Analytical Sciences

Determination of Iron Monosulfide and Iron Disulfide in Suspensions by an Electrochemical Method Using a Platinum-Silver Twin-Electrode

Xiaojun DIAO and Katsuhiro SUMI

Department of Environmental Systems Engineering, Kochi University of Technology, 185 Miyanokuchi, Tosayamada, Kami, Kochi 782-8502, Japan

New electrochemical technique with a Pt-Ag twin electrode is proposed for the determining the contents of iron sulfides (FeS and FeS₂) in a suspension. After electrolytic oxidation with a Pt electrode, Fe²⁺ was measured by linear sweep voltammetry. From relations of the charge amount from the baseline to the peak in the voltammogram of Fe²⁺ with the content of FeS or FeS₂, linear calibration curves (a) and (b) were prepared, respectively. After measurements of Fe²⁺, Fe²⁺ and S⁰ were reduced with a Pt electrode to remove Fe²⁺ and to produce S²⁻. With an Ag electrode, Ag₂S was deposited on Ag. A linear curve (c) was prepared from a relation between the charge amount of the Ag₂S peak part and the FeS content. However, in the suspension of FeS₂, Ag₂S can not be detected. When this method is applied to a mixed suspension of FeS and FeS₂, the content of FeS can be determined with curve (c), whereas curves (a) and (b) were not effective in the mixed suspension.

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