Evaluation of the sustainability of integrated hydrothermal synthesis of zeolites obtained from Waste

Abstract

The high Si and Al contents in the amorphous phase of coal fly ash have been used for its conversion into zeolites. This process converts a toxic low-value by-product into a product used in a number of environmental applications, but has the disadvantage of introducing contaminants. Despite the large number of studies on the conversion of fly ash into zeolites, few report this drawback or discuss the efficiency of the proposed processes from a technical or ecological perspective. In this respect, the present study conducts a detailed assessment of two routes for integrated hydrothermal synthesis of zeolites 4A and Na-P1 obtained from coal fly ash. The processes are evaluated and compared in relation to the presence of undesirable metals and elements in the different steps of synthesis, as well as the feedstock and final product. Different performance parameters are presented and applied in the assessment of both processes and the most sustainable is recommended.