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• 作者：Sabine M. Leisinger ; Barbara Lothenbach ; Gwenn Le Saout ; Ralf K&#228 ; gi ; Bernhard Wehrli ; C. Annette Johnson
• 刊名：Environmental Science & Technology
• 出版年：2010
• 出版时间：December 1, 2010
• 年：2010
• 卷：44
• 期：23
• 页码：8983-8988
• 全文大小：212K
• 年卷期：v.44,no.23(December 1, 2010)
• ISSN：1520-5851

文摘

Chromate is a toxic contaminant of potential concern, as it is quite soluble in the alkaline pH range and could be released to the environment. In cementitous systems, CrO₄²⁻ is thought to be incorporated as a solid solution with SO₄²⁻ in ettringite. The formation of a solid solution (SS) could lower the soluble CrO₄²⁻ concentrations.

Ettringite containing SO₄²⁻ or CrO₄²⁻ and mixtures thereof have been synthesized. The resulting solids and their solubility after an equilibration time of 3 months have been characterized. For CrO₄-ettringite at 25 °C, a solubility product log K_S0 of −40.2 ± 0.4 was calculated: log K_{CrO4−ettringite} = 6log{Ca²⁺} + 2log{Al(OH)_k">4^k">−} + 3log{CrO_k">4^k">2−} + 4log{OH⁻} + 26log{H₂O}. X-ray diffraction and the analysis of the solution indicated the formation of a regular solid solution between SO₄- and CrO₄-ettringite with a miscibility gap between 0.4 ≤ XCrO₄ ≤ 0.6. The miscibility gap of the SO₄- and CrO₄-ettringite solid solution could be reproduced with a dimensionless Guggenheim fitting parameter (a₀) of 2.03.

The presence of a solid solution between SO₄- and CrO₄-ettringite results in a stabilization of the solids compared to the pure ettringites and thus in an increased uptake of CrO₄²⁻ in cementitious systems.