The treatment of zeolite with a solution of NaOH at different concentr
ations creates modified forms of natural zeolites. These modified zeol
ites exhibit an increased uptake of caesium and a satisfactory uptake
of cobalt. The structural changes in the modified zeolites were studie
d by XRD analysis, which reveals the mineral compositions of the studi
ed materials. The thermodynamic properties of the modified zeolites we
re studied by means of DTA and thermogravimetry, and the chemical comp
osition too was determined.