Immobilization and fixation of molybdenum (6) by Portland cement
- Univ. of Aberdeen, Old Aberdeen (United Kingdom). Dept. of Chemistry
The immobilization of molybdenum (6) in Portland cement has been studied. Analytical methods are reviewed. As a precursor to studies using commercial cements, the cement constituent phases Ca[sub 3]Al[sub 2]O[sub 6] and Ca[sub 3]SiO[sub 5] and mixtures of Ca[sub 3]Al[sub 2]O[sub 6] and gypsum (CaSO[sub 4][center dot]2H[sub 2]O) have been synthesized and subsequently hydrated with an aqueous solution containing initially 2,000 ppm Mo. The aqueous Mo contents decrease slowly over the first 12 days before attaining a steady-state concentration, ca. 40--50 ppm. Its main speciation is as molybdate, MoO[sub 4][sup 2[minus]]. Commercial Portland cement was also studied; chemically soluble Mo was determined following pore fluid extraction. The 28-day Mo concentration, in the pore fluid, was in the range 50--80 ppm. the insoluble Mo in Portland cement is distributed mainly between powellite, CaMoO[sub 4], and a calcium aluminate sulfate hydrate with a very small amount in cement gel, a hydrated calcium silicate. The synthesis and characterization data are reported for Ca[sub 3]Al[sub 2]O[sub 6][center dot]CaMoO[sub 4][center dot]10--14H[sub 2]O (Mo-AFm). Solubility data are reported for synthetic powellite and Mo-AFm at 25 C.
- OSTI ID:
- 7174140
- Journal Information:
- Waste Management; (United States), Journal Name: Waste Management; (United States) Vol. 14:2; ISSN WAMAE2; ISSN 0956-053X
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
400201* -- Chemical & Physicochemical Properties
BUILDING MATERIALS
CEMENTS
CHEMICAL ANALYSIS
CHEMICAL REACTIONS
ELEMENTS
MANAGEMENT
MATERIALS
METALS
MOLYBDENUM
PHASE TRANSFORMATIONS
PORTLAND CEMENT
PROCESSING
SOLIDIFICATION
TRANSITION ELEMENTS
WASTE MANAGEMENT
WASTE PROCESSING