ABSTRACT
I. Features of Synthetic Zeolites 128 A. History 128 B. Structure 128 C. Physical and chemical properties 131 D. Zeolite A in detergents 133 E. Manufacturing process 133
II. Environmental Distribution of Zeolite A 137 A. Zeolite A in sewage 137 B. Elimination of zeolites in sewage treatment plants 152 C. Zeolite concentrations in raw and treated waste waters
and sludges 156 D. Zeolite A in soils 158 E. Zeolite A in surface waters 159
III. Chemical Stability of Zeolite A in the Aquatic Environment 161 A. Analytical methods 161 B. Stability in the aquatic phase 162
IV. Impact of Zeolite A on the Heavy Metal Distribution in Waters 167 A. Ion exchange theory and the environmental relevance of
heavy metal ion exchange 167 B. Model tests of heavy metal ion exchange, desorption, and
remobilization 169 C. Heavy metal ion exchange during sewage treatment 182
188 127
References
I. FEATURES OF SYNTHETIC ZEOLITES
A. History Mineral zeolites were discovered by the Swedish amateur mineralogist Baron von Cronstedt in 1756. They were first exploited industrially exactly 140 years later, as ion exchangers in the sugar industry. The zeolites owe their name to the fact that they release large amounts of water on heating. Von Cronstedt derived the name from the Greek zeo (I boil) and lithos (stone). The term “ molecular sieves” now used in many sectors as a synonym for industrially manufactured zeolites was introduced by McMain. The suitability of zeolites for separation processes at the molecular level had been discovered by Weigel and Steinhoff in 1925, and 1 year later McMain succeeded in finding a practical application (sorption) for this property [1,2].
