ALFERROCK

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:

#

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:

yes

Type of method:

other: test was conducted in vessels in accordance with the OECD guideline 29.

Specific details on test material used for the study:

SOURCE OF TEST MATERIAL
- Source (i.e. manufacturer or supplier) and lot/batch number of test material: Fluorchemie GmbH Frankfurt, lot/batch number: 00-00 05 03
- State of matter and appearance: Reddish brown to brownish grey odorless powder


STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: Store in accordance with local regulations. Avoid creating dusty conditions and prevent wind dispersal.
- Stability in the medium, i.e. sensitivity of the test material to hydrolysis and/or photolysis: stable
- Solubility and stability of the test material in the solvent/vehicle and the exposure medium: stable
- Reactivity of the test material with the incubation material used (e.g. plastic ware): none


FORM AS APPLIED IN THE TEST (if different from that of starting material)
- Specify the relevant form characteristics if different from those in the starting material, such as state of aggregation, shape of particles or particle size distribution: material supplied in its finest form (refer to IUCLID section 4.5)

Key result

Type of test:

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

Mean dissolved conc.:

481 µg/L

Element analysed:

Al

Loading of aqueous phase:

100 mg/L

Incubation duration:

28 d

Test conditions:

pH 8, filtration of sample (3 kDa)

Type of test:

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

Mean dissolved conc.:

50.7 µg/L

Element analysed:

Al

Loading of aqueous phase:

100 mg/L

Incubation duration:

28 d

Test conditions:

pH 6, filtration of sample (3 kDa)

Type of test:

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

Mean dissolved conc.:

356 µg/L

Element analysed:

Al

Loading of aqueous phase:

100 mg/L

Incubation duration:

7 d

Test conditions:

pH 8, filtration of sample (3 kDa)

Type of test:

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

Mean dissolved conc.:

46.6 µg/L

Element analysed:

Al

Loading of aqueous phase:

100 mg/L

Incubation duration:

7 d

Test conditions:

pH 6, filtration of sample (3 kDa)

Details on results:

Silicon is the element with the highest concentration detected. The ecotoxicologically relevant metal element with the highest concentrations detected is Aluminium. The concentrations of other metal elements analysed can be found in the tables below.

The 7 and 28 days endpoint background corrected concentrations are:

Table 2:         7 days endpoint background corrected concentrations (measured concentrations below LOD or between LOD and LOQ were estimated, negative values are due to mathematic background subtraction):

Target pH	Filtration	Fe conc. [µg/L]	Al conc. [µg/L]	Ti conc. [µg/L]	Si conc. [µg/L]	Zr conc. [µg/L]	Cr conc. [µg/L]	P conc. [µg/L]	V conc. [µg/L]
6.0	0.2 µm	-0.026	53.1	-0.149	724	0.000	-0.062	-0.737	0.341
	3 kDa	-0.034	46.6	0.088	702	0.000	0.345	-0.730	0.205
8.0	0.2 µm	0.455	356	0.000		0.000	-0.042	0.246	1.22
	3 kDa	0.056	364	-0.017		0.000	0.555	-0.395	1.46

 

Table 3:         28 days endpoint background corrected concentrations (measured concentrations below LOD or between LOD and LOQ were estimated, negative values are due to mathematic background subtraction):

Target pH	Filtration	Fe conc. [µg/L]	Al conc. [µg/L]	Ti conc. [µg/L]	Si conc. [µg/L]	Zr conc. [µg/L]	Cr conc. [µg/L]	P conc. [µg/L]	V conc. [µg/L]
6.0	0.2 µm	0.000	54.6	-0.041	987	0.000	0.000	-0.327	0.807
	3 kDa	0.000	50.7	0.018	954	0.000	0.000	-0.489	0.442
8.0	0.2 µm	0.000	472	0.032		0.000	0.282	-0.491	-0.086
	3 kDa	0.663	481	0.008		0.000	0.191	-0.402	1.46

 

Conclusions:

The neutralisation and reduction products of bauxite residue from refinement process were tested in a 7- and 28-day T/D test according to the OECD guideline 29. The ecotoxicologically relevant metal element with the highest concentration detected was aluminium.

Executive summary:

The neutralisation and reduction products of bauxite residue from refinement process were tested in a screening test (1-day) and a full 7- and 28-day T/D test at pH 6 and pH 8 according to the OECD guideline 29 (loading 100 mg/L). The concentrations of Fe, Al, Ti, Si, Zr, Cr, P and V were quantified via gas chromatography (ICP-MS, ICP-OES). Concentrations were corrected with background concentrations of the water blanks. Before chemical analysis water samples were filtrated through 0.2 µm and 3 kDa filters. 

Aluminium was the ecotoxicologically relevant metal element with highest concentration detected at pH 8 after 28 days: 481 µg/L after 3kDa filtration. Silicon was detected at higher concentration, but was regarded as not relevant for potential ecotoxicity of the test item. Except Zr all elements analysed were detected at pH 6 or 8 after 7 and 28 days. Depending on the type of element analysed, the LODs varied between 0.025 µg/L (Ti) and 4.28 µg/L (P), the recovery rates between 70.4% (Al) and 100 % (Si, Cr, Fe, V, Al, P, Ti, Zr). No clear trend with regards to concentration magnitude and type of filtration (different pore size of filters) was observed.

Description of key information

The highest ecotoxicologically relevant metal species dissolved from test specimen in a T/D test (OECD 29) was aluminium with a concentration of 481 µg Al/L detected after 28 days with pH 8.

Key value for chemical safety assessment

Water solubility:

481 µg/L

at the temperature of:

21.5 °C

Additional information

Max. concentration of Al in T/D test after 28 days, loading 100 mg/L, pH 8.