Zirconium praseodymium yellow zircon

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) `mass balance (%) after completion of the transformation test´ is missing (b) the between- and within-vessel variation was not always below the demandet limits (<20 % and <10 % respectively)

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.:

0.02 µg/L

Element analysed:

Si

Loading of aqueous phase:

100 mg/L

Incubation duration:

24 h

Test conditions:

pH8, 25.1°C

Type of test:

screening transformation/dissolution test - sparingly soluble metal compounds

Mean dissolved conc.:

0.13 µg/L

Element analysed:

Si

Loading of aqueous phase:

100 mg/L

Incubation duration:

24 h

Test conditions:

pH6, 25.1°C

Type of test:

screening transformation/dissolution test - sparingly soluble metal compounds

Mean dissolved conc.:

3.05 µg/L

Element analysed:

Pr

Loading of aqueous phase:

100 mg/L

Incubation duration:

24 h

Test conditions:

pH 8, 25.1°C

Type of test:

screening transformation/dissolution test - sparingly soluble metal compounds

Mean dissolved conc.:

21.66 µg/L

Element analysed:

Pr

Loading of aqueous phase:

100 mg/L

Incubation duration:

24 h

Test conditions:

pH6, 25.1°C

Type of test:

screening transformation/dissolution test - sparingly soluble metal compounds

Mean dissolved conc.:

< 0.077 µg/L

Element analysed:

Zr

Loading of aqueous phase:

100 mg/L

Incubation duration:

24 h

Test conditions:

pH 6 and ph 8, 25.1°C

Type of test:

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

Mean dissolved conc.:

< 0.069 µg/L

Element analysed:

Si

Loading of aqueous phase:

100 mg/L

Incubation duration:

7 d

Test conditions:

T: 20.8 °C, O2: 7.3 mg/L, pH: 6.19

Remarks on result:

other: < LOD

Type of test:

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

Mean dissolved conc.:

0.159 µg/L

Element analysed:

Zr

Loading of aqueous phase:

100 mg/L

Incubation duration:

7 d

Test conditions:

T: 20.8 °C, O2: 7.3 mg/L, pH: 6.19

Remarks on result:

other: S.D.: ± 0.0401 µg/L

Type of test:

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

Mean dissolved conc.:

86.25 µg/L

Element analysed:

Pr

Loading of aqueous phase:

100 mg/L

Incubation duration:

7 d

Test conditions:

T: 20.8 °C, O2: 7.3 mg/L, pH: 6.19

Remarks on result:

other: S.D.: ± 17.17 µg/L

Type of test:

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

Mean dissolved conc.:

< 0.069 µg/L

Element analysed:

Si

Loading of aqueous phase:

1 mg/L

Incubation duration:

24 h

Test conditions:

T: 20.1 °C, O2: 8.6 mg/L, pH: 6.14

Remarks on result:

other: < LOD

Type of test:

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

Mean dissolved conc.:

< 0.077 µg/L

Element analysed:

Zr

Loading of aqueous phase:

1 mg/L

Incubation duration:

24 h

Test conditions:

T: 20.1 °C, O2: 8.6 mg/L, pH: 6.14

Remarks on result:

other: < LOD

Type of test:

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

Mean dissolved conc.:

0.155 µg/L

Element analysed:

Pr

Loading of aqueous phase:

1 mg/L

Incubation duration:

24 h

Test conditions:

T: 20.1 °C, O2: 8.6 mg/L, pH: 6.14

Remarks on result:

other: S.D.: ± 0.0262 µg/L

Key result

Type of test:

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

Mean dissolved conc.:

< 0.069 µg/L

Element analysed:

Si

Loading of aqueous phase:

1 mg/L

Incubation duration:

7 d

Test conditions:

T: 20.3 °C, O2: 7.6 mg/L, pH: 6.19

Remarks on result:

other: < LOD

Key result

Type of test:

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

Mean dissolved conc.:

0.168 µg/L

Element analysed:

Zr

Loading of aqueous phase:

1 mg/L

Incubation duration:

