Environmentally Friendly Zeolites

Zeolite Application in Wastewater Treatment

“…Zeolite Definition. The term zeolite, derived from the Greek words zein (boil) and lithos (rock), was first used to name a mineral that expanded upon being heated, in 1758 by the Swedish mineralogist Alex Fredrick Cronsted [25,31]. The reason for this peculiar behavior was only revealed in the year 1857, when it was discovered that these materials have a microporous crystalline structure, capable of storing water inside its pores and releasing it if heated, in theoretically infinite cycles of hydration and dehydration.…”

“…The reason for this peculiar behavior was only revealed in the year 1857, when it was discovered that these materials have a microporous crystalline structure, capable of storing water inside its pores and releasing it if heated, in theoretically infinite cycles of hydration and dehydration. At this time, it was also discovered the presence of compensation cations in zeolite crystalline structures and the ability they have to be removed by other ions in solution, through cation exchange [25,32]. Although these properties were important in several industrial sectors, these minerals remained unused for more than 200 years.…”

“…This property gives zeolites the ability to be used as molecular sieves and catalysts, in gas separation and the petrochemical industry, respectively. Based on pore diameter, with openings smaller than 20 Å, zeolites are classified as microporous materials [25,38,[41][42][43]. The union of different types of rings leads to the formation of even more complex structures called cages (Figure 1(b)).…”

“…Its use on an industrial scale only started in 1905, when economically exploitable sedimentary deposits were discovered, which enabled its application in the detergent industry [33]. The first zeolite synthesis was reported in 1948 [25], during the attempt to recreate the hydrothermal conditions of its formation in nature, and the process has been widely studied since then. Currently, 230 species of zeolites are known, categorized into 133 different crystalline structures, according to rules defined by the International Zeolite Association (IZA) [33,34].…”

“…Among them, zeolite is a class of material that has attracted the attention of the scientific community and has the potential to be used as an adsorbent in the elimination of contaminating elements in effluents. These minerals, found in nature or synthesized, have a microporous crystalline structure (with pores opening smaller than 20 Å) [25], which guarantees their application for several purposes, such as gas separation [26], water softeners [27], catalyst [28], addition for Portland cement [29], and applica-tions in health and animal food [30]. Exchangeable cations in the microporous structure and negative electrical charge are two of the properties that allow its application as an adsorbent, for the proper treatment of effluents.…”