Conversion of South African clays into high quality zeolites

•Clays from South Africa were used as feedstock material for synthesis of zeolites.•Depending on synthesis conditions and clay type, different zeolites were synthesized.•The SiO2/Al2O3 ratio of the synthesis mixture influenced the type of zeolite.

Clays obtained from South Africa were used as feedstock materials for the synthesis of zeolites. The conventional alkaline hydrothermal treatment of the starting material (90 °C for 8 h) was preceded by a fusion step (550 °C for 1.5 h) to improve the solubility of aluminium and silicon. Various characterization techniques such as X-ray diffraction (XRD), X-ray fluorescence (XRF), scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy were employed to probe the properties of the as-received clays as well as the resulting zeolitic phase. The synthesized zeolite X and hydroxy-sodalite were of high crystalline quality hence making clay materials a cheaper alternative for producing high quality zeolites.

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