Synthesis of zeolite A from Ethiopian kaolin

•Zeolite A is synthesized from Ethiopian natural kaolin.•The kaolin can be used raw or purified giving both highly crystalline zeolite A.•Zeolite A can be synthesized with Na2O/SiO2 = 0.44 and 90% crystallinity.•Cubic rounded edge crystals are obtained.•The cation exchange capacity is 295 mg CaCO3/g (4.6 meq Ca2+/g).

Zeolite A is synthesized using natural kaolin from Ethiopia. Raw kaolin and mechanically purified kaolin from Ansho, southern part of Ethiopia, have been surveyed. The starting kaolin and the final zeolite A samples were characterized by X- Ray Diffraction (XRD), elemental analysis (ICP), Scanning Electron Microscopy (SEM), Thermogravimetric Analysis (TGA) and Cation Exchange Capacity (CEC). Metakaolinization was achieved by calcining the kaolin in air at 600 °C within 3 h, much lower than the temperatures previously reported in the literature. The optimization of the hydrothermal synthesis includes various NaOH concentrations at 100 °C, for different reaction time. Zeolite A with molar ratio SiO2/Al2O3 = 2.04 and Na2O/SiO2 = 0.44 was obtained with 90% crystallinity using solid/liquid (1.25 g/25 ml) and reaction time of 3 h which is significantly lower than the literature value that can reach up to 24 h. In this study, cubic crystal with rounded edge of zeolite A having cation exchange capacity of 295 mg CaCO3/g (4.6 meq Ca2+/g) of anhydrous zeolite is obtained that can be a good candidate for detergent formulation.

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