7 d

Test conditions:

T: 20.3 °C, O2: 7.6 mg/L, pH: 6.14

Remarks on result:

other: S.D.: ± 0.0175 µg/L

Key result

Type of test:

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

Mean dissolved conc.:

2.096 µg/L

Element analysed:

Pr

Loading of aqueous phase:

1 mg/L

Incubation duration:

7 d

Test conditions:

T: 20.3 °C, O2: 7.6 mg/L, pH: 6.14

Remarks on result:

other: S.D.: ± 0.8786 µg/L

Key result

Type of test:

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

Mean dissolved conc.:

< 0.069 µg/L

Element analysed:

Si

Loading of aqueous phase:

1 mg/L

Incubation duration:

28 d

Test conditions:

T: 21.7 °C, O2: 7.0 mg/L, pH: 6.14

Remarks on result:

other: < LOD

Key result

Type of test:

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

Mean dissolved conc.:

< 0.077 µg/L

Element analysed:

Zr

Loading of aqueous phase:

1 mg/L

Incubation duration:

28 d

Test conditions:

T: 21.7 °C, O2: 7.0 mg/L, pH: 6.14

Remarks on result:

other: < LOD

Key result

Type of test:

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

Mean dissolved conc.:

0.791 µg/L

Element analysed:

Pr

Loading of aqueous phase:

1 mg/L

Incubation duration:

28 d

Test conditions:

T: 21.7 °C, O2: 7.0 mg/L, pH: 6.14

Remarks on result:

other: S.D.: ± 0.3980 µg/L

Details on results:

Test conditions are closely in accordance with guideline:
- Vessel Variation:
The within-vessel variations from the 100 mg/L loadings were between 9.38 and 30.27 % (Zr) (i.e.>10 % - not guideline comform).
The between-vessel variation was 25.22 % (Zr) (i.e.>20 %- not guideline comform) at and the 7- day endpoint.
The within-vessel variations from the 100 mg/L loadings were between 0.05 and 0.09 % (Pr) (i.e. ≤10 %).
The between-vessel variation was 19.91 % (Pr) (i.e.≤ 20 %) at and the 7- day endpoint.

UN/SCEGHS/3/INF.5/Add.9 guideline requires for a standard set-up of three replicate test vessels and two replicate samples per test vessel at each sampling time, it is reasonable to anticipate that for a constant loading of a substance, tested in a narrow particle size (e.g. 37 - 44 μm) and total surface area range, the within-vessel variation in transformation data should be less than 10 % and the between-vessel variation should be less than 20 %. If we consider the final average the VC within vessels and between vessels is slightly higher than 10 % and 20 %, as requested by the guideline UN/SCEGHS/3/INF.5/Add.9, but taking into account the precision of the analytical method estimated at 3.52 % for Zirconium and 6.73 % for Praseodymium, it is acceptable.

The within-vessel variations from the 1 mg/L loading were between 0.08 and 3.87 % (i.e.≤10 %) for Zr and Pr.
The between-vessel variation was 41.91 (Pr) (i.e.>20 %) and 10.42 % (Zr) (i.e.≤ 20 %) at the 7-day endpoint. The final average the VC between vessels is slightly higher than 20 %, as requested by the guideline UN/SCEGHS/3/INF.5/Add.9. This may be due to no homogeneous dissolution of the Praseodymium, but taking into account that the determinations are very low is acceptable.
- The air oxgen concentrations were in the range of 5.0 mg/L and 10.0 mg/L. There were only two data (16 days, 1 mg/L loading) with 5.1 mg/L and 5.0 mg/L below the acceptable limit (>70 % of air O2 concentration = 5.46 mg/L). All the other data and also all the average data of the samples were above the acceptable limit.
- The temperature was in the range from 19.9 °C to 22.3 °C (i.e. between 20-25 °C +/- 2 °C).
- The pH was in the range of 6.0 to 6.2 (i.e. in the range of pH 6 + 0.2 units)

Silicon ions have not been found in aqueous solutions with 1 mg/L and 100 mg/L loadings. Praseodymium and zirconium ions dissolved/transformed in aqueous solutions. The maximum solubility for Pr was observed after 7-days for the 100 mg/L loading in the 7-d test and after day 4 for Zr. Dissolved concentrations for Zr were lower at day 7 indicating a possible re-precipitation of the metal salt. The maximum solubility for the 1 mg/L loading was observed after 7-days in the 28-d test. Dissolved concentrations were lower at day 10, 16 and 28 indicating also a possible reprecipitation of the metal salts.

