Zirconium hafnium phosphates

X-Ray diffraction studies have identified a distorted octahedral environment about zirconium in KZr2(P04)3, and the structures of zirconium phosphates have been discussed in terms of their utility as chemical sieves.Some preparative and structural aspects of the normal sulphates of zirconium and hafnium have been reviewed and X-ray studies have shown that the sulphates Zr20(S04)3,5H20 and Hf20(S04)3,5H20 are isostructural and are more accurately represented as M2(OH)2(S04)3,4H20. Other studies of zirconates and hafnates and related mixed oxide systems are summarized in Table 2. 

Hafnium chloride, 4 121 Hafnium phosphate, precipitation of, with zirconium phosphate, 3 71... 

In the tributyl phosphate extraction process developed at the Ames Laboratory, Iowa State University (46—48), a solution of tributyl phosphate (TBP) in heptane is used to extract zirconium preferentially from an acid solution (mixed hydrochloric—nitric or nitric acid) of zirconium and hafnium (45). Most other impurity elements remain with the hafnium in the aqueous acid layer. Zirconium recovered from the organic phase can be precipitated by neutralization without need for further purification. 

The anhydrous perchlorates of zirconium and hafnium, M(C104)4, are colorless volatile crystalline solids. The action of water yields the hydrates M0(C104)2-8H20, which decompose to MO2 on heating. Mixed perchlorates, Q [M(C104) +4], are documented. lodates of zirconium and hafnium, M(I03)4, with a square antiprismatic anion are, like the phosphates, insoluble in nitric acid. 

The Arsenazo III method has been applied for determination of zirconium (and hafnium) in silicate rocks [2,97], titanium dioxide [98], phosphate rocks [99], cast iron and steel... 

It is used in the mining industry to recover metals such as copper and nickel. Parasite plants, based on solvent extraction, are used in the phosphate industry to recover by-product uranium from crude phosphoric acid. The uranium concentration in phosphoric acid is very low but, because of the high volume of phosphoric acid that is produced to meet agricultural needs, considerable uranium can be recovered using solvent extraction. In the nuclear industry [5], solvent extraction is used to purify uranium and plutonium [using the plutonium and uranium recovery by extraction (PUREX) process], zirconium from hafnium, and for many other applications. It is also used in environmental applications to clean soil, say, to remove polychlorinated biphenyls (PCBs), dioxins, pesticides, and other hazardous pollutants. 

In its natural state, zirconium, which is an important material of construction for nuclear reactors, is associated with hafnium, which has an abnormally high neutron-absorption cross section and must be removed before the zirconium can be used. Refer to the accompanying flowsheet for a proposed liquid/liquid extraction process wherein tributyl phosphate (TBP) is used as a solvent for the separation of hafnium from zirconium. [R. P. Cox, H. C. Peterson, and C. H. Beyer, Ind. Eng. Chem., 50(2, 14 (1958).]... 

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