Cation exchange and it’s role on soil behaviour

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Cation Exchange And It’s Role On Soil Behavior

Presented by Sh.Maghami
Instructor : Dr.Nikoodel

Autumn ,1391

Contents

Chapter 1) Introduction
• Deffinitions
• Why do soils have CEC
• Basics of Clay content & CEC

Chapter 2) Clay Structure
• How do clays Have a CEC
• Isomorphous substitution
• Foundations and differences of Clays structures
• Some properties of clay minerals

Chapter 3) Surface Properties
• Surface Properties Relations

Chapter 4) Engineering Properties

• The physical properties affected by surface phenomenones

Cation Exchange
What expect you to know

How the soil properties
could related to each other Cation Exchange &
Cation Echange Capacity (CEC)

How CEC effect CEC Agents and what
on soil properties ?
What properties affected ?
Cation Is their relationship
to soil

What is the relation Describing the clay structures
of surface properties and the differences between those .
of the soil

Chapter 1

INTRODUCTION
 Definitions
Cation Exchange
Cation Exchange Capacity
Why do soils have CEC

Definitions

Soil colloids will attract and hold positively
charged ions to their surface Replacement Cation Exchange
of one ion for another from solution

For every cation that is adsorbed, one goes back into soil solution

In soil science the maximum quantity of
total cations , of any class, that a soil is
Cation Exchange Capacity capable of holding, at a given pH
(CEC) value, available for exchange with the
soil solution (meq+/100g)

Why do soils have CEC ?

The cation exchange capacity (CEC) of the soil is determined by
the amount of clay and/or humus that is present .
Clay & Humus : Cation warehouse or reservoir of the soil

Sandy soils with very little OM Low CEC

Clay soils with high levels of OM much greater capacity
to hold cations .
(negative soil particles attract the positive cations)

Sand Clay

Si2O4 SiAlO4-
No charge. Negative charge.
Does not retain cations Attracts and retains cations

CLAY STRUCTURE
How do clays Have a CEC
Isomorphous substitution
Foundations and differences of Clays structures
1:1 Clays
2:1 Clays
Some properties of clay minerals

Why do clays have a CEC?

If the mineral was pure silica and
oxygen (Quartz), the particle would
not have any charge.

Figure 1 ) SiO 2 Structure

Isomorphous substitution

 However, clay minerals could contain aluminum as well as silica.
They have a net negative charge because of :
 the substitution of silica (Si4+) by aluminum (Al3+)
 in the clay. This replacement of silica by aluminum in the clay
mineral’s structure is called “isomorphous substitution”, and the
result is clays with negative surface charge

Figure 2)
Tetrahedron - SiO4 Octahedron - Al(OH)6

How clays are forming basically ?

Sharing of O or OH groups

Sheets and unit layers
(a) Tetrahedral sheet (b) Octahedral sheet

Si Al

Figure 3) Sheets Formation

How clays are forming basically ?

Exposed Oxygen
Si
Shared Oxygen
Al
Hydrogen
Balance Oxygen Charge

Figure 4) Clays unit structure

Clay Types

 A) 1:1 Type Minerals Si
Mostly Kaolinite
Al 7Ao

Si

Al

Hydrogen bonding between layers. This gives 1:1 Figure 5) 1:1 clays
type minerals a very rigid structure .

 Well crystallized Fixed lattice type
Low cation adsorption  No interlayer activity
Little isomorphous substitution  No shrink-swell
Larger particle size (0.1 - 5 m m)  Only external surface

Clay Types

 B) 2:1 Type Minerals
1. Expanding lattice
Si
 Smectite group
 Mostly Montmorillonite 18Ao Al
Si

Ca Mg H2O
 Freely expanding
 Water in interlayer Si
 Large shrink-swell
 Small size
Al
 Poorly crystallized
Large internal surface Si
Isomorphous substitution
 Large cation adsorption
 Adsorbed cations in interlayer
Figure 6) 2:1 expanding clays

Clay Types

- - - Si - - -
-
 2. Non-expanding lattice
 Fine-grained micas or illite Al
10Ao
Si
Some distribution of Al for Si in the tetrahedral
layers leads to permanent net negative charge K
-K- K- K- K K -
--K
------- Si
Al+3 and K+ substitute for Si+4 (tetrahedral sheet)
Al
weathering at edges = release of K+
Si
very limited expansion -------
medium cation adsorption
limited internal surface
properties between kaolinite and vermiculite
Figure 7) 2:1 non expanding clays

