Lithium Nickel Cobalt Aluminium Oxide

Water solubility

Description of key information

Information obtained in a Transformation/dissolution test was used in estimate the water solubility of the substance.
Water solubility of the individual elements contained in the substance (Li, Al, Co, Ni) were determined (at pH 6, 100 mg/l loading rate and after 7 days stirring) as:
Li: 0.9974 mg/l
Al: 0.017 mg/l
Co: 0.01359 mg/l
Ni: 0.148 mg/l

Key value for chemical safety assessment

Water solubility:

1 mg/L

at the temperature of:

20 °C

Additional information

The water solubility of the substance was estimated from data obtained from a Transformation/dissolution test, which was conducted in preference to the standard ecotoxicological studies.

The Transformation/dissolution test is designed to determine the rate and extent to which metals and sparingly soluble metal compounds can produce soluble available ionic and other metal-bearing species in aqueous media under a set of standard laboratory conditions representative of those generally occurring in the environment.

Based on the chemical composition of the test material, monitoring of the individual metallic elements was considered the most scientifically correct method of analysis and calculation.

It was considered that the data relating to water solubility from this study would provide a level of information equivalent to that which would be produced from a standard water solubility study (such as EU Method A6/OECD method 105) and as such it was considered unnecessary to conduct a standard water solubility study. The transformation/dissolution test was carried out through an experimental design that follows the recommendations of the OECD guidance document on transformation/dissolution (T/D) (OECD 2001).

Experimental design:

First a pH screening test was performed for 24 hours at 200 RPM at pHs 6, 7 and 8, at 100 mg/L loading and later an acute test (7 days) and a chronic test (28 days) were performed at the pH of maximum release of most eco-toxicological relevant metals, pH 6. Therefore, tests were conducted over 7 days, at loadings of 1, 10 and 100 mg/L and over 28 days at 1 mg/L loading. The tests were

carried out in modified OECD 203 media (ISO 6341), at a stirring rate of 100 rpm. The test media was modified and if needed, buffered with CO2, in order to achieve the desired pH 6.

Results:

The most applicable results to estimate water solubility were considered to be the results of the 7 day acute test (pH 6) at the 100 mg/l loading rate.

100 mg/L (loading rate)          pH6
Time, h	Li, µg/L	Al, µg/L	Co, µg/L	Ni, µg/L
O h	692.8	36	0.74	21.1
168 h	997.4	17	13.59	148.0

 

The results show that each individual component has a water solubility of <1 mg/l and therefore conclude that the substance is highly insoluble in water.

In addition the above results are a worst case scenario as the results were obtained from the test with the highest loading rate (100 mg/L) and the pH (pH 6) of maximum solubilisation and maximum release of the most eco-toxicological relevant metals.

In the pH range 6 -8 maximal solubilisation of the metals was observed at pH 6. At pH 7 and 7 less metals solubilize.

Please refer to the Transformation/dissolution test (Additional ecotoxicological information) for further details on the study.