Extraction of Zirconium and Hafnium from Zircon

A chemical analysis of a typical Florida zircon is given in Table 7.10 [B2]. In addition to the compounds listed in this table, zircon often contains a few hundredths of a percent of uranium and thorium. These elements must be removed from zirconium in subsequent processing because they would form fission products if present in zirconium cladding. 

Zircon is quite resistant to chemical attack. The three most important processes for breaking down zircon chemically and separating zirconium plus hafnium from silicon are 

Fusion with alkalis, followed by solution in acid 

The first process makes ZrCU the second, a zirconium salt and the third, K ZrF . The most suitable extraction process depends, in part, on the chemical form in which the zirconium is wanted and on the subsequent steps to be used in separating hafnium (Sec. 7) and in preparing zirconium metal (Sec. 8). 

Chlorination of zircon has been the process mainly used in the United States because it produces ZrCU, which is used in the Kroll process for making zirconium metal (Sec. 8.3), and because ZrCU was the feed material for the first process developed for separating hafnium from zirconium, using thiocyanate extraction (Sec. 7.3). 

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