Use of Mechanochemical Activation and Ultrasonic Treatment for the Synthesis of LTA Zeolite

The processes of LTA zeolite synthesis from mixtures of metakaolin and solid sodium hydroxide with an overstoichiometric quantity of alumina (molar composition of the mixture Al2O3·2SiO2: NaOH: Al2O3 = 6: 12: 2) were examined in relation to the treatment method used in the first step (mechanochemical activation or ultrasonic treatment). Formation of cubic sodium aluminate in the first step was established in both cases. Subsequent heat treatment in the case of mechanical activation resulted in the synthesis of the LTA zeolite, and in the case of ultrasonic treatment, in the synthesis of sodium aluminosilicates. After final hydrothermal crystallization the LTA zeolite quantity exceeded 95 wt %. The zeolite phase morphology was shown to depend on the treatment method used in the first step of the synthesis.