Lanthanum removal

Only chemical interferences were observed sodium and potassium ionized in the air-acetylene flame, and aluminum ionized in the nitrous oxide-acetylene flame magnesium and calcium exhibited evidence of interference by both phosphorus and aluminum. All the other elements were found to be interference-free. The addition of 1000 ppm of cesium as an ionization suppressor effectively removed the ionization interference in the sodium and potassium solutions. Similarly, 1000 ppm of lanthanum removed the interference due to phosphorus and aluminum in the magnesium and calcium solutions and suppressed the ionization of aluminum. 

Sodium fluoroborate [13755-29-8] M 109.8, m 384 , d 2.47, pK -4.9 (for fluoroboric acid H30 BF4 ). Crystd from hot water (50mL/g) by cooling to 0 . Alternatively, purified from insoluble material by dissolving in a minimum amount of water, then fluoride ion was removed by adding cone lanthanum nitrate in excess. After removing lanthanum fluoride by centrifugation, the supernatant was passed... 

Lanthanum is a naturally occurring trivalent rare earth element (atomic number 57). Lanthanum carbonate quickly dissociates in the acidic environment of the stomach, where the lanthanum ion binds to dietary phosphorus, forming an insoluble compound that is excreted in the feces. Lanthanum has been shown to remove more than 97% of dietary phosphorus... 

To finish with another trend for NO removal consisting in NO direct decomposition, we would like to depict the infrared study of NO adsorption and decomposition over basic lanthanum oxide La203 [78], In this case, the basic oxygens are proposed to lead to N02 and N03 spectator species, whereas the active sites for effective NO decomposition are described as anion vacancies, which are often present in transition metal oxides. This last work makes the transition with the study of DeNO, catalysts from the point of view of their ability to transfer electrons, i.e. their redox properties. 

Nelson We have the phospholamban knockout mouse model, and John Lederer was able to peel out a component of the decay that was due to reuptake. We didn t see any difference between the control and the knockouts. Presumably it is happening, but we couldn t see any difference in the decay in the phospholamban knockouts, as was seen in heart muscle, nor could we see any effect of lanthanum or zero Na+. Examining the decay of the spark would be a good indicator of local Ca2+ removal, though. It would also be worth examining the decay of the BK current. 

The metallothermic reduction of the oxides by La produces the metals Sm, Eu, Tm, Yb, all having high vapour pressures. The reaction goes to completion due to the removal of the rare earths by volatilization from the reaction chamber (lanthanum has a low vapour pressure). The remaining rare earth metals (Sc, La, Ce, Pr, Nd, Y, Gd, Tb, Dy, Ho, Er, Lu) can be obtained by quantitative conversion of the oxides in fluorides, followed by reduction with Ca. The metallothermic reduction of the anhydrous rare earth chlorides could be also used to obtain La, Ce, Pr and Nd. The molten electrolysis can be applied to obtain only the first four lanthanide metals, La, Ce, Pr and Nd, because of the high reactivity of the materials that limits the operating temperatures to 1100°C or lower. 

The rare earth (RE) ions most commonly used for applications as phosphors, lasers, and amplifiers are the so-called lanthanide ions. Lanthanide ions are formed by ionization of a nnmber of atoms located in periodic table after lanthanum from the cerium atom (atomic number 58), which has an onter electronic configuration 5s 5p 5d 4f 6s, to the ytterbium atom (atomic number 70), with an outer electronic configuration 5s 5p 4f " 6s. These atoms are nsnally incorporated in crystals as divalent or trivalent cations. In trivalent ions 5d, 6s, and some 4f electrons are removed and so (RE) + ions deal with transitions between electronic energy sublevels of the 4f" electroiuc configuration. Divalent lanthanide ions contain one more f electron (for instance, the Eu + ion has the same electronic configuration as the Gd + ion, the next element in the periodic table) but, at variance with trivalent ions, they tand use to show f d interconfigurational optical transitions. This aspect leads to quite different spectroscopic properties between divalent and trivalent ions, and so we will discuss them separately. 

Other rare earths, including yttrium (29) and lanthanum (30) are active for SO2 removal as shown on Table III. 

Figure 17 shows a comparison of the fresh SO2 removal ability for these five major types of commercially available SOx catalysts. The materials were tested at 1350 F at various concentrations with a very low capacity cracking catalyst. The magnesia-based catalyst is much better than lanthanum-based catalyst followed by platinum or cerium on alumina and finally alumina alone. The reverse order in activity observed for the lanthanum-based and cerium additives, compared to the relative results given previously for lanthanum and cerium, was not investigated, but may be related to the presence of cerium on the lanthanum-based additive (27). 

