Coal fly ash-slag-based geopolymers: Microstructure and metal leaching

This study deals with the use of fly ash as a starting material for geopolymeric matrices. The leachable concentrations of geopolymers were compared with those of the starting fly ash to evaluate the retention of potentially harmful elements within the geopolymer matrix. Geopolymer matrices give ris...

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Bibliographic Details
Published in:Journal of hazardous materials 2009-07, Vol.166 (1), p.561-566
Main Authors: Izquierdo, Maria, Querol, Xavier, Davidovits, Joseph, Antenucci, Diano, Nugteren, Henk, Fernández-Pereira, Constantino
Format: Article
Language:English
Subjects:
Adsorption
Applied sciences
Carbon - chemistry
Chemical engineering
Coal
Coal Ash
Crystallization, leaching, miscellaneous separations
Environmental Pollutants - isolation & purification
Exact sciences and technology
Fly ash
Geopolymers
Hazardous Waste - prevention & control
Leaching
Metals, Heavy - isolation & purification
Other industrial wastes. Sewage sludge
Particulate Matter - chemistry
Pollution
Polymers - chemistry
Trace pollutants
Wastes
Water Purification - methods
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Summary:This study deals with the use of fly ash as a starting material for geopolymeric matrices. The leachable concentrations of geopolymers were compared with those of the starting fly ash to evaluate the retention of potentially harmful elements within the geopolymer matrix. Geopolymer matrices give rise to a leaching scenario characterised by a highly alkaline environment, which inhibits the leaching of heavy metals but may enhance the mobilization of certain oxyanionic species. Thus, fly ash-based geopolymers were found to immobilise a number of trace pollutants such as Be, Bi, Cd, Co, Cr, Cu, Nb, Ni, Pb, Sn, Th, U, Y, Zr and rare earth elements. However, the leachable levels of elements occurring in their oxyanionic form such as As, B, Mo, Se, V and W were increased after geopolymerization. This suggests that an optimal dosage, synthesis and curing conditions are essential in order to obtain a long-term stable final product that ensures an efficient physical encapsulation.
ISSN:0304-3894
1873-3336
DOI:10.1016/j.jhazmat.2008.11.063