Clay Types

 Chlorites :
 Mg replace K+ of illite
 Similar to illite

 Vermiculite :
 similar to Smectite
 more structured
=> limited expansion
 Rather large cation
adsorption

Figure 8) Clays comparison

Table 1) Summary of Properties :

Major Clay
particles Surface Area (m2/g) Interlayer Cation
properties Size (um)
External Internal Spacing (nm) Sorption
differences

Kaolinite 0.1-5.0 10-50 - 0.7 5-15

Smectite <1.0 70-150 500-700 1.0-2.0 85-110

Vermiculite 0.1- 5.0 50-100 450-600 1.0-1.4 100-120

Illite 0.1-2.0 50-100 5-100 1.0 15-40

Humus coatings - - - 100-300

What happens in soil

R-H+
R-H+

R-H+ + 4 Na+

R-H+

R-Na+

R-Na+
+ 4 H+
R-Na+
R-Na+
Figure 9) what happens in soil

Conclusion

From the previous discussion , it is obvious that the amount and type
of clay in the soil determines cation exchange capacity.

Non
Clays In addition, the type of clay also affects
cation exchange capacity. There are
Kaolinite
three types of aluminosilicate clays in
temperate region soils:

CEC , Shrinkage & Swelling
Illite
Montmorillonite

Figure 10) CEC comparison

How tight an ion is held .

1) Ion’s hydrated radius
 • Smaller radius = tighter hold

2) Magnitude of ion’s charge
 • Higher charge = tighter hold

Al3+ > Ca2+ > Mg2+ > K+, NH4 + > Na+ > Li+

How likely an ion species is to be adsorbed is determined by its
concentration in the soil solution
Higher concentration = more adsorption

High concentration of one ion species relative to another ion species can
supersede the effect of radius and charge

Chapter 3

SURFACE PROPERTIES
Surface Properties Relations

Surface Properties Relations

 There are some important correlations between some surface
properties of soil ,that have to be obvious .

 This Properties are :

Reason of differences

Montmorillonite
1m

Area : 18 m2 Area : 6 m2

Figure 11)

CEC & SSA Relationship

 Many researchers (e.g., Farrar and Coleman 1967; De Kimpe et al. 1979; Cihacek and
Bremner 1979; Newman 1983; Tiller and Smith 1990) have found :
 Surface Area to relate closely to Cation Exchange Capacity of soils.
 The surface activity of a clayey soil can be described in part by its CEC
or by its Specific Surface Area (Locat et al. 1984).

 Gill and Reaves (1957) presented SSA versus CEC with a correlation
coefficient of r2 = 0.95, which is similar to Mortland’s (1954) and Reeve’s
et al. (1954) findings. Farrar and Coleman (1967) presented results for
19 British Clays, which show a relatively
linear correlation between CEC and SSA.

 All of these equations can be found in Table 2 .

Table 2) Equations between CEC and SSA

Correlation Equations for Relationships Between CEC and Surface Area .

CEC=0.15SA-1.99 Southestern US Clay Gill and Reaves (1957)

CEC=0.28SA+2 British Clay Soils Farrar and Coleman (1967)

CEC=0.12SA+3.23 Israel soils Banin and Amiel (1970)

CEC=0.14SA+3.6 Osaka Bay Clay Tanaka (1999)

Figure 12) SSA versus CEC

Correlation Between CECCEC and SSAClay Soils of Israel.
Correlation Between and SSA for for Osaka Bay Clay.
(after Banin and Amiel 1970)
(after Tanaka 1999)

Figure 13) CF versus CEC

Relationship Between Cation Exchange Capacity and Clay Fraction.
Relationship between Surface Area and Clay Fraction for
Sensitive Canadian Clays. (after Locat et al. 1984)
(after Davidson et al. 1952)

Total surface area of different clays

According to this chart it is expected to cation exchange capacity
have an increasing trend from montmorillonit to kaolinite .

