The influence of a Cr-dopant on the properties of α-FeOOH particles precipitated in highly alkaline media

The Speciation of Cd in Cd–Fe Coprecipitates: Does Cd Substitute for Fe in Goethite Structure?

“…As active components in tropical and subtropical soils, iron (hydr)­oxides have special surface properties and are attached to the surface of soil particles as coatings, which significantly influence the fixation, migration, and transformation of pollutants. Goethite is one of the most common iron (hydr)­oxide minerals in soils. − The association mechanisms of heavy metals with goethite mainly include adsorption, isomorphous substitution, and precipitation. − Many cations, such as Al 3+ , Cd 2+ , Cr 3+ , Mn 3+ , Ni 2+ , Cu 2+ , Zn 2+ , and Pb 2+ , can be incorporated into goethite structure by replacement of lattice Fe 3+ during the formation and transformation of goethite. ,,− The maximum substitution of Cd in goethite can reach up to ∼10 mol % (Cd/Cd + Fe) under laboratory conditions, even in the presence of Al 3+ . ,, Cd-substitution in goethite results in a series of changes in the mineral structure, morphology, reactivity toward various nutrients and pollutants and stability upon dissolution. ,,,, …”

Spatial distribution of crystalline corrosion products formed during corrosion of stainless steel in concrete

“…Since these Cr-substituted iron oxide-hydroxides were until now only found on synthesized iron oxide-hydroxides, further research has to be performed on other reinforcing steel types with different Cr and Ni contents to confirm that such a substitution would occur naturally during corrosion of Cr alloyed steel in concrete under high pH and low oxygen availability. As earlier discussed, previous research on synthesized Cr-substituted iron oxidehydroxides [18,28,30,31] have shown that the presence of Cr influences the size of the crystals. A similar behaviour could be expected in the case of corrosion products formed during corrosion of Cr-rich reinforcing steel in concrete.…”

“…The maps show that a certain amount of chromium is present in corrosion products that formed during corrosion of 16 wt.% Cr steel. Previous research performed on synthesized particles of different iron oxide-hydroxide has shown that cations such as Cr 3 + , Cu 2 + , Mn 2 + , and Al 3 + can substitute for iron in goethite, akaganeite, lepidocrocite, or magnetite [18,[28][29][30][31]. Cook et al [18] used Mössbauer and Raman spectrometry to characterize corrosion products that formed on weathering steel in natural environments, demonstrating that a layer of nano-sized chromium substituted goethite crystals formed close to the steel surface.…”

“…Until now, research on laboratory samples and long-term exposure of real concrete reinforced structures to marine environments have shown that, besides longer initiation periods, these steels have a prolonged propagation period (i.e., more time is needed to achieve a certain level of corrosion activity) [25,26]. The available literature on corrosion products formed under the influence of alloying elements concentrates mainly on synthesized iron oxide-hydroxides, created and tested under laboratory-controlled conditions [12,[27][28][29][30][31]. These studies have demonstrated that adding specific alloys influences the type of iron-hydroxide phases created during the corrosion process.…”