The Solubility of Tugarinovite (MoO₂) in H₂O at Elevated Temperatures and Pressures

Abstract

The solubility of tugarinovite (MoO 2 ) in pure water was investigated at temperatures between 400 and 800 ∘ C and at pressures ranging between 95 and 480 MPa by using in situ synchrotron X-ray fluorescence (SXRF) to separately analyze high temperature aqueous solutions in a hydrothermal diamond anvil cell (HDAC). The concentration of molybdenum in the fluid at 400 and 500 ∘ C was below detection; however, at temperatures between 600 and 800 ∘ C, the solubility of tugarinovite increased with increasing temperature by two orders of magnitude. The molybdenum concentration at 600 ∘ C and 800 ∘ C is 44 ppm and 658 ppm, respectively. The results complement the data of Kudrin (1985) and provide the first measurement of MoO 2 solubility at pressure and temperature conditions comparable to intrusion-related Mo deposit formation. The data are also relevant to the study of water chemistry and corrosion product transport in supercritical-water-cooled reactors, where Mo-bearing steel alloys interact with aqueous solutions at temperatures greater than 600 ∘ C. The application of in situ SXRF to solubility measurements of sparingly soluble minerals is recommended because it circumvents analytical uncertainties inherent in determinations obtained by quenching and weight loss measurements.

Binary Cooperative Thermal Treatment of Cellulose and MoS2 for the Preparation of Sustainable Paper-Based Electrochemical Devices for Hydrogen Evolution

“…To further investigate the chemical modification occurring during the thermal treatment we obtained Raman spectra from C- and D-Crystals. In the case of D-Crystal, it is possible to verify the presence of oxides such as monoclinic MoO 2 − in some regions (Figure S3). Figure d shows the X-ray diffraction (XRD) data for C-MoS 2 and D-MoS 2 samples along with the PP.…”

Development of Porous MoO2 Pellet Target for 99Mo/99mTc Generator

“…MoO 2 is almost insoluble in water [15,16] and contains more 98 Mo per volume compared with MoO 3 . This insolubility provides the possibility of processing the irradiated target by water, rather than dissolving the entire quantity of molybdenum oxide in the alkali solution.…”

The role of sulfur in molybdenum transport in hydrothermal fluids: Insight from in situ synchrotron XAS experiments and molecular dynamics simulations

“…In pure water, the hydrogen molybdate (HMoO 4 -) and molybdate (MoO 4 2-) ions are thought to be dominant, and their ionization constants were determined up to 300 ˚C by Minubayeva and Seward (2010); molybdic acid, H 2 MoO 4 (aq), predominates only under highly acidic conditions, especially at T>100 ˚C (Borg et al 2012). Recently, Dadze et al (2017) obtained the solubility constants for crystalline MoO 3 (s) in acidic solutions up to 350 ˚C as H 2 MoO 4 (aq) and HMoO 4 -, and Saha et al (2017) used a hydrothermal diamond anvil cell to measure MoO 2 (s) solubilities in pure water of 44 ppm and 658 ppm at 600 and 800 ˚C, respectively; however, they were not able to determine the oxidation state and predominant Mo species in the solutions. In pure, low density water vapour, a neutral MoO 3 (H 2 O) n (aq) with hydration number n up to 3 at 360 ˚C was proposed based on the solubility of MoO 3 (s) .…”