Rapal 01, Paval, Serox, Argalum

Water solubility

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

transformation / dissolution of metals and inorganic metal compounds

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Series on Testing and Assessment No. 29 (23-Jul-2001): Guidance document on transformation/dissolution of metals and metal compounds in aqueous media

GLP compliance:

no

Other quality assurance:

ISO/IEC 17025 (General requirements for the competence of testing and calibration laboratories)

Type of method:

other: 24-h transformation/dissolution screening

Specific details on test material used for the study:

Test item name: Aluminium oxides obtained from Al production residues through mechanical, dissolution, filtration and washing processes
A 1:1:1 w/w mixture of T0468/01, T0469/01 and T0470/01 was prepared at ECTX on 15-01-2021 based on dried materials (ECTX no.: T0471/01)
T0468/01: Manufacturer 1: Raffmetal SpA, Sample name: RAPAL 01, Batch no.:-
T0469/01: Manufacturer 2: Befesa Aluminio S.L, Sample name: Paval, Batch no.: 04400A 002971
T0470/01: Manufacturer 3: Intals, Sample name: ArgAlum®, Batch no.:-
Element(s) of interest: Aluminium, copper, nickel, zinc and fluoride
Physical form: Solid, (in the powder form)
Colour: Grey

Type of test:

screening transformation/dissolution test - sparingly soluble metal compounds

Mean dissolved conc.:

13.3 µg/L

Element analysed:

aluminium

Loading of aqueous phase:

100 mg/L

Incubation duration:

24 h

Test conditions:

pH 6

Type of test:

screening transformation/dissolution test - sparingly soluble metal compounds

Mean dissolved conc.:

58.1 µg/L

Element analysed:

aluminium

Loading of aqueous phase:

100 mg/L

Incubation duration:

24 h

Test conditions:

pH 8

Type of test:

screening transformation/dissolution test - sparingly soluble metal compounds

Mean dissolved conc.:

9.2 µg/L

Element analysed:

copper

Loading of aqueous phase:

100 mg/L

Incubation duration:

24 h

Test conditions:

pH 6

Type of test:

screening transformation/dissolution test - sparingly soluble metal compounds

Mean dissolved conc.:

3 µg/L

Element analysed:

copper

Loading of aqueous phase:

100 mg/L

Incubation duration:

24 h

Test conditions:

pH 8

Type of test:

screening transformation/dissolution test - sparingly soluble metal compounds

Mean dissolved conc.:

0.2 µg/L

Element analysed:

nickel

Loading of aqueous phase:

100 mg/L

Incubation duration:

24 h

Test conditions:

pH 6

Type of test:

screening transformation/dissolution test - sparingly soluble metal compounds

Mean dissolved conc.:

0.11 µg/L

Element analysed:

nickel

Loading of aqueous phase:

100 mg/L

Incubation duration:

24 h

Test conditions:

pH 8

Type of test:

screening transformation/dissolution test - sparingly soluble metal compounds

Mean dissolved conc.:

5.3 µg/L

Element analysed:

zinc

Loading of aqueous phase:

100 mg/L

Incubation duration:

24 h

Test conditions:

pH 6

Type of test:

screening transformation/dissolution test - sparingly soluble metal compounds

Mean dissolved conc.:

0.7 µg/L

Element analysed:

zinc

Loading of aqueous phase:

100 mg/L

Incubation duration:

24 h

Test conditions:

pH 8

Type of test:

screening transformation/dissolution test - sparingly soluble metal compounds

Mean dissolved conc.:

0.305 mg/L

Element analysed:

fluoride

Loading of aqueous phase:

100 mg/L

Incubation duration:

24 h

Test conditions:

pH 6

Type of test:

screening transformation/dissolution test - sparingly soluble metal compounds

Mean dissolved conc.:

0.19 mg/L

Element analysed:

fluoride

Loading of aqueous phase:

100 mg/L

Incubation duration:

24 h

Test conditions:

pH 8

Details on results:

The temperature of the test solutions fluctuated between 21.5 °C and 21.8 °C, which was in line with the test conditions of 20 °C – 23 °C.
The test item has no immediate influence on the pH of the test system. The pH measured in the medium at the start of the test and in the blank and test item vessels during the test at pH 6 and pH 8 varied from 5.99 to 6.03 and from 8.01 to 8.03, respectively. The measured data at pH 6 and pH 8 were within the specifications of ± 0.2 units of pH.
The dissolved oxygen concentration measured in the blank and test item vessels at pH 6 and pH 8 varied from 8.46 to 8.53 mg/L O2 and from 8.45 to 8.52 mg/L O2, respectively. These values were higher than the required value of ± 6 mg/L O2 at 22 °C, corresponding to a minimal saturation level in the air of 70 %.
The measured TOC of the test media were <1.0 mg/L C and below the required level of 2.0 mg/L C as laid down in the OECD Test Guidance no.29.
The test media at the start of the test and the blank control vessels during the test showed concentrations below or close to the limits of detection of 0.6 μg/L Al, 0.08 μg/L Cu, 0.01 μg/L Ni and 0.3 μg/L Zn. The detection limits were determined as the rounded-up values of three times the standard deviation of each element of all blank (pH 6 and pH 8) measurements in this study (N = 12). In the fluoride measurements with ion chromatography, a peak is detectable from 0.005 mg/L F.

The following observations could be made in the test vessels at the nominal pH 6 with a loading of 100 mg/L Al2O3 salt slag:
 An average dissolved concentration of 13.3 ± 0.4 μg/L Al was found at the 24 hours endpoint with a between-vessel coefficient of variation of 3 % (N = 3), which met the <20 % quality criterion at the 24 hours endpoint. The within-vessel coefficients of variation met the <10 % quality criterion for all test vessels.
Based on the specific surface area of the Al2O3 salt slag powder (i.e. 42.1 m2/g test item), an aluminium release per surface of 3.2 μg/m2 was estimated at the 24 hours endpoint.
Based on the test item's aluminium content (32.58 % Al) and the average dissolved aluminium concentration, an aluminium release of 0.041 % could be estimated at the 24 hours endpoint.
 An average dissolved concentration of 9.02 ± 0.17 μg/L Cu was found at the 24 hours endpoint with a between-vessel coefficient of variation of 2 % (N = 3), which met the <20 % quality criterion at the 24 hours endpoint. The within-vessel coefficients of variation met the <10 % quality criterion for all test vessels.
Based on the specific surface area of the Al2O3 salt slag powder (i.e. 42.1 m2/g test item), a copper release per surface of 2.1 μg/m2 was calculated at the 24 hours endpoint.
Based on the copper content of the test item (0.40 % Cu) and the average dissolved copper concentration, a copper release of approximately 2.3 % could be calculated at the 24 hours endpoint.
 An average dissolved concentration of 0.20 ± 0.02 μg/L Ni was found at the 24 hours endpoint with a between-vessel coefficient of variation of 8 % (N = 3), which met the <20 % quality criterion at the 24 hours endpoint. The within-vessel coefficients of variation met the <10 % quality criterion for all replica test vessels.
Based on the specific surface area of the Al2O3 salt slag powder (i.e. 42.1 m2/g test item), a nickel release per surface of 0.047 μg/m2 was calculated at the 24 hours endpoint.
Based on the nickel content of the test item (0.045 % Ni) and the average dissolved nickel concentration, a nickel release of approximately 0.44 % could be calculated at the 24 hours endpoint.
 An average dissolved concentration of 5.3 ± 0.2 μg/L Zn was found at the 24 hours endpoint with a between-vessel coefficient of variation of 4 % (N = 3), which met the <20 % quality criterion at the 24 hours endpoint. The within-vessel coefficients of variation met the <10 % quality criterion for all test vessels.
Based on the specific surface area of the Al2O3 salt slag powder (i.e. 42.1 m2/g test item), a zinc release per surface of 1.3 μg/m2 was calculated at the 24 hours endpoint.
Based on the test item's zinc content (0.15%Zn) and the average dissolved zinc concentration, a zinc release of approximately 3.6 % could be calculated at the 24 hours endpoint.
 An average dissolved concentration of 0.305 ± 0.010 mg/L F was found at the 24 hours endpoint with a between-vessel coefficient of variation of 3 % (N = 2), which met the <20 % quality criterion at the 24 hours endpoint. The within-vessel coefficients of variation met the <10 % quality criterion for all test vessels.
Based on the specific surface area of the Al2O3 salt slag powder (i.e. 42.1 m2/g test item), a fluoride release per surface of 73 μg/m2 was estimated at the 24 hours endpoint.
Based on the test item's fluoride content (0.99 % F) and the average dissolved fluoride concentration, a fluoride release of 31 % could be estimated at the 24 hours endpoint.

