Hydrothermal reactions of fly ash. [Quarterly] report, April 1, 1944--July 30, 1994
The reactions which occur when fly ash is treated under hydrothermal conditions are being investigated. This is being done for two primary reasons. The first of these is to determine the nature of the phases that form, to assess the stabilities of these phases in the ambient environment and, finally, to assess whether these phases are capable of sequestering hazardous species. The second reason for undertaking this proposed study is that, depending on the composition of the ash and the presence of selected additives, it may be possible under hydrothermal conditions to form compounds which have cementitious properties.Formation of four classes of compounds, which bracket likely fly ash compositional ranges, have been selected for study. These are calcium silicate hydrates, calcium silicosulfates, calcium aluminosulfates, andalkali aluminosilicates. The specific compounds fabricated will be determined and their stability regions assessed. As a part of stability assessment, the extent to which selected hazardous species are sequestered will be determined. Finally, the cementing properties of these compounds will be established. During the last quarter, the hydrothermal behavior of tobermorite from fly ash were studied. Tobermorite (Ca{sub 5}Si{sub 6}H{sub 2}O{sub l8}{center_dot}4H{sub 2}O) was successfully synthesized from fly ash-based materials by adjusting the bulk compositions to that of the systems made with the pure starting materials. Tobermorites have a layer structures and were discovered as a new group of cation exchangers, which exhibit partial exchange of structural Ca{sup 2+} for divalent metals, such as Co{sup 2+} and Ni{sup 2+} etc. [Al+Na]-substituted tobermorites have been shown to have reversible exchange and high selectivity for alkali cations such as Cs. Therefore, tobermorites synthesized from fly ash waste forms could be recognized as materials with potential applications in heavy metal removal from aqueous solutions.
- Research Organization:
- Pennsylvania State Univ., University Park, PA (United States)
- Sponsoring Organization:
- USDOE, Washington, DC (United States)
- DOE Contract Number:
- FG22-91PC91302
- OSTI ID:
- 10177096
- Report Number(s):
- DOE/PC/91302-11; ON: DE94017375; BR: AA1525050
- Resource Relation:
- Other Information: PBD: [1994]
- Country of Publication:
- United States
- Language:
- English
Similar Records
Hydrothermal reactions of fly ash. [Quarterly] report, January 1, 1994--March 31, 1994
Hydrothermal reactions of fly ash. [Quarterly] report, April 1, 1993--June 31, 1993