Cobalt zinc aluminate blue spinel

Water solubility

Link to relevant study record(s)

Reference

Endpoint:

transformation / dissolution of metals and inorganic metal compounds

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2009-08-03 to 2010-03-10

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Remarks:

deviations from the guideline, which do not effect the validity of the study: (a) The 28-day test with a loading of 1 mg/L was conducted at pH 6 instead of 5.5 (b) `mass balance (%) after completion of the transformation test´ is missing.

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

Deviations:

yes

Remarks:

please refer to the field "Rationale for reliability incl. deficiencies" above

GLP compliance:

yes

Type of method:

other: GF AAS

Type of test:

screening transformation/dissolution test - sparingly soluble metal compounds

Mean dissolved conc.:

0.016 µg/L

Element analysed:

Co

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.:

0.055 µg/L

Element analysed:

Co

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.:

0.06 µg/L

Element analysed:

Al

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.:

57.187 µg/L

Element analysed:

Al

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.:

8.657 µg/L

Element analysed:

Zn

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.:

8.146 µg/L

Element analysed:

Zn

Loading of aqueous phase:

100 mg/L

Incubation duration:

24 h

Test conditions:

pH 6

Type of test:

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

Mean dissolved conc.:

76.43 µg/L

Element analysed:

Al

Loading of aqueous phase:

100 mg/L

Incubation duration:

7 d

Test conditions:

pH: 6.4 - 6.6, temp.: 21.2 °C

Type of test:

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

Mean dissolved conc.:

< 0.068 µg/L

Element analysed:

Zn

Loading of aqueous phase:

100 mg/L

Incubation duration:

7 d

Test conditions:

pH: 6.4 - 6.6, temp.: 21.2 °C

Remarks on result:

other: < LOD

Type of test:

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

Mean dissolved conc.:

< 0.113 µg/L

Element analysed:

Co

Loading of aqueous phase:

100 mg/L

Incubation duration:

7 d

Test conditions:

pH: 6.4 - 6.6, temp.: 21.2 °C

Remarks on result:

other:

Type of test:

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

Mean dissolved conc.:

42.077 µg/L

Element analysed:

Al

Loading of aqueous phase:

1 mg/L

Incubation duration:

24 h

Test conditions:

pH: 6.09 - 6.19, temp.: 19.9 °C

Remarks on result:

other: S.D.: ± 3.9073 µg/L

Type of test:

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

Mean dissolved conc.:

< 0.068 µg/L

Element analysed:

Zn

Loading of aqueous phase:

1 mg/L

Incubation duration:

24 h

Test conditions:

pH: 6.09 - 6.19, temp.: 19.9 °C

Remarks on result:

other: < LOD

Type of test:

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

Mean dissolved conc.:

< 0.113 µg/L

Element analysed:

Co

Loading of aqueous phase:

1 mg/L

Incubation duration:

24 h

Test conditions:

pH: 6.09 - 6.19, temp.: 19.9 °C

Remarks on result:

other: < LOD

Key result

Type of test:

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

Mean dissolved conc.:

48.75 µg/L

Element analysed:

Al

Loading of aqueous phase:

1 mg/L

Incubation duration:

7 d

Test conditions:

pH: 6.06 - 6.12, temp.: 21.2 °C

Remarks on result:

other: S.D.: ± 1.6496 µg/L

Key result

Type of test:

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

Mean dissolved conc.:

< 0.07 µg/L

Element analysed:

Zn

Loading of aqueous phase:

1 mg/L

Incubation duration:

7 d

Test conditions:

pH: 6.06 - 6.12, temp.: 21.2 °C

Remarks on result:

other: < LOD

Key result

Type of test:

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

Mean dissolved conc.:

< 0.11 µg/L

Element analysed:

Co

Loading of aqueous phase:

1 mg/L

Incubation duration:

7 d

Test conditions:

pH: 6.06 - 6.12, temp.: 21.2 °C

Remarks on result:

other: < LOD

Key result

Type of test:

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

Mean dissolved conc.:

23.48 µg/L

Element analysed:

Al

Loading of aqueous phase:

1 mg/L

Incubation duration:

28 d

Test conditions:

pH: 6.06 - 6.11, temp.: 21.9 °C

Remarks on result:

other: S.D.: ± 5.5425 µg/L

Key result

Type of test:

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

Mean dissolved conc.:

< 0.068 µg/L

Element analysed:

Zn

Loading of aqueous phase:

1 mg/L

Incubation duration:

28 d

Test conditions:

pH: 6.06 - 6.11, temp.: 21.9 °C

Remarks on result:

other: < LOD

Key result

Type of test:

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

Mean dissolved conc.:

< 0.113 µg/L

Element analysed:

Co

Loading of aqueous phase:

1 mg/L

Incubation duration:

28 d

Test conditions:

pH: 6.06 - 6.11, temp.: 21.9 °C

Remarks on result:

other: < LOD

Details on results:

Test conditions are in accordance with guideline:
- The within-vessel variations from the 100mg/L loadings were between 0.007 and 0.0504 % (i.e. ≤10 %). The between-vessel variation was 3.5120 % (i.e.≤20 %) at and the 7- day endpoint.
The within-vessel variations from the 1mg/L loading were between 0.008 and 0.3554 % (i.e. ≤10 %). The between-vessel variation was 3.3838 % (i.e.≤20 %) at the 7-day endpoint.

