The document summarizes the extraction process of zirconium. Zircon sand is mined and purified to extract zirconium minerals. Zirconium chloride is produced via chlorination of zirconia and then reduced with magnesium using the Kroll process to produce zirconium sponge. The sponge is further purified using vacuum treatment to remove magnesium chloride and excess magnesium, producing ductile zirconium. Zirconium has applications in the nuclear industry as a cladding material due to its low neutron absorption cross-section and corrosion resistance at high temperatures in water. It is also used in alloys for aircraft applications due to strength retention at elevated temperatures.

1. Extraction of Zirconium
Department of MME
Extraction of Non-Ferrous Metals

2. Details about of Zr
Atomic Number: 40
Atomic Weight: 91.22 amu
Density: 6.45 gm/cm3
Melting Point: 1852 ℃
Boiling Point: 3580 ℃
Common Minerals of Zr
Zircon: ZrSiO4
Mineral associated with beach sands along with other minerals (Ructile, Ilimenite,
and Monazite) and oxides of metals such as Fe and Mg.

3. Treatment of Zircon
Beach sands are mined and screened to remove oversized particles. The heavy sands are
concentrated by jigs, tables, spirals, and riffles. Further processing involves the magnetic and
electrostatic separation of magnetite titanium minerals. Quartz and silica are removed by gravity
separation. The final product is clean zircon mineral.
Methods employed for treatment of Zircon:
Direct graphite reduction of zircon in an inert atmosphere yields 90% of metal as ZrC, most of
silica eliminated as volatile SiO. Graphite reduction in presence of air gives carbonitride.
Conventional method includes: direct chlorination of zircon to ZrCl4; NaOH treatment to produce
soluble sodium zirconate; and treatment with K2SiF6 to produce double salt K2ZrF6.
All these methods require high temperature.
The chemical behavior of Hf is similar to Zr, all the Hf present in the original ore finds its way
into the zirconium compounds.

4. Methods of separating Hf from Zr
(1) Fractional crystallization of Double compounds K2ZrF6 and K2HfF6  This double salts have
different solubility in dilute (1%) HCl solution. The solubility of Hf compound is much higher.
16-20 steps are necessary to reduce Hf content to the specified level
(2) Solvent Extraction used for Zr-Hf separation. This is most widely used method.
(3) Fractional Distillation of Volatile Compounds mixture of ZrO2 and HfO2 may be differentially
chlorinated. Some separation is possible due to the different vapor pressure of ZrCl4 and HfCl4.
(4) Anion Exchange Methods some anion exchange resins have been satisfactorily used for
separation of Hf from Zr.

5. Methods of separating Hf from Zr (continue..)
(5) Pyrometallurgical Methods Pyrometallurgical processes are not very successful owing to the
similarities in properties of Hf and Zr. Methods that claim partial success are:
(A) Differential oxidation of tetrachlorides.
𝑍𝑟𝐶𝑙4 𝑔 + 𝑂2 = 𝑍𝑟𝑂2 𝑠 + 2𝐶𝑙2
𝐻𝑓𝐶𝑙4 𝑔 + 𝑂2 = 𝐻𝑓𝑂2 𝑠 + 2𝐶𝑙2
(B) Formation of the lower chloride of zirconium.
3𝑍𝑟𝐶𝑙4 (𝑔) + 𝑍𝑟 𝑠 = 4𝑍𝑟𝐶𝑙3(𝑠)
(C) Differential reaction of the double chlorides with alkali chlorides.
𝑍𝑟𝐶𝑙4 + 2𝑁𝑎𝐶𝑙 = 𝑁𝑎2 𝑍𝑟𝐶𝑙6
𝐻𝑓𝐶𝑙4 + 2𝑁𝑎𝐶𝑙 = 𝑁𝑎2 𝐻𝑓𝐶𝑙6

6. Extraction of Zr: Production of Zirconium Sponge
 Kroll’s process is employed.
 Anhydrous zirconium tetrachloride vapors are reduced
by Mg in argon (Ar) atmosphere.
 Excess Mg and MgCl2 are removed by high-vacuum
treatment.
 Zirconium is obtained as partially sintered sponge-like
product.

7. Production of ductile Zr
Zirconium tetrachloride is the initial raw material produced by chlorination of zirconia-carbon
briquettes at 750℃ in silica brick lined furnace. The briquettes are heated by graphite electrodes
embedded in the charge itself. The chloride vapors from the furnace are condensed in double-walled
Inconel condensed at 150-200℃ to yield dense crystal.
The Mg reduction is carried in a specially designed SS retort under slight positive pressure of Ar. The
tetrachloride and metal are initially loaded into separate containers inside the retort. Some of the
volatile impurities are removed by Ar flushing at 150-200℃. Subsequently, the temp. is raised and
the tetrachloride is distilled in controlled fashion, i.e. it is made to react at the surface of the molten
Mg. There are provisions to control excessive rise in temp. and pressure, and for automatic and/or
manual bleeding of chloride vapors. At the end of the reaction, reactor contains Zr sponge that is
recovered by magnesium chloride.
Separation of magnesium chloride and excess Mg is carried out another heavy walled Inconel retort
under a vacuum of 1micron Hg at 900℃. The resulting sponge is pyrophoric and precautions needed
during its collection.
Addition of small quantity of Na to Mg during initial stage of reduction improves purity of the
sponge and its crushability which facilitate collection. It might be attribute to the gettering action of
Na in the initial stage and scavenging of sodium chloride during Mg reduction.

8. Uses or Applications of Zr
Nuclear applications
 Absorption cross-section for thermal neutrons is very low for Zr (only 0.15 barn per atom, where
as Al-8.21 and Fe-2.4) valued for cladding element in nuclear reactor.
 Corrosion resistance of Zr in water at elevated temp. and its mechanical strength at high-temp. is
better than Al. It’s thermal conductivity is adequate for use in nuclear fuel element. At high temp.,
Zr has lower thermal stress because of its lower coefficient of expansion.
 On the basis of neutron economy, corrosion resistance, mechanical strength, and other properties,
Zr-alloys are ideal choice for cladding of fuel and other core components in water-cooled nuclear
power system.
Nonnuclear applications
 Zr find applications as getters in the form of fine powder, in photoflash and detonator applications,
in flash bulbs in the form of thin foils, and in ceramics as an oxide.
 Zr added to electric furnace steel (as Zr-Si-Fe alloy) to improve various properties.
 It found applications in light-weight alloys of Mg-Zr, Mg-Zn-Zr, Mg-Th-Zr and Mg-rare earth-Zr
have superior strength at elevated temp. (therefore, used in aircraft industry).