Kaolinite
0 50

Illite
600
100

Montmori
llonite
700
150
0
100
200
300
400
500
600
700
800
900 M2/g
Figure 16) Surface area of clays Internal External

Figure 14) Cation activity chart

Cation Activity Chart (after Kolbuszewski et al. 1965)

Chapter 4

ENGINEERING PROPERTIES
How the surface properties affect on soil physical
properties

Introduction

 Many properties of the fine-grained soils
are attributed to cation exchange, which
is a surface phenomenon .
 By replacing the existing cations in the
exchange complex, several improvements
can be effected in the soil properties.
 These beneficial changes are in the form
of reduction in plasticity, increase in the
strength, and reduction in the
compressibility. Figure 11) Lime Stabilization

The addition of lime to a soil supplies an excess of calcium ions, and cation
exchange can take place with divalent calcium, Ca+2 replacing all other
monovalent cations. The base exchange phenomenon has been used by
several investigators to explain the effects of chemical stabilization.
(K. Mathew 1997)

Diagram

Following previous session ,some
1: Atterberg Limits soil engineering properties
changes that found to be related
2: Dispersion ,directly or not ,with Cation
Exchange process are discussed
3: Hydraulic conductivity

4: Swelling Potential

5: Compressibility

6: Consoildation

1 : Atterberg Limits

 Sridharan et al. (1975) tested seven natural soils containing
montmorillonite as the dominant clay mineral and showed the
relationship between the Atterberg limits and Clay Fraction
(CF), SSA and CEC. The Liquid Limit versus CEC shows somewhat
of a linear trend, as indicated in Figure 19.
LL%

CEC
Figure 15) CEC versus LL% (Sridharan et al.1975)

Figure 16) LL versus CEC

Relationship Between Cation Exchange Capacity and Liquid Limit.

Figure 17) PL versus CEC

 This Slide Removed For More Reviews…

Figure 18) IP versus CEC

Relationship Between Cation Exchange Capacity and Plasticity Index

Figure 19) SL versus CEC

Relationship Between Cation Exchange Capacity and Shrinkage Limit.

Shrinkage Limit

 The shrinkage of clay soils is often said to depend not only on the
amount of clay, but also on its nature (Greene-Kelly 1974).
 Montmorillonitic soils = high water adsorption = high shrinkage
(Smith 1959)

Clay %
optimum clay content (Sridharan 1998).
30 and 50 %.

Table 3) Equations between PL , LL & SA

The Plastic and Liquid limit has been highly correlated with CEC and
Specific Surface Area (Smith et al. 1985; Gill and Reaves 1957; Farrar and
Coleman 1967; Odell et al. 1960), as seen in Table 3 .

Correlation Equations for Relationships Between PL ,LL ,and SA
CEC=0.55LL-12.2 British Clay Soils Farrar and Coleman (1967)
CEC=1.74LL-38.15 Clays from Israel Smith et al. (1985)
CEC=3.57PL-61.3 Clays from Israel Smith et al. (1985)
PL=0.43SAext.+16.95 African/Georgia/Missoury Hammel et al. (1983)
PL=0.064SA+16.60 Clays from Israel Smith et al. (1985)

2: Dispersion

 Surface area may also play a significant role in controlling the behavior
of dispersive clays through surface charge properties (e.g., Heinzen et al.
1977; Harmse et al. 1988; Sridharan et al. 1992; Bell et al. 1994).

Sodic soils are typically highly dispersive.

 Sodic soils have a high concentration of exchangeable Na+ ,therefore
much of the negative charge on the clay is neutralized by Na+, creating
a thick layer of positive charge that may prevent clay particles from
flocculating.
----------
+ + + + + + + +
---------- + + + + + + + +
+ + + + + + + +
2+ 2+ 2+ + + + + + + + +
2+ 2+ 2+ + + + + + + + +
------------- -------------

3: Hydraulic conductivity

 A laboratory study of the hydraulic conductivity (HC) of a marine clay
with monovalent, divalent and trivalent cations revealed large
differences in HC .

 RAO et all 1995 suggests that HC is significantly affected by the valency
and size of the adsorbed cations .

An increase in the valency of the adsorbed cations Higher HC
For a constant valency
An increase in the hydrated radius of the adsorbed cations Lower HC

 As per Ahmed et al (1969) and Quirk and Schofield (1955) HC is related
to exchangeable cations in the following order
 Ca = Mg > K > Na

4: Swelling Potential

 The more montmorillonite in the mixture, the more internal
surface and the surface area.
 As the surface area increases, the swelling potential increases
 De Bruyn et al. (1957) presented results and a classification of
various soils using Specific Surface Area and moisture contents.
His criteria state that soils with :

TSSA < 70 m2/g & w % < 3% non-expansive (good) .
TSSA > 300 m2/g & w % > 10% expansive (bad) .

Figure 21) Swelling versus SSA

Swelling

Specific Surface Area

(De Bruyn et al ,1957)

5: Compressibility

It has been established that the thickness of the double layer is sensitive
to changes in cations present on the surface (Van Olphen 1963).

