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Published in Anthony Peter Gordon Shaw, Thermitic Thermodynamics, 2020
As one might infer from Table 5.21b and equation 5.85, the Fe + FeS2 → 2FeS pseudocomproportionation is favorable and somewhat exothermic. Pseudocomproportionations are chemical reactions that resemble actual comproportionations in a stoichiometric context. Several pyrotechnic examples involve peroxides and persulfides, which contain the O22− and S22− anions, respectively. For example, the favorable and extremely exothermic Zn + ZnO2 → 2ZnO reaction entails the oxidation of zinc (Zn ⇌ Zn2+ + 2e−) and the reduction of peroxide (O22− + 2e− ⇌ 2O2−). Both ZnO and ZnO2 contain zinc in the +2 oxidation state. Like pyrite, hauerite (MnS2) is a persulfide that contains M2+ cations and S22− anions [115]. Therefore, the hypothetical Mn + MnS2 → 2MnS reaction is a pseudocomproportionation because MnS also contains Mn2+ cations [116]. On the other hand, the analogous Mn + MnO2 → 2MnO reaction is a genuine comproportionation (compare equations 5.88 and 5.89 to see why).
Biotechnological Avenues in Mineral Processing: Fundamentals, Applications and Advances in Bioleaching and Bio-beneficiation
Published in Mineral Processing and Extractive Metallurgy Review, 2023
Srabani Mishra, Sandeep Panda, Ata Akcil, Seydou Dembele
To make a comprehensive and concise description of the biochemistry of leaching, two different sulphur transformation pathways, based on the type of sulphide mineral, e.g., acid soluble and acid-insoluble sulphides, are accepted. They are: (1) thiosulfate pathway (for acid-insoluble sulphide minerals such as pyrite (FeS2), molybdenite (MoS2), and tungstenite (WS2)) and (2) polysulfide pathway (acid-soluble sulphide minerals such as orpiment (As2S3), realgar (As4S4), chalcopyrite (CuFeS2), troilite (FeS), pyrrhotite (Fe7S8), hauerite (MnS2), galena (PbS), and sphalerite (ZnS) (Sajjad et al. 2019; Sand et al. 2001; Schippers et al. 2014; Vera, Schippers and Sand 2013, 2013; Zhang et al. 2010). In both the pathways, role of the microorganism is to produce oxidant such as Fe3+ and SO42-via ferrous and elemental sulphur oxidation respectively (Sajjad et al. 2019).