The water adsorption properties of sepiolite having dolomite supplied from Eskisehir region and their exchanged forms (K+, Na+, Mg2+ and Ca2+) were investigated. The sepiolite samples were characterized using XRD, TG-DTA, DSC and nitrogen adsorption methods. The
temperature ranges were determined for the dehydrations of hydroscopic and zeolitic water as 30–200°C, for the dehydration
of the bound water as 250–750°C and for the dehydroxylation of hydroxyls as 810–850°C in the sample. It was observed that
the value of percent mass loss for natural and modified samples varied in the range from 36.70 to 39.05%. Two mass loss steps
for all samples were observed using a differential scanning calorimetry (DSC) in the range of 30–550°C. Adsorption isotherms
for water on natural and modified forms were obtained at pressures up to 2.39 kPa. Uptake of water increased as K-SEP.<Na-SEP.<Mg-SEP.<Ca-SEP.
for sepiolite samples at 293 K.