Nickel impurity

This relationship is shown in Eigure 6.4 for a series of copper alloys. The variation of resistivity with temperature is approximately linear over a wide temperatme range, and near absolute zero the alloys have a relatively temperatme-independent residual resistivity. Notice that as the level of nickel impurities increases, so do both the residual... 

Nickel and cobalt often occur with copper, and must be separated in pure form from hydrometallurgical leach liquors. Organic acid extractants can quite readily separate copper from cobalt and nickel, but the separation of cobalt from nickel is rather difficult. In one Ni/Co separation process, di-2-ethyl hexyl phosphoric acid (D2EHPA) is used as extractant, with strict control of the pH of the aqueous phase to take full advantage of the slightly different equilibrium constants for the Co and Ni reactions. Pulsed column contactors are used rather than mixer-settlers, and nickel impurity is removed from the loaded organic phase by scrubbing it with a cobalt-rich phase. 

The nickel concentration on this particle is extremely low with traces of the nickel impurity at the external surface. This low nickel concentration means that the particle in Figure 2 was in the refinery unit only a short time, otherwise more nickel would be present for the average particle (by bulk chemical analysis) contains 900ppm Ni and 4700 ppm V. The particle in this image contains a disproportionate amount of vanadium relative to nickel. If the nickel on the external skin of the catalyst accumulates by nickel porphyrin cracking at the first surface contacted, then vanadium must arrive not only by cracking vanadyl porphyrins but also by some other means like transfer from older catalyst particles in the FCC unit. The high vanadium concentration relative to nickel on new catalyst particles provides evidence that vanadium has interparticle mobility as well as intraparticle mobility. 

The purpose of our work was to simulate vibrational spectra of ZnO crystals containing nickel impurities in different charge states with respect to the lattice and also to analyze vibrational structures of EA spectra of ZnO Ni based on calculations of localized vibrations induced by the impurities. 

Special attention is given to the localized vibrations with the symmetries Ai and E. According to a group-theoretic analysis, they are active in the EA spectra of ZnO Ni crystals. The frequencies of such localized vibrations induced by nickel impurities in ZnO crystals are listed in Table 4. 

On the basis of the combined HP-XPS/SFG data, a quantitative analysis of CO coverages at various pressures and temperatures was carried out (253). Figure 27d displays the CO coverage on Pd(l 1 1) as a function of the CO background pressure. It is emphasized again that gas cleanliness is crucial to the success of such experiments. When CO was used as received (purity 99.997%), iron and nickel impurities were detected on the surface, and these caused dissociation of CO and produced various carbon species (cf. Fig. 13d) (253). 

What property allows copper to be purified in the presence of iron and nickel impurities Explain. 

Another Important concept introduced by Taylor was that of heterogeneity of surface-active centers.(25-26) This stemmed from observation of R. N. Pease that minute amounts of carbon monoxide, much smaller than the amount necessary to cover the surface, were sufficient to poison the surface of a copper catalyst. Taylor proposed that there were active centers on the surface while others argued that nickel impurities segregated preferentially on the surface and acted as catalyst. The variation of the heats of adsorption with surface coverage as determined by R. Beebe was used as evidence supporting the concept of active centers. In spite of the contradictory interpretation of the same experimental data, the concept of active centers has been a fruitful one. It inspired Imaginative research in the field of metal and oxide catalysis and has its present day expression in sophisticated surface physics studies. Subsequent work by coworkers of Turkevich at Princeton refined the nature of active centers in monodisperse metal particles and crystalline oxide catalysts. 

NH3 is used (with an inline-filter), it should first be bubbled through an ammoniacal solution of EDTA ca. 0.01 mol/L) to reduce copper and nickel impurities before passing into distilled water. Alternatively, gaseous NH3 may be obtained from a 25 % ammonia solution (a.g.) by heating. 

Patton (1973k) describes modem commercial wet process preparation methods. One starts with a cadmiiun chloride solution free of iron and nickel impurities low levels of zinc chloride may be added at this point. Over a period of about an hour or more a... 

S Motojima, S Yokoe, K Sugiyama. Pillar crystal growth of boron phosphide from the vapor in the presence of nickel impurity. J Cryst Growth 49 1, 1980. 

Early attempts to control vanadium deactivation involved the addition of amorphous alumina to the cracking catalyst matrix. This was not particularly suitable because alumina increased coke formation and led to wider dispersion of nickel impurities. Hydrodesulfurization of FCC feeds is nseful it not only removes sulfhr, but the desulfurisation catalyst also adsotbs a significant proportion of the metal porphyrins. 

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