Environmentally Friendly Zeolites

In this chapter, the main aspects of the study of zeolites including the chronology of the research, structural descriptions and classification of the zeolitic materials are described.

Studies focusing on zeolite synthesis in the field of sol-gel chemistry have been carried out since the 1940s. The large number of studies on this subject is due to both the scientific interest in the complexity and diversity of molecular sieves and the potential applicability of nanoporous solids in industrial processes (Livage in Advanced zeolite science and applications. Studies in surface science and catalysis. Elsevier, Amsterdam, pp. 1–42, 1994; Cundy and Cox in Microporous Mesoporous Mater 82:1–78, 2005).

In early 1980s, the knowledge of zeolite synthesis was already considerable, especially in relation to zeolite synthesis based on the use of inorganic structure-directing cations. At the same time, many studies began to explore the use of new sources of silicon and aluminum such as coal ash and ash from rice husk. The interest in these alternative sources of silicon and aluminum stemmed from two reasons: the first reason is to reduce the cost of zeolite synthesis of and the second reason is to add value to waste or natural raw materials such as clays. Adding value to waste is of great interest because these materials are usually environmental liabilities and using these materials in synthesis can generate profits and contribute to environmental remediation. This chapter addresses eco-friendly zeolite synthesis with the focus of using natural raw materials and waste. An overview of synthesis using these raw materials is presented, focusing on the main parameters studied in zeolite synthesis from alternative sources. The main advances in the syntheses using this type of material are presented.

In this chapter, we described some ecofriendly synthesis studied and published by present and former members of LABPEMOL (Federal University of Rio Grande do Norte, Brazil), some of them in collaboration with other research groups. As described in the previous chapters, all the synthesis included in this section followed the hydrothermal synthesis (Fig. 4.1). The first step was referred to the gel formation, at room temperature (r. t.) or with heating. Then, the gel was transferred to an autoclave and introduced in a static oven at the required temperature for a variable number of days. And, finally, the solid product was recovered by filtration, washed and dried.