Zirconium sulphite

Removal of silica from the nitrate or chloride solution is desirable before, for example, any final solvent purification process. Methods have been based upon precipitation of zirconium sulphite, sulphate, phthalate, or oxychloride, etc. 

Popov [84POP] studied the complexation of zirconium(lV) by the sulphite ion and postulated the formation of the species Zr(0H)3803 in the pH range 0.54 to 1.44. The formation of this species was premised on the belief that Zr(OH)3 was the dominant species in the pH range studied. It is likely that in this pH range, and for the Zr concentration used in the experiments (0.085 - 1.801 x 10 M), that Zr(OH)( is not the only major Zr hydrolysis species. Further, it is also likely that a mixture of polynuclear and mononuclear species form (see discussion in Appendix D). As such, this review... 

In the U.K. process, the purified zirconium is precipitated from solution as the sulphite, which is then treated with ammonia and calcined to the oxide, for conversion to pure chloride and finally to metal. 

The demand for hafnium metal is small. Figure 9.7 shows how it can be obtained in a high state of purity as a by-product from the manufacture of zirconium. The conversion of the pure by-product solution to oxide is via sulphite as in the case of zirconium, and similarly several alternative precipitants would each be satisfactory. The Van Arkel iodide decomposition process has been shown, in its cheapest form, i.e. based upon a carbide feed. Either of the two metal-producing stages shown for zirconium are equally applicable. 

Scott K, Cheng H, Taama W (1999) Zirconium and Ebonex as cathodes for sulphite ion oxidation in sulphuric acid. J Appl Electrochem 29 1329-1338... 

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