The following observations could be made in the test vessels at the nominal pH 8 with a loading of 100 mg/L Al2O3 salt slag:
 An average dissolved concentration of 58.1 ± 1.0 μg/L Al was found at the 24 hours endpoint with a between-vessel coefficient of variation of 2 % (N = 3), which met the <20 % quality criterion at the 24 hours endpoint. The within-vessel coefficients of variation met the <10 % quality criterion for all test vessels.
Based on the specific surface area of the Al2O3 salt slag powder (i.e. 42.1 m2/g test item), an aluminium release per surface of 14 μg/m2 was estimated at the 24 hours endpoint.
Based on the test item's aluminium content (32.58 % Al) and the average dissolved aluminium concentration, an aluminium release of 0.18 % could be estimated at the 24 hours endpoint.
 An average dissolved concentration of 3.01 ± 0.04 μg/L Cu was found at the 24 hours endpoint with a between-vessel coefficient of variation of 1 % (N = 3), which met the <20 % quality criterion at the 24 hours endpoint. The within-vessel coefficients of variation met the <10 % quality criterion for all test vessels.
Based on the specific surface area of the Al2O3 salt slag powder (i.e. 42.1 m2/g test item), a copper release per surface of 0.72 μg/m2 was calculated at the 24 hours endpoint.
Based on the copper content of the test item (0.40 % Cu) and the average dissolved copper concentration, a copper release of approximately 0.75 % could be calculated at the 24 hours endpoint.
 An average dissolved concentration of 0.11 ± 0.00 μg/L Ni was found at the 24 hours endpoint with a between-vessel coefficient of variation of 4 % (N = 3), which met the <20 % quality criterion at the 24 hours endpoint. The within-vessel coefficients of variation met the <10 % quality criterion for all replica test vessels.
Based on the specific surface area of the Al2O3 salt slag powder (i.e. 42.1 m2/g test item), a nickel release per surface of 0.025 μg/m2 was estimated at the 24 hours endpoint.
Based on the nickel content of the test item (0.045 % Ni) and the average dissolved nickel concentration, a nickel release of approximately 0.23 % could be calculated at the 24 hours endpoint.
 An average dissolved concentration of 0.7 ± 0.0 μg/L Zn was found at the 24 hours endpoint with a between-vessel coefficient of variation of 15 % (N = 3), which met the <20 % quality criterion at the 24 hours endpoint. The within-vessel coefficients of variation met the <10 % quality criterion for all test vessel.
Based on the specific surface area of the Al2O3 salt slag powder (i.e. 42.1 m2/g test item), a zinc release per surface of 0.17 μg/m2 was calculated at the 24 hours endpoint.
Based on the test item's zinc content (0.15%Zn) and the average dissolved zinc concentration, a zinc release of approximately 0.49 % could be calculated at the 24 hours endpoint.
 An average dissolved concentration of 0.190 ± 0.008 mg/L F was found at the 24 hours endpoint with a between-vessel coefficient of variation of 4 % (N = 2), which met the <20 % quality criterion at the 24 hours endpoint. The within-vessel coefficients of variation met the <10 % quality criterion for all test vessels.
Based on the specific surface area of the Al2O3 salt slag powder (i.e. 42.1 m2/g test item), a fluoride release per surface of 45 μg/m2 was estimated at the 24 hours endpoint.
Based on the test item's fluoride content (0.99 % F) and the average dissolved fluoride concentration, a fluoride release of 19 % could be estimated at the 24 hours endpoint.

Conclusions:

Based on the results of the experiments, we may conclude that nominal “pH 6” is the pH where the highest dissolved copper, nickel, zinc and fluoride concentrations were measured. However, for aluminium, the highest dissolved concentrations were measured at nominal “pH 8”.

Average highest dissolved concentrations for Cu, Ni, Zn and F (pH 6) were 9.2, 0.2, 5.3 and 305 µg/l, respectively.
Highest dissolved Al (pH 8) was 58.1 µg/l.

