tetraammine palladium (II) hydrogen carbonate

Adsorption / desorption

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

adsorption / desorption: screening

Type of information:

experimental study

Adequacy of study:

key study

Study period:

25 November 1997 - 18 March 1998

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Remarks:

To GLP

Qualifier:

according to guideline

Guideline:

OECD Guideline 106 (Adsorption - Desorption Using a Batch Equilibrium Method)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Type of method:

batch equilibrium method

Media:

soil

Radiolabelling:

no

Test temperature:

21.0 ± 1.5 °C

Details on study design: HPLC method:

Not applicable

Analytical monitoring:

no

Details on sampling:

No data

Matrix no.:

#1

% Org. carbon:

1.8

pH:

5.5

CEC:

14.5 meq/100 g soil d.w.

Details on matrix:

COLLECTION AND STORAGE
- Geographic location: Leamington Spa, England
- Collection procedures: No data
- Sampling depth (cm): No data
- Storage conditions: in the dark at ambient temperature
- Storage length: No data
- Soil preparation (e.g.: 2 mm sieved; air dried etc.): Air-dried and ground to less than 2 mm before storage. Equilibration of the soil was performed by gently shaking the soil and glass double-distilled water together for a period of 24 hours prior to the start of the test.

PROPERTIES
- Soil texture: No data
- % sand: No data
- % silt: No data
- % clay: No data
- Horizon: No data
- Soil taxonomic classification: Typical brown eath
- Soil classification system: Bearsted series
- Soil series: No data
- Soil order: No data
- pH: 5.5
- Organic carbon (%): 1.8
- CEC (meq/100 g): 14.5
- Carbonate as CaCO3: 0.09 g/kg
- Insoluble carbonates (%): No data
- Extractable Cations (Ca, Mg, Na, K, H) (MEQ/100 g): 2.84, 0.84, <0.005, 0.46, 5.21
- Special chemical/mineralogical features: No data
- Clay fraction mineralogy: No data
- Moisture at 1/3 atm (%): 1.71% (w/w)
- Bulk density (g/cm3): No data
- Biomass (e.g. in mg microbial C/100 mg, CFU or other): No data

Details on test conditions:

An aliquot of test material (0.0747 g) was dulited to 100 mL with distilled water, prior to further dilution by a factor of 100 with 0.015M calcium chloride (CaCl2) solution. Duplicate (A and B) wet soil/test solutino mixtures, as well as a wet soil/0.01M CaCl2 solution (soil control) were prepared. A control consisting of test solution with no soil was also prepared.

The adsorption equilibrium phase involved continuous shaking for 16 hours, followed by centrifugation and analysis of a 25 mL aliquot by atomic absorption spectroscopy (AAS). The supernatent removed during the adsorption step was replaced with an equivalent volume of 0.01 M CaCl2 solution, prior to re-equilibration for a further 16 hours. Centrifugation and AAS analysis was repeated for the desorption phase. The desorption step was repeated using a further aliquot of 0.01M CaCl2 soution.

Standard solutions of test material were prepared in 0.01M CaCl2 solution at a nominal concentration of 5.0 mg/L.

Sample No.:

#1

Duration:

16 h

Initial conc. measured:

24.8 mg/kg soil d.w.

Sample No.:

#2

Duration:

16 h

Initial conc. measured:

24.6 mg/kg soil d.w.

Sample no.:

#1

Duration:

16 h

Conc. of adsorbed test mat.:

20.2 mg/kg soil d.w.

Sample no.:

#2

Duration:

16 h

Conc. of adsorbed test mat.:

20 mg/kg soil d.w.

