Effects of CH₄ and CO₂ on the sulfidization of goethite and magnetite: an in situ Raman spectroscopic study in high-pressure capillary optical cells at room temperature

Author： Wang Menghan Chou I-Ming Lu Wanjun De Vivo Benedetto

Publisher： E. Schweizerbart'sche Verlagsbuchhandlung

E-ISSN： 1617-4011|27|2|193-201

ISSN： 0935-1221

Source： European Journal of Mineralogy, Vol.27, Iss.2, 2015-03, pp. : 193-201

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Abstract

Reactions of goethite and magnetite with sulfide solutions under CH₄ and/or CO₂ atmospheres were monitored in situ with Raman spectroscopy in the high-pressure capillary optical cells (HPOCs) at room temperature. Isolated systems were created in the enclosed HPOCs for the study of the mineral–solution interactions to prevent oxidation during the experiments. We observed that iron (oxyhydr)oxide minerals were inert to sulfide solution under CH₄ atmosphere, and that the addition of CO₂ to this system triggered the sulfidization reactions and produced iron monosulfide; mackinawite was identified in the solid phase immersed in the solution after six hours and pyrrhotite in the solid phase exposed to the vapor phase after 5 days. Mackinawite formed in the aqueous phase was metastable, and dissolved after about 10 days. The observed sulfidization of iron (oxyhydr)oxide minerals was through a replacement reaction rather than a dissolution–precipitation process.