Development of a Process for Producing Zirconium-rich Alkali-resistant Glasses Containing Heavy Metals Present in Fly Ashes from Municipal Solids Waste Incineration

The objective of this study is to develop a process for producing alkali-resistant zirconium-containing glasses for use as a heavy metal retention matrix contained in fly ashes. For this, we have developed 5 glass compositions: Two alkali-resistant model glasses type CEMFIL, V1 (with zirconium and without heavy metals) and V2 (with zirconium and heavy metals), then three glasses of fly ashes V3 (without zirconium and with heavy metals), V4 (with 30% of V3, zirconium and heavy metals) and V5 (with 60% of V3, zirconium and heavy metals). V4 and V5 are obtained using V3 as raw material and supplementing with SiO2, ZrO2 and Na2O to give them alkali-resistant properties. Differential thermal analysis show a glass transition temperature Tg of 656°C for V1, 616°C for V2, 615°C for V3, 641°C for V4 and 664°C for V5. Extremely small peaks of alumina can be observed on the V1, V2 and V3 glasses and peaks of ZrO2 only on the V5 glass. Surface analysis of glasses show that they are essentially homogeneous although we note the presence of some heterogeneities: V1 and V2 contain small crystals of ZrO2, V3 has a slight crystallization of Fe chromite spinel (CrO4) and V5 contains large crystals rich in zirconium. This study has shown that all glasses are totally amorphous. Also, alkali-resistant fly ashes glasses V4 and V5 are the most resistant to leaching and the least attacked in alkaline medium than CEMFIL type glasses V1, V2 and V3.