Porous structure of the clinoptilolite has a heterogeneous nature. Two types of porosities
such as primary porosity and secondary one are observed. The primary porosity
can be defined as microporosity presented by nanotube system of the clinoptilolite
3-dimensional aluminosilicate framework. Mesoporosity and macroporosity form the
secondary porosity. The mesoporosity is formed by slot pores determined mainly by
cleavability of the zeolite crystallite. The macropores consist of pores of various forms
which are located between blocks of the zeolite crystallite and other minerals in the
clinoptilolite rock. The nitrogen adsorption/desorption method can be used for only
mesopores and not for evaluation of micropores of raw clinoptilolite. The evaluation
of the clinoptilolite microporosity by nitrogen adsorption/desorption method can be
made after acid treatment when micropores of the aluminosilicate framework are unblocked
during acid leaching.