Improving reactivity of fly ashes towards zeolite synthesis by using alkaline fusion pretreatments

Abstract

The increased demand for electricity has created the need to build large thermoelectric power plants where coal is the primary fuel used. This fact suggests the generation of significant amount of solid combustion residue. Fly ashes represent almost 70% of all coal combustion products. For this reason, different investigations are focused on developing new recycling techniques for coal fly ash [1]. This paper analyzes the effects of different pretreatments conditions, different synthesis mixture compositions and reaction times on the fly ash conversion to NaA zeolite by hydrothermal synthesis. A residual fly ash (Thermoelectric Central of San Nicolás, Buenos Aires, Argentina) with or without pretreatment (calcination and/or fusion with Na2CO3) was alkaline-treated and reacted under controlled conditions of temperature and autogenous pressure. The zeolitic phases conversion was evaluated at different reaction times by XRD and Rietvield method.