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303. CADMIUM REMOVAL FROM WATER STREAMS BY NOVEL SORBENTS:SURFACE COMPLEXATION MODELLINGGeorge Gallios 1 , Natalia Chubar 2 and Igor Zhuravlev 21Aristotle University of Thessaloniki, School of Chemistry,Lab. General &Inorganic Chemical Technology,Thessaloniki GR-541 24, Greece2Institute for Sorption and Endoecology Problems, National Academy of Science ofUkraine,13 General Naymov Str., Kiev-164, UkraineAbstractCadmium is an important element with many industrial uses; however, in its ionic formin water streams is extremely toxic and strict environmental laws impose its removal fromwaste water streams. As a high priority pollutant is has been studied quite extensively therecent years. However, a good review of the literature shows that all sorbents used so far werequite ineffective in the acidic pH region. As the natural pH of Cd containing water steams isfrom 2.5 to 5 it is important to find a sorbent which would be effective in this pH region,especially when water recycling is considered. Another problem is the instability of thesorbents in acidic pH values. For this reason two novel sorbents, a zirconium phosphate and asynthetic zeolite (alumino-phosphato-silicate) were studied for Cd removal from water streams.They were found quite promising as both were stable in the pH values studied (i.e., 3 to 8). Hezirconium phoshate was found a very good sorbent for Cd with capacities 80 mg/g at pH 7, 70mg/g at pH 5 and 35 mg/g at pH 3. As it was found to be very stable at pH 3 is is proposed as agood sorbent for treating Cd containing water streams for recycling. A surface complexationmodel was also made for the syntetic zeolite and the constants of Cd sorption on the zeolitewere determined. Using the model it was possible to predict the sorbent behaviour as a functionof pH.