Extraction of silica from cogon grass and utilization for synthesis of zeolite NaY by conventional and microwave-assisted hydrothermal methods

High purity silica is obtained after leaching glassy blade and trunk of cogon grass in HCl acid with various concentrations (1.5, 2.0, 2.5 and 3.0 M) and calcination at 500 degrees C for 4 h. The silica yield from the blade from all acid-leached samples is around 9 wt%, higher than that from the trunk (around 4 wt%). The sample leached with 2 M HCl has the highest silica purity (99.34 +/- 0.02 wt%) and is further used in the syntheses of zeolite NaY by conventional and microwave-assisted hydrothermal methods (CH and MH). The NaY-CH has a larger particle size, BET surface area and total acidity than that NaY-MH. Interestingly, the NaY-MH has a larger external surface area and stronger acid strength. (C) 2017 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.