Sorption of Selenite and Selenate to Cement Minerals
详细信息 查看全文
- 作者：Isabel Baur and C. Annette Johnson
- 刊名：Environmental Science & Technology
- 出版年：2003
- 出版时间：August 1, 2003
- 年：2003
- 卷：37
- 期：15
- 页码：3442 - 3447
- 全文大小：111K
- 年卷期：v.37,no.15(August 1, 2003)
- ISSN：1520-5851
文摘
The sorption of selenite and selenate to ettringite (3CaO·Al2O3·3CaSO4·32H2O), "monosulfate" (3CaO·Al2O3·CaSO4·12H2O), and calcium silicate hydrate (C-S-H) wasinvestigated in order to understand Se immobilization bycement in hazardous wastes. Sorption kinetics were fastwith equilibrium between the minerals and Se species reachedwithin 1 d. Selenite is suggested to sorb by surfacereactions, and for ettringite, a sorption maximum of 0.03mol kg-1 was determined. Distribution ratios (Rd) for selenitewere 0.18, 0.38, and 0.21 m3 kg-1 for ettringite, monosulfate,and C-S-H, respectively. At high selenite additions,CaSeO3 was precipitated with a solubility product of Kso= 10-7.27 (I = 0, 25 
C). Selenate sorbed only weakly toettringite (Rd = 0.03), and no significant sorption toC-S-H was found. In contrast, sorption to monosulfatewas strong (Rd = 2.06). With increasing selenate addition,XRD analyses revealed changes in the interlayer distanceof monosulfate, in parallel with an increase of the ettringitefraction. Substitution of sulfate is suggested to be therelevant process. This indicates that selenate is sorbedmore efficiently by monosulfate-rich cement, while the cementcomposition is of minor importance for selenite sorption.
C). Selenate sorbed only weakly toettringite (Rd = 0.03), and no significant sorption toC-S-H was found. In contrast, sorption to monosulfatewas strong (Rd = 2.06). With increasing selenate addition,XRD analyses revealed changes in the interlayer distanceof monosulfate, in parallel with an increase of the ettringitefraction. Substitution of sulfate is suggested to be therelevant process. This indicates that selenate is sorbedmore efficiently by monosulfate-rich cement, while the cementcomposition is of minor importance for selenite sorption.