Metal ions magnetic properties

In wastewater treatment, several investigations have reported about chitosan magnetic microspheres. Rorrer et al. prepared the porous-magnetic chitosan beads to remove of cadmium ions from waste water [62]. These beads can effectively remove Cd from waste water. The adsorption efficiency was influenced by the beads size. To improve uptake properties of metal ions, Zhou et al. prepared magnetic chitosan microspheres chemically modified with thiourea (TMCS). Compared to the unmodified ones, the uptake properties of metal ions such as Hg, Cu, and Ni ions was improved significantly. The adsorption kinetics followed the pseudo-second-order equation [63]. To improve the selectivity of metal ions, magnetic chitosan resin modified by Schiffs base derived from thiourea and... 

Within the periodic Hartree-Fock approach it is possible to incorporate many of the variants that we have discussed, such as LFHF or RHF. Density functional theory can also be used. I his makes it possible to compare the results obtained from these variants. Whilst density functional theory is more widely used for solid-state applications, there are certain types of problem that are currently more amenable to the Hartree-Fock method. Of particular ii. Icvance here are systems containing unpaired electrons, two recent examples being the clci tronic and magnetic properties of nickel oxide and alkaline earth oxides doped with alkali metal ions (Li in CaO) [Dovesi et al. 2000]. 

Medical Uses. A significant usage of chelation is in the reduction of metal ion concentrations to such a level that the properties may be considered to be negligible, as in the treatment of lead poisoning. However, the nuclear properties of metals may retain then full effect under these conditions, eg, in nuclear magnetic resonance or radiation imaging and in localizing radioactivity. 

Until about 20 years ago, the valence bond model discussed in Chapter 7 was widely used to explain electronic structure and bonding in complex ions. It assumed that lone pairs of electrons were contributed by ligands to form covalent bonds with metal atoms. This model had two major deficiencies. It could not easily explain the magnetic properties of complex ions. 

Much research focuses on the structures, properties, and uses of the complexes formed between d-metal ions acting as Lewis acids and a variety of Lewis bases, partly because they participate in many biological reactions. Hemoglobin and vitamin B12, for example, are both complexes—the former of iron and the latter of cobalt (Box 16.1). Complexes of the d-metals are often brightly colored and magnetic and are used in chemistry for analysis, to dissolve ions (Section 11.13), in the... 

The valences of the rare-earth metals are calculated from their magnetic properties, as reported by Klemm and Bommer.14 It is from the fine work of these investigators that the lattice constants of the rare-earth metals have in the main been taken. The metals lutecium and ytterbium have only a very small paramagnetism, indicating a completed 4/ subshell and hence the valences 3 and 2, respectively (with not over 3% of trivalent ytterbium present in the metal). The observed paramagnetism of cerium at room temperature corresponds to about 20% Ce4+ and 80% Ce3+, that of praseodymium and that of neodymium to about 10% of the quadripositive ion in each case, and that of samarium to about 20% of the bipositive ion in equilibrium with the tripositive ion. 

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