Abstract
The NaOH/metakaolin ratio and crystallization time were studied for the synthesis of zeolite NaA from a sample of kaolin from a Capim mine. The tests were carried out by using statistical design with axial points and replication of the central point. The samples obtained were characterized by X-ray diffraction (DRX), scanning electron microscopy and chemical analysis using a microprobe EPMA. The results showed that there is a relationship between the amount of NaOH added and crystallization time. The tests carried out using the lowest NaOH/metakaolin ratio (0.5) and the shortest time (4 h) produced a non-crystalline material. On the other hand, increasing the NaOH/metakaolin ratio and the crystallization time led to the formation of a NaA phase with a high structural level, but with the presence of a sodalite phase as an impurity.
Highlights
Kaolin is a type of clay with various applications such as ceramics, adsorbents, and a source of Si and Al for the synthesis of zeolites
Loiola et al (2012)[4] showed that a NaA type zeolite synthesized from metakaolin more efficiently removed Ca2+ from water than commercial zeolite A
This work aims to study different ratios of NaOH/ metakaolin according to crystallization time by using statistical design to define a domain in which these synthesis parameters can be optimized
Summary
Kaolin is a type of clay with various applications such as ceramics, adsorbents, and a source of Si and Al for the synthesis of zeolites. Loiola et al (2012)[4] showed that a NaA type zeolite synthesized from metakaolin (produced from a Brazilian kaolin calcined at 900 °C for 2 h) more efficiently removed Ca2+ from water than commercial zeolite A. Liu et al (2013)[5] synthesized a zeolite with magnetic properties by adding Fe3O4 from a metakaolin. It was used in the following conditions: SiO2/Al2O3 = 2.3, Na2O/SiO2 = 1.4, H2O/Na2O = 50, and crystallization time of 8 h at 95 °C, and an efficiency of over 95% was observed for the removal of lead and copper. Cation exchange with Ca+2 in zeolite NaA synthesized from kaolin, with a cation exchange capacity of 183.40 meq/100 g, has produced an adsorbent for arsenic[6]
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