One-shot of the hydrothermal route for synthesis of zeolite LTA using kaolin

Abstract

The zeolite LTA (Z-LTA) was successfully produced from synthesis kaolin and well-crystallized using a hydrothermal method. The kaolin was heated in the furnace for 4 hours at temperatures of 500, 600, 700, and 800 0C, resulting in a metakaolinization process that transformed it into an amorphous state. The Z-LTA mixture was obtained by dissolving metakaolin in a sodium hydroxide (NaOH) solution without adding any other silica or alumina sources. Before going through the hydrothermal synthesis process, the solution mixture was aged for 24 hours. The crystal morphology and degree crystallinity (%) of Z-LTA were evaluated using the various molarity (M) of sodium hydroxide (NaOH) and crystallization time (hr). The degree crystallinity of the Z-LTA increases from 62.83% to 86.8% when the molarity of NaOH is increased from 0.5M to 1M but does not increase when the molarity of NaOH is increased to 1M and 2M (80.77% and 67.78%), respectively. The degree crystallinity (%) Z-LTA based on molarity proceeded with the various crystallization time (hr) factors. 1M NaOH with 9hr give highest degree crystallinity (88.45%) compared to other time, 12hr (86.16 %), 16hr (87.11%), 24hr (86.80%) and 30hr (86.59%) respectively. The structure of crystal morphology with the presence of Na, Al, O, and Si was clearly seen in SEM images of the Z-LTA at a 1M NaOH, 9hr crystallization time (Z-LTA, 1M 9hr). The particle size of (Z-LTA, 1M 9hr) is smaller, which is 0.329 µm compared to kaolin, 0.497 µm. Under low alkali conditions, the hydrothermal process has been shown to be successful in generating high crystallinity from natural kaolin. As a result, by using simple chemical methods, this technology still makes low-cost commercial items from natural materials.