Heulandite HEU and Clinoptilolite

Hydrated and partially dehydrated NH4-exchanged heulandite (HEU, isostruc-tural with clinoptilolite) were investigated by micro-infrared spectroscopy [479]. Absorptions typical of NH4+ and structural water were observed. 

The formation of acid centers in (highly siliceous) offretite and zeoHte Omega (cf. also below) was spectroscopically studied also by TsitsishviU and coworkers [489]. At some variance with Barthomeuf and colleagues, TsitsishviU et al. concluded that all types of OH groups observed by IR were acid as indicated on NH3 adsorption except those (silanol groups) giving rise to the band at 3740 cm.  

---