Applications of Fly Ash Zeolites: Case Studies

Abstract

As a word of mouth, zeolites were first employed for industrial applications by the sugar industries, way back in 1896, which recognized their high adsorptive capacity. In the late 60s, the catalytic properties of zeolites for petrochemical processes, especially the fluid catalytic cracking (FCC) process, were discovered. Currently, around 300,000 tons of synthetic zeolites are being used annually, in catalytic and adsorptive applications. In addition, 250,000 tons of natural zeolites (mainly Clinoptilolite) are being consumed, per annum, as additives in the construction materials and paper industries , waste water treatment , soil improvement , animal feed additive and as cat litters . The potential of industrial applications of zeolitic materials vary as a function of the prevalent zeolite type. The X type zeolite has a large pore size (7.3 Å) and a high CEC (500 meq./100 g), and these properties make them an interesting zeolites for separation process which led to it name as a “molecular sieve ” and a high cation exchange material, as compared to Hydroxy-sodalite having less pore size (2.3 Å). The zeolites with high Al/Si have been opined to account for the high CEC (viz., Na-P1, 4A, X, KM, Chabazite, Herschelite, and Faujasite ). Owing to their high CEC, these zeolites have a high potential for their application in waste water decontamination , the removal of heavy metals and ammonium from solutions. The potential applications of synthesized ash zeolites are presented in the following sections.