Zirconium concentration

Niobium-Zirconium Nb-0-75Zr has excellent mechanical properties and similar corrosion resistance to pure niobium higher zirconium concentrations reduce the corrosion resistance. 

Yield of polyethylene (g/liter) Time (h) Temperature (°C) Zirconium concentration Relative molecular weight (viscometric)... 

A second solvent extraction process (Pharex) was developed to partition the transcurium actinides from the americium and curium in the Tramex product ( 3) The Pharex process utilized 2-ethylhexyl phenylphosphonic acid as the extractant for the transcurium actinides. During early operations/ the selectivity of the Pharex extractant was found to be severely reduced by the presence of zirconium ions, which were introduced into the process solutions by corrosion of Zircaloy-2 equipment in TRU. At zirconium concentrations above 10 ppm, the achievable separation began to be diminished and, at 100 ppm, a practical separation could not be made (4). Thus, a replacement for the Pharex process was needed, and the LiCl AIX process was the most immediate alternative ... 

With increasing zirconium concentration the molecular weight decreases nearly linearly. This leads to the conclusion that chain transfer occurs via a bimetallic mechanism. 

The precipitation of the zirconium-molybdenum material is a function of acid strength, temperature and time. The rate of precipitation is lower with lower temperatures, low zirconium concentrations and higher acid strengths. There also appears to be an induction period before the onset of precipitation. Discussed here is the characterization of the zirconium molybdate solids, as obtained separately from nitric acid solutions chemical analyses, thermogravimetry and X-ray powder diffraction were used to characterize these solids. 

Zirconium solution, 0.005 M in 4 Af HCl (0.4561 g Zr in 1 litre). Dissolve a weighed portion of zirconium chloride or zirconium nitrate in 25 ml of HCl (1+1) and evaporate the solution until salt crystals appear, then dilute with 4 M HCl to 1 litre. Determine the zirconium in the solution gravimetrically as Zr02, and dilute with 4 M HCl to give a zirconium concentration of exactly 0.005 M. 

Fig. 5 Variation of the specific surface area with A the zirconium concentration and without template, B the Ci3(EO)6 / Zr molar ratio, [CufEOs] = 50 wt.%.

Specific surface area and microporous volume data for intercalated clays prepared with different zirconium concentrations. 

The XRD patterns of zirconium sulfate pillared clays obtained after 90 hours of intercalation with different zirconium acetate concentrations using 0.5 as sulfate to Zr ratio and the same clay concentration as used earlier are presented in Fig. 5. The diffraction data show the appearance of two first order reflections. The first one is at 23.4 A for the lowest zirconium concentration and appears as a shoulder at the same distance for 0.05 mol/L concentration. The second reflection is observed at approximately 12.3 A for the lowest concentration and at 13.7 A for 0.1 mol/L zirconium acetate. The first one results from the intercalation of sulfated zirconium species. Those species are more voluminous than the non sulfated one which gives a distance spacing at only 19.6 A. The better intercalation of sulfated zirconium species at low Zr concentration is probably due to the slow progress of polycondensation reactions. This process reduces the number of different zirconium species and gives a better cristallinity of the solid. Table 2 summarizes the textural properties of samples prepared with different zirconium concentrations. The decrease of the surface area with the decrease of the Zr concentration is probably due to the increase of the sodium clay layers by comparison with the intercalated layers. The microporous volume increases when the Zr concentration decreases. The higher microporosity is due to the important basal distance of this sample. 

In this part the effect of zirconium concentration on the textural thermal stability is investigated. Fig. 11 shows the variation of the microporous volume as a function of temperature for two Zr concentrations (0.1 mol/L and 0.025 mol/L). As shown, the Zr concentration seems to be important to the thermal stability of the microporosity. In fact, the microporosity of the sample prepared with 0.025 mol/L develops a higher thermal stability than that prepared with 0.1 mol/L zirconium. The polymeric phase deposited on the clay layers appears to be responsible for this loss of microporosity. An insignificant increase in the surface area between 120 °C and 400 °C is observed for the sample prepared with Zr concentration of 0.025 mol/L,... 

When the Zr concentration and the S04 Zr ratio increase, the formation of a polymeric phase is accentuated. For low S04 Zr ratio, the pillars in the intercalated clay fraction consist of non sulfated polycations. But when the zirconium concentration is low (0.025 mol/L) and the S04 Zr ratio is high, the intercalation of sulfated polycations occurs. These preparation conditions give a solid with a high textural thermal stability. Sulfate ions linked to Zr-pillars seem to be more stable than those incorporated in the polymeric phase. Those sulfate ions dispersed in the solid could generate an interesting catalytic behaviour that merits further study. 

