Influence of an aging step on the synthesis of zeolite NaA from Brazilian Amazon kaolin waste

The synthesis of zeolite NaA from kaolin waste was conducted subjecting the reaction mixture to an aging step before autoclaving at high temperature. This waste, from Brasilian Amazon, is deposited in large basins and display excellent quality. In this aging step, the reaction mixture was agitated for 24 hat room temperature, and after this time, the synthesis was performed for varying times of 1, 2, 3, 4, 6, 12, 18, 20 and 24 h at a constant temperature of 110 degrees C. The kaolin waste and synthesis products were characterized through X-ray diffractometry, scanning electron microscopy and chemical analysis. The results showed that the kaolin waste consists primarily of kaolinite. Zeolite NaA was obtained after 4 h. However, zeolite NaA was obtained with a high degree of purity and a high degree of structural order only for times of 6, 12, 18, 20 and 24 h. This study showed that zeolite NaA can be produced in shorter times through the synthesis route used. The production of zeolite NaA from kaolin waste could be an excellent way to minimize environmental impacts and decrease processing costs. (C) 2019 The Authors. Published by Elsevier B.V.