Computational methods:

- Adsorption and desorption coefficients (Kd): K = [(G - Ce.Vo) / M.Ce] x 1000
- Freundlich adsorption and desorption coefficients: No data
- Slope of Freundlich adsorption/desorption isotherms: Not applicable
- Adsorption coefficient per organic carbon (Koc): Koc = K x 100 / %OC
- Regression coefficient of Freundlich equation: Not applicable
- Other: Percentage of test material absorbed (A) = [(G - Ce.Vo) / G] x 100

G: quantity of test material recovered from soil-less control (mg)
Ce: concentration of test material remaining on solution after the adsorption step (mg/L)
Vo: total volume of aqueous phase (L)
M: dry mass of soil emplyed (g)
%OC: percent organic carbon content of soil

Sample No.:

#1

Type:

Kd

Value:

> 44 dimensionless

Temp.:

21 °C

% Org. carbon:

1.8

Sample No.:

#1

Type:

log Koc

Value:

> 3.39 dimensionless

Temp.:

21 °C

% Org. carbon:

1.8

Sample No.:

#2

Type:

Koc

Value:

> 43.7 dimensionless

Temp.:

21 °C

% Org. carbon:

1.8

Sample No.:

#2

Type:

log Koc

Value:

> 3.39 dimensionless

Temp.:

21 °C

% Org. carbon:

1.8

Details on results (HPLC method):

Not applicable

Adsorption and desorption constants:

Overall adsorption coefficient = >43.7

Recovery of test material:

Quantity of test material recovered from soil-less control = 0.133 mg

Concentration of test substance at end of adsorption equilibration period:

The aqueous phase concentration following the adsorption phase was <0.458 mg/L in both samples

Concentration of test substance at end of desorption equilibration period:

The aqueous phase concentrations following the first and second desorption phases were <0.476 and <0.432 mg/L, respectively, in both samples.

Sample no.:

#1

Duration:

16 h

% Adsorption:

> 89.7

Sample no.:

#2

Duration:

16 h

% Adsorption:

> 89.7

Sample no.:

#1

Duration:

16 h

% Desorption:

< 18.9

Sample no.:

#2

Duration:

16 h

% Desorption:

< 18.9

Transformation products:

not measured

Details on results (Batch equilibrium method):

No data

Statistics:

No data

The moisture content of soil was determined to be 1.71% w/w.

Tables 4.5 -4.11 in the attached document present the results of the adsorption/desorption phases.

Validity criteria fulfilled:

not specified

Conclusions:

In a guideline (OECD TG 106) study, to GLP, the soil adsorption coefficient of tetraamminepalladium(II) hydrogen carbonate was determined to exceed 2.43 x 10^3 (log10(Koc) >3.39).

Executive summary:

The adsorption/desorption characteristics of tetraamminepalladium(II) hydrogen carbonate were evaluated in an OECD Test Guideline 106 study, conducted according to GLP.

 

Aqueous CaCl2 solutions containing test material and wet soil were prepared in duplicate. Control solutions of CaCl2, both with and without wet soil, were also prepared. Adsorption and desorption equilibrium phases involved continuous shaking for 16 hours, followed by centrifugation and analysis of a 25 mL aliquot by atomic absorption spectroscopy. The supernatant removed at each stage was replaced by an equal volume of CaCl2 solution.

 

The overall test material adsorbed was in excess of 89.7% (w/w). The soil adsorption coefficient of tetraamminepalladium(II) hydrogen carbonate was determined to be greater than 2.43 x 10^3 (log10(Koc) >3.39).

Reference 2

Endpoint:

adsorption / desorption

Remarks:

adsorption

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: No guideline followed and is not GLP compliant, however, study meets generally accepted scientific methods and is described in sufficient detail

Principles of method if other than guideline:

Laboratory study, no guideline followed

GLP compliance:

not specified

Type of method:

batch equilibrium method

Media:

sediment

Radiolabelling:

no

Test temperature:

23 +/- 1 degrees Celsius

Analytical monitoring:

not specified

Details on sampling:

Field collected whole water samples were spiked with Pd to a concentration of 10 µg l-1 and shaken for 48 hours, followed by fractionation using 0.45 µm filtration.

