Synthesis and Characterization of LTA Zeolite from Angren Kaolin: Evaluation of a Regional Feedstock for Zeolite Production

Linde Type A (LTA) zeolite was synthesized from purified Angren kaolin (Uzbekistan) by a metakaolin route. Raw kaolin was beneficiated by dispersion–decantation to reduce iron, calcined at 700 °C, and crystallized in NaOH solution at 100 °C. Products were characterized by powder X-ray diffraction (PXRD), X-ray fluorescence (XRF), Raman spectroscopy, N₂ physisorption and thermal analysis (TGA/DTA). PXRD confirmed crystalline LTA as the major phase (cubic lattice parameter a = 24.68 ± 0.02 Å), with residual quartz from the precursor. XRF gave a near-ideal bulk composition (Si/Al = 1.07, Na/Al = 0.98), confirming sodium incorporation, and Raman corroborated minor quartz and anatase impurities. The low N₂ BET area (~2.5 m² g⁻¹) reflects restricted access of the 4 Å LTA windows to N₂ at −196 °C rather than absence of microporosity. Thermogravimetric analysis showed a ~13 wt% loss of zeolitic water below 300 °C, confirming a hydrated microporous framework. Locally sourced Angren kaolin can thus be converted into crystalline LTA, a candidate material for gas-separation and ion-exchange applications.