potassium titanium oxide (K2Ti6O13)

Adsorption / desorption

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

adsorption / desorption: screening

Type of information:

read-across from similar mixture/product

Adequacy of study:

key study

Study period:

2006

Reliability:

2 (reliable with restrictions)

Principles of method if other than guideline:

Concentrations of Titanium (and other metals) determined in co-located water and sediment samples from 20 locations. [These data points can be used (in CSR) to calculate Kd values for partitioning from water to sediment; and 10th, 50th and 90th percentile values of Log Kd calculated.]

GLP compliance:

no

Type of method:

other:

Media:

sediment

Radiolabelling:

no

Analytical monitoring:

yes

Details on sampling:

20 sampling sites were randomly chosen within a marsh area situated in the East Rand near Johannesburg, South Africa. The sampling sites were situated within a wetland stream running north-south for 22 km (see attached map). The area has been the subject of mining for a considerable period of time, and the wetland arose due to many years of regular pumping out (dewatering) of underground mine workings. The stream has a low gradient resulting in swampy conditions for most of its course. Care was taken to ensure that the sampling sites were representative of the variety of contexts (geological and environmental) of the area.

Surface water: At each sampling site two surface water samples were collected and filtered through a 0.45 µm nylon membrane filter using a hand-held vacuum pump. One of the samples was acidified with 3 M HNO3 to a pH of less than 2 to prevent metal precipitation. The water samples were stored in plastic bottles pre-rinsed with HNO3 and de-ionised water. The bottles were stored at 4°C.

Sediment: surface sediments were sampled close to the sediment-water interface by completely inserting an inverted 50 mL polypropylene centrifuge vial. After digging the vial out, they were capped without leaving any head space. The vials were stored in an anearobic jar (anoxic conditions maintained through the use of a BBL gas pack). The jars were stored on ice.

Computational methods:

Kd was calculated using the equation: Kd = Cs(mg/kg)/Cw(mg/L), where Cw and Cs denote the metal concentration in the water and solid phases, respectively.

Remarks on result:

other: Kd value (equilibrium coefficient values, L/kg) (for sediment water) 120226 (90th percentile Kd estimated from Roychoudhury et al)

	Ti SW conc	Ti sed conc
Samples	µg/L	mg/kg
M01	30.8	3924
M02	28.7	3427
M03	26.5	1289
M04	39.7	1314
M05	324.3	1906
M06	39.9	2929
M07	39.9	5359
M08	38.9	2568
M09	34.1	1396
M10	47.2	3880
M11	40.2	3637
M12	170.4	5108
M13	47.6	4017
M14	158.2	3061
M15	179.1	4268
M16	186.8	4436
M17	186.6	5263
M18	178.7	4252
M19	192.2	4868
M20	200.2	2337

Conclusions:

The mean, max and min Kd for the partitioning of Titanium from water to sediment, in situ, has been derived by analysing for the Titanium content from water/sediment samples co-located in 20 locations in a mining region of the East Rand in South Africa.

Executive summary:

This investigation constitutes a robust survey of the Titanium content in sediment and water, across a range of sites in a mining area in South Africa. The results are consistent with the known behaviour of Titanium, which has a strong tendency to be found in solid residue form, rather than in the aqueous phase.

Reference 2

Endpoint:

adsorption / desorption

Remarks:

adsorption

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

2009.

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: see 'Remark'

Remarks:

The report describes the development of a soil extraction methodology designed to return 'water leachable' measurements for elements in the top horizons of soils (these fractions are regarded as bioaccessible). Effectively, the data generated compares the water extractable fraction to the total element content, and hence, allows the calculation of soil partitioning values. The work described aimed to generate a methodology that can be used in international geochemical surveys, and has been robustly conducted as part of an international collaboration, by a National organisation (Geological Survey of Canada). Whilst blanks and standard solutions were included, no Standard Reference Materials for water-leaches of solid samples are currently available, and so it was not possible to monitor the accuracy of these extractions.

Principles of method if other than guideline:

A methodology was sought to achieve a high sample throughput procedure for determining the 'bioaccessible' (i.e. water leachable) fraction of a wide-range of elements (including Titanium, amongst many other metals), in environmental soil samples. Effectively, this amounted to a desorption methodology, albeit with a desorption phase determined to be sufficiently long to achieve equilibrium. The total elemental content was also determined (using four-acid digestion).

GLP compliance:

not specified

Type of method:

other:

Media:

soil

Radiolabelling:

no

Analytical monitoring:

yes

Details on sampling:

A- and C-horizon soils and a surficial sample from a depth of 5 cm were collected at approximately 40 kn intervals from 220 sites along two transects: A north-south transect extended from northern Manitoba to the US-Mexico border near El Paso, Texas, and a west-east transect following the 38th parallel from just north of San Francisco to the Virginia shore.

Details on matrix:

161 soil samples (see Details on sampling).

Computational methods:

The partition coefficient Kd for soil-water was calculated for elements where both four-acid digestion and water-leach data were available, and the number of non-detects was <20%. This included Titanium.

Kd is defined as : Kd = Total element in soil/Total dissolved element

A relationship exists between the proportion of an element extracted by the water-leach and the Kd. In this study, it involves allowing for the 40:1 solute:soil ratio:

Kd = 40/(leachable proportion).

In the report, values reported as logKds.

