Distribution ratios are reported for extraction of niobium(V), tantalum(V), molybdenum(Vl), and tungsten(V1) into methyl isobutyl ketone from various aqueous mixtures of hydrofluoric, hydrochloric, and sulfuric acids. Quantitative separations cannot be obtained by simple batch extractions, so a column chromatographic technique was employed using a Teflon-6 support impregnated with methyl isobutyl ketone. Sequential elution with eluents of different compositions separates niobium(V) and tantalum(V), molybdenum(Vl), and tungsten(VI), and a mixture of all four elements from each other. Using radioactive tracers, as little as 0.1 ppm of one metal was separated from the others.
Apparatus 10 Reagents Separation Procedure Analysis of Column Effluents Results and Discussion PART II. REVERS ED-PHASE CHROMTOGRAPHIC SEPARATION 23 OP NIOBIUM, TANTALUÎ-Î, MOLYBDENUM, AND TUNGSTEN PROM EACH OTHER LITERATURE SURVEY 24 EXPERIMENTAL 28 Apparatus 23 Reagents Analytical Procedures RESULTS AND DISCUSSION Distribution Ratios 40 Theory of Chromatographic Separations Separations LITERATURE CITED AOENOWLEDGMENTS • Schoeller's salicylate procedure (1), for the separation of niobium and tantalum from titanium. In this method, the oxa lates of these metal ions are decomposed with calcium chloride in the presence of sodium salicylate, and the earth acids are precipitated as salicylate complexes. The titanium-salicylate complex is soluble, but it coprecipitates. The niobium and tantalum recovery is often not complete and the precision is not very good. Another procedure, described by Bedford (2), is over fifty years old but is still used. It involves a fusion of the earth acid oxides with potassium carbonate and precipita tion of the niobium and tantalum by magnesium sulfate and ammonium chloride. The oxides of niobium, tantalum, titanium, and zirconium are precipitated but alkali tungstate remains in solution. ?or about twenty-five years tannin, introduced by Schoeller, was in constant use for earth acid analysis, Schoeller and Powell (3), give detailed instructions for obtaining proper conditions for the separation of many metal ions. The reagent, N-benzoyl-îT-phenyl-hydroxylamine, has been used for obtaining precipitates of niobium, tantalum, and titanium that are virtually free from almost all other ele ments, including tungsten (4), Various precipitating condi tions are used to precipitate consecutively niobium, tantalum, and titanium. Dams and Hoste (5), were only moderately successful in an chloric-hydrofluoric acid solutions. The use of hydrogen peroxide in separation procedures, rather than hydrofluoric acid or organic acids, has the advantage that determinations or further separations are simplified. Several cation exchange separations have been reported (7-11) which employ acidic solutions of hydrogen peroxide to elute niobium, tantalum, molybdenum, and tungsten as anionic complexes. However, only one or two of these metals are sep arated from a few other metals in the procedures reported, and elution conditions vary considerably. A method using a single eluent, that would separate niobium, tantalum, molyb denum, and tungsten as a group from a fairly large number of elements would have a definite advantage. The research of Part I of this thesis was intended to achieve this goal. Anion exchange separations of niobium, tantalum, molyb denum, and tungsten are reported using organic acids or hydro fluoric-hydrochloric acid mixtures as eluents. An anion exchange separation of niobium, tantalum, molybdenum, tung sten, zirconium, and titanium from each other uses various combinations of organic acids, hydrochloric acid, and hydro gen peroxide as eluents (12). Good results are reported for analyses of the s...
Apparatus 10 Reagents Separation Procedure Analysis of Column Effluents Results and Discussion PART II. REVERS ED-PHASE CHROMTOGRAPHIC SEPARATION 23 OP NIOBIUM, TANTALUÎ-Î, MOLYBDENUM, AND TUNGSTEN PROM EACH OTHER LITERATURE SURVEY 24 EXPERIMENTAL 28 Apparatus 23 Reagents Analytical Procedures RESULTS AND DISCUSSION Distribution Ratios 40 Theory of Chromatographic Separations Separations LITERATURE CITED AOENOWLEDGMENTS • Schoeller's salicylate procedure (1), for the separation of niobium and tantalum from titanium. In this method, the oxa lates of these metal ions are decomposed with calcium chloride in the presence of sodium salicylate, and the earth acids are precipitated as salicylate complexes. The titanium-salicylate complex is soluble, but it coprecipitates. The niobium and tantalum recovery is often not complete and the precision is not very good. Another procedure, described by Bedford (2), is over fifty years old but is still used. It involves a fusion of the earth acid oxides with potassium carbonate and precipita tion of the niobium and tantalum by magnesium sulfate and ammonium chloride. The oxides of niobium, tantalum, titanium, and zirconium are precipitated but alkali tungstate remains in solution. ?or about twenty-five years tannin, introduced by Schoeller, was in constant use for earth acid analysis, Schoeller and Powell (3), give detailed instructions for obtaining proper conditions for the separation of many metal ions. The reagent, N-benzoyl-îT-phenyl-hydroxylamine, has been used for obtaining precipitates of niobium, tantalum, and titanium that are virtually free from almost all other ele ments, including tungsten (4), Various precipitating condi tions are used to precipitate consecutively niobium, tantalum, and titanium. Dams and Hoste (5), were only moderately successful in an chloric-hydrofluoric acid solutions. The use of hydrogen peroxide in separation procedures, rather than hydrofluoric acid or organic acids, has the advantage that determinations or further separations are simplified. Several cation exchange separations have been reported (7-11) which employ acidic solutions of hydrogen peroxide to elute niobium, tantalum, molybdenum, and tungsten as anionic complexes. However, only one or two of these metals are sep arated from a few other metals in the procedures reported, and elution conditions vary considerably. A method using a single eluent, that would separate niobium, tantalum, molyb denum, and tungsten as a group from a fairly large number of elements would have a definite advantage. The research of Part I of this thesis was intended to achieve this goal. Anion exchange separations of niobium, tantalum, molyb denum, and tungsten are reported using organic acids or hydro fluoric-hydrochloric acid mixtures as eluents. An anion exchange separation of niobium, tantalum, molybdenum, tung sten, zirconium, and titanium from each other uses various combinations of organic acids, hydrochloric acid, and hydro gen peroxide as eluents (12). Good results are reported for analyses of the s...
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