Adsorption, Ion Exchange and Catalysis

This chapter emphasizes the role of adsorption, ion exchange, and catalysis in environmental protection. Adsorption includes the uptake of gaseous or liquid components of mixtures from the external or internal surface of porous solids. The ability to exchange ions is due to the properties of the structure of the materials. Catalysis is one of the most important technologies used extensively in industries for production and in waste treatment for the removal of pollutants. There are many common features among these processes. Ion exchange is similar to adsorption, since mass transfer from a fluid to a solid phase is common in both processes. Ion exchange is also a sorption process, but ions are the sorbed species in contrast to adsorption, where electrically neutral species are sorbed. The first step in heterogeneous catalysis is the adsorption of the molecules and the development of catalysis is closely related to the evolution of adsorption. Furthermore, catalysis of reactions by ion exchangers can be explained in terms of the catalytic activity of the exchanging ions and is analogous to homogeneous-phase catalysis by dissolved electrolytes. The adsorption on inexpensive and efficient solid supports is a simple and economical viable method for the removal of dyes from water and wastewater. Ion exchange is mainly used in wastewater treatment. Finally, Earth ecosystems result in the growth of environmental catalysis. So, catalysts are not only used to promote processes in the production field, but also to reduce the emissions of undesirable or hazardous compounds to the environment.