Geochemical characteristics of a sulphidic waste rock and implications for environmental rehabilitation

E. Mylona1,*, A. Xenidis1, G. Gaidajis2, K. Adam3

1 Laboratory of Metallurgy, School of Mining and Metallurgical Engineering,  National Technical University of Athens, 15780 Zografos, Athens, Greece
2 Department of Production Engineering & Management, Democritus University of Thrace, University Library Building, 67100 Xanthi, Greece
3 Environmental, Chemical & Metallurgical services (ECHMES) Ltd., 40-42 Mikras Asias st., Athens 11527, Greece

Accepted 5 March 2005


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

Keywords: Waste rock, Sulphides, Acid drainage, Limestone, Rehabilitation

* Corresponding author
   E-mail : mmmpem@central.ntua.gr