Commercial catalysts vary in the degree to which they are regenerable at reactor temperatures as shown on Figure 18. The initial SO2 removal for all five materials was adjusted to an equal basis by varying the amount of additive used 0.8% magnesia-based, 3% lanthanum-based, 10% of both cerium/alumina and... 

The removal of the radical electron corresponds to the first oxidation process. The resulting cation should be diamagnetic. The first reduction is relatively easy, because filling of the HOMO leads to the closed shell species La Cg2T Theoretical calculations predicted that the location of the lanthanum within the cage is off-center, which allows a stronger interaction with carbon atoms of the fullerene sphere [81- 3]. 

After removing cerium (and thorium), the nitric acid solution of rare earths is treated with ammonium nitrate. Lanthanum forms the least soluble double salt with ammonium nitrate, which may be removed from tbe solution by repeated crystallization. Neodymium is recovered from this solution as the double magnesium nitrate by continued fractionation. 

Radium in hydrochloric acid solution may be separated effectively by ion exchange methods using cation exchange-resin columns. A weak HCl solution is passed through the column. The absorbed metals on the ion-exchange column are eluted with ethylenediaminetetraacetic acid (EDTA) at pH 6.25 or with ammonium citrate at pH 7.8. With either eluant, radium is eluted last, after removing barium and then lanthanum, calcium, magnesium, and other metals. 

The monazite sand is heated with sulfuric acid at about 120 to 170°C. An exothermic reaction ensues raising the temperature to above 200°C. Samarium and other rare earths are converted to their water-soluble sulfates. The residue is extracted with water and the solution is treated with sodium pyrophosphate to precipitate thorium. After removing thorium, the solution is treated with sodium sulfate to precipitate rare earths as their double sulfates, that is, rare earth sulfates-sodium sulfate. The double sulfates are heated with sodium hydroxide to convert them into rare earth hydroxides. The hydroxides are treated with hydrochloric or nitric acid to solubihze all rare earths except cerium. The insoluble cerium(IV) hydroxide is filtered. Lanthanum and other rare earths are then separated by fractional crystallization after converting them to double salts with ammonium or magnesium nitrate. The samarium—europium fraction is converted to acetates and reduced with sodium amalgam to low valence states. The reduced metals are extracted with dilute acid. As mentioned above, this fractional crystallization process is very tedious, time-consuming, and currently rare earths are separated by relatively easier methods based on ion exchange and solvent extraction. 

Anions such as sulphate and phosphate form involatile salts with metal ions and reduce the reading of the sample solution. These anions may be removed by the addition of lanthanum chloride which precipitates them out and replaces them with the chloride anion. 

From this early availability and use of mischmetal grew a demand for bastnasite ore. In these alloys, about one-half of the present rare earths are cerium. In the mid-to-late sixties, a more economical source of cerium was introduced which was, in essence, a concentrate from which the lanthanum had been removed. This material allowed for the production of alloys whose rare earth concentration was about 90% cerium. These rare earthbearing materials have the approximate analyses shown in Table I and are now used commercially, with the high cerium source predominating in the United States. 

In 1899 AncLrt Debieme, a young chemist who had served as prepa-rateur under Charles Friedel and who was an intimate friend of the Curie family, discovered that another radioactive element is carried down with the precipitate of the rare earths produced by adding ammonium hydroxide to a solution obtained by dissolving pitchblende (40). This element, which he named actinium, was discovered independently in 1902 by F. Giesel, who removed it with the lanthanum and cerium (41) and called it emanium. 

Waters are the subject of a voluminous literature, and various methods have been proposed to overcome some of the interferences encountered, e g. by adding ascorbic acid or lanthanum to remove interferences when determining lead in hard water. Saline waters present particular problems (e.g. from background absorption), and a preliminary separation may be advisable. 

Hopkins (161) found that a steady decrease in n-heptane cracking activity occurred over La- and Ca-exchanged Y zeolites as the catalyst calcination temperature was increased from 350° to 650°C. The lanthanum form was about twice as active as the calcium form. Reduction in activity with increasing activation temperature was attributed to removal of acidic framework hydroxyl sites as dehydration becomes more extensive. The greater activity of La—Y with respect to the calcium form was thought to result from the greater hydrolysis tendency of lanthanum ion, which would require more extensive dehydration to result in the same concentration of acidic OH groups as found on Ca—Y. 

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