Kaolinite fusion in carbonate media: KAlSiO4-NaAlSiO4 phase transformations and morphological study

Abstract

Abstract: In this study, we report the thermal decomposition, phase transformation, and morphological change of two-component kaolinite-K2CO3 (KK) and three-component kaolinite- K2CO3-Na2CO3 (KKN) solid mixtures calcined at different temperatures. First, the conversion of kaolinite to the hexagonal and orthorhombic phases of KAlSiO4 via heat treating in solid alkali media of K2CO3 is investigated. Then, the phase transformations and morphological changes for MAlSiO4 as the product (M = K, K0.75Na0.25, K0.5Na0.5, K0.25Na0.75, Na), from KAlSiO4 to NaAlSiO4, are completely examined at 800 °C and 1100 °C. The as-made phases were characterized utilizing XRD, FT-IR, EDX and FE-SEM techniques. The results demonstrated that the most important factors having remarkable effect on the formation of different phases are the mole ratio of K/Na in initial applied carbonate media and the calcination temperature. The study provides the basic data and the methods for efficient and extensive application of natural kaolinite.