Time-dependent leaching of coal fly ash by chelating agents
The rates of leaching of several transition-metal ions from coal fly ash by pH 7.4 solutions of the chelating agents citric acid, EDTA, histidine, and glycine have been measured. These results are compared to leaching of the same fly ash by 0.5 M HCl, 0.10 M pH 7.4 Tris buffer, 0.5 M NH/sub 4/OH, and canine serum. The general order of leaching ability is HCl>>EDTA approx. citric acid > histidine > glycine approx. Tris. Canine serum is more effective as a leaching agent than one would predict on the basis of its concentrations of citrate and histidine, so that other biological chelators, possibly cysteine, appear to be important leaching agents. For the trace elements Zn, Mn, Cr, Ni, and Cu, the initial leaching rates with 0.5 M HCl range from 350 to 850 ..mu..g of metal per gram of ash per day (ppm/day). The rates drop by 1-2 orders of magnitude within 24 h and then level off at 1-10 ppm/day. The initial rates with EDTA and citric acid are also high, approx.100-400 ppm/day, but they fall off even more rapidly than the HCl leaching rates. The leaching of vanadium is exceptionally rapid, with initial rates of 1000-3000 ppm/day. In addition, EDTA and citric acid leach over 50% of the acid-soluble vanadium compared to only 10-35% of the other transition metals.
- Research Organization:
- Univ. of California, Davis
- OSTI ID:
- 5130161
- Journal Information:
- Environ. Sci. Technol.; (United States), Vol. 17:3
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
01 COAL, LIGNITE, AND PEAT
FLY ASH
LEACHING
TRANSITION ELEMENTS
AIR POLLUTION
CHELATING AGENTS
CITRIC ACID
COAL
CONCENTRATION RATIO
GLYCINE
HISTIDINE
PH VALUE
TIME DEPENDENCE
TRACE AMOUNTS
AEROSOL WASTES
AMINO ACIDS
ASHES
AZOLES
CARBONACEOUS MATERIALS
CARBOXYLIC ACIDS
DISSOLUTION
ELEMENTS
ENERGY SOURCES
FOSSIL FUELS
FUELS
HETEROCYCLIC ACIDS
HETEROCYCLIC COMPOUNDS
HYDROXY ACIDS
IMIDAZOLES
MATERIALS
METALS
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
POLLUTION
RESIDUES
SEPARATION PROCESSES
WASTES
500200* - Environment
Atmospheric- Chemicals Monitoring & Transport- (-1989)
010800 - Coal
Lignite
& Peat- Waste Management