Investigation of the structure and ionic conductivity of intercalated kaolinites with potassium acetate in hydrous and anhydrous phases

Abstract

The intercalated kaolinite with potassium acetate (K-KAc), with ca. 91.9% intercalation ratio, was prepared. Thermogravimetric and variable-temperature X-ray powder diffraction analyses disclosed that a small amount of water is easily absorbed into the interlayer space of the K-KAc. The previously reported phase with the 14.2 Å interlayer distance is actually the hydrous K-KAc, which has an approximate formula of Al₂Si₂O₅(OH)₄·0.5KAc·0.25H₂O. The crystal structures of hydrous and anhydrous phases of K-KAc were simulated in the density functional theory framework, demonstrating that the interactions between the K⁺ and acetate ions and the inner surface of kaolinite are significantly strengthened in the anhydrous phase with regard to the hydrous phase. The ionic conductivity of K-KAc indicated that the mobility of the interlayer ions is strongly improved by thermal activation and the conductivity increased by four orders of magnitude from 363 to 423 K.