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Minerals 2018, 8(2), 76; https://doi.org/10.3390/min8020076

Effect of Dissolved Silica on Immobilization of Boron by Magnesium Oxide

1
Graduate School of Engineering, Hokkaido University, Sapporo, Hokkaido 060-8628, Japan
2
Kankyo Zairyo Engineering Co., Ltd., Ota-ku, Tokyo 144-0052, Japan
3
Faculty of Engineering, Hokkaido University, Sapporo, Hokkaido 060-8628, Japan
*
Author to whom correspondence should be addressed.
Received: 1 February 2018 / Revised: 16 February 2018 / Accepted: 22 February 2018 / Published: 24 February 2018
(This article belongs to the Special Issue Environmental Mineralogy)
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Abstract

The effect of silica on the immobilization reaction of boron by magnesium oxide was investigated by laboratory experiments. In the absence of silica, due to dissolution of the magnesium oxide, boron was removed from solutions by the precipitation of multiple magnesium borates. In the presence of silica, magnesium silica hydrate (M-S-H) was formed as a secondary mineral, which takes up boron. Here 11B magic-angle spinning nuclear magnetic resonance (MAS-NMR) and Fourier transform infrared spectrometer (FT-IR) data show that a part of the boron would be incorporated into M-S-H structures by isomorphic substitution of silicon. Another experiment where magnesium oxide and amorphous silica were reacted beforehand and boron was added later showed that the shorter the reaction time of the preceding reaction, the higher the sorption ratio of boron. That is, boron was incorporated into the M-S-H mainly by coprecipitation. The experiments in the study here show that the sorption of boron in the presence of silica is mainly due to the incorporation of boron during the formation of the M-S-H structure, which suggests that boron would not readily leach out, and that stable immobilization of boron can be expected. View Full-Text
Keywords: immobilization; boron; magnesium oxide; magnesium silicate hydrates (M-S-H) immobilization; boron; magnesium oxide; magnesium silicate hydrates (M-S-H)
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Nozawa, S.; Sato, T.; Otake, T. Effect of Dissolved Silica on Immobilization of Boron by Magnesium Oxide. Minerals 2018, 8, 76.

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