Details on matrix:

Location: lower catchment of the Tugela river and its estuary, South Africa
Collection date: March 2006 (rainy season)

Details on test conditions:

Concentration of suspended particulate matter: between 150 and 200 mg l-1 (although one of the samples contained approximately 600 mg l-1 of suspended matter due to resuspension of bed sediment)
Concentration of suspended particulate matter in saline sample (estuarine mixing experiments): approximately 15 mg l-1 suspended matter
Salinity of seawater: 33.6 %
pH (freshwater): between 6.8 and 7.9
pH (seawater): 8.4
Dissolved organic carbon concentration: between 1.0 and 2.7 mg l-1 (although one sample contained a DOC concentration of 106 mg l-1)

Type:

other: log Kd

Value:

3.59

Temp.:

23 °C

Remarks on result:

other: Mean for all salinities, standard deviation 0.41

Type:

other: log Kd

Value:

3.39

Temp.:

23 °C

Remarks on result:

other: Mean for freshwaters, standard deviation 0.40

Type:

other: log Kd

Value:

3.84

Temp.:

23 °C

Remarks on result:

other: Mean for estuarine waters, standard deviation 0.04

Type:

other: log Kd

Value:

4.21

Temp.:

23 °C

Remarks on result:

other: Single value for seawater, salinity 33 %

Kd values are slightly affected by salinity with slightly higher partitioning at salinities above 10 ‰, partitioning in freshwaters showed a limited range of variation. The overall variation in log Kd for palladiumwas between 2.7 and 4.2 in river waters, estuarine (mixtures), and seawater. A mean log Kd of 3.59 (stdev 0.41) was observed for all salinities, a mean log Kd of 3.39 (stdev 0.40) was observed for freshwaters only, a mean log Kd of 3.84 (stdev 0.04) was observed for estuarine waters only, and a single log Kd of 4.21 was determined in seawater (salinity 33 ‰).

Table 1. Adsorption results

Salinity (%)	Kd (L/kg)	Log Kd
3.00	3000	3.48
3.50	3500	3.48
5.00	5000	3.70
5.00	5000	3.70
5.00	5000	3.70
5.50	5500	3.74
6.00	6000	3.78
7.00	7000	3.85
7.00	7000	3.85
8.00	8000	3.90
16.28	16280	4.21

Validity criteria fulfilled:

not specified

Conclusions:

Kd values are slightly affected by salinity with slightly higher partitioning at salinities above 10 ‰, partitioning in freshwaters showed a limited range of variation. The overall variation in log Kd for palladium was between 2.7 and 4.2 in river waters, estuarine (mixtures), and seawater. A mean log Kd of 3.59 (stdev 0.41) was observed for all salinities, a mean log Kd of 3.39 (stdev 0.40) was observed for freshwaters only, a mean log Kd of 3.84 (stdev 0.04) was observed for estuarine waters only, and a single log Kd of 4.21 was determined in seawater (salinity 33 ‰).

Executive summary:

This study has a reliability rating of 2, as it does not follow a standard guideline and is not GLP compliant, but meets generally accepted scientific methods and is described in sufficient detail.

This study investigated the partitioning of several precious metals in river water and mixtures of river water and seawater mimicking an estuarine salinity gradient. Separations were performed by filtration at 0.45 µm, with subsequent Pd analysis by ICP-MS.

Kd values are slightly affected by salinity with slightly higher partitioning at salinities above 10 ‰, partitioning in freshwaters showed a limited range of variation. A mean log Kd of 3.39 (stdev 0.40) was observed for freshwaters, a mean log Kd of 3.84 (stdev 0.04) was observed for estuarine waters only, and a single log Kd of 4.21 was determined in seawater (salinity 33 ‰).

Reference 3

Endpoint:

adsorption / desorption

Remarks:

adsorption

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: No guideline followed and not GLP compliant, however, study meets generally accepted scientific methods and is described in sufficient detail

Principles of method if other than guideline:

Laboratory study, no guideline followed

GLP compliance:

not specified

Type of method:

batch equilibrium method

Media:

sediment

Radiolabelling:

no

Test temperature:

25 degrees Celsius

Analytical monitoring:

no

Details on matrix:

Two semi-arid topsoil samples collected around Cape Town, South Africa (Tokai forest and Table Mountain) and one wetland sediment sample from Zandvlei Wetland.

Details on test conditions:

pH-dependent (pHs = 3, 5, 6, 7 and 8) adsorption experiments of the individual PGEs on the solids were carried out at a constant temperature (25 C). Solids (1.0 g) were suspended in 0.1 M KCl background electrolyte and adjusted to the appropriate pH. After pH stabilization (6 days), Pt, Pd and Rh were added to each tube and the mixtures horizontally shaken for 4 days at 250 rpm. Their pH values were subsequently measured and readjusted intermittently if needed. The samples were then centrifuged for 20 min at 1400 rpm and the supernatants filtered, using a 0.45 lm PTFE flow through filter. The PGE concentrations in the solid and liquid phases were analyzed using ICP-MS.

