Reaction mass of disodium hexatitanium tridecaoxide and disodium trititanium heptaoxide

Hydrolysis

Link to relevant study record(s)

Reference

Endpoint:

hydrolysis

Remarks:

Abiotic transformation in water as a function of pH

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

1 hour

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Justification for type of information:

It is suspected that the substance will degrade under acidic conditions to form water soluble sodium salts and insoluble titanium oxides.
This specific experiment was conducted to look for evidence of this process.
In addition, literature searches were perofrmed for stability in acid
This work has been performed to support the avoidance of animal testing by demonstrating degradation to titanium dioxide and sodium chloride.

Reason / purpose for cross-reference:

assessment report

Qualifier:

no guideline followed

Principles of method if other than guideline:

Sodium titanate was mixed in distilled water and in molar HCl. After mixing for one hour at room temperature, the liquids were filtered and washed to leave a clear filtrate and residual solid on the filters. The filtrates were dried to determine if any soluble fractions and the solids formed from solution were weighed to give an approximate quantitative result.

100 mg of sodium titanate mixed in 100 ml of distilled water or 1M HCl at 20 C

GLP compliance:

no

Radiolabelling:

no

Analytical monitoring:

no

Duration:

1 h

pH:

1

Temp.:

20 °C

Initial conc. measured:

< 1 mg/L

Remarks:

From loading of 1000 mg/l, ca 300 mg NaCl is estimated to have been formed

Duration:

1 h

pH:

10

Temp.:

20 °C

Initial conc. measured:

< 1 mg/L

Remarks:

From loading of 1000 mg/l, ca 200 mg NaCl is estimated to have been formed

No.:

#1

No.:

#2

Details on hydrolysis and appearance of transformation product(s):

The two degradation products are reported in literature and observations confirmed appearance of insoluble white solid and soluble crytalline residues.

100 mg of sodium titanate mixed in 100 ml of distilled water or 1M HCl at 20 C resulted in 20 mg and 30 mg of solid crystallising from filtrate respectively; the acid treatment clearly led to a higher yield, suggesting more dissociation. However, even the 20 mg formed with distilled water implied some degradation.

 

In terms of Na solubility, loading at 1000 mg/l resulted in ca 120 mg Na (300 mg NaCl) when mixed in acid and ca 80 mg Na (200 mg NaCl) in deionised water. It is assumed that a trace of Ti will have passed through filters, but with reported Ti solubility < 1 mg/l, this will be negligible.

 

Further work is needed to identify the solid residues on the filter and crystallising from the filtrate. It is also considered important to work on environmentally relevant concentrations to determine if the rate of dissociation / hydrolysis is faster and/or more complete.

 

The proposed reaction scheme is:

 

Na₂O₃Ti + 2HCl    to      2NaCl + TiO₃H₂     to       TiO₂ + H₂O + 2NaCl

The theoretical route of degradation is less clear in deionised watr, but is likely to result in formation of sodium hydroxide

 

Theoretical yield of NaCl from 0.1 g sodium titanate (0.0007 moles) with excess 0.1 mole hydrochloric acid is ca 80 mg

Conclusions:

This experiment indicates that there is formation of soluble salts from mixing in excess acid or mixing in dilute forms in distilled water.

In terms of Na solubility, loading at 1000 mg/l resulted in ca 120 mg Na (300 mg NaCl) when mixed in acid and ca 120 mg Na (200 mg NaOH) in deionised water. It is assumed that a trace of Ti will have passed through filters, but with reported Ti solubility < 1 mg/l, this will be negligible.

Under both sets of conditions, sodium seems to dissociate to form soluble salts.

Description of key information

The substance is an inorganic compound and is not expected to undergo true hydrolysis in the environment but it is known to demonstrate some abiotic degradation with the formation of soluble salts (eg sodium chloride in hydrochloric acid).