**1. Introduction**

Clay and clay minerals have attracted wide interest for application in various sectors including process industries, agricultural sectors, engineering and construction sectors, environmental remediation and water treatment [1]. This is not only due to their abundance and inexpensiveness but also because of their physicochemical properties such as chemical and

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

mechanical stability, larger specific surface area, higher charge density, layered structure, higher cation exchange capacity [2].

By definition clays are naturally occurring alumino-silicate materials composed mainly of fine grained materials with colloid fraction of soils, rocks, sediments and water [3–5]. Clay minerals are composed of groups of small crystalline particles of one or more members of a group of minerals. These minerals originate from weathering of silicate minerals [6, 7]. Common minerals that constitute clay minerals are kaolinite, illite, mica, vermiculite and montmorillonite or smectite. This chapter presents a review on mineralogical and chemical properties of clay minerals, their surface modification and their application in arsenic and fluoride removal potential from water.