Executive summary:

The ECTX (2021) Transformation / Dissolution Screening study according to OECD29 is reliable without restrictions and can be used as a key study for this endpoint. 'Aluminium, magnesium and silicon oxides and hydroxides from refinement of aluminium salt slag residues' displayed the highest solubility of aluminium at pH 8 and of copper, nickel, zinc and fluoride at pH 6. Average dissolution for 'Aluminium, magnesium and silicon oxides and hydroxides from refinement of aluminium salt slag residues' of Cu, Ni, Zn and F (at pH 6) were 9.2, 0.2, 5.3 and 305 µg/l, respectively. Highest dissolved Al (at pH 8) was 58.1 µg/l.

 

Interpretation of results: insoluble (< 1 mg/L for all constituents at 100 mg/L loading)

 

 

Reference 2

Endpoint:

transformation / dissolution of metals and inorganic metal compounds

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Series on Testing and Assessment No. 29 (23-Jul-2001): Guidance document on transformation/dissolution of metals and metal compounds in aqueous media

GLP compliance:

no

Other quality assurance:

ISO/IEC 17025 (General requirements for the competence of testing and calibration laboratories)

Type of method:

other: transformation/dissolution test

Specific details on test material used for the study:

Test item name: Aluminium oxides obtained from Al production residues through mechanical, dissolution, filtration and washing processes
A 1:1:1 w/w mixture of T0468/01, T0469/01 and T0470/01 was prepared at ECTX on 15-01-2021 based on dried materials (ECTX no.: T0471/01)
T0468/01: Manufacturer 1: Raffmetal SpA, Sample name: RAPAL 01, Batch no.:-
T0469/01: Manufacturer 2: Befesa Aluminio S.L, Sample name: Paval, Batch no.: 04400A 002971
T0470/01: Manufacturer 3: Intals, Sample name: ArgAlum®, Batch no.:-
Element(s) of interest: Aluminium, copper, nickel, zinc and fluoride
Physical form: Solid, (in the powder form)
Colour: Grey

Type of test:

full transformation/dissolution test - metals and sparingly soluble metal compounds

Mean dissolved conc.:

0.8 µg/L

Element analysed:

copper

Loading of aqueous phase:

1 mg/L

Incubation duration:

7 d

Test conditions:

pH 6

Type of test:

full transformation/dissolution test - metals and sparingly soluble metal compounds

Mean dissolved conc.:

1.2 µg/L

Element analysed:

copper

Loading of aqueous phase:

1 mg/L

Incubation duration:

28 d

Test conditions:

pH 6

Type of test:

full transformation/dissolution test - metals and sparingly soluble metal compounds

Mean dissolved conc.:

8 µg/L

Element analysed:

fluoride

Loading of aqueous phase:

1 mg/L

Incubation duration:

28 d

Test conditions:

pH 6

Details on results:

The temperature of the test solutions fluctuated between 21.4 °C and 22.1 °C, which was in line with the test conditions of 20 °C – 23 °C.
The pH measured in the blank and test item vessels at pH 6 varied from 5.98 to 6.07. All measured data were within the specifications of pH 6.0 ± 0.2.
The dissolved oxygen concentration measured in the blank and test item vessels at pH 6 varied from 8.40 to 8.54 mg/L O2. These values were higher than the required value of ± 6 mg/L O2 at 22 °C, corresponding with a minimum saturation level in the air of 70 %.
The measured TOC of the medium was <1 mg/L C and below the required level of 2.0 mg/L C as laid down in the OECD Test Guidance no.29.
The test medium at the start of the test and the blank control vessel during the test showed no average concentrations above the limit of detection for copper (0.5 μg/L Cu). The detection limit was determined as three times the standard deviation of the copper measurements of all blank control samples in this study rounded up to one significant figure (N = 30). For fluoride measurements, a limit of detection (no visual peak) of 0.005 mg/L F was estimated.

