An optimization of synthesis technique for Na-X zeolite from coal-fly ash using Taguchi experimental design

Abstract

Na-X Zeolite was made from Class-F coal fly ash from a thermal power plant in the Indian state of Gujarat. The objective of this study is to maximize Na-X zeolite crystallization by using alkaline fusion hydrothermal treatment. The authors have also optimized the process variables using the L9 orthogonal Taguchi method. The operating parameters investigated are fusion temperature, fusion time, liquid/solid (L/S) ratio, and alkaline solution concentration. The XRF analysis of coal fly ash reveals that quartz (SiO2), mullite (Al2O3.SiO4), and a small fraction of hematite and magnetite are the major minerals. The highly crystalline zeolite (ZT-5) was synthesized in a 0.3 M NaOH solution at a fusion temperature of 550 °C for 12 h. with a 1.3 L/S ratio. Contrary to the CFA graph, the zeolite (ZT-5) XRD pattern displays prominent peaks between 20 and 40°. The SEM images illustrate the transition from a smooth spherical texture to a highly crystalline lattice structure in the morphology of zeolite. A sharp stretch around 440 and 460 cm−1 and weak bend around 660 and 694 cm−1 show the relative O-T-O deformation and the change in shape of the Al-O-H bonds, as measured by FT-IR absorption.