slag, copper smelting

Water solubility

Description of key information

Complex metal containing substance

Poor solubility in water

Transformation/dissolution tests and bio-accesability tests are more applicable to metals and are available from the Section 5.6  "Environmental fate and pathways -additional information on environmental fate" and Section 7.1.1 "Toxicological information - toxicokinetics"  

Key value for chemical safety assessment

at the temperature of:

30 °C

Additional information

Water solubility study according to OECD 105 was performed (Liipo, et all, 2010,Report 10081-ORC) The water solubility test method is intended for essentially pure substances and gives saturation mass concentration of the substance in water at a given temperature.

Given the fact that the tested material is complex low soluble metal containing substance, some uncertainties associated with the results were considered:

- For a complex substance, the measured solubility is dependent on the amount of test substance added. According to Guidance R7.A, p.87 test shall be performed at least two loadings rates 100 mg/l and 1000 mg/l).Water solubility in the study (Liipo, et all, 2010,Report 10081-ORC) was determined at high loading 5g/100 ml.Additional study on the effect of loading was performed (Karhu and Kinnunen,2010, Report 10059-ORC-T). Smaller sample size decreased analyzed soluble concentrations ( Cu <0.1 mg/l)

-  The equilibration period was much longer than normal (14-16 days), therefore consideration has to be given to the possible breakdown of the test item during the extended test period (Guidance R7.A, p.87). The agitation of the flasks might cause abrasion and increase solubility. Additional study performed to determine the effect on agitation speed on the water solubility (Kinnunen, 2010, Report 10125-ORC-T). It has been shown that agitation of the flasks may cause abrasion and despite centrifugation, tiny particles may be included in the solution and cause increase of analysed concentration further interpreted as higher solubility. Water solubility of Cu, Ni, Zn, Pb, As in the range of <0.2 mg/l observed.

- When dealing with test substances with water low solubility precautions need to be taken to avoid the introduction of dispersed material into the final extract. Additional study performed to determine the effect on different parameters in the flask method(Karhu and Kinnunen, 2010, Report 10059-ORC-T). Filtration of the samples clearly decreased the water solubility results. This would suggest that agitation may rub off the surface of the test material and that these tiny particles were not completely settled down by centrifugation. Solubility of Cu in the range <0.2 mg/l observed for filtered samples (filter < 0.45 µm)

 

Given the uncertainties above copper slag was still slightly soluble in water solubility test performed after long agitation time of 14-16 days at high loading of 5g/100ml. Consideration of sample filtration , low loading and low stirring rate suggest water solubility of <0.2 mg/l

 

Transformation/dissolution (OECD, 2001) is more suitable for metals and sparingly soluble metal compounds (see IUCLID Section 5.6).The outcomes of the transformation/dissolution tests were used for aquatic classification

 

In vitro bio-accessibility tests were carried out to assess the solubility of metals in copper slag in extraction solvent that resembles gastric fluid (using HCl 0.07N at pH 1.5) in accordance with the ASTM D 5517-07 standard see IUCLID Section 7.1). The outcome of bio-elution test was used to support classification for human hazards.