Table 2: IR bands characteristic of the purified bentonite spectrum.

Transmission vibrational frequency (cm−1)StrengthFunctional groups

3632MediumOH stretching
3437MediumH2O stretching
1638WeakH2O bending
1042BroadSi-O stretching
915BroadAl-OH-Al bending
884MediumAl-OH-Fe bending
842MediumAl-OH-Mg bending
795WeakSi-O stretching of quartz and silica
622WeakAl-O + Si-O out-of-plane vibration
522BroadAl-O-Si bending