The Anodic Oxidation of Iron Pyrite Powder in a Cationic Surfactant‐Styrene‐Aqueous Sodium Hydroxide Emulsion

Abstract

A study was made of the electro-oxidation of iron pyrite powders on polystyrene-surfactant filmed platinum electrodes using a suspension in a styrene-cationic surfactant-2N aqueous sodium hydroxide emulsion. In addition, a study was made in a thin layer cell in which the powder was trapped adjacent to the electrode. The film on the electrode allowed one to apply approximately an additional 1.7V before encountering interference from electrolysis of water. Without a film, one sees only one oxidation wave associated with a one electron oxidation of $2 = to $2-. In the filmed system, there are four oxidation reactions that can be studied $2(~ = --~ $2(~1-+ e [1] Fe(~+ + OH 1/2 Fe20.~,~ + e [2] S21si = ~ $2 ~ + 2e [3]and fourth, oxidation of organic compounds formed by the trapping of the $2-and $2 ~ free radicals.

The Electro‐oxidation of Some Insoluble Inorganic Sulfides, Selenides, and Tellurides in Cationic Surfactant‐Aqueous Sodium Hydroxide Systems

“…This paper is a report on an extension of the previous studies (9)(10)(11) to electro-oxidation of several other sulfides and some selenides and tellurides suspended in surfactant systems. The purpose of these studies was to investigate the possible use of these surfactant systems in electroanalysis of insoluble powders and in areas of massive electrolysis such as electrolytic roasting of minerals.…”

“…Recently, as part of a series of studies on the uses of cationic surfactants in the electro-oxidation of insoluble, difficulty oxidizable compounds (1)(2)(3)(4)(5)(6)(7)(8), it was reported that it was possible to electrolytically oxidize iron pyrite (9,10) and galena (11) powders in a cationic surfactant-aqueous sodium hydroxide system. Previously, electrolytic oxidation studies of these sulfide minerals to obtain answers to questions in the field of mineral processing have primarily utilized crystalline electrodes or powders mounted in graphite paste or epoxy cements (12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26).…”

“…The previous studies (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11) have shown that cationic surfactants affect these electro-oxidations in two ways. They solubilize the solids and form a hydrophobic film on the electrode, increasing the oxidation potential of water by 0.9V.…”

“…Anionic and neutral surfactants solubilize insoluble solid powders but do not appreciably increase the oxidation potential of water. In order to separate these two effects two types of cells (9,11) have been used: (i) a beaker cell for study of slurries of the powdered compounds (in this cell both the solubilization and filming effects were evident); (ii) a sandwich cell (in this cell the solid was trapped next to the electrode by a piece of filter paper and thus one observed only the filming effect).…”

A Review of Transition Metal Boride, Carbide, Pnictide, and Chalcogenide Water Oxidation Electrocatalysts

“…A faradaic efficiency of <100% implies that the consumed total charges may be partially utilized for the irreversible oxidation of the MX y material. Furthermore, a voltammetric study for MX y oxidation in cationic surfactant-containing NaOH aqueous solution is a critical way to check MX y ’s oxidation potentials and its oxidation mechanism (e.g., sulfide → sulfur → sulfite → sulfate). − The MX y oxidation voltammetric peak is partially/fully overlapped with the OER voltammetric wave most of the time. In this system, as the cationic surfactant increases the water oxidation potential (by 0.9 V), it is possible to separate the water and MX y oxidation reactions and directly observe the MX y oxidation voltammetric peaks, which has already been previously used for examining the oxidation of some chalcogenides such as FeS 2 , NiS, MnS, MoS 2 , PbS, NiSe, MnSe, MoSe 2 , NiTe, MnTe 2 , and MoTe 2 . − Revealing the MX y oxidation potential, of which further extension is expected, may lead to a discussion regarding the possibility that the actually applied potential to drive the OER causes the MX y oxidation.…”