Chapter 8 Properties and Behaviour of Iron in Clay Minerals

Method development for evaluating the redox state of Callovo-Oxfordian clayrock and synthetic montmorillonite for nuclear waste management

“…However, the probability to have two neighboring structural Fe(III) is low and therefore this mechanism is possible but probably the least likely. The second mechanism reaction (2) and (3) is similar to that proposed for the reduction with sodium dithionite (Stucki, 2006). This process seems to be more likely because Fe(III) ions do not have to be neighbors.…”

Biological beneficiation of kaolin: A review on iron removal

“…Iron (Fe) comprises about 6% of the earth's mass, and therefore is the fourth most abundant element in the world after oxygen, silicon, and aluminum (Dong, 2012;Stucki, 2013). Biotite, pyroxene, amphibole, olivine, ilmenite, magnetite, and pyrite are the most important iron bearing minerals in soils which in all of them, iron is predominantly in bivalent state (Cornell and Schwertmann, 2004).…”

“…Biotite, pyroxene, amphibole, olivine, ilmenite, magnetite, and pyrite are the most important iron bearing minerals in soils which in all of them, iron is predominantly in bivalent state (Cornell and Schwertmann, 2004). Weathering causes the release of Fe II from rocks and formation of Fe III oxide/hydroxides which move through the crust mechanically or via complexation/ reduction by organic compounds and microbes, and then mix with clay silicates by precipitating and coating soil grains or scatter throughout the bulk of the clay as a separate phase (Ambikadevi and Lalithambika, 2000;Cornell and Schwertmann, 2004;Štyriaková et al, 2012;Stucki, 2013). Also, iron may present in clays as structural style either in oxidized form bound the aluminosilicate lattice in both the octahedral and tetrahedral sheets or as a compensating iron ion which substitutes for aluminum in silicate structure (Štyriaková and Štyriak, 2000;Mockovčiaková et al, 2008;Štyriaková et al, 2012;Stucki, 2013).…”

“…Physical approaches include intense magnetic separation which is able to remove iron and titanium impurities, gravity separation, and hydrocyclones (Prasad et al, 1991;de Mesquita et al, 1996;Guo et al, 2010;He et al, 2011). Chemical methods involve leaching the iron content of clay by organic and inorganic acids such as oxalic, citric or hydrochloric acid (Prasad et al, 1991;Ambikadevi and Lalithambika, 2000;Musiał et al, 2011), and reductive leaching by potent reducers, like sodium dithionite plus aluminum sulfate, sulfur dioxide plus aluminum or zinc powder, sodium formaldehyde sulfoxylate, hydroxyl ammonium acid sulfate, and hydrazine (de Mesquita et al, 1996;Ambikadevi and Lalithambika, 2000;Štyriaková et al, 2003;Stucki, 2013;Zegeye et al, 2013). Also, combined remediation processes are froth flotation and flocculation (Prasad et al, 1991;Lee et al, 2002;Guo et al, 2010;He et al, 2011).…”

Stability of Clay Barriers Under Chemical Perturbations

“…In these sedimentary formations some iron-bearing minerals exist. Iron may be present (1) in the structure of clay minerals (Fe(II) and Fe(III), the latter being predominant (Stucki, 2013)); (2) in the structure of pyrite or siderite (Fe(II)), (3) adsorbed on the edge surfaces of the clay mineral, or (4) in an exchangeable form in the interlayer space (Hadi et al, 2013;Didier et al, 2014). Oxidation will occur in the anaerobic host-rock during construction (excavation, drilling operations) and operations (gallery ventilation) in a geological repository.…”