Anionic impurities

Solvent extraction—purification of wet-process phosphoric acid is based on preferential extraction of H PO by an organic solvent vs the cationic impurities present in the acid. Because selectivity of acid over anionic impurities is usually not sufficient, precipitation or evaporation steps are included in the purification process for removal. Cmde wet-process acid is typically concentrated and clarified prior to extraction to remove post-precipitated sludge and improve partition of the acid into the solvent. Concentration also partially eliminates fluoride by evaporation of HF and/or SiF. Chemical precipitation of sulfate (as Ba or Ca salts), fluorosiUcates (as Na salt), and arsenic (as sulfides) may also be used as a prepurification step preceding solvent extraction. 

The sodium hydroxide is titrated with HCl. In a thermometric titration (92), the sibcate solution is treated first with hydrochloric acid to measure Na20 and then with hydrofluoric acid to determine precipitated Si02. Lower sibca concentrations are measured with the sibcomolybdate colorimetric method or instmmental techniques. X-ray fluorescence, atomic absorption and plasma emission spectroscopies, ion-selective electrodes, and ion chromatography are utilized to detect principal components as weU as trace cationic and anionic impurities. Eourier transform infrared, ft-nmr, laser Raman, and x-ray... 

All subsequent preparations of Cf metal have used the method of choice, that is, reduction of californium oxide by La metal and deposition of the vaporized Cf metal (Section II,B) on a Ta collector 10, 30, 32, 45, 91, 97, 120). The apparatus used in this work is pictured schematically in Fig. 16. Complete analysis of Cf metal for cationic and anionic impurities has not been obtained due to the small (milligram) scale of the metal preparations to date. Since Cf is the element of highest atomic number available for measurement of its bulk properties in the metallic state, accurate measurement of its physical properties is important for predicting those of the still heavier actinides. Therefore, further studies of the metallic state of californium are necessary. 

Secondary mineral deposits formed by precipitation contain relatively smaller amounts of impurities in the solid (Cs) than that in the liquid (Ci) due to their small distribution coefficient (repulsion coefficient), k = Cs/C. However, both cations such as Mn2+ and Fe3+ and molecular anion impurities such as S032, PO/ and N03 and organic molecules are included in the carbonate. 

The detection limits and the analyte-to-matrix ratios for inorganic and organic anion impurities in boric acid, obtained using hydrostatic or electro-kinetic injection and with sample stacking (the capillary is filled with the sample up to the detector, a voltage is applied to preconcentrate the sample anions at the sample-buffer interface, a reversed EOF is used to remove the matrix components and... 

Comparison of limits of detections (LOD) and analyte-to-matrix ratios (ATMR) for inorganic and organic anion impurities in boric acid obtained using hydrostatic and electrokinetic injection and sample stacking [40]... 

In general anionic impurities shift the ZPC to a more acid value cationic impurities shift it to more basic values. 

Dehydration, dehydroxylation, and increased crystallinity can be expected to decrease the ZPC. The presence of anionic impurities or of pH-independent potential-determining anions will decrease the ZPC. 

Delmau, L.H., Bonnesen, P.V., Moyer, B.A. 2004. A solution to stripping problems caused by organophilic anion impurities in crown-ether based solvent extraction systems A case study of cesium removal from radioactive wastes. Hydrometallurgy 72 (1-2) 9-19. 

Anionic impurities as F and Cl- result mainly from specific powder preparation and purification processes and can be determined by spectroscopic methods [224]. 

Delmau, L. H., Bonnesen, P. V., and Moyer, B. A. A Solution to Stripping Problems Caused by Organophilic Anion Impurities in Crown-Ether Based Solvent Extraction Systems, A Case Study of Cesium Removal from Radioactive Wastes, Hydrometallurgy 72(1,2) (2004), 9-19. 

MODELING OF DEHYDRATION AND DEHYDROGENATION IN ZIRCONIA WITH ANION IMPURITY... 

Keywords dehydration, dehydrogenation, nanoparticles, zirconia, anion impurity, hydrogen, tight-binding theory, electronic structure. 

The present work is devoted to research of influence anion impurity (B,C,N,0,F, Ne) on binding energy of hydrogen and water with a surface zirconia nanocrystal particle. 

Anion impurity atom placed in the next unit anion sublattice considered nanoparticle on a place of one of atoms of oxygen. One-electronic wave functions in a particle with anion an impurity were searched as decomposition on nuclear functions which can be submitted as ... 

For zirconia without anion impurity, orbital connected with hydrogen is absent in the forbidden gap and appear in the conduction band (Figs. 2-6 on the left side). Thus, hydrogen on surface of zirconia must be shallow donor (i.e. with one donor electron on the each hydrogen). 

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