期刊
JOURNAL OF ENVIRONMENTAL CHEMICAL ENGINEERING
卷 9, 期 3, 页码 -出版社
ELSEVIER SCI LTD
DOI: 10.1016/j.jece.2021.105171
关键词
Fly ash; Cement; Ettringite; Hydrocalumite; Pozzolanic reaction; Anionic species
资金
- Japan Society for the Promotion of Science (JaJSPS) KAKENHI research grants [JP19H00883]
This study investigates the immobilization mechanisms of undesirable anionic species released from fly ash blended cement. The dissolution tests reveal the stabilities of several species, with selenite being the only element that excessively elutes under current mixing conditions, posing a potential environmental risk.
There are few reports to explore immobilization of undesirable anionic species released from fly ash (FA) blended cement. This study clarifies the stabilities of several undesirable anionic species, through dissolution tests under a different matrix. The immobilization mechanism mainly involves co-precipitation with ettringite and hydrocalumite, the marginal formation of insoluble Ca salts, and occlusion in calcium silicate hydrates and amorphous phases produced during the pozzolanic reaction. The products released some amounts of chromate, arsenate, and selenite but not borate in dissolution tests. Elution of borate was the most effectively immobilized by Ca additives, owing to selective incorporation in ettringite. Moreover, selenite showed a trend of dissolving in acidic conditions, presumably owing to the dissolution of CaSeO3 with relatively high K-sp in addition to coprecipitation with hydrocalumite and ettringite. Under the present mixing condition of cementation, only selenite is a cautionary species which excessively eluted over the environmental standard.
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