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Leaching pyrite from coal waste: results of diagnostic study.

Authors
Chaiken-RF; Dalverny-LE
Source
Pittsburgh, PA: U.S. Department of the Interior, Bureau of Mines, RI 9569, 1995 Jan; :1-49
Link
NIOSHTIC No.
20024430
Abstract
The U.S. Bureau of Mines conducted an experimental and theoretical study of coupled chemical kinetic and mass transport processes during leaching of pyrite from coal in a counterflow, "trickle-bed" column reactor. Spatial and temporal data on reactant and product concentrations were used as solutions to appropriate continuity equations, which in turn define chemical kinetic reaction rates. Data from four 180- by 30-cm column leaching experiments using coal, coal waste, and air-water and air-FeCl lixiviants have been analyzed. The rate of leaching was found 3 to be diffusion limited (probably by Fe ) and not controlled by bacterial action. Rates of pyrite oxidation were 3+ found to vary with elapsed time (80 to 225 days) and followed a bell-shaped curve, sometimes with a delay before start of reaction. Maximum rates of reaction ranged from 3 to 10 (mmol/d)/L (column) for coal waste and 0.4 (mmol/d)/L (column) for coal. Reaction was 30 to 80 pct complete, probably due to precipitation of product salts (e.g., jarosites), which impede transport of oxidant through the coal. An absorption-desorption model of solids leaching, which considers the role of heterogeneous porosity in solids leaching, was used to describe time-dependent leaching rates.
Keywords
Mining-industry; Chemical-extraction; Chemical-reactions; Coal-mining; Waste-treatment; Environmental-protection
CAS No.
1309-36-0; 7439-89-6
Publication Date
19950101
Document Type
Report of Investigations
Fiscal Year
1995
NTIS Accession No.
PB96-107073
NTIS Price
A03
Identifying No.
RI-9569
ISSN
1066-5552
NIOSH Division
PRC
Source Name
Pittsburgh, PA: U.S. Department of the Interior, Bureau of Mines, RI 9569
State
PA
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