Sorption isotherms of water vapour on bentonite from the Rokle locality of northwest Bohemia in the Czech Republic were measured and analysed after being treated with heat. Protracted sorption measurements were performed at 30 degrees C in the range of water vapour relative pressures between 0.12 and 0.94.
Prior to sorption measurements, the bentonite samples were exposed to flowing dry nitrogen for 18 hours at 115, 220 and 300 degrees C. Compared to the sample heated at 115 degrees C, the bentonite samples that were treated at 220 and 300 degrees C exhibited a decrease in water vapour sorption capacity.
This decrease in sorption capacity was accompanied by structural changes that were confirmed by X-ray diffraction analysis.