## 3 Wastes in Zeolite Synthesis  
### Kaolin Waste  
The production of kaolin has a long background of almost 150 million years, being an important clay with industrial value and consumption, mostly by the paper industry, representing 40% of production. In this field, it is used to fill the cellulose fibers and as coating agent for production of high-gloss paper with good printability [189]. It is useful in clay-based ceramics [190] and refractories [191], fierglass, fillers, and extenders in rubber [192], paint [193], and plastic and adhesives [194]. Other uses include pesticide and herbicide carrier [195], manufacturing of zeolites [196], catalyst support, and cosme [197]. Other applications are in plastics production [198] as antiblocking for infrared radiation absorption in agriculture, and the hydroxyl groups present on surface of calcined kaolin may improve its heat resistance [199]. This aluminosilicate mineral is found in sedimentary deposits. The main mineralogical content is kaolinite (Al\({}_{2}\)Si\({}_{2}\)O\({}_{5}\)(OH)\({}_{4}\)), occurring with feldspar, mica, quartz, illite, montmorillonite, ilmenite, bauxite, zircon, kyanite, silliminate, graphite, atapulgite, halloysite, and oxides such as hematite and rutile. The process of formation is by rock weathering, a process called kaolinization. With plate-like morphology, its characteristics include refractory capacity, highly stable chemical structure, and being a good raw material for ceramic production [199; 200]. Industrial kaolin waste is produced from beneficiation being deposited in open-pit lagoons. Its use as an aluminum and silicon source is a highlight due to low operational cost and the great amount generated, where each ton of kaolin produces 9 tons of waste [201]. Actually, the recycle and reuse of wastes reduce production costs, giving alternative materials for many sectors. There are two types of kaolin waste generated. The first results from the separation of sand from ore, i.e., rich in quartz. The second is from the wet sieving process, separating the finer fraction to obtain a pure kaolin. This second residue has optimal characteristics for production of metakaolinite with high reactivity because of its extremely fine particles. Kaolinite is present in high quantity in this second compound [202]. One compound that gives great performance in synthesis of materials from kaolin waste is nullite (2 Al\({}_{2}\)O\({}_{3}\) 3 SiO\({}_{2}\)) because of its unique composition of stable Si and Al. Its properties comprise high melting point, low coefficient of thermal expansion, great strain resistance, and supporting high temperatures with great chemical stability [203]. Besides this, the formation of metakaolinite from dehydroxylation of kaolinite enables a facile route for zeolite synthesis, generating different types of zeolite structures for each starting material. The use of kaolinite to be attacked with NaOH gives hydroxysolatile as the main product. Nonetheless, when metakaolinite is used, zeolite A is formed significantly [204]. Kaolin waste has been used for faujasite zeolite synthesis with thermal activation of material by calcination at 700 \({}^{\circ}\)C. The ideal conditions to obtain optimal crystallinity involve a molar composition of 7 Na\({}_{2}\)O-Al\({}_{2}\)O\({}_{3}\)-3 SiO\({}_{2}\)-H\({}_{2}\)O. The zeotilization reaction occurs at 90 \({}^{\circ}\)C in 48 h without aging [205]. Wastes from two different regions of kaolin exploration in Brazil (Rio Capim and Jari) were used to obtain sodalite under equal conditions of Bayer process, verifying that the waste from Jari region was more reactive for sodalite formation, presenting less crystallinity and increased reactivity. The experimental conditions reached for zeolite synthesis were 150 \({}^{\circ}\)C and Na\({}_{2}\)O/Al\({}_{2}\)O\({}_{3}\) = 2.0, which gave a partial reaction of kaolinite for product generation.