Lime (chemical), hydraulic

Adsorption / desorption

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

adsorption / desorption: screening

Data waiving:

study scientifically not necessary / other information available

Justification for data waiving:

other:

Justification for type of information:

In soil as well as in sediment-water systems, lime (chemical) hydraulic will react and release calcium ions and hydroxyl ions. Therefore, no data are available on the adsorption capacity of the molecule as such neither does it makes sense to perform a study for this. Relevant information on adsorption/desorption of lime (chemcial) hydraulic can be broadened to data on adsorption/desorption of calcium. Some reliable studies on the adsorption capacity of calcium cations are therefore added as supporting information to the dossier. Next to calcium ions, also hydroxyl ions will be released to the environment. The behaviour of hydroxyl ions depends on the pH buffer capacity of the tested medium. The pH buffer capacity is controlled by a whole range of processes (mineral dissolution/precipitation, protonation/deprotonation of pH dependent charge sites, reaction with CO2, biological processes etc.) and as such, Kd values are not relevant for the fate and behaviour of OH- in soils or sediment.

Reference 2

Endpoint:

adsorption / desorption: screening

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Qualifier:

equivalent or similar to guideline

Guideline:

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

Principles of method if other than guideline:

In a first series of experiments, the chemical composition of centrifuged soil water from several soil horizons from three different podzolised soils was determined during different sampling occasions. The concentration of exhangeable cations was determined using a BaCl2 extraction.
For this first series of experiments, this IUCLID entry only focusses on the results for Ca obtained from extractions of the B2 horizon of the Hyytiälä soil obtained during 4 sampling occasions.
A second series of experiments included a series of batch equilibrium experiments in which the adsorption and desorption of Ca was studied in B2 horizon of the Hyytiälä soil. In these experiments, 2 g of soil was shaken for 8 days with 20 mL of different solutions with or without added Ca (0.218 mM CaCl2) and increasing pH levels.

GLP compliance:

not specified

Type of method:

batch equilibrium method

Media:

soil

Radiolabelling:

no

Analytical monitoring:

yes

Details on matrix:

B horizon of Hyytiälä soil, a podzolised soil of which the basic soil properties are presented by Ilvesniemi et al. (2000).

Details on test conditions:

See experimental method description.

Type:

Kd

Value:

37.6 L/kg

Remarks on result:

other: Experiment 1, sample 1.

Type:

Kd

Value:

42 L/kg

Remarks on result:

other: Experiment 1, sample 2.

Type:

Kd

Value:

49.1 L/kg

Remarks on result:

other: Experiment 1, sample 3.

Type:

Kd

Value:

5.3 L/kg

Remarks on result:

other: Experiment 2, sample 4.

Type:

Kd

Value:

38 L/kg

Remarks on result:

other: Experiment 2.

Adsorption and desorption constants:

Experiment 1:

Sample 1:
Sorbed: 22.61 mg Ca/kg
Not-sorbed: 0.60 mg Ca/kg
Kd: 37.6 l/kg

Sample 2:
Sorbed: 37.84 mg Ca/kg
Not-sorbed: 0.90 mg Ca/kg
Kd: 42.0 l/kg

Sample 3:
Sorbed: 42.48 mg Ca/kg
Not-sorbed: 0.87 mg Ca/kg
Kd: 49.1 l/kg

Sample 4:
Sorbed: 11.38 mg Ca/kg
Not-sorbed: 2.14 mg Ca/kg
Kd: 5.3 l/kg

Experiment 2:

For this experiment, only a Kd was calculated for that treatment in which 0.218 mM CaCl2 was added to the solution but no HCl was added (i.e., adsorption experiment at soil pH, i.e. at a pH of ca. 5.1).
Sorbed: 29.68 mg Ca/kg
In solution: 0.78 mg Ca/L
Kd: 38.0 l/kg.

Conclusions:

From the results of this study, Kd values could be calculated for adsorption of Ca to soil particles from the B horizon of a podzolized soil. In a first set of experiments exchangeable Ca2+ was measured in centrifugates of 4 samples of the soil under consideration. These experiments yielded Kd values of 5.3 to 49.1 L/kg. The second set of experiments were batch equilibrium experiments with the B2 horizon of the same soil and different solutions (with or without added CaCl2 and/or HCl). From the results of the experiment with added CaCl2 and without added HCl, a Kd of 38.0 could be calculated, which agrees very well with those from the first set of experiments.

