Abstract
Magnesium silicate hydrate (MSH) gel was formed by reacting magnesium oxide (MgO) with silica fume (SF) in distilled water. The MSH was prepared using a MgO/SF molar ratio of 1.0 (40:60 weight ratio). Samples were analyzed during hydration process up to 300 days at room temperature. The MSH characterization has been carried out using a range of analytical techniques. Quantitative analysis was achieved using thermogravimetric analysis (TG/DTG) with a de-convolution technology. The structure of MSH gel was characterized using solid state nuclear magnetic resonance (29Si NMR) and Fourier transform infrared (FT-IR) spectroscopy. Transmission electron microscopy (TEM) was used to investigate MSH microstructure. Compared with natural magnesium silicate hydrate minerals, the structure of MSH gel is highly disordered and generates on the surface of particles, producing a shell structure with cavity. The molecular structure of MSH phase is layered. The results also show that the extent of polymerization of MSH gel is related to the solution pH during hydration.
Highlights
The magnesium oxide (MgO)-SiO2 -H2 O system has been reported to have potential application for radioactive waste encapsulation [1,2,3,4,5,6,7]
After 7 days, MgO remains as the major crystalline phase but by 28 days the MgO has fully reacted to form Mg(OH)2 and amorphous Magnesium silicate hydrate (MSH)
Hydration in the MgO-SiO2 -H2 O system can be divided into four stages: pre-induction period
Summary
The MgO-SiO2 -H2 O system has been reported to have potential application for radioactive waste encapsulation [1,2,3,4,5,6,7]. MgO-SiO2 -H2 O means this system has potential to be used for the encapsulation of mixed Aluminum and Mg(OH)2 -rich (Magnox) wastes resulting from the nuclear industry [4,6]. Due to the unique properties of the generated MSH gel, the understanding of the reaction mechanism and characterization of the microstructure and molecular structure have been studied recently [19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39]
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