases were firstly removed from the
sample by application of heat and evacuation. Then the temperature
was reduced to that of liquid nitrogen and the adsorbing gas (nitrogen)
was admited in incremental doses. BET isoterm plot which is
used to determine the total surface area of the samplewas obtained
by using the adsorbed gas versus gas pressure data. The specific surface
areawas calculated by dividing the total surface area to sample
weight.