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Geochemical characteristics
of a sulphidic waste rock and implications for environmental rehabilitation
The geochemical behaviour of the sulphidic waste rock produced from the
Stratoni mines, Greece, was investigated in the present study. An extensive
laboratory testwork, including the execution of chemical-mineralogical
analysis, static and kinetic tests on a bulk waste rock sample (-50mm) and
its different particle size fractions was conducted. Based on the acid base
accounting test results, the whole sample assaying 2.9% S had neutralisation
potential ratio (NPR) of 5.5 and was classified as non-acid generating. The
majority of the contained sulphur, i.e. 85%, was distributed in the -4mm
waste rock size fraction, whereas all the different size fractions had
significant neutralisation potential, i.e. 380-590kg CaCO3/t,
derived from the contained calcite and dolomite. Acid leaching of the bulk
waste rock sample indicated that only 2.8% of the contained alkalinity was
sufficiently reactive to neutralise the acidity introduced. The respective
amount of the -4mm size fraction was higher, i.e. 6.4%, and may be
attributed to the higher percentage of reactive fine particles and the more
uniform distribution of water flow. Homogeneous mixing of the -4mm size
fraction with ground limestone further increased the reactive alkalinity
resulting in the effective neutralisation of acidity throughout the test
period of 30 weeks |
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