Effect of Hydrogel Molar Composition on the Synthesis of LTA-type Zeolites in the Utilization of Technogenic Silica Gel

Abstract

Resource saving and creation of environmentally safe environment are the guidelines of modern world policy in the field of waste management. This paper considers a possible method of utilization of a by-product of aluminum fluoride production—silica gel—as an alternative high-silica raw material for hydrothermal synthesis of LTA-type zeolites. To obtain synthetic zeolites, industrial silica gel was subjected to sulfuric acid purification and used to obtain one of the hydrogel components—sodium silicate. As a result of investigation of the influence of hydrogel molar composition on the phase composition of the obtained samples, the optimal molar ratios of SiO₂:Al₂O₃, Na₂O:Al₂O₃ and H₂O:SiO₂ were identified. The phase composition of the obtained samples and morphological pattern were evaluated using X-ray diffraction and scanning electron microscopy techniques. According to the obtained results, the use of hydrogel of composition 1.8SiO₂:Al₂O₃:4Na₂O:28H₂O allows to obtain a monophase of LTA type zeolite with high ion exchange capacity, the particles of which have a regular cubic shape with the size of the main fraction up to 10 μm.