Synthesis of Zeolites from Industrial Wastes, pp. 469-498
Authors: (Pojanie Khummongkol, Rewadee Anuwattana - Environmental Technology Division, School of Energy Environment and Materials, King Mongkut’s University of Technology, Thonburi and others)
Abstract: Zeolites have a limitless potential in their application and in their ability to contribute to a cleaner and safer environment. Zeolites not only safeguard the environment by their diversified applications, but can also be synthesized from a variety of waste products. Over the last 40 years synthetic zeolites have been produced on a commercial scale (eg. A, X, Y, L, P, ZSM-5). Recent research has paid more attention to turning wastes into more value added products. Their potential abilities depend on whether they can be synthesized according to their properties. The technology of synthesizing zeolite from wastes is comprised three steps: the dissolution step of Si4+ and Al3+ in waste materials, the condensation step of silicate and aluminate ions in alkali solution to make aluminosilicate gel, and the crystallization step of aluminosilicate gel to make zeolite crystal. The raw materials include discharge from an optical fiber manufacturing, slag from iron smelting plants, waste from glass manufacturing plants, fly ash, paper sludge and oil shale ash. The aluminum-containing waste may be added to enhance the Si/Al ratio for a select type of zeolite. The aluminum-containing waste can be selected from the group consisting of aluminum dross, aluminum dust collection ash, crystalline aluminum hydroxide sludge, aluminum cleaning waste liquid, aluminum alloy cleaning waste liquid, metal aluminum scrap, aluminum alloy scrap, and alumina scrap. In this chapter, recent technologies on synthesis of zeolite derived from various industrial wastes are described. Parameters affecting the high crystallinity of the synthesis product including the rate of crystallization, induction period, and heating rates will be presented in the text. The synthesis products obtained are characterized by XRD and SEM. Conventional and microwave heating treatments are described in comparison.