Thermal stability and water-binding ability of nontronite concluded from powder X-ray diffraction, thermogravimetry, and dielectric measurements.

• Water molecules and Ca2+ ions located between mineral layers play a significant role in the dielectric response. • Nontronite annealed approx. 350 °C rebinds water very easily. • Nontronite annealed up to 440 °C partially loses its water–binding capacity. • Total loss of the water–binding ability and tenfold reduction of electrical permittivity is observed after exceeding 643 °C. • The results obtained from TG, XRD, and dielectric measurements are consistent. The effect of annealing temperature on the ability to rebind water by nontronite was investigated. Nontronite is a type of layered mineral that belongs to the smectite group of clay minerals. It was found that annealing the mineral at temperatures lower than 350 °C causes loss of the interlayer water. However, after moisten water is reabsorbed to a large degree. When the mineral was annealed at approx. 640 °C, it loses definitely the ability to bind water. [Display omitted] [ABSTRACT FROM AUTHOR]