Paramagnetic minerals

Most of the above apphcations are in clarification duties. The use of HGMS to dewater relatively concentrated, paramagnetic mineral slurries has been demonstrated on 2 to 12 wt % feed concentration of synthetic malachite (7) concentrated to 40%. The magnetic collection was optimized at flow velocities of 1 mm/s, and product concentrations greater than 40% were not possible unless the collected material could be removed from the matrix with less than the equivalent of one canister of washwater. 

Table 10.3 shows susceptibility values for paramagnetic minerals. 

TABLE 10.3 Mass Susceptibility and Volume Susceptibility k of Some Paramagnetic Minerals... 

Uranium dioxide [1344-57-6], UO2, is found ki nature as the mineral pitchblende and as a component ki uraninite. The crystalline soHd melts at 2878°C and is paramagnetic with a room temperature magnetic moment of 3.2 )Xg. The density has been found to range from 10.79 to 10.95 g/cm, lower values are... 

McMillan has reviewed the chemistry of Ag(II) and Ag(IlI). Paramagnetism and electron spin resonance studies confirm the presence of Ag(ll) (as opposed to equimolar Ag(I)+Ag(III)). The colours of Ag(II) solutions in various mineral acids indicate the existence of complexes, the oxidising power of which is apparent from their decomposition even at 0 °C, although high acidity promotes stability. Rapid isotope exchange between Ag(I) and Ag(n) is considered to result from the equilibrium... 

ESR spectroscopy can be used with adsorbed paramagnetic ions to study the liquid associated with mineral surfaces. Cu(II) and Mn(II) have been used in his type of investigation, although difficulties are encountered with observing a resonance from Mn(II) in distorted environments. Measurements of Cu(II) on silica at room temperature and above have shown that adsorbed water behaves in the same manner as bulk water, but at lower temperatures it experiences a decreased mobility (61). On freezing two types of water are found one which is freezable and undergoes crystallization and the other which is unfreezable, in which the ice structure cannot be formed because of the surface interaction. NMR, IR and differential thermal... 

The Na+- and Ca2+-saturated montmorilIonite, saponite and beidel-lite were obtained from Dr. J. L. McAtee, Chemistry Department, Baylor University. These minerals had been purified and prepared by methods described by Callaway and McAtee (15). Included in this paper for purposes of comparison are relevant data from previous studies in which hectorite and vermiculite had been doped with paramagnetic probes ( 7, 10). The chemical formulae of the low-Fe smectites and mermiculite are reported in Table I. 

NMRD studies (0.01-30 MHz) on bentonite suspensions showed that the water-proton spin-lattice relaxation rates are dominated by magnetic interactions with paramagnetic centers entrapped in the mineral matrix (89). The 1/Ti values were linearly dependent on the concentration of the... 

Lepidocrocite is paramagnetic at room temperature. The Neel temperature of 77 K is much lower than that of the other iron oxides and is the result of the layer-like structure of this mineral. The sheets of Fe(0,0H)6 octahedra are linked by weak hydrogen bonds, hence magnetic interactions are relatively weak. The saturation hyperfine field is also lower than for any other iron oxide (Tab. 6.2). In the antiferromagnetic state, the spins are ordered parallel to the c-axis with spins in alternate layers having opposite signs. A decrease of T by 5 K was observed for Al-lepidocrocites with an Al/(Fe-i-Al) ratio of 0.1 (De Grave et al., 1995). 

The origin of Aeolian dust from Chinese desert to Japanese islands was studied with ESR of dust, mostly fine grains of quartz.132 Suspended particulate matter (SPM) collected by environmental protection agency was measured with ESR.133 Dust soot of automobiles was also measured to check the motor combustion rate. Adsorption of NO, Mn2+ and Gd3 on clay minerals, bentonite and se-piolite134 has been studied using paramagnetic ions as tracers for radioactive elements. And studies have been carried out on how divalent and trivalent cations diffuse and blocked by surrounding clay minerals, in the context of their leak from nuclear waste repository to the environment.135... 

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