ASTM D7503-10

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Designation: D7503 − 10
Standard Test Method for
Measuring the Exchange Complex and Cation Exchange
Capacity of Inorganic Fine-Grained Soils
This standard is issued under the fixed designation D7503; 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.
1. Scope specify how data are collected, recorded, and calculated are
regarded as the industry standard. In addition, they are repre-
1.1 This test method describes the procedures for measuring
sentative of the significant digits that should generally be
the soluble and bound cations as well as the cation exchange
retained. The procedures do not consider material variation,
capacity (CEC) of fine-grained inorganic soils. Clay minerals
purpose for obtaining the data, special purpose studies, or any
in fine-grained soils carry a negative surface charge that is
considerations for the objectives of the user. Increasing or
balanced by bound cations near the mineral surface. These
reducing the significant digits of reported data to be commen-
bound cations can be exchanged by other cations in the pore
surate with these considerations is common practice. Consid-
water, which are referred to as soluble cations. The cation
eration of the significant digits to be used in analysis methods
exchange capacity is a measure of the negative surface charge
for engineering design is beyond the scope of this standard.
on the mineral surface. The CEC generally is satisfied by
calcium (Ca), sodium (Na), magnesium (Mg), and potassium 1.5 The values stated in SI units are to be regarded as the
(K), although other cations may be present depending on the standard, unless other units are specifically given.
environment in which the soil exists. This test method was
2. Referenced Documents
developed from concepts described previously in Lavkulich
(1981) (1) and Rhoades (1982) (2). In soils with appreciable
2.1 ASTM Standards:
gypsum or calcite, dissolution of these minerals will release Ca
D653 Terminology Relating to Soil, Rock, and Contained
in solution that may affect the measurement. Fluids
D1193 Specification for Reagent Water
1.2 In this test method, the soluble salts from the mineral
D2216 Test Methods for Laboratory Determination of Water
surface are washed off with de-ionized water and then the
(Moisture) Content of Soil and Rock by Mass
concentration of soluble salts within the extract is measured.
D3740 Practice for Minimum Requirements for Agencies
The bound cations of the clay are measured by using a solution
Engaged in Testing and/or Inspection of Soil and Rock as
containing an index ion that forces the existing cations in the
Used in Engineering Design and Construction
bound layer into solution. The total concentrations of bound
D6026 Practice for Using Significant Digits in Geotechnical
and soluble cations in this solution are measured. The CEC is
Data
measured by displacing the index ion with another salt solution
E145 Specification for Gravity-Convection and Forced-
and measuring the amount of the displaced index ion.
Ventilation Ovens
1.3 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
3. Terminology
responsibility of the user of this standard to establish appro-
3.1 For definitions of other terms used in this standard, see
priate safety and health practices and determine the applica-
Terminology D653.
bility of regulatory limitations prior to use.
3.2 Definitions of Terms Specific to This Standard:
1.4 All observed and calculated values shall conform to the
3.2.1 acid wash, n—the process of initially rinsing equip-
guide for significant digits and rounding established in Practice
ment with tap water, followed by a rinse with 10 % HNO
D6026. The procedures in Practice D6026 that are used to
solution, and then finally rinsing 3 times with DI water.
3.2.2 bound cations (BC), n—cations that are adsorbed
(bound) to mineral surfaces that may be exchanged.
ThistestmethodisunderthejurisdictionofASTMCommitteeD18onSoiland
Rock and is the direct responsibility of Subcommittee D18.04 on Hydrologic
Properties and Hydraulic Barriers.
Current edition approved July 1, 2010. Published August 2010. DOI: 10.1520/ For referenced ASTM standards, visit the ASTM website, www.astm.org, or
D7503-10 contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
The boldface numbers in parentheses refer to a list of references at the end of Standards volume information, refer to the standard’s Document Summary page on
this standard. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D7503 − 10
objective testing, sampling, inspection, etc. Users of this standard are
3.2.3 cation exchange capacity (CEC), n—the total negative
cautioned that compliance with Practice D3740 does not in itself ensure
charge on mineral surface to be satisfied by bound cations.
reliable results. Reliable results depend on many factors. Practice D3740
3.2.4 exchange complex, n—the collection of bound cations
provides a means of evaluating some of these factors.
satisfying the CEC.
