TITLE:
Suppression of Pyrite Oxidation by Surface Silica Coating
AUTHORS:
K. Kollias, E. Mylona, K. Adam, N. Papassiopi, N. Papassiopi, A. Xenidis
KEYWORDS:
Acid Mine Drainage, Mine Wastes, Pyrite, Silica Coating
JOURNAL NAME:
Journal of Geoscience and Environment Protection,
Vol.2 No.4,
July
11,
2014
ABSTRACT: The exposure of pyrite (FeS2) to
atmospheric conditions during mining activity causes a series of complex
oxidation reactions, resulting to acid generation and the subsequent release of
toxic heavy metals in the surrounding aquatic and terrestrial ecosystems. The
produced acidic mine waters, known as acid mine drainage (AMD), constitute one
the major environmental problems of both operating and abandoned mixed
sulphide, coal and other mine sites where sulphidic minerals are encountered. A
sustainable approach to the environmentally safe pyrite-bearing extractive
waste management is related to the prevention of oxidation by developing
artificial coatings on the pyrite surfaces. In this study, experiments
performed to study the conditions of the silica coating formation on the FeS2
particles contained in a pyrite concentrate are presented. Batch tests
involving the treatment of pyrite samples with a coating solution, consisting
of Na2SiO3, H2O2 and buffered pH, were performed under a liquid to solid ratio
(L/S) 100 l/kg. The effect of parameters including SiO2 concentration (5 - 50
mM), pH values (5.0 - 8.0) and contact time up to 24 hours, was investigated. Parameters
examined to monitor the silica coating formation process include analysis of
Fe, Si,
and H2O2 in the
aqueous phase. Scanning electron microscopy with energy dispersive spectrometry
(SEM/EDS) was used for the examination of the chemically modified surfaces of
silica-treated pyrite samples.