It is known that zircon is decomposed at high temperatures in
a reducing media.16 The decomposition temperature is lowered
if a fluxing agent such as NaOH, Na2CO3 or CaCO3 is used. In
this study, to decompose zircon sand, NaOH was chosen as a
fluxing agent due to the fact that the decomposition reaction is
occurred at a lower temperature than in the case of Na2CO3 or
CaCO3 addition.
About 1 mol zircon (industrial grade) was mixed with 4 mol
NaOH pellets (Merck) in agat mortar. Thermal treatment was
carried out at temperatures between 600 and 950 ◦C for 5 h.
Then, the decomposed intermediate products were washed with
water or 1–5% H2SO4 solution in order to remove Na based
compounds formed during process.