5. Apparatus
3.2.5 fine-grained soils, n—any soil with more than 50 %
passing the No. 200 US standard sieve.
5.1 Drying Oven, capable of maintaining a uniform tem-
3.2.6 inorganic soils, n—any soil with a loss of ignition
perature of 105 6 5 °C that meets the requirements of
(LOI) less than 1 %. Specification E145.
3.2.7 soluble cations (SC), n—cations in the soil that are not
5.2 No. 10 U.S. Standard Sieve
bound to the mineral surface.
5.3 Desiccator, containing silica gel.
4. Significance and Use
5.4 Laboratory Balance, 20 g capacity, 60.001 g accuracy
4.1 Fine-grained soils are used in waste containment sys-
and precision.
tems as barriers to flow and contaminant transport. Liquids
5.5 Weighing Paper, or small weighing dish.
contained by these barriers can contain ions that may interact
with the mineral surfaces in fine-grained soils.
5.6 End Over End Shaker, capable of 30 rpm.
4.2 The liquid passing through the pores of fine-grained soil
5.7 Capped Containers should tightly fit in the end over end
can interact with the mineral surface, and affect the physical
shakerholdingcompartmentwithcapacitieslargerthan40mL.
and chemical characteristics of the soil. This method can be
5.8 500 mL Filtering Flask, connectable to low-pressure
used as part of an evaluation of these interactions.
NOTE1—Thequalityoftheresultproducedbythisstandarddependson vacuum line, acid washed (See Fig. 1).
the competence of the personnel performing the test and the suitability of
5.9 Flexible Tubing, appropriate size to connect filtering
the equipment and facilities used. Agencies that meet the criteria of
Practice D3740 are generally considered capable of competent and flask to the low-pressure vacuum line (See Fig. 1).
FIG. 1 Experimental Setup for Vacuum Filtration
D7503 − 10
NOTE 2—Oven-dried soils should not be used for determining CEC,
5.10 Buchner Funnel, 55 mm or 90 mm diameter, acid
soluble cations, or bound cations because gypsum (CaSO •2H O) is
4 2
washed (See Fig. 1).
transformed to plaster of paris (CaSO • ⁄2 H O) at high temperatures, and
4 2
5.11 Wash Bottle, for dispensing solutions, new or acid
plaster of paris is more soluble in water than gypsum.
washed.
9. Determination of Soluble Cations
5.12 Graduated Cylinder, for measuring solution portions,
acid washed. 9.1 Use only air-dry soil that passes the No. 10 US Standard
Sieve.
5.13 2.5 µm Ashless Filter Paper that covers the surface of
Buchner funnel.
9.2 Add mass of air-dry soil corresponding to 2 g of soil
solids and 100 mL of Type II DI water to a covered container
5.14 250 mL Volumetric Flasks, class A flask for precision
that fits tightly into the shaker.
and accuracy.
9.3 Place the containers in an end-over-end shaker and
6. Reagents
shake for1hat30 rpm.
6.1 Reagent Water: Use only ASTM Type II water as
9.4 Vacuumfilterthemixtureineachcontainerusing2.5µm
defined in Specification D1193.
ashless filter paper.
6.2 Ammonium Acetate, 1M: Dissolve 77.08 g of 99.9 %
9.5 Transfer the extract to a 100 mLacid washed volumetric
pure NH OAc in Type II DI water (See Specification D1193)
flask, preserve with 1 mL HNO , and fill to volume.
andfilltovolumeina1000mLvolumetricflask.AdjustthepH
9.6 Analyze each extract for cation concentration (in mg/L)
of the solution to 7 with ammonium hydroxide or acetic acid.
usinginductivelycoupledplasmaspectrometry,atomicabsorp-
Approximately 1 L of NH OAc is needed per 6 samples.
tion, or another suitable method.
6.3 Isopropanol: Reagent grade.
NOTE 3—Low solid to liquid ratios can result in peptization and
6.4 Potassium Chloride, 1M: Dissolve 74.6 g of 99 % pure hydrolysis in some cases. If these reactions are of concern a lower solid to
liquid ratio such as 1:2 can be used.
KCl in Type II DI water and fill to volume in a 1000 mL
volum
...