Dealumination is a common phenomena occures during acid
leaching or acid rctluxing of mordenite to prepare acidic zeolite. But
there is no comprehensive repo rt on dealumination which can take
place in mordenitcs that are made acidic by ion.exchnge with
ammonium sa lt so lution followed by ca lcination. OUf UV Diffuse
Reflectance Spectrosco~y on acidic mordenite prepared by
ion ~exchangc with NH4 + and followed by ca l cin~tion at 5500C shows
dislodging some of the framework aluminium from their tetrahedral
si tes . Inspection of UV absorption spectrum of the as.synthesized
mordenitc reveals existence of one type of structural A1 only. Whereas,
in acidic form of mordeniLc two types of aluminium were observed. Two
bands of 220 and 280nm in the acidic mordenite were assigned to lattice
and extra· lattice aluminium respectively. Appearing 280nm band in the
acidic mordenite prepared by treatment with nitric acid shows
extra· lattice aluminium in both types of acidic mordenites may arise
from the same AI species and the same environment.