Comment on “Pyrite dissolution in acidic media” by M. Descostes, P. Vitorge, and C. Beaucaire

In a recent paper, Descostes et al. (2004) present data
on a series of pyrite oxidation batch experiments conducted near pH 2 and 3 where they demonstrate very well the
non-stoichiometric dissolution/oxidation of pyrite in acidic solutions through an extensive laboratory investigation
of S/Fe ratios. The authors utilized this data to propose a
‘mechanism’ of pyrite oxidation based on these data. They
conclude that measured sulfur deficiencies are due to a set
of reactions involving thiosulfate ðS2O3
2
Þ and tetrathionate ðS4O6
2
Þ as the primary argument for presenting a
specific pathway controlling pyrite oxidation. Using data
taken from current literature, we challenge these assumptions regarding thiosulfate and tetrathionate reactivity and
redefine these results in the context of a more complex,
and more consistent, representation of pyrite oxidation
pathways