Synthesis and Leaching of Zirconium-rich Alkali-resistant Glasses Containing Heavy Metals Present in Fly Ashes Incineration |Chapter 4 | Chemical and Materials Sciences: Research Findings Vol. 6

 

Glasses containing zirconium are used to produce glass fibres due to their alkali-resistant nature. The presence of zirconium slows the deterioration of the glasses. This study developed a process for producing alkali-resistant zirconium-containing glasses for use as a heavy metal retention matrix contained in fly ashes. These alkali-resistant zirconium-containing glasses were synthesised to undergo leaching tests. To synthesize these alkali-resistant glasses, 5 glass compositions were developed: two alkali-resistant model glasses type CEMFIL, V1 (with zirconium and without heavy metals) and V2 (with zirconium and heavy metals) and 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 were obtained using V3 as raw material and supplementing with SiO2, ZrO2 and Na2O to give them alkali-resistant properties. Chemical composition of the various glasses was determined by a micro-analyser with an ion probe or electron microprobe of brand CAMECA SX50 with a potential difference of about 10 kV at Paris VI University. Differential thermal analyses, structural analyses, as well as the observation of the surface of the glasses were carried out at the CNRS/CEMHTI laboratory in Orléans. Differential thermal analysis showed 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 have been observed on the V1, V2 and V3 glasses and peaks of ZrO2 only on the V5 glass. Surface analysis of glasses showed that they were essentially homogeneous, although we noted the presence of some heterogeneities: V1 and V2 with small crystals of ZrO2, V3 had a slight crystallisation of Fe chromite spinel (CrO4), and V5 contained large crystals rich in zirconium. Glasses leaching in basic medium led to the development of hydrated film on the glass surface characterised by hydrogen enrichment and sodium depletion irrespective of the glass. After static leaching tests in a basic medium, SEM and electron microprobe analyses revealed that all glasses were covered with a weathering film. These weathering films were enriched in zirconium (V1, V2, V4, and V5) and depleted in Na. Glasses V4 and V5 had the most zirconium-enriched alteration films and also appeared to be the least affected.

 

Author(s) Details

K.M. Mbemba
Université Paris-Est Marne-la Vallée, 5 Boulevard Descartes 77420 Champs-sur-Marne, France, Université Marien NGOUABI, Unité de Chimie du Végétal et de la Vie, Faculté des Sciences et Techniques, B.P. 69, Brazzaville, République du Congo and Centre de Recherche et d’innovation des Projets de Technologie (CRIPT), Cité Scientifique, Avenue de Gascogne, Brazzaville, République du Congo.

 

S. Djanarthany
Université Paris-Est Marne-la Vallée, 5 Boulevard Descartes 77420 Champs-sur-Marne, France.

 

G. Matzen
Université d’Orléans, CNRS/CEMHTI, 1D Avenue de la Recherche Scientifique 45071 Orléans Cedex 2, France.

 

Please see the book here :-https://doi.org/10.9734/bpi/cmsrf/v6/6751