Formation of calcium and magnesium molybdate complexes in dilute aqueous solutions and evaluation of powellite solubility in spent oil shale

Technical Report · Thu Feb 01 04:00:00 EST 1990

OSTI ID:6554591

Essington, M E; Huntington, G S

In order to increase our understanding of the chemistry of molybdenum (Mo) in spent oil shale disposal environments, predict fate and behavior, and assess the effectiveness of proposed mitigation techniques, we feel that is imperative to understand the processes controlling Mo aqueous- and solid-phase distribution. Recent research supports the significance of alkaline earth and alkali metal ion pairs with molybdate in aqueous solutions. The objectives of this study were to measure the ion association constants (log Q) for the formation of calcium and magnesium molybdate ion pairs by potentiometric titration at pH 7 and 25{degree}C in NaNO{sub 3} ionic media. The measured values were then used to examine the equilibrium solubility of powellite (CaMoO{sub 4}) in KNO{sub 3} solutions and spent oil shale systems. Powellite solubility data were evaluated using log Q for CaMoO{sub 4}{sup 0} formation, resulting in a calculated log K{sub sp} for powellite dissolution of -7.84. Application of an ion association model that used the molybdate ion pair formation data shows that spent oil shale leachates are undersaturated with respect to powellite. The results of this study show that molybdate ion pair formation in spent oil shale solutions may be significant and that soluble Mo concentrations may not be supported by powellite dissolution. 31 refs., 10 figs., 4 tabs.

• Research Organization: Western Research Inst., Laramie, WY (USA)
• Sponsoring Organization: DOE/FE
• DOE Contract Number: FC21-86MC11076
• OSTI ID: 6554591
• Report Number(s): DOE/MC/11076-2851; ON: DE90009663
• Country of Publication: United States
• Language: English

Related Subjects

04 OIL SHALES AND TAR SANDS
040500* -- Oil Shales & Tar Sands-- Properties & Composition
041000 -- Oil Shales & Tar Sands-- Environmental Aspects
ALKALI METAL COMPOUNDS
ALKALINE EARTH METAL COMPOUNDS
AQUEOUS SOLUTIONS
CALCIUM COMPOUNDS
DISPERSIONS
DISSOLUTION
ENVIRONMENTAL TRANSPORT
EQUILIBRIUM
ION PAIRS
LEACHING
MAGNESIUM COMPOUNDS
MASS TRANSFER
MATHEMATICS
MIXTURES
MOLYBDATES
MOLYBDENUM COMPOUNDS
NITRATES
NITROGEN COMPOUNDS
OXYGEN COMPOUNDS
POTASSIUM COMPOUNDS
POTASSIUM NITRATES
POTENTIOMETRY
REFRACTORY METAL COMPOUNDS
REGRESSION ANALYSIS
SEPARATION PROCESSES
SOLUBILITY
SOLUTIONS
SPENT SHALES
STATISTICS
TITRATION
TRANSITION ELEMENT COMPOUNDS