BEHAVOIR OF H_2O MOLECULES IN THE CHANNELS OF NATROLITE: A THERMAL ANALYSIS AND X-RAY POWDER DIFFRACTION STUDY

摘要

The thermal behavior of natrolite (Na_(16)Al_(16)Si_(24)O_(80) cenre dot 16H_2O) and the interplay between dehydration/rehydration and crystal structural changes were studied by thermogravimetric analysis (TG) and temperature- and atmosphere-controlled X-ray powder diffraction (XRD). Natrolite dehydration occurred as a discrete reaction with an abrupt and single-stage weight loss in the TG curve. The dehydrated phase, a-metanatrolite (Na_(16)Al_(16)Si_(24)O_(80), formed during dehydration and the reaction was accompanied by a structural phase transition. The dehydration reaction is inhibited by the build-up of PH_2O in intercrystallite pore spaces, with a dehydration onset temperature of approx 255 deg C with a 4-mg sample, increasing to approx 255 deg C with an 18-mg sample.