Hydration of Magnesium Oxide in the Waste Isolation Pilot Plant

Abstract

Magnesium oxide (MgO) is the only engineered barrier being emplaced in the Waste Isolation Pilot Plant (WIPP), a U.S. Department of Energy repository for transuranic waste. MgO will lower dissolved concentrations of actinides by consuming CO 2 from possible microbial activity, by buffering the pH between 8.5 and 9.5, and by reducing the amount of free water in the repository. This paper discusses results from experiments measuring the hydration of MgO. Results suggest that periclase (MgO) hydrates rapidly to brucite (Mg(OH) 2 ) in deionized water and 4 M NaCl solution at 90°C; the hydration rate decreases as temperature decreases. In ERDA-6, a NaCl-rich WIPP brine, MgO hydrates directly to brucite; in GWB, a high-Mg brine, periclase hydrates to magnesium chloride hydroxide hydrate(s) until the dissolved Mg 2+ concentration decreases, and brucite becomes the stable phase. Under humid conditions MgO fully hydrates at higher humidities(> 50%). All data are consistent with diffusion-limited hydration reactions.

Materials properties of magnesium and calcium hydroxides from first-principles calculations

“…3 Brucite Mg(OH) 2 has demonstrated similar effectiveness in waste water treatment [4][5][6][7] and and high antibacterial efficiency against several tested bacterial strains. 8 There is an interesting experience of employing Mg(OH) 2 as a precursor for magnesium oxide refractory ceramics, 9 or as a flame retardant in various polymer compositions and smoke suppressants.…”

Appendix SOTERM-2009 Actinide Chemistry Source Term

“…For the reaction of MgO with GWB brine, PA uses a magnesium concentration of ~0.6 M (see Table 2), which is supported by experimental results showing a magnesium concentration ~0.7 M (Snider 2003b). This reaction was also investigated by Altmaier et al (2003) and Harvie, Møller, Weare (1984).…”

Electronic and optical properties of magnesium and calcium hydroxides: the role of covalency and many-body effects

“…In addition to significant usage in building and engineering fields, its functional properties are widely implemented in a variety of applications; the primers range from water treatment methods [3] to dental therapy [4]. Brucite, Mg(OH) 2 , has also demonstrated similar effectiveness in waste water treatments [5][6][7][8] and a high antibacterial efficiency against several tested bacterial strains [9]. There has been a novel application of Mg(OH) 2 as a precursor for magnesium oxide refractory ceramics [10]…”