Zeolites Synthesized from Class F Fly Ash and Sodium Aluminate Slurry

A Class F fly ash was combined with a sodium aluminate slurry (3:1 Na:Al) in an attempt to synthesize zeolites from a highly alkaline waste stream. The reaction was studied as a function of composition (3:2, 1:1, and 1:2 fly ash:slurry), time (1, 3, and 7 days), and temperature (80°, 130°, and 180°C). X‐ray diffraction analyses of the products indicated that the fly ash and sodium aluminate had combined to form Zeolite A at 80°C, and NaP 1 (a gismondene‐type) and an unnamed hydroxysodalite‐type at 130° and 180°C. The fact that the pH of the reactants decreased from initial values in excess of 13 to near neutral (7–9) after reaction signifies that the bulk of the sodium had been incorporated into zeolitic phases. Because of the unique adsorptive and cation exchange capabilities of zeolites and the fact that some samples formed reasonably hard monoliths, zeolitic materials formed in this way might make excellent waste forms for “mixed wastes” which contain both radioactive and hazardous chemical species.