Improvements in the synthesis of zeolites with low Si/Al ratio from Venezuelan sodium silicate for an environmentally friendly process

Abstract

<p>LTA and FAU zeolites were successfully synthesized from a Venezuelan sodium silicate solution, by hydrothermal crystallization under autogenous pressure at 100°C, with 2–24h crystallization times. The synthesized materials were characterized by XRD, BET specific surface area and SEM. A series of synthesis tests were performed to study the influence of the molar composition of the starting mixture over zeolites crystallization. The effect of crystallization time for a particular synthesis mixture composition was studied for both zeolites types. The reuse as alkaline medium of the mother liquor separated during filtration, and the effect of the aging before crystallization were additionally studied. The experimental result are in agreement with the crystallization mechanism proposed for zeolites synthesis in liquid phase. The use of a 2SiO2:Al2O3:6.Na2O:240H2O synthesis mixture composition allows obtaining LTA zeolite within 2h of crystallization. For FAU zeolite, no aging period was needed when starting with a 4SiO2:Al2O3:6.6Na2O:264H2O composition. It was possible to synthesize both zeolites with high purity and crystallinity and with adequate water adsorption properties.</p>

Facile synthesis of zeolite NaX using rice husk ash without pretreatment

“…Besides the predominant formation of zeolite NaX, the sample still contained a little zeolite NaP1. Similar results of NaX at a ratio of 4.0 using different feedstock were reported [3,36].…”

“…Similar trend was reported by Hildebrando et al (2014) [39]. The formation of NaP1 was more significant when changing this molar ratio and a decrease of Al used favored the formation of zeolite NaP1 [36,40]. The control of the SiO 2 /Al 2 O 3 molar ratio was crucial to achieve single-phase zeolite NaX.…”

Removal of Pb(II) in Aqueous Solutions Using Synthesized Zeolite X from Ecuadorian Clay

“…In summary, the synthesis conditions were set based on previous work on zeolite synthesis from aluminosilicate gels (García, López, García, Casanova, and Goldwasser, 2016).…”

Zeolitización de arcillas rojas de Ecuador y aplicación en la adsorción de CO2

“…Una vez determinada la relación SiO 2 /Al 2 O 3 de la arcilla, se tomó esta como la relación correspondiente para la mezcla de síntesis, las relaciones Na 2 O/SiO 2 y H 2 O/ SiO 2 fueron tomadas con base en trabajos anteriores sobre síntesis de zeolitas a partir de geles aluminosilicatos (García et al, 2016;López et al, 2018).…”

“…Para la síntesis se utilizó el método de fusión alcalina recomendado por diversos autores, para la obtención de zeolitas a partir de arcillas, porcelana y cenizas (Ayele et al, 2016;Wajima y Ikegami, 2009;Bai et al, 2018). Las condiciones de síntesis fueron las mismas para las tres arcillas, con ligeras diferencias en la relación SiO 2 /Al 2 O 3 , comparadas con las indicadas en las referencias de García et al (2016) y López et al (2018). Se ensayaron dos temperaturas y tiempos de calcinación de la arcilla con NaOH, previo al tratamiento hidrotérmico.…”