Zeolites K-F and W (EDI and MER types) were synthesized hydrothermally using a natural rock as raw material. Chemical treatments were carried out on a diatomitic rock (containing opaline silica) from Crotone (Calabria, Italy) in order to separate/obtain potassium silicate, a reagent necessary for synthesizing zeolites. Synthesis experiments were performed by mixing the obtained siliceous solution with potassium hydroxide and alumina in varying proportions at 150°C and room pressure. Four synthesis series were performed to form zeolite K-F (EDI) and zeolite W (MER).
The chemical-physical and morphological characterization of the zeolite phases were carried out. Cell parameters were calculated using the Rietveld method. Infrared, thermal and nuclear magnetic resonance (29Si) experiments confirmed the high quality of the zeolite products. The amorphous phase in the synthesis powders was estimated with quantitative phase analysis using the combined Rietveld and reference intensity ratio methods.