Concentrates of lead and zinc compounds with sulfur resulting from hydrometallurgy (hot acid leaching, super-hot acid leaching and flotation)

Water solubility

Description of key information

The study was conducted according to the OECD Guidance Document on Transformation/Dissolution of Metals and Metal Compounds in Aqueous Media (no 29). All parts of the experimental set‐up were performed, as far as practicable, according to good laboratory practice (GLP) in order to achieve scientifically sound data. Total concentrations in solution of Ag, Cd, Cu, Ni, Pb, S and Zn were analysed by means of ICP-OES (Thermo Fisher Scientific 6500 icap duo). 

Key value for chemical safety assessment

Water solubility:

8.3 mg/L

at the temperature of:

21.5 °C

Additional information

This UVCB substance is a moist solid powder and insoluble to water. Therefore, the transformation/dissolution study (OECD guidance 29) was conducted for the substance and the results of this study were used for the chemical safety assessment. The transformation and dissolution study (OECD guidance 29) results indicated that the release at pH 6 was higher for all studied elements compared to release at pH 8. Therefore the following 7 and 28 day studies were conducted at pH 6. Based on the screening test results (loading rate 100 mg/L), the most critical components for the assessment were lead and zinc, with releases of 8282 µg/L and 75.4 µg/L, respectively. The other minor leachable metals were silver (34.7 µg/L), cadmium (0.48 µg/L) and copper (17.2 µg/L).

Results from the 7 day T/D test (loading rate 100 mg/L, pH 6) showed similar trend in release rates: 12333 µg/L (Pb), 91.4 µg/L (Zn), 15.6 µg/L (Cu), 31.4 µg/L (Ag) and 0.056 µg/L (Cd). In the 28 day test with lower loading rate (1 mg/L, pH 6), only concentrations of Pb (362.4 µg/L) and Zn (3.2 µg/L) were over the detection limits or blank sample values. Based on the sulphur concentrations of the eluates and the mineralogical information on the composition of the substance, the metals are most probably appearing in the water solutions in form of sulphates and/or sulphides.

According to T/D study results, the readily soluble constituent was lead. Therefore, the 24-h screening study result of lead was selected as a key value for water solubility. The overall results of this study including also the results of other soluble constituents were used for the derivation of the environmental classification and evaluation the hazards of the substance.