Optimization of Parameters and Methodology for the Synthesis of LTA-Type Zeolite Using Light Coal Ash

Abstract

The synthesis of zeolites using waste as a source of Si and Al is well known, and light coal ash has been studied to minimize the problems of waste management and mitigate environmental effects. The residue used in this work was supplied by Coal Workers Assistance Society (SATC) Criciúma–SC/Brazil, and had 24.09% Al2O3 and 54.25% SiO2 in its chemical composition. Synthesis studies using this residue with the objective of obtaining LTA zeolites were carried out by hydrothermal means, alkaline fusion, and the combination of the two methods, varying parameters such as crystallization time, Na/T ratio, OH/ratio, ultrasound exposure, gel agitation temperature, and the alkaline melting temperature of the residue. The results were characterized by X-ray diffraction (XRD) techniques and scanning electron microscopy (SEM-FEG). It was possible to obtain 70% crystalline zeolite type LTA for the first time at mild conditions with temperatures below 200 °C by alkaline fusion with smaller amounts of NaOH and short times (2 h). Thus, suitable parameters were determined for future scaling.