Remarks on result:

other: Kd values (equilibrium coefficient values, L/kg) (for soil) minimum 38194, median 792501, maximum 6194411

Summary statistics for Titanium, 161 soil samples:

Log Kds (L/kg)

Minimum:                                               4.582

1st quartile:                                             5.707          

Median:                                                  5.899

3rd quartile:                                          6.109

Maximum:                                               6.792

MAD (Median Absolute Deviation):        0.303

Mean:                                                     5.901

Standard Deviation:                                 0.338       

Conclusions:

The Kds values for 161 soil samples collected across a range of North American soil types, gave a median Log Kds value of 5.899 L/kg.

Executive summary:

This investigation constitutes a significant survey of the Titanium soil content of a range of North American soils. The methodology developed to analyse the water-leach component for 161 soil samples was robust, and the log Kds values derived from this data (and the total Titanium content of the soils) gave a high level of consistency with the mean and median being very similar (5.899 and 5.901 L/kg, respectively). The geographical extent from which the soil samples were obtained (north-south and east-west transects across North America) indicates that the Log Kds values are likely to be representative for soils, generally.

Reference 3

Endpoint:

adsorption / desorption

Remarks:

adsorption

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

2001

Reliability:

2 (reliable with restrictions)

Principles of method if other than guideline:

Partitioning of 41 elements (including Titanium) between solids and water was studies by filtration in situ in Czech freshwaters. Field-based distribution (partition) coefficients, Kd, between suspended matter and filtrate were determined.

GLP compliance:

no

Type of method:

other:

Media:

other: suspended matter/water

Radiolabelling:

no

Details on sampling:

Water samples were taken from 54 Czech rivers at 119 localities. Samples were passed through perforated polycarbonate filters (0.4 µm) in the field, immediately after collection, cooled and transported to the laboratory. Samples for analysis by FAAS. GFAAS and ICP-MS (publication doesn't indicate which analysis method was used for Titanium) were acidified by adding 1 mL of HNO3 (1:1 purified by sub-boiling distillation) on the day of collection, to a pH of about 1.5. The filters were boiled with distilled water acidified by HNO3 for 10 min before use, dried at 105°C, weighed and transported to the field in petri dishes. A hand pump filter system was used (airpressure of 5.3 kg/cm2). 200 mL of river water was generally filtered, and another 100 mL taken for analysis of water physico-chemical properties of the water.

Computational methods:

Kd = Cs/CL (L/g), where Cs is the concentration in the solid phase (mol/g), and CL is the concentration in the liquid phase (mol/L)

Remarks on result:

other: Kd values (equilibrium coefficient values, L/kg) (partition coefficient suspended solids water) median 229087

The river waters analysed had a mean pH of 7.74 (range 6.9 to 8.8), ionic strength 7.8 mmol/L, specific conductance 538 µS/cm at 25°C, alkalinty 1.9 mmol/L, and suspended particulate matter 9.9 mg/L (range 1.0 - 124 mg/L).

Values for the Log Kd for Titanium for the individual samples was not reported in the publication. However, the median Log Kd of 2.36 (L/g) was given.

Conclusions:

The in situ median Log Kd (from 119 samples) for partitioning of Titanium from water to suspended matter in environmental river samples collected in the Czech Republic, was 2.36 L/g.

Reference 4

Endpoint:

adsorption / desorption: screening

Remarks:

It is a data waining to the testing proposal related to 9.3.1. of Annex VIII.

Data waiving:

study technically not feasible

Justification for data waiving:

the study does not need to be conducted because the physicochemical properties of the substance indicate that it can be expected to have a low potential for adsorption

Justification for type of information:

The Partition Coefficient can be waived for inorganic substance.

Reference 5

Endpoint:

adsorption / desorption: screening

Remarks:

Selection in accordance to Validation Assistant Wizard. It is a data waining to the testing proposal related to 9.3.3. of Annex IX.

Data waiving:

study technically not feasible

Justification for data waiving:

the study does not need to be conducted because the physicochemical properties of the substance indicate that it can be expected to have a low potential for adsorption

Justification for type of information:

It is a data waining to the testing proposal related to 9.3.3. of Annex IX.
According to Column 2, 9.3.3., the study need not be conducted if, based on the physicochemical properties the substance can be expected to have a low potential for adsorption (e.g. the substance has a low octanol water partition coefficient).

Description of key information

The substance is inorganic. Therefore, Koc is not relevant. Representative

values for median Kd(soil-water), mean Kd(sediment-water) and median Kd(suspended matter-water) have been derived for Titanium from literature publications, which can be used for risk assessment purposes for this substance.

Key value for chemical safety assessment

Other adsorption coefficients

Type:

other: log kd (soil-water)

Value in L/kg:

5.899

Other adsorption coefficients

Type:

other: log kd (sediment-water)

Value in L/kg:

4.566

Other adsorption coefficients

Type:

other: log kd (suspended matter-water)

Value in L/kg:

5.36

Additional information

Titanium has a strong tendency to partition into the solid phase as it has a strong tendency to form aggregates, and exist in the solid phase rather than form free ions in solution. Consequently, partitioning of Titanium containing substances tend not to be dependent on pH or redox conditions (which can often affect speciation and behaviour in the case of other metals). As such, the adsorption values derived from literature publications for total Titanium in the field can also be considered as appropriate for use with this substance.

For potssium hexatitanate, in accordance with Regulation (No) 1907/2006 (REACH) Annex XI, the adsorption coefficient could not be determined using the technique specified in the OECD draft guideline( July 1997): Estimation of the Adsorption Coefficient (Koc) on Soil and on Sewage Sludge using High Performance Liquid Chromatography (HPLC). This is due to the low solubility of the substance in water and organic solvents. Furthermore, the substance is not expected to have the potential for adsorption.