An Optimization of Synthesis Technique for Na-X Zeolite from Coal-Fly Ash Using Taguchi Experimental Design

Abstract

Abstract The coal fly ash (Class-F) from a thermal power plant in the Gujarat state of India was used to synthesize Na-X Zeolite. The objective of this study is to maximize Na-X zeolite crystallisation by the use of 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 0.3 M NaOH solution at fusion temperature of 550 °C for 12 hours with 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 cm-1 and 460 cm-1 and weak bend around 660 cm-1 and 694 cm-1 shows the relative O-T-O deformation and the change in shape of the Al-O-H bonds, as measured by FT-IR absorption.