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Chromium-bearing waste slag: evaluation of leachability when exposed to simulated acid precipitation

Conference · · Am. Soc. Test. Mater., Spec. Tech. Publ.; (United States)
OSTI ID:6464545
;
Waste slag dumps constitute a large potential source of chromium contamination of groundwaters, particularly under the enhanced leaching action of acid precipitation. Laboratory leaching experiments were carried out to determine the composition factors controlling the chromium leachability of waste slags when exposed to acidic solutions designed to simulate acid precipitation. Two critical slag composition factors were found to control the chromium leachability: the calcium oxide (CaO)/silicon dioxide (SiO/sub 2/) ratio and the magnesium content. It was determined that above a 2.0 CaO/SiO/sub 2/ ratio, chromium exists in slag as calcium chromite, which can be vulnerable to leaching by acid precipitation, especially if it is oxidized to calcium chromate when exposed to the environment over an extended period. Experimental results showed that maximum chromium leachability from industrial slags occurred when the composition of the slag was at about a 2.0 CaO/SiO/sub 2/ ratio. Between a 1.0 and 2.0 CaO/SiO/sub 2/ ratio, in the presence of sufficient magnesium, picrochromite (MgO X Cr/sub 2/O/sub 3/) was formed, which is very stable towards oxidation and was resistant to dissolution by simulated acid precipitation.
Research Organization:
U.S. Department of the Interior Bureau of Mines, Twin Cities Research Center, Minneapolis, MN
OSTI ID:
6464545
Report Number(s):
CONF-8303191-
Conference Information:
Journal Name: Am. Soc. Test. Mater., Spec. Tech. Publ.; (United States) Journal Volume: STP-851
Country of Publication:
United States
Language:
English

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Related Subjects

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATION
320305* -- Energy Conservation
Consumption
& Utilization-- Industrial & Agricultural Processes-- Industrial Waste Management
520200 -- Environment
Aquatic-- Chemicals Monitoring & Transport-- (-1989)
54 ENVIRONMENTAL SCIENCES
ACIDIFICATION
ALKALINE EARTH METAL COMPOUNDS
BENCH-SCALE EXPERIMENTS
CALCIUM COMPOUNDS
CALCIUM OXIDES
CHALCOGENIDES
CHROMIUM
DISSOLUTION
ELEMENTS
INDUSTRIAL WASTES
LAND POLLUTION
LEACHING
MAGNESIUM COMPOUNDS
MAGNESIUM OXIDES
MANAGEMENT
METALS
OXIDES
OXYGEN COMPOUNDS
POLLUTION
PRECIPITATION
PROCESSING
SEPARATION PROCESSES
SILICON COMPOUNDS
SILICON OXIDES
SIMULATION
SLAGS
TRANSITION ELEMENTS
WASTE MANAGEMENT
WASTE PROCESSING
WASTES
WATER POLLUTION