Reference 3

Endpoint:

adsorption / desorption

Remarks:

desorption

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Qualifier:

no guideline available

Principles of method if other than guideline:

The purpose of this study was to investigate the evolution of the pH value in soil after mixing the soil with calcium hydroxide and percolating the lime-treated soil with deionized water. The following parameters were determined: pH, Ca(OH)2 in the percolate, and Ca2+ in the percolate. From the obtained results the fate of Ca(OH)2 in soil was deduced.

GLP compliance:

not specified

Type of method:

other: soil percolation study

Media:

soil

Radiolabelling:

no

Test temperature:

20°C

Analytical monitoring:

yes

Details on sampling:

Agricultural soil (Parabraunerde, loess) from research field Meckenheim (near Bonn) was taken from 0-30 cm horizon (plowing depth).

Details on matrix:

- soil horizon Ah
- soil source well known and analysed over years by university Bonn, institute of agricultural chemistry and plant nutrition, Prof. Scherer

Details on test conditions:

- 4 test vessels per concentration and time point
- 4 control vessels
- each test vessel filled with 1040 g soil and mixed with 1040 mg calcium hydroxide
- water added to 70 % available water capacity
- all 8 vessels were percolated with deionized water (the amount of water added was calculated to result in a percolate of 100 mL)

Remarks on result:

other: No meaningful Kd values could be calculated from this study because no total or exchangeable Ca concentrations were reported

Adsorption and desorption constants:

No meaningful Kd values could be calculated from this study because no total or exchangeable Ca concentrations were reported. However, the study provides evidence that 1) Ca(OH)2 can only be washed out by percolation directly after addition to soil, 2) Ca is adsorbed to mineral particles in soil after only a few hours, and 3) due to the buffer capacity of the soil the pH of the soil - which increases immediately after liming - returns back to normal after only a few hours (i.e., 6 hours).

	time (h)	pH-value	Ca(OH)2	Ca
			[mg/L]	[mg/L]
	control	6.4		95
	0	10.8	43	114
	6	6.2		125
	12	6.4		142
	24	7		85
	48	7.4		62
	72	7.7		75

Conclusions:

The results of the percolation test show, that Ca(OH)2 can only be washed out by percolation directly after addition to the soil. After 6 hours the calcium hydroxide has adsorbed to mineral particles in the soil. The absorption energy is higher than the potential dissolution in water.

Reference 4

Endpoint:

adsorption / desorption: screening

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

test procedure in accordance with national standard methods with acceptable restrictions

Qualifier:

equivalent or similar to guideline

Guideline:

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

Principles of method if other than guideline:

The objective of this study is to test the effect of an industrial lime-stabilized sludge deposited on an acid soil. First a leachate is obtained of the sludge (simulating leaching due to rainfall from a sludge deposited over a soil bed). The composition of the leachate (Ca, Na, K, Mg, Ni and Zn) was studied. Then batch equilibrium experiments were performed with the leachate and the soil and adsorption of cations from the leachate to soil particles was monitored during 6 hours.

GLP compliance:

not specified

Type of method:

batch equilibrium method

Media:

soil/sewage sludge

Radiolabelling:

no

Test temperature:

20 ± 2 °C

Analytical monitoring:

yes

Details on matrix:

The sludge was taken from four places in a waste water treatment plant of a chemical factory manufacturing special textiles. The sludges were mixed with calcium oxide (lime) to stabilize pH at 12. Quantity of lime added was 20% on a dry weight basis.
The soil was taken from an agricultural zone of the center of Asturias (Spain). 5-20 cm, dried (105°C), sieved < 2 mm.

Type:

Kd

Value:

11.3 L/kg

Type:

other: log Kd

Value:

1.05 dimensionless

Adsorption and desorption constants:

Kd = 11.3 L/kg for Ca2+ (based on exchangeable Ca, not on total Ca).
Log Kd = 1.05

Conclusions:

In this study, batch equilibrium experiments were performed with agricultural soil and a leachate obtained by simulating the interaction of rainfall with a lime-stabilized sludge (20% CaO) applied to the soil. During the 6-h batch equilibrium experiment, Ca2+ concentration decreased due to adsorption to soil particles. The Kd for Ca2+ was calculated to be 11.3 L/kg. Further, although the pH of the leachate was quite high, the high buffer capacity of the soil maintained the pH, hence there would be no problem with the deposition of the sludge under consideration.

Description of key information

Determining a Kd-value for lime (chemical) hydraulic is not relevant, since this molecule reacts with water to release calcium ions and hydroxyl ions. Reliable Kd-values for calcium range from 5.3 L/kg to 49.1 L/kg and are added as supportive information. The Kd-concept is not relevant for hydroxyl ions, since the behaviour of these ions depends on the pH buffer capacity of the tested medium.