ASTM C1733-21
(Test Method)Standard Test Method for Distribution Coefficients of Inorganic Species by Batch Method
Standard Test Method for Distribution Coefficients of Inorganic Species by Batch Method
SIGNIFICANCE AND USE
4.1 The distribution coefficient, Kd, is an experimentally determined ratio quantifying the distribution of a chemical species between a given fluid and solid material sample under certain conditions, including the attainment of constant aqueous concentrations of the species of interest. The Kd concept is used in mass transport modeling, for example, to assess the degree to which the movement of a species will be delayed by interactions with the local geomedium as the solution migrates through the geosphere under a given set of underground geochemical conditions (pH, temperature, ionic strength, etc.). The retardation factor (Rf) is the ratio of the velocity of the groundwater divided by the velocity of the contaminant, which can be expressed as:
where:
ρb = bulk density of the porous medium (mass/length3), and ηe = effective porosity of the medium (unitless) expressed as a decimal.
4.2 Because of the sensitivity of Kd to site specific conditions and materials, the use of literature derived Kd values is strongly discouraged. For applications other than transport modeling, batch Kd measurements also may be used, for example, for parametric studies of the effects of changing chemical conditions and of mechanisms related to the interactions of fluids with solid material.
SCOPE
1.1 This test method covers the determination of distribution coefficients, Kd, of chemical species to quantify uptake onto solid materials by a batch sorption technique. It is a laboratory method primarily intended to assess sorption of dissolved ionic species subject to migration through pores and interstices of site specific geomedia, or other solid material. It may also be applied to other materials such as manufactured adsorption media and construction materials. Application of the results to long-term field behavior is not addressed in this method. Kd for radionuclides in selected geomedia or other solid materials are commonly determined for the purpose of assessing potential migratory behavior of contaminants in the subsurface of contaminated sites and out of a waste form and in the surface of waste disposal facilities. This test method is also applicable to studies for parametric studies of the variables and mechanisms which contribute to the measured Kd.
1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.
1.4 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
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This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: C1733 − 21
Standard Test Method for
Distribution Coefficients of Inorganic Species by Batch
1
Method
This standard is issued under the fixed designation C1733; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
INTRODUCTION
As an aqueous fluid migrates through geologic media or contacts an engineered material, certain
reactions occur that are dependent upon the chemistry of the fluid itself and upon the chemistry and
geochemistry of other fluids and solid phases with which it comes in contact. These chemical and
geochemicalinteractionsaffecttherelativeratesatwhichchemicalspeciesinthemigratingfluid(such
as ions) travel with respect to the advancing front of water. Processes of potential importance in
retarding the transport of chemical species in the migrating fluid (movement of species at velocities
less than the ground-water velocity) include ion exchange, adsorption, complex formation, precipi-
2+ 2+
tation (or coprecipitation, for example Ba and Ra co-precipitating as a sulfate), redox reactions,
and precipitate filtration. Partitioning may be caused by processes that include adsorption,
precipitation, and coprecipitation that cannot be described easily by equations and, furthermore, these
solute removal mechanisms may not instantaneously respond to changes in prevailing conditions and
may not be entirely reversible.
An empirical ratio known as the distribution coeffıcient (K ) is defined as the mass of the solute on
d
the solid phase per unit mass of solid phase divided by the mass of solute in solution per unit volume
of the liquid phase (Eq 1).This ratio has been used to quantify the collective effects of these processes
for the purpose of modeling (usually, but not solely, applied to ionic species). K is used to assess the
d
degreetowhichachemicalspecieswillberemovedfromsolution(permanentlyortemporarily)asthe
fluidmigratesthroughthegeologicmediumorcontactsasolidmaterial;thatis, K isusedtocalculate
d
the retardation factor that quantifies how rapidly an ion can move relative to the rate of ground-water
movement.
This test method is for the laboratory determination of the K , which may be used by qualified
d
experts for estimating the retardation of contaminants for given underground geochemical conditions
based on a knowledge and understanding of important site-specific factors. It is beyond the scope of
this test method to define the expert qualifications required, or to justify the application of laboratory
data for modeling or predictive purposes. Rather, this test method is considered as simply a
measurement technique for determining the degree of partitioning between liquid and solid, under a
certain set of conditions, for the species of interest.
Justification for the K concept is generally acknowledged to be based on expediency in
d
modeling-averaging the effects of attenuation reactions. In reference to partitioning in soils,
equilibrium is assumed although it is known that this may not be a valid assumption in many cases.