H4] for an aqueous solution of the feed of concentration 3.5 Afin NaNOa and 3.0 in HNO3, in contact with 60 percent TBP in kerosene. Distribution coefficients will be higher at the bottom of the cascade, where the aqueous zirconium concentration is lower this will be neglected in the present treatment, but will be taken into account in Sec. 6.6. 

Figure 4.19 is a plot of zirconium concentration versus hafnium concentration in the organic phase, with points for the extracting section from Table 4.9 and points for the scrubbing section from Table 4.10. The point of intersection occurs at... 

Table 7.1 gives the annual production of zirconium concentrate by the principal producing countries of the non-Communist world, excluding the United States. 

N in sodium nitrate, containing no more than 30 g zirconium/liter. Under these conditions, the distribution coefficient of zirconium is around 1.5, favoring the organic phase, and that of hafnium is only one-tenth as great, so that the separation factor is 10. Unlike thiocyanate extraction, zirconium concentrates in the organic phase with TBP. 

The zirconium concentration in the Earth s crust varies considerably, ranging from 150 to 300 mg kg of soil (Miller 1965). The average zirconium content of freshwater is between 0.002 and 0.02 mg kg , and in seawater between 0.02 and 0.5 pg kg . However, according to others (Bruland 1983) the concentration is 0.01-0.04 pg kg mainly in the form of Zr(OH)° and Zr(OH)j ). It is improbable that industrial emissions of zirconium compounds lead to significant increases in these values. Zirco-... 

Recent studies with modern analytical techniques have shown much lower values for human body fluids. The mean zirconium concentration in whole human blood was found to be 9.6 5.8 pg L in the UK Master Mix (a collection of blood samples from humans in the UK), and 19.7 8 pg L for the mean value of individual blood samples (98 subjects). These values are in fair agreement with an estimate of 5.0 pg L in Italian blood samples. Here, the Zr concentration was derived on the basis of the measured concentration of hafnium, under the assumption of a Zr/Hf ratio of about 40, as found in soils and rocks. Morita etal. (1994), using ICP-MS, found a mean human serum Zr concentration of... 

Plant uptake of zirconium from soil and fertilizers has been demonstrated. In animals, zirconium and zirconia are absorbed either by oral intake or inhalation. In humans it must be assumed that insoluble zirconium compounds are taken up by inhalation because increased zirconium concentrations have been detected in the lungs of miners. The concentrations in the lung lymph nodes were higher than in non-exposed persons zirconium was also detected in blood and urine (Clayton and Clayton 1981). 

The major portion of ingested water-soluble zirconium salts is converted into zirconium oxides in the small intestine. Zirconium concentrations in the brain, kidneys, liver, lungs, and muscle of between 0.01 and 0.06 jg g were found by Hamilton et al. (1972/1973). In the lymph nodes, concentrations vary between 0.03 and 0.06 j,g g (wet weight), but these values should be rechecked using modern analytical methods. 

From the study of the literature, it clearly emerged that a considerable number of Zr-carbonate species exist (including polynuclear complexes and ternary carbonato-hydroxo species). The domain of existence of the various species apparently depends on absolute Zr and carbonate concentrations, COa/Zr total concentration ratios and pH. Nevertheless, there is convincing evidence that Zr(C03)4 is the limiting complex when carbonate concentrations are in large excess of zirconium concentrations i.e. COa/Zr ratios above ca. 10). Although the results and the re-interpretations obtained in... 

Figure A-7 Total zirconium concentration plotted against the concentration of zirconium in the organic phase.

Samples of Zr0Cl2 8H20 (leading to zirconium concentrations of 1 mM) were acidified with varying amounts of H2S04and Na2S04 (from 0.1 to 7 M) and the difference in the UV-absorption spectra were detailed at 2200, 2350, 2500, 2600 and 2700 A ... 

These experiments are similar to those described in [80MAL/CHU], but the solutions were sulphate free, less concentrated ([Zr]tot = 0.013 to 0.1 M) and had lower total carbonate to zirconium concentration ratios (COs/Zr ranging from 2 to 5). In contrast to the results reported by [80MAL/CHU], there is no evidence for the formation of a tetracar-bonate complex. The absorption peak characteristic of the free carbonate ion appears already at COs/Zr = 3 (pH = 9.6), suggesting that the limiting complex has two carbonate ligands. 

The data obtained at 1000 Torr pressure (5 ppm SO2/N2) suggests a significant dependence on eomposition with regards to the extent of sulfation (Figure 2). Specifically, the 90 at.% system demonstrated a substantial quantity of chemisorbed surface sulfur species. This observation is consistent with the observations noted with the sulfation analysis of ceria-only model catalysts. However, the intermediate compositional range was relatively insensitive to sulfur adsorption, while high zirconium concentrations indicated the... 

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