28 days, 1 mg/L

Time	Samples	pH	Temp. (ºC)	O2 (mg/L)	Si (μg/L)	Zr* (μg/L)	Pr (μg/L)
2 h	Average	6.08	20.2	8.3	<0.0687	<0.025	0.1984 ± 0.0405
18 h	Average	6.09	20.3	7.7	<0.0687	<0.077	0.2229 ± 0.0124
24 h	Average	6.14	20.1	8.6	<0.0687	<0.077	0.1553 ± 0.0262
4 d	Average	6.12	20.7	8.2	<0.0687	<0.077	0.7962 ± 0.7660
7 d	Average	6.14	20.3	7.6	<0.0687	0.1678 ± 0.0175	2.0962 ± 0.8786
10 d	Average	6.19	20.7	7.2	<0.0687	0.1595 ± 0.024	1.8010 ± 0.7076
16 d	Average	6.16	20.0	5.9	<0.0687	<0.077	1.0736 ± 0.1334
28 d	Average	6.14	21.7	7.0	<0.0687	<0.077	0.7914 ± 0.3980

*Data from external laboratory

Conclusions:

The transformation/dissolution of ZIRCON PRASEODYMIUM YELLOW ZIRCON resulted in the following dissolved concentrations:

loading, time Si [μg/l] Zr [μg/l] Pr [μg/l]
1 mg/L, 7 days <0.0687 (1 mg/L, 28 days <0.0687 (100 mg/L,7 days <0.0687 (
As dissolved Si, Zr and Pr concentrations were below 90 µg/L (86.25 ± 17.17 µg Pr/L, 7d-test, 100mg/L, after 7 days) even at the highest loading of 100 mg/L, referring to a solubility of <0.1 %, the pigment can be considered environmentally inert.

Description of key information

The solubility of zirconium praseodymium yellow zircon in environmental media is low. In a GLP-conform transformation/dissolution screening test with a loading of 100 mg/L, a slightly higher Pr and Si release was observed at pH 6, whereas the release of Zr was below LOD at both pH. Transformation/dissolution at a loading of 1 mg/L resulted in dissolved Si concentrations below the LOD (< 0.07 microg/L) at pH 6 after 7 and 28 days. The dissolved Zr and Pr concentrations at pH 6 were 0.17 microg/L and 2.1 microg/L after 7 days, respectively, and < LOD (0.08 microg/L) for Zr and 0.79 microg/L for Pr after 28 days (Grane, 2010). The particle size of the tested sample (BET surface area 0.52 m2/g) is representative for the particle size marketed. Thus, the extent to which "Zirconium praseodymium yellow zircon" can produce soluble available ionic and other metal-bearing species in aqueous media is limited.

 

Additional information

The transformation/dissolution of zirconium praseodymium yellow zircon resulted in the following dissolved concentrations:

loading, time	Si [μg/L]	Zr [μg/L]	Pr [μg/L]
1 mg/L, 7 days	<0.0687 (<LOD)	0.1678 ± 0.0175	2.0962 ± 0.8786
1 mg/L, 28 days	<0.0687 (<LOD)	<0.077 (<LOD)	0.7914 ± 0.3980
100 mg/L,7 days	<0.0687 (<LOD)	0.159 ± 0.0401	86.25 ± 17.17

 

 

 

 

As dissolved Si, Zr and Pr concentrations were below 90 µg/L (86.25 ± 17.17 µg Pr/L, 7d-test, 100mg/L, after 7 days) , referring to a solubility of <0.1 %, the pigment can be considered environmentally inert.