Registration Dossier

Environmental fate & pathways

Hydrolysis

Currently viewing:

Administrative data

Link to relevant study record(s)

Description of key information

Zirconium tetrachloride was found to decompose within less than 5 seconds when introduced in an aqueous medium at room temperature. The decomposition occurred together with evolution of hydrogen chloride. This very fast hydrolysis precludes from any further testing according to OECD 111 or equivalent method.

Key value for chemical safety assessment

Half-life for hydrolysis:
0.08 min
at the temperature of:
25 °C

Additional information

The introduction of zirconium tetrachloride into water leads to the complete decomposition of the original structure, and it has not been possible to reform zirconium tetrachloride from the solution. This statement has been proved by a study designed on the basis of OECD guideline 111 to consider the chemical behaviour of zirconium tetrachloride in water and its kinetic. The objective of this non-conventional test was to demonstrate the hydrolysis rate and the kinetic of the reaction through the measurement of pH and Cl- in solution. Results have shown that the following reaction occurs within 5 seconds :

ZrCl4 + H2O -> ZrOCl 2 + 2 HCl

 

From the literature, it was reported that zirconium tetrachloride decomposes with the liberation of hydrogen chloride and hydrated forms of zirconium. If the aqueous solution is evaporated to dryness, a solid of empirical composition ZrOCl2x 8H20 is precipitated. However, it seems that in aqueous solution there is no chlorine bound to zirconium atoms. Therefore, it seems that the forms which prevail in solution is the zyrconyl ions ZrO2+but this form prevails only during the prevalence of a certain range of acid concentrations. However, the ZrO group persists through many chemical changes of zirconium compound, and it is therefore, more convenient to designate compounds of ZrO2 type (with water of hydratation) as zyrconyl compounds (Blumenthal WR, 1958, The Chemical Behaviour of Zirconium)

In the present dossier, an additional experiment was conducted which has consisted by neutralizing the hydrolysate with NaOH. After addition of the NaOH to the hydrolysate a white precipitate was observed. The white precipitate is likely to be unsoluble form of zirconium such as ZrO2.