- The air oxgen concentrations were all in the range of 6.2 mg/L and 10.9 mg/L above the acceptable limit (>70 % of air O2 concentration = 6.16 mg/L).
- The temperature was in the range from 19.9 °C to 22.7 °C (i.e. between 20 -25 °C +/-2 °C).
- The pH was in the range of 6.01 to 6.19 (i.e. in the range of pH 6 + 0.2 units)

Cobalt and Zinc ions have not been found in aqueous solutions with 1mg/L and 100 mg/L loadings. Aluminum ions dissolved/transformed in aqueous solutions. The maximum solubility was observed after 24 h for the 100 mg/L loading in the 7-d test. Dissolved concentrations were lower at day 7 indicating a possible reprecipitation of the metal salts. The maximum solubility was observed after 10 days for the 1 mg/L loading in the 28-d test. Dissolved concentrations were
lower at day 16 and 28 indicating also a possible re-precipitation of the metal salts.

28 days, 1mg/L

Time	Samples	pH	Temp. (ºC)	O2 (mg/L)	Al (μg/L)	Zn (μg/L)	Co (μg/L)
2 h	Average	6.10	22.1	8.5	51.7588 ± 2.6660	<0.0675	<0.1128
18 h	Average	6.15	20.4	10.2	45.0883 ± 4.0679	<0.0675	<0.1128
24 h	Average	6.13	19.9	10.7	42.0767 ± 3.9073	<0.0675	<0.1128
4 d	Average	6.10	20.3	7.1	38.2660 ± 5.1475	<0.0675	<0.1128
7 d	Average	6.08	21.2	8.2	48.7496 ± 1.6496	<0.0675	<0.1128
10 d	Average	6.10	21.8	7.3	57.0041 ± 9.8716	<0.0675	<0.1128
16 d	Average	6.08	21.8	7.3	36.9810 ± 3.4442	<0.0675	<0.1128
28 d	Average	6.09	21.9	7.1	23.480 ± 5.5425	<0.0675	<0.1128

Conclusions:

The transformation/dissolution of COBALT ZINC ALUMINATE BLUE SPINEL was tsted according to OECD test series no. 29 (Guidance document on transformation/dissolution of metals and metal compounds in aqueous media). The transformation/dissolution of cobalt zinc aluminate blue spinel at pH 6, the pH that maximises dissolution,resulted in the following dissolved metal ion concentrations:
 
loading, time            Al [µg/L]                     Zn [µg/L]        Co [µg/L]
1 mg/L, 7 days          48.75 +/- 1.65           < 0.07             < 0.11
1 mg/L, 28 days        23.48 +/- 5.54           < 0.07             < 0.11
100 mg/L, 7 days      76.43 +/- 2.68           < 0.07             < 0.11
 
As the sum of dissolved Al, Zn and Co concentrations was < 50 µg/L and < 25 µg/l at a loading of 1 mg/L after 7 and 28 days, respectively, and < 80 µg/L at a loading of 100 mg/L, COBALT ZINC ALUMINATE BLUE SPINEL is considered environmentally inert. The particle size of the tested material (BET surface area 5.92 m2/g) is representative for the marketed particle sizes.

Description of key information

The solubility of cobalt zinc aluminate blue spinel in environmental media is low. In a GLP-conform transformation/dissolution test by Grane (2010) at pH 6 (the pH that maximises dissolution) with a loading of 100 mg/L, a dissolved Al concentration of 76.43 microg/L was determined whereas dissolved Zn and Co concentrations were below the limit of detection after 7 days. Transformation/dissolution at a loading of 1 mg/L resulted also in dissolved Zn and Co concentrations below the limit of detection after 7 and 28 days. Dissolved Al concentrations at pH 6 amount to 48.75 microg/L and 23.48 microg/L after 7 and 28 days, respectively. The particle size of the tested material (BET surface area 5.92 m2/g) is representative for the marketed particle sizes. Thus, the extent to which "Cobalt zinc aluminate blue spinel" can produce soluble available ionic and other metal-bearing species in aqueous media is limited and Cobalt zinc aluminate blue spinel can be considered environmental inert.