Mg2+ uptake by synthetic tobermorite and xonotlite

O. P. Shrivastava; S. Komarneni; E. Breval

doi:10.1016/0008-8846(91)90034-F

Mg²⁺ uptake by synthetic tobermorite and xonotlite

O. P. Shrivastava, S. Komarneni, E. Breval

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Abstract

Synthetic crystalline calcium silicate hydrates Ca₅Si₆O₁₆(OH)₂·4H₂O and Ca₆Si₆O₁₇(OH)₂ which are identical to the silicate minerals 11Å tobermorite and xonotlite respectively show Mg²⁺ uptake in aqueous solutions. When placed in solutions initially of 100-1000 ppm in Mg²⁺, 11Å tobermorite takes up a maximum of 3.5 wt% of Mg after equilibration for 15 days at 25°C whereas the uptake level in xonotlite is as high as 3.7% after equilibration for 7 days. However, Mg²⁺ uptake by both the phases did not reach an equilibrium. The studies of magnesium uptake appear to be useful in delineating the mechanisms of ion exchange in calcium silicate minerals. The uptake appears to be a combined effect of reversible ion exchange on broken bonds and outer planar surfaces and irreversible reaction of Mg²⁺ with the calcium silicates which led to Ca release. These mechanisms were corroborated by the morphological and chemical studies of the exchanged products, Mg_xCa_5-xSi₆O₁₆(OH)₂·nH₂O and Mg_xCa_6-xSi₆O₁₇(OH)₂ using a transmission electron microscope (TEM) with energy dispersive spectrometry (EDS).

Original language	English (US)
Pages (from-to)	83-90
Number of pages	8
Journal	Cement and Concrete Research
Volume	21
Issue number	1
DOIs	https://doi.org/10.1016/0008-8846(91)90034-F
State	Published - Jan 1991

All Science Journal Classification (ASJC) codes

Building and Construction
General Materials Science

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title = "Mg2+ uptake by synthetic tobermorite and xonotlite",

abstract = "Synthetic crystalline calcium silicate hydrates Ca5Si6O16(OH)2·4H2O and Ca6Si6O17(OH)2 which are identical to the silicate minerals 11{\AA} tobermorite and xonotlite respectively show Mg2+ uptake in aqueous solutions. When placed in solutions initially of 100-1000 ppm in Mg2+, 11{\AA} tobermorite takes up a maximum of 3.5 wt% of Mg after equilibration for 15 days at 25°C whereas the uptake level in xonotlite is as high as 3.7% after equilibration for 7 days. However, Mg2+ uptake by both the phases did not reach an equilibrium. The studies of magnesium uptake appear to be useful in delineating the mechanisms of ion exchange in calcium silicate minerals. The uptake appears to be a combined effect of reversible ion exchange on broken bonds and outer planar surfaces and irreversible reaction of Mg2+ with the calcium silicates which led to Ca release. These mechanisms were corroborated by the morphological and chemical studies of the exchanged products, MgxCa5-xSi6O16(OH)2·nH2O and MgxCa6-xSi6O17(OH)2 using a transmission electron microscope (TEM) with energy dispersive spectrometry (EDS).",

author = "Shrivastava, {O. P.} and S. Komarneni and E. Breval",

year = "1991",

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doi = "10.1016/0008-8846(91)90034-F",

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T1 - Mg2+ uptake by synthetic tobermorite and xonotlite

AU - Shrivastava, O. P.

AU - Komarneni, S.

AU - Breval, E.

PY - 1991/1

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N2 - Synthetic crystalline calcium silicate hydrates Ca5Si6O16(OH)2·4H2O and Ca6Si6O17(OH)2 which are identical to the silicate minerals 11Å tobermorite and xonotlite respectively show Mg2+ uptake in aqueous solutions. When placed in solutions initially of 100-1000 ppm in Mg2+, 11Å tobermorite takes up a maximum of 3.5 wt% of Mg after equilibration for 15 days at 25°C whereas the uptake level in xonotlite is as high as 3.7% after equilibration for 7 days. However, Mg2+ uptake by both the phases did not reach an equilibrium. The studies of magnesium uptake appear to be useful in delineating the mechanisms of ion exchange in calcium silicate minerals. The uptake appears to be a combined effect of reversible ion exchange on broken bonds and outer planar surfaces and irreversible reaction of Mg2+ with the calcium silicates which led to Ca release. These mechanisms were corroborated by the morphological and chemical studies of the exchanged products, MgxCa5-xSi6O16(OH)2·nH2O and MgxCa6-xSi6O17(OH)2 using a transmission electron microscope (TEM) with energy dispersive spectrometry (EDS).

AB - Synthetic crystalline calcium silicate hydrates Ca5Si6O16(OH)2·4H2O and Ca6Si6O17(OH)2 which are identical to the silicate minerals 11Å tobermorite and xonotlite respectively show Mg2+ uptake in aqueous solutions. When placed in solutions initially of 100-1000 ppm in Mg2+, 11Å tobermorite takes up a maximum of 3.5 wt% of Mg after equilibration for 15 days at 25°C whereas the uptake level in xonotlite is as high as 3.7% after equilibration for 7 days. However, Mg2+ uptake by both the phases did not reach an equilibrium. The studies of magnesium uptake appear to be useful in delineating the mechanisms of ion exchange in calcium silicate minerals. The uptake appears to be a combined effect of reversible ion exchange on broken bonds and outer planar surfaces and irreversible reaction of Mg2+ with the calcium silicates which led to Ca release. These mechanisms were corroborated by the morphological and chemical studies of the exchanged products, MgxCa5-xSi6O16(OH)2·nH2O and MgxCa6-xSi6O17(OH)2 using a transmission electron microscope (TEM) with energy dispersive spectrometry (EDS).

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Mg²⁺ uptake by synthetic tobermorite and xonotlite

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