Type:

other: log Kd

Value:

2.64

Temp.:

25 °C

Remarks on result:

other: Overall mean, standard deviation 0.48

Table 1. Duplicate Kd values for Pd partitioning to soil and sediment samples

Added Pt (mg/L)	Sediment		Forest Soil		Mountain Soil
0.05	130.3	165.7	71.6	78.5	429	339.7
0.1	201.2	206.4	134.6	129.3	3746	316.2
0.15	233.3	212.3	163.3	165.7	490.4	371.3
0.5	614.6	676.6	1147.2	1010.9	614.6	820.6
1	1227.1	1279.3	1177.2	1258.5	798.3	711.4
1.5	2077.1	2170.6	1200.5	1512.4	469.5	416.6
3	5132.7	5353.9	875.9	1018.5	117.4	212.2
5	84.7	101.9	911.4	719.6	84.7	116.4

Table 2. Duplicate Log₁₀Kd values for Pd partitioning to soil and sediment samples

Added Pt (mg/L)	Sediment		Forest Soil		Mountain Soil
0.05	2.11	2.22	1.85	1.89	2.63	2.53
0.1	2.30	2.31	2.13	2.11	2.57	2.50
0.15	2.37	2.33	2.21	2.22	2.69	2.57
0.5	2.79	2.83	3.06	3.00	2.79	2.91
1	3.09	3.11	3.07	3.10	2.90	2.85
1.5	3.32	3.34	3.08	3.18	2.67	2.62
3	3.71	3.73	2.94	3.01	2.07	2.33
5	1.93	2.01	2.96	2.86	1.93	2.07

Validity criteria fulfilled:

not specified

Conclusions:

Kd values are reported for each metal and soil at eight different metal concentrations, Freundlich adsorption model parameters are also reported as well as rate constants for adsorption and desorption. In order to account for the variability in Pd partitioning between different systems the overall mean (n=48, ± standard deviation) log Kd values are used, 2.64 ±0.48 for Pd.

Executive summary:

This study has a reliability rating of 2, as it does not follow a standard guideline and is not GLP compliant, but meets generally accepted scientific methods and is described in sufficient detail.

Partitioning of Pd, Rh, and Pt to two semi-arid soils and one wetland sediment sample was studied over a range of metal concentrations. 25 ml of metal solution was added to 1.5 g of air dried and sieved soil or sediment, and the partitioning of the metals was determined by analysis of the dissolved phase before and after a 24 hour equilibration period following centrifugation and filtration at 0.45 µm. Metal concentrations were determined by ICP-MS.

Kd values are reported for each metal and soil at eight different metal concentrations, Freundlich adsorption model parameters are also reported as well as rate constants for adsorption and desorption. In order to account for the variability in Pd partitioning between different systems the overall mean (n=48, ± standard deviation) log Kd values are used, 2.64 ±0.48 for Pd.

Reference 4

Endpoint:

adsorption / desorption

Remarks:

adsorption

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: No guideline followed and not GLP compliant, however, study meets generally accepted scientific methods and is described in sufficient detail

Principles of method if other than guideline:

Laboratory study, no guideline followed

GLP compliance:

not specified

Type of method:

batch equilibrium method

Media:

sediment

Radiolabelling:

no

Test temperature:

20 +/- 2 degrees Celsius

Analytical monitoring:

not specified

Details on matrix:

Location: River Plym ad its estuary, southwest England

Details on test conditions:

Experiments were performed on 3 types of samples: untreated, chemically reduced or chemically oxidised sediment material. Sediment was added to filtered river water samples, which were spiked with metals and shaken for up to 96 hours, followed by fractionation using 0.45 µm filtration.

