**1. Introduction**

282 Ion Exchange Technologies

[20] Ergozhin E.E., Akimbaeva A. M. Organomineral system based on oligomers. In: Proceedings of the IX International Conference on the chemistry and physical chemistry

of oligomers, 13–16 september 2005, Odessa,Ukraine.

Species of toxic heavy metals cause serious damage to the ecosystem and as a result of this fact there is an increase in research on processes for wastewater treatment. Many of these processes are based on adsorptive properties or ion exchange some of these materials which immobilize the heavy metal species. Recently, various materials of natural or synthetic origin, such as bagasse, coal ash, carbonates, phosphates and zeolites, have been tested for its sorption capacity. Zeolites are commonly used for sorption of heavy metals due to their physical and chemical properties (thermal stability, defined molecular structure and ion exchange capacity).

The synthesis of zeolites from some mineral phases has been investigated by several researchers. It is well established that the coal ash composed mainly of phases such as quartz (SiO2), mullite (Al4+2xSi2-2-xO10-x), hematite (Fe2O3) and magnetite (Fe3O4) can produce zeolites from alkaline hydrothermal treatment. But the mechanism of hydrothermal synthesis is still not very detailed. In general, increasing the temperature tends to favor the formation of hydrated aluminosilicate phase.

Zeolites synthesized from the coal ash, its adsorptive capacity are dependent on certain reaction conditions, for example, the concentration of metal cation in solution and the temperature at which sorption occurs. However, temperature and reaction time in the stage of the synthesis zeolite are also considered important variables affecting the behavior of the adsorptive materials such as zeolites of heavy metals in solution.

This chapter presents a study based on the sorption of cations of heavy metals by zeolites synthesized from hydrothermal treatment of coal ashes produced in Brazil.

© 2012 Nascimento et al., licensee InTech. This is an open access chapter 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. © 2012 Nascimento et al., licensee InTech. This is a paper 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.
