Iron partitioning

Irifune T. and Isshiki M. (1998) Iron partitioning in a pyrolite mantle and the nature of the 410-km seismic discontinuity. Nature 392, 702-705. 

Iron is the most abundant 3d transition metal in the Earth s interior its existence in the lower-mande minerals can affect a broad spectrum of the minerals physical and chemical properties [4,5]. Current consensus for the iron abundance and valence states in the major lower-mantle minerals is that iron exists mainly as ferrous iron (Fe ) with a concentration level of 20% in ferropericlase, whereas iron exhibits two main valence states, Fe + and ferric iron (Fe ), with a concentration level of 10% in perovskite [4,5]. The Fe content in perovskite and postperovskite shows a strong correlation with the concentration of Al [6-9]. The iron content in postperovskite is still under debate as it can depend on a number of Actors including the iron partitioning coefficient between lower-mantle minerals and potential chemical reactions with iron-rich materials at the core-mantle boundary [6-9]. 

The assessment of k is of some importance since it relates to the question as to how much if any of the free energy of activation barrier is due to the spin-forbidden character of the transition. From the experimental point of view, Eq. (49) shows that the transmission coefficient k and the activation entropy AS appear in the temperature-independent part of the rate constant and thus cannot be separated without additional assumptions. Possible approaches to the partition of — TAS have been discussed in Sect. 4 for spin transition complexes of iron(II) and iron(III). If the assumption is made that the entropy of activation is completely due to k, minimum values between 10 and 10 are obtained for iron(II) and values between 10 and 10 for iron(III). There is an increase of entropy for the transition LS -+ HS and thus the above assumption implies that the transition state resembles the HS state. On the other hand, volumes of activation indicate that the transition state should be about midway between the LS and HS state. This appears indeed more reasonable and has the... 

Temperature and sulfur fugacity estimated from iron and zinc partitioning between coexisting stannite and sphalerite and coexisting stannoidite and sphalerite... 

Stannite is the most common tin sulfide mineral in the ore deposits associated with tin mineralization. This mineral sometimes contains appreciable amounts of zinc, together with iron. Several workers have suggested that the zinc and iron contents of stannite are related to temperature. With respect to the study of the phase relationships in the pseudobinary stannite-kesterite system. Springer (1972) proposed zincic stannite as a possible geothermometer mainly based on the chemical compositions of the two exsolved phases (stannite and kesterite). Nekrasov et al. (1979) and Nakamura and Shima (1982) experimentally determined the temperature dependency of iron and zinc partitioning between stannite and sphalerite. 

Iron and zinc partitioning between stannite and sphalerite is represented by the exchange reaction. 

Nekrasov et al. (1979) and Nakamura and Shima (1982) reported a temperature dependency of iron and zinc partitioning between stannite and sphalerite (Fig. 1.177)... 

Coprecipitation is a partitioning process whereby toxic heavy metals precipitate from the aqueous phase even if the equilibrium solubility has not been exceeded. This process occurs when heavy metals are incorporated into the structure of silicon, aluminum, and iron oxides when these latter compounds precipitate out of solution. Iron hydroxide collects more toxic heavy metals (chromium, nickel, arsenic, selenium, cadmium, and thorium) during precipitation than aluminum hydroxide.38 Coprecipitation is considered to effectively remove trace amounts of lead and chromium from solution in injected wastes at New Johnsonville, Tennessee.39 Coprecipitation with carbonate minerals may be an important mechanism for dealing with cobalt, lead, zinc, and cadmium. 

Bordin, G., J. McCourt, and A. Rodriguez. 1994. Trace metals in the marine bivalve Macoma balthica in the Westerschelde estuary, the Netherlands. Part 2 intracellular partitioning of copper, cadmium, zinc and iron — variations of the cytoplasmic metal concentrations in natural and in vitro contaminated clams. Sci. Total Environ. 151 113-124. 

Most of the zinc introduced into aquatic environments is sorbed onto hydrous iron and manganese oxides, clay minerals, and organic materials, and eventually is partitioned into the sediments (USEPA 1987). Zinc is present in sediments as precipitated zinc hydroxide, ferric and manganic... 

Use the solar Fe I curve of growth in Fig. 3.12 to deduce the solar iron abundance, using 9i0n = 0.9 and given that Fe I has an ionization potential of 7.87 eV and that the partition function of Fe II is 42. Compare the result with the one in Table 3.4. 

Note that iron is sufficiently ionized in the solar atmosphere that the abundance of Fe I can be neglected and its partition function (or the ground-state statistical weight gi) and the electron pressure cancel out. 

Ford, R.G., Bertsch, P.M., Farley, K.J. 1997. Changes in transition and heavy metal partitioning during hydrous iron oxide aging. Environmental Science and Technology, 31, 2028-2033. 

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