The K for a specific chemical species may be defined as the ratio of the mass sorbed per unit of
d
solid phase to the mass remaining per unit of solution, as expressed in the above equation. The usual
units of K are mL/g (obtained by dividing g solute/g solid by g solute/mL solution, using
d
concentrations obtained in accordance with this test method).
Major difficulties exist in the interpretation, application, and meaning of laboratory-determined K
d
2
values relative to a real system of aqueous fluid migrating through geologic media (1). The K
d
concept is based on an equilibrium condition for given reactions, which may not be attained in the
natural situation because of the time-dependence or kinetics of specific reactions involved. Also,
migrating solutions always follow the more permeable paths of least resistance, such as joints and
fractures, and larger sediment grain zones.This tends to allow less time for reactions to occur and less
sediment surface exposure to the migrating solution, and may preclude the attainment of local
chemical equilibrium.
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C1733 − 21
Sorption phenomena also can be strongly dependent upon the concentration of the species of
interest in solution. Therefore, experiments performed using only one concentration of a par
...
This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: C1733 − 20 C1733 − 21
Standard Test Method for
Distribution Coefficients of Inorganic Species by Batch
1
Method
This standard is issued under the fixed designation C1733; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
INTRODUCTION
As an aqueous fluid migrates through geologic media or contacts an engineered material, certain
reactions occur that are dependent upon the chemistry of the fluid itself and upon the chemistry and
geochemistry of other fluids and solid phases with which it comes in contact. These chemical and
geochemical interactions affect the relative rates at which chemical species in the migrating fluid (such
as ions) travel with respect to the advancing front of water. Processes of potential importance in
retarding the transport of chemical species in the migrating fluid (movement of species at velocities
less than the ground-water velocity) include ion exchange, adsorption, complex formation, precipi-
2+ 2+
tation (or coprecipitation, for example Ba and Ra co-precipitating as a sulfate), redox reactions,
and precipitate filtration. Partitioning may be caused by processes that include adsorption,
precipitation, and coprecipitation that cannot be described easily by equations and, furthermore, these
solute removal mechanisms may not instantaneously respond to changes in prevailing conditions and
may not be entirely reversible.
An empirical ratio known as the distribution coeffıcient (K ) is defined as the mass of the solute on
d
the solid phase per unit mass of solid phase divided by the mass of solute in solution per unit volume
of the liquid phase (Eq 1). This ratio has been used to quantify the collective effects of these processes
for the purpose of modeling (usually, but not solely, applied to ionic species). K is used to assess the
d
degree to which a chemical species will be removed from solution (permanently or temporarily) as the
fluid migrates through the geologic medium or contacts a solid material; that is, K is used to calculate
d
the retardation factor that quantifies how rapidly an ion can move relative to the rate of ground-water
movement.
This test method is for the laboratory determination of the K , which may be used by qualified
d
experts for estimating the retardation of contaminants for given underground geochemical conditions
based on a knowledge and understanding of important site-specific factors. It is beyond the scope of
this test method to define the expert qualifications required, or to justify the application of laboratory
data for modeling or predictive purposes. Rather, this test method is considered as simply a
measurement technique for determining the degree of partitioning between liquid and solid, under a
certain set of conditions, for the species of interest.
Justification for the K concept is generally acknowledged to be based on expediency in
d
modeling-averaging the effects of attenuation reactions. In reference to partitioning in soils,
equilibrium is assumed although it is known that this may not be a valid assumption in many cases.
The K for a specific chemical species may be defined as the ratio of the mass sorbed per unit of
d
solid phase to the mass remaining per unit of solution, as expressed in the above equation. The usual
units of K are mL/g (obtained by dividing g solute/g solid by g solute/mL solution, using
d
concentrations obtained in accordance with this test method).
1
This test method is under the jurisdiction of ASTM Committee C26 on Nuclear Fuel Cycle and is the direct responsibility of Subcommittee C26.13 on Spent Fuel and
High Level Waste.
Current edition approved Feb. 1, 2020Feb. 1, 2021. Published April 2020March 2021. Originally approved in 2010. Last previous edition approved in 2017 as C1733 – 17a.
DOI: 10.1520/C1733-20.10.1520/C1733-21.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
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---------------------- Page: 1 ----------------------
C1733 − 21
Major difficulties exist in the interpretation, application, and meaning of laboratory-determined K
d
2
values relative to a real system of aqueous fluid migrating through geologic media (1)). . The K
d
concept is based on an equilibrium condition for given reactions, which may not be attained in the
natural situation because of the
...
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