Zirconium salts, purification

The main drawback of silica is its high solubility at pH 8.0 and above, although this problem may partly be circumvented by pre-treatment with mixtures of zirconium salts (5). In addition to this, the availability of beads of porous silica gels possessing only moderate pore sizes (< 50 nm column 3 of Table 1) has hindered the development of HPAC into a major purification technique for large biological molecules such as proteins and enzymes. It has only recently been possible to obtain beaded silica gels of wide pore size (>50 nm). 

Zirconium sulfophenylphosphonate can be prepared by the reaction of a water soluble zirconium salt with sulfophenylphosphonic acid. This phosphonic acid has been described in patent literature [ref. 22], but diere is no evidence of its actual synthesis. We found that sulfophenylphosphonic acid can be syndierized by the reaction of phenylphosphonic dichloride with CISO3H or SO3. The reaction of phenylphosphonic dichlmide with excess CISO3H proceeds smoothly to m-sulfophenylphosphonic dichlmide at 150 °C and to the phosphonic acid on subsequent hydrolysis. Purification of the acid requires removal of excess sulfate by barium precipitation, followed by ion exchange to remove excess barium. For a sulfate-fiee synthesis, we tried the direct sulfonation of phenylphosphonic acid with liquid SO3- The sulfonation proceeds readily at 125 °C, with excess SO3 relative to stoichiometry. We found that 1 1 ratios of S03 phenylphosphonic acid are insufficient for complete sulfonation, even under forcing conditions, due to the competitive formation of mixed anhydrides of sulfophenylphosphonic acid and SO3, depicted in fig. 4. This competitive formation results in a consumption of greater than 1 mole of SO3 per mole of phenylphosphonic acid. These anhydrides are thermally stable but may be converted to sulfophenylphosphonic acid by hydrolysis however, this method also requires sulfate removal from the final product. 

Electron-beam melting of zirconium has been used to remove the more volatile impurities such as iron, but the relatively high volatiUty of zirconium precludes effective purification. Electrorefining is fused-salt baths (77,78) and purification by d-c electrotransport (79) have been demonstrated but are not in commercial use. 

The phthalic anhydride/urea process may also be employed to convert tetra-chloro phthalic anhydride to green copper hexadecachloro phthalocyanine by condensation. In this case, titanium or zirconium dioxides, particularly in the form of hydrated gels, are used instead of the molybdenum salts which are used in the phthalic anhydride process [23]. There is a certain disadvantage to the fact that the products lack brilliance and require additional purification. 

Double deprotonation of the bifunctional mono-CpH/alcohol racemic ligand linked by the 2,6-pyridyl unit followed by salt metathesis with ZrGL yielded the ansa-Cp/oxo zirconium dichloride complex 555, but with the concomitant formation of the undesired complex 556 incorporating the mono-anionic form of the ligand and the simple adduct of the neutral ligand and Z1CI4 0 (Scheme 126). The latter two undesired species have been structurally characterized however, complex 555 obtained forms an insoluble oligomeric species after the loss of THF upon purification. 

V. The fact that ZrOClg SHgO dissolves readily in water and is insoluble in 7-8N (25-30%) hydrochloric acid allows this compound to be used as an intermediate in the purification of Zr salts. Although complete isolation of zirconium cannot be achieved, this method eliminates not only Al, Fe, Nb, Ta, the rare earths and many other elements, but also Ti, the removal of which otherwise involves great difficulties. Thus, for example, the Al content may be reduced from 0.035% to 0.0015% by only one recrystallization the decrease in Fe content is of the sahie order of magnitude. Reprecipitation of the o Q chloride is thus more effective than that of the sulfate, described on p. 1232. 

The purification step of hafnium removal from zirconium is carried out under an inert atmosphere (preferably argon), by using a CuCl2-bearing molten salt with the following reaction ... 

---