The following observations could be made in the test vessels:
 with a loading of 1 mg/L of Al2O3 salt slag, the following amounts of copper were measured during the test:
An average dissolved copper concentration (N = 9) of 0.8 ± 0.0 μg/L Cu at the 7 days sampling point and 1.2 ± 0.0 μg/L Cu at the 28-day endpoint were measured with a between-vessel variation of 2 % and 4 %, respectively, which met the <20 % quality criterion at the7 days and 28 days endpoints. The within-vessel coefficients of variation met the <10 % quality criterion for all test vessels.
Based on the specific surface area of the Al2O3 salt slag powder (i.e. 42.1 m2/g test item), a copper release per surface of 0.019 mg/m2 and 0.029 mg/m2 was calculated at the 7 days and 28 days endpoints, respectively.
Based on the copper content in the test item (0.40 % Cu) and the average dissolved copper concentration in the test solutions, a copper release of 20 % and 30 % could be estimated at the 7 days and 28 days extraction endpoints, respectively.
 with a loading of 1 mg/L of Al2O3 salt slag, the following amounts of fluoride were measured during the test:
An average dissolved fluoride concentration (N=9) of 0.008mg/LF at the 28days endpoint was measured with a between-vessel variation of 16 %, which met the <20 % quality criterion at the 28 days endpoint. The within-vessel coefficients of variation met the <10 % quality criterion for all test vessels.
Based on the specific surface area of the Al2O3 salt slag powder (i.e. 42.1 m2/g test item), a fluoride release per surface of 0.19 mg/m2 was estimated at the 7 days and 28 days endpoints.
Based on the fluoride content in the test item (0.99 % F) and the average dissolved fluoride concentration in the test solutions, a fluoride release of 81 % could be estimated at the 7 days and 28 days extraction endpoints.

Conclusions:

During this transformation/dissolution study on 'Aluminium, magnesium and silicon oxides and hydroxides from refinement of aluminium salt slag residues' at a loading of 1 mg/L, it was shown that:
• For copper, an average concentration of 0.8 μg/L Cu (CVoverall = 2 %; N = 9) was found after 7 days, and 1.2 μg/L Cu (CVoverall = 4 %; N = 9) was found after 28 days of exposure to the standard medium at pH 6. The 7 days dissolution results corresponded with a copper release of 20 % (or 0.019 mg/m2). The 28 days dissolution results corresponded with a copper release of 30 % (or 0.029 mg/m2).
• For fluoride, an average concentration of 0.008 mg/L F (CVoverall = 15 %; N = 9) was found after 28 days of exposure to the standard medium at pH 6. This dissolution result corresponded with a fluoride release of 81 % (or 0.19 mg/m2).

Executive summary:

The ECTX (2021) Transformation / Dissolution Study according to OECD29 is reliable without restrictions and can be used as a key study for this endpoint.

'Aluminium, magnesium and silicon oxides and hydroxides from refinement of aluminium salt slag residues' at a loading of 1 mg/L to standard medium at pH 6, showed the following average dissolved concentrations:

For copper: 0.8 μg/L Cu and 1.2 μg/L Cu after 7 days and 28 days, respectively.

For fluoride: 8 μg/L F after 28 days.

 

This information on the dissolution of Cu and F are taken into account for the environmental classification (bioavailability) of 'Aluminium, magnesium and silicon oxides and hydroxides from refinement of aluminium salt slag residues'.

 

 

 

 

Description of key information

As water solubility testing is not appropriate for complex metal and sparingly soluble metals and metal compounds transformation / dissolution testing was performed.

 

Dissolution concentrations of aluminium, copper, nickel, zinc  and fluoride were determined at pH 6 and pH 8 in a 24-h screening test. Average highest dissolution for 'Aluminium, magnesium and silicon oxides and hydroxides from refinement of aluminium salt slag residues' at a loading of 100 mg/L to standard medium of Cu, Ni, Zn and F (at pH 6) were 9.2, 0.2, 5.3 and 305 µg/l, respectively. Highest dissolved Al (at pH 8) was 58.1 µg/l.

Interpretation of results: insoluble (< 1 mg/L for all constituents at 100 mg/L loading).

 

Full (7 & 28-d) T/D testing at pH6 was performed to screen Cu and F dissolution. 'Aluminium, magnesium and silicon oxides and hydroxides from refinement of aluminium salt slag residues' at a loading of 1 mg/L to standard medium at pH 6, showed the following average dissolved concentrations: For copper: 0.8 μg/L Cu and 1.2 μg/L Cu after 7 days and 28 days, respectively. For fluoride: 8 μg/L F after 28 days. This information on the dissolution of Cu and F are taken into account for the environmental classification (Cu and F bioavailability) of 'Aluminium, magnesium and silicon oxides and hydroxides from refinement of aluminium salt slag residues'.