Type:

other: log Kd

Value:

> 2.7 - < 3

Temp.:

20 °C

Remarks on result:

other: Dependent on treatment of the sediment material

Experiments with Pd were at, or close to, steady state within 24 hours, and exhibited limited changes in adsorption following chemical reduction or chemical oxidation of the sediment particles. Unusually, initial Pd adsorption was followed by a degree of desorption prior to steady-state being reached. Low adsorption of Pd from river water may be due to its affinity for dissolved ligands present in the river water. Log Kd values of between 2.7 and 3.0 were derived, depending upon the treatment of the sediment material.

Validity criteria fulfilled:

not specified

Conclusions:

Log Kd values of between 2.7 and 3.0 were derived for Pd, depending upon the treatment of the sediment material.

Executive summary:

This study has a reliability rating of 2, as it does not follow a standard guideline and is not GLP compliant, but meets generally accepted scientific methods and is described in sufficient detail.

This study investigated the partitioning of several precious metals between river water and surficial sediment material, with an emphasis on the kinetics of the reactions. Separations were performed by filtration at 0.45 µm, with subsequent Pd analysis by ICP-MS. Experiments were performed with samples of untreated, chemically reduced, and chemically oxidised sediment material. Experiments with Pd were at, or close to, steady state within 24 hours, and exhibited limited changes in adsorption following chemical reduction or chemical oxidation of the sediment particles. Unusually, initial Pd adsorption was followed by a degree of desorption prior to steady-state being reached. Low adsorption of Pd from river water may be due to its affinity for dissolved ligands present in the river water.

Log Kd values of between 2.7 and 3.0 were derived, depending upon the treatment of the sediment material.

Description of key information

The soil adsorption coefficient of tetraamminepalladium hydrogen carbonate was determined to exceed 2.43 x 10^3 (log10(Koc) >3.39) (Hogg and Bartlett, 1998).

The log Kd for suspended particulate matter (SPM) in freshwater is 3.39 (stdev 0.40) and the average Kd is 2455 L/kg. Where wastewater is discharged to marine water it is recommended to use the measured partition coefficient in seawater, log Kd 4.21 (i.e. Kd is 16220 L/kg). The log Kd for soil is 2.64 (stdev 0.48) and the average Kd is 436.5 L/kg.

Key value for chemical safety assessment

Other adsorption coefficients

Type:

log Kp (solids-water in suspended matter)

Value in L/kg:

3.39

at the temperature of:

23 °C

Other adsorption coefficients

Type:

log Kp (solids-water in soil)

Value in L/kg:

2.64

at the temperature of:

25 °C

Additional information

The adsorption/desorption characteristics of tetraamminepalladium(II) hydrogen carbonate were evaluated in an OECD Test Guideline 106 study, conducted according to GLP. The soil adsorption coefficient of tetraamminepalladium hydrogen carbonate was determined to be greater than 2.43 x 10^3 (log10(Koc) >3.39) (Hogg and Bartlett, 1998).

Two studies have determined the partitioning of palladium between river water and suspended particulate matter. Both studies showed relatively consistent results for experiments performed in freshwaters, and similar partitioning was also observed in both estuarine and marine water in the key study (Turner et al., 2006; Cobelo-Garcia et al., 2008). An additional study, on the partitioning of palladium to two soils and one sediment, provides information relevant to the soil compartment (Sako et al., 2009).

 

Average partition coefficients have been derived in cases where multiple partition coefficients are available for the same type of system (e. g. partitioning to suspended particulate matter in surface waters). The average values have been derived by calculating the log values of the individual partition coefficients (Kd). Following log transformation, the mean and standard deviation are calculated to define an "average" partition coefficient and its associated standard deviation, assuming a log-normal distribution of Kd values. The log Kd across all waters studied is 3.59 and the average Kd across all salinities is 3890.5 L/kg (st dev 0.41). Averaging of Kd values obtained from tests at different salinities hides a clear difference in the partitioning behaviour of palladium between fresh and marine waters, with stronger partitioning being observed in marine water. Consequently, separate Kd values are recommended for assessments of freshwater and marine systems. The log Kd for freshwater is 3.39 (stdev 0.40) and the average Kd is 2455 L/kg. The log Kd for marine water is 4.21, and the Kd is 16220 L/kg. The log Kd for soil is 2.64 (stdev 0.48) and the average Kd is 436.5 L/kg.