Abstract
This study aimed to investigate the oxidation mechanism of pyrite crystallographic direction by cutting pyrite samples to expose their (100), (110), and (111) planes. Differences in the oxidation rates of pyrite planes in acid solution were determined. The morphological changes of pyrite were evaluated by scanning electron microscopy and hyperdepth-3D microscopy. The oxidation products of pyrite were examined by Raman spectroscopy and X-ray photoelectron spectroscopy. Results showed that the aqueous oxidation of pyrite produced Fe(OH)3, Fe2O3, Fe2(SO4)3, and S8 on the surface. Moreover, the morphologies of corrosion patterns differed from one crystal plane to another: square, rectangular, and triangular etch pits were found on the (100), (110), and (111) planes, respectively. The corrosion patterns reflected the symmetrical arrangement of the crystallographic planes in the lattice on which they formed.
Highlights
Pyrite, accompanied with other sulfide ores, is considered the most abundant metal sulfide in theEarth’s crust and is frequently found in massive hydrothermal deposits, igneous rocks, and sedimentary beds [1,2,3]
Pyrite oxidation in acid solutions, which is the main source of AMD, should be investigated
The reported results and conclusions do not conform with oxidation mechanism and kinetics [11]
Summary
Pyrite, accompanied with other sulfide ores, is considered the most abundant metal sulfide in the. Natural pyrite contains many heavy metals, such as Ag, Au, Cd, Co, Cu, Mo, Ni, Pb, Se, Sb, Sn, Te, and Zn [4]. AMD or ARD has become a long-term environmental problem, affecting the ecological environment through the dissolution of rocks, acidification of aquifers, and mobilization of heavy metals. Surface oxidation of pyrite aids in the extraction of valuable metals from pyrite deposits. This study aimed to systematically investigate the surface oxidation of pyrite to understand its oxidation mechanism and to find means to reduce the source of AMD. All these studies provide detailed information about the atomic structure of crystal directions and some possibilities in investigating the surface changes during pyrite oxidation. The directional oxidation rate and morphologies of pyrite surface were investigated. The results on surface morphology can provide a complete understanding of pyrite oxidation
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