Analysis of Iron Oxyhydroxides and Oxides Converted from Green Rust in Aqueous Solution

Abstract

In order to clarify the influence of reaction conditions on the formation of iron oxyhydroxides and oxides obtained from hydroxysulfate green rust (GR), the X-ray diffraction method was used for analyzing the solid particles formed during conversion. GR was synthesized from solutions of ferric sulfate, ferrous sulfate, and sodium hydroxide. The suspension containing GR was oxidized by passing oxygen gas. X-ray absorption spectroscopy and transmission electron microscopy were used for analyzing the chemical state and structure of the solid particles separated from the suspension, respectively. The results revealed that GR was converted primarily to a-FeOOH, and g-FeOOH and Fe 3 O 4 were found to be partially formed during the conversion depending on the temperature and oxygen flow rate. Furthermore, the addition of manganese was shown to enhance the formation of Fe 3 O 4 . These results indicate that the formation of different structures of iron oxyhydroxides and oxides in an aqueous solution is sensitive to the reaction conditions.

Characteristic Behavior of Nickel Ions during Transformation of Green Rust to Ferric Oxyhydroxides in Aqueous Solution

“…We have investigated the formation conditions of the iron oxyhydroxides and oxides obtained from GR2(SO 4 2À ) by aerial oxidation. [17][18][19] The results indicate that the transformation of GR2(SO 4 2À ) into the iron oxyhydroxides and oxides is sensitive to oxidation conditions such as reaction temperature and oxidation rate. Furthermore, it is shown that the foreign elements influence the oxidation products that are transformed from GR2(SO 4 2À ).…”

Characterization of Formation and Oxidation of Green Rust (Cl−) Suspension

“…12 ) to iron oxides and oxyhydroxides has been studied. [12][13][14] The results show that the oxidation of GR(SO 4…”

“…Thus, GR is considered to be transformed into iron oxides and oxyhydroxides through dissolution and precipitation of Fe(II) and Fe(III) ions in an aqueous solution by atmospheric oxygen. [10][11][12][13][14] Therefore, GR is considered to be an important precursor oxide that would help to understand the reaction conditions in the transformation of GR into different iron oxides in aqueous solution.…”

Reduction of Copper Ions in Green Rust Suspension and Oxidation of Green Rust Containing Metallic Copper

“…We have succeeded at synthesizing GR2(SO 4 2À ) by using chemical method and characterize the transformation process of GR2(SO 4 2À ) into the iron oxyhydroxides and oxides by aerial oxidation. [10][11][12][13] The results show that the transformation of GR2(SO 4 2À ) into the iron oxyhydroxides and oxides is sensitive to oxidation conditions such as reaction temperature, oxidation rate and existence of foreign elements.…”

“…6,7) Since GR is stable in an aqueous solution of relatively low potential, it is transformed into the iron oxyhydroxides and oxides through the dissolution and precipitation of Fe(II) and Fe(III) ions in an aqueous solution by oxygen gas in air. [8][9][10][11][12][13] Therefore, it is important to elucidate the influence of the addition of an alloying element on the transformation of the iron oxyhydroxides and oxides from the GR in an aqueous solution, in order to understand a role of the element on the transformation of the corrosion products. We have succeeded at synthesizing GR2(SO 4 2À ) by using chemical method and characterize the transformation process of GR2(SO 4 2À ) into the iron oxyhydroxides and oxides by aerial oxidation.…”