The graph shows the action of zeolite on the NAA heavy water. Display omitted Square 1 - zeolite with sodium promotes ion exchange of calcium and magnesium present in water hard. ► Square 2 - water free of calcium and magnesium captured by zeolite. ► Square 3 - calcium and magnesium present in hard water withheld in the sites of adsorption. Zeolite 4A (LTA) has been successfully synthesized by a hydrothermal method, where kaolin was used as silica and alumina source. The synthesized zeolite was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), laser granulometry, and FTIR spectroscopy. XRD data from the Rietveld refinement method confirmed only one crystallographic phase. Zeolite A morphology was observed by SEM analysis, and it showed well-defined crystals with slightly different sizes but with the same cubic shape. Particle size distribution of the crystals was confirmed by laser granulometry, whereas FTIR spectroscopy revealed significant structural differences between the starting material and the final zeolite product used as water softener.