SYNTHESIS OF NaY ZEOLITE FROM COAL. FLY ASH AND ITS APPLICATION IN THE REMOVAL OF AZO DYE FROM WASTE WATER

Abstract

Zeolites are among the least-known products for environmental pollution control, separation science and technology. Due to their unique porous properties, they are used in various applications in petrochemical cracking, ion-exchange and separation and removal of gases and solvents. The preparation of synthetic zeolites from chemical reagents is expensive. Therefore, in order to reduce costs, zeolite researchers are seeking cheaper aluminosilicates bearing raw materials, such as clay minerals and fly ash, to produce synthetic zeolites. This work concerns the synthesis of NaY zeolite derived from low-cost materials like fly ash (FA). The motivation for using these sources as the starting materials in zeolite synthesis is driven by factors, such as they are cheap and available in bulk quantities, are currently under-utilized, have high workability. The raw materials can be activated by several routes, but the most common routes are: (1) classic alkaline hydrothermal synthesis and (2) alkaline fusion prior to hydrothermal synthesis. In this work the second method was adapted. In the second approach, an alkaline fusion step was conducted prior to hydrothermal treatment, because it plays an important role in enhancing the hydrothermal conditions for zeolite synthesis. On the other hand, this approach was adopted because it can dissolve more aluminosilicates. The method adapted, mineralizer, concentration and times have strong effects on the type and degree of crystallinity of the synthesis products. On the other hand, the type and chemical composition of the as-synthesized products are strongly dependent on the chemical composition of the starting material. The raw materials have very high contents of Si02 and A1203, with Si02/A1203 ratios appropriate for the synthesis of low-Si zeolitic materials with high crystallinity. An examination of the effect of microwave radiation on the zeolite formation and crystallization time was undertaken as microwave radiation of zeolitic gel heated at a faster rate than conventional heating. This resulted in the formation of nuclei at faster rate which decreased the time required for zeolite formation. Finally, the potential application of the raw materials and their as-synthesized product in the removal of Acid Orange 7 was investigated.