The divalent and trivalent cations in the adsorbed complex of clayey soil
are known to reduce the thickness of the diffuse double layer by one-half
and one-third. respectively (Mitchell 1976)

An increase in valency leads to a reduction in compressibility , and at a
constant valency an increase in the hydrated radii of the adsorbed
cations resulted in an increase in compressibility. Further, it has been
found that preconsolidation pressure increases with valency of the
cations.(K. Mathew 1997).

Figure 22)Cc versus SSA

(De Bruyn et al ,1957)

References :
 AMY B. CERATO ;2003 ; INFLUENCE OF SPECIFIC SURFACE  Greene-Kelly, R. 1974. Shrinkage of Clay Soils: A Statistical
AREA ON GEOTECHNICAL CHARACTERISTICS OF FINE- Correlation with Other Soil Properties .
GRAINED SOILS.  Smith R.M. 1959. Some Structural Relationships of Texas
 Paul K. Mathew and S. Narasimha Rao ; 1997 ; EFFECT OF LIME Blackland Soils with Special Attention to Shrinkage and
ON CATION EXCHANGE CAPACITY OF MARINE CLAY . Swelling .
 Paul K. Mathew· and S. Narasimha Raoz ;1997 ; INFLUENCE OF  Sridharan, A. and Prakash, K. 1998. Mechanism Controlling the
CATIONS ON COMPRESSIBILITY BEHAVIOR OF A MARINE CLAY Shrinkage Limit of Soils.
 S. NARASIMHA RAO AND PAUL K. MATHEW ;1999 ; EFFECTS  Sridharan, A., and Nagaraj, H.B. 2000. Compressibility
OF EXCHANGEABLE CATIONS ON HYDRAULIC CONDUCTIVITY Behaviour of Remoulded, Fine-Grained Soils and Correlation
OF A MARINE CLAY . With Index Properties .
 Paul K. Mathew! and S. Narasimha Rao2 ;1997 ; EFFECT OF LIME  Smith, C.W., Hadas, A., Dan, J., and Koyumdjisky, H., 1985.
ON CATION EXCHANGE CAPACITY OF MARINE CLAY . Shrinkage and Atterberg Limits Relation to Other Properties of
 EWA T. STI~PKOWSKA ;1989 ; Aspects of the Clay/ Electrolyte/ Principle Soil Types in Israel.
Water System with  Grabowska-Olszewska, B. 1970. Physical Properties of Clay Soils
 Special Reference to the Geotechnical Properties of Clays. as a Function of Their Specific Surface.
 Sridharan, A. and Rao, G.V. 1975. Mechanisms Controlling the  Heinzen, R.T. and Arulanandan, K., 1977. Factors Influencing
Liquid Limits of Clays. Dispersive Clays and Methods of Identification.
 Locat, J. Lefebvre, G, and Ballivy, G., 1984.  Tanaka, H. and Locat J. 1999. A Microstructural Investigation of
Mineralogy, Chemistry, and Physical Property Interrelationships Osaka Bay Clay .
of Some Sensitive Clays from Eastern Canada .  Banin, A., and Amiel, A. 1970. A Correlative Study of The
 SHAINBERG, N. ALPEROVITCH, AND R. KEREN; 1988 ; EFFECT Chemical and Physical Properties of a Group of Natural Soils of
OF MAGNESIUM ON THE HYDRAULIC CONDUCTIVITY OF Na- Israel.
SMECTITE-SAND MIXTURES  Kolbuszewski, J., Birch, N., and Shojobi, J.O. (1965) Keuper Marl
 Uehara, G. 1982. Soil Science for the Tropics . Research.
 Manja Kurecic and Majda Sfiligoj Smole ;2012 ; Polymer  Davidson, D.T. and Sheeler, J.B., 1952. Clay Fraction in
Nanocomposite Hydrogels for Water Purification . Engineering Soils: Influence of Amount on Properties.
 Angelo Vaccari ;1998 ; Preparation and catalytic properties of  Işık Yilmaz ⁎, Berrin Civelekoglu ;2009; Gypsum: An additive for
cationic and anionic clays . stabilization of swelling clay soils .
 College of Agriculture and Life Sciences ,Cornell University ; 2007  Yeliz Yukselen-Aksoy a,, Abidin Kaya ;2010 ; Method
; Cation Exchange Capacity dependency of relationships between specific surface area and
soil physicochemical properties

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Engineering Geology Department
, Tarbiat Modares University
,Tehran Iran .
Shahram.maghami@modares.ac.ir

Cation exchange and it’s role on soil behaviour

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