1. Cation Exchange And It’s Role On Soil Behavior
Presented by Sh.Maghami
Instructor : Dr.Nikoodel
Autumn ,1391

2. Contents Chapter 1) Introduction Chapter 2) Clay Structure
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

3. Cation What expect you to know Cation Exchange How the soil properties
could related to each other
Cation Exchange &
Cation Echange Capacity (CEC)
How CEC effect
on soil properties ?
What properties affected ?
CEC Agents and what
Is their relationship
to soil
Cation
What is the relation
of surface properties
of the soil
Describing the clay structures
and the differences between those .

4. Introduction Chapter 1 Definitions Why do soils have CEC2 3 4
Introduction
Definitions
Cation Exchange
Cation Exchange Capacity
Why do soils have CEC

5. Cation Exchange Cation Exchange Capacity (CEC)
Chapter 1 2 3 4
Definitions
Soil colloids will attract and hold positively
charged ions to their surface Replacement
of one ion for another from solution
For every cation that is adsorbed, one goes back into soil solution
Cation Exchange
In soil science the maximum quantity of total cations , of any class, that a soil is capable of holding, at a given pH value, available for exchange with the soil solution (meq+/100g)
Cation Exchange Capacity
(CEC)

6. Chapter 1 2 3 4
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 .
Sandy soils with very little OM
Clay soils with high levels of OM
(negative soil particles attract the positive cations)
Clay & Humus : Cation warehouse or reservoir of the soil
Low CEC
much greater capacity to hold cations .
Sand Clay
No charge Negative charge.
Does not retain cations Attracts and retains cations
Si2O4
SiAlO4-

7. Clay Structure How do clays Have a CEC Isomorphous substitution1
Chapter 2 3 4
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

8. 1
Chapter 2 3 4
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

9. Isomorphous substitution1
Chapter 2 3 4
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

10. How clays are forming basically ?1
Chapter 2 3 4
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

11. How clays are forming basically ?1
Chapter 2 3 4
How clays are forming basically ?
Exposed Oxygen Si Al
Shared Oxygen
Hydrogen
Balance Oxygen Charge
Figure 4) Clays unit structure

12. A) 1:1 Type Minerals Clay Types Mostly Kaolinite Si Al 7Ao
Chapter 2 3 4
Clay Types
A) 1:1 Type Minerals
Mostly Kaolinite Si Al
7Ao
Hydrogen bonding between layers. This gives 1:1 type minerals a very rigid structure .
Figure 5) 1:1 clays
Well crystallized
Low cation adsorption
Little isomorphous substitution
Larger particle size ( m m)
Fixed lattice type
No interlayer activity
No shrink-swell
Only external surface

13. B) 2:1 Type Minerals 1. Expanding lattice Clay Types Smectite group
Chapter 2 3 4
Clay Types
B) 2:1 Type Minerals
1. Expanding lattice
Smectite group
Mostly Montmorillonite Si Al Ca
H2O
18Ao Mg
Freely expanding
Water in interlayer
Large shrink-swell
Small size
Poorly crystallized
Large internal surface
Isomorphous substitution
Large cation adsorption
Adsorbed cations in interlayer
Figure 6) 2:1 expanding clays

14. - - - - - - - - - - - - - - - - - - - - - - - - - - - -1
Chapter 2 3 4
Clay Types
2. Non-expanding lattice
Fine-grained micas or illite Si 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)
weathering at edges = release of K+
very limited expansion
medium cation adsorption
limited internal surface
properties between kaolinite and vermiculite Al
charges from broken edges and hydroxyls are variable and pH-dependent
charges from isomorphous substitution are permanent and do not vary with pH Si
Figure 7) 2:1 non expanding clays

15. Vermiculite : Chlorites : Clay Types similar to Smectite1
Chapter 2 3 4
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

16. Table 1) Summary of Properties :
Chapter 2 3 4
Table 1) Summary of Properties :
Size (um)
Surface Area (m2/g)
External Internal
Interlayer
Spacing (nm)
Cation
Sorption
Kaolinite
10-50 -
0.7
5-15
Smectite
<1.0
70-150
85-110
Vermiculite
50-100
Illite
5-100
1.0
15-40
Humus
coatings
Major Clay particles properties differences

17. + 4 Na+ + 4 H+ What happens in soil R-H+ R-H+ R-H+ R-H+ R-Na+ R-Na+1
Chapter 2 3 4
What happens in soil
R-H+
R-H+
+ 4 Na+
R-H+
R-H+
R-Na+
+4Na+
R-Na+
+ 4 H+
R-Na+
R-Na+
Figure 9) what happens in soil

18. CEC , Shrinkage & Swelling1
Chapter 2 3 4
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 three types of aluminosilicate clays in temperate region soils:
Kaolinite
Illite
CEC , Shrinkage & Swelling
Amount and kind of clay. From the previous discussion , it is obvious that the amount of clay in the soil determines cation exchange capacity. In addition, the type of clay also affects cation exchange capacity. There are three types of aluminosilicate clays in temperate region soils: Kaolinite, illite and montmorillonite groups. Due to differences in their crystalline structure and composition the kaolinitic group has low cation exchange capacity, illite as intermediate and the montmorillonite group has the greatest cation exchange capacity. Each soil, because of its parent material or the mode of formation, will be dominated by one type of clay or perhaps a mixture. The montmorillonite type also has the characteristic of a high degree of shrinkage and swelling upon drying and wetting. This is a distinct disadvantage in urban soils where construction is a major activity. It also reduces slope stability.
Montmorillonite
Figure 10) CEC comparison

19. 1) Ion’s hydrated radius
Chapter 2 3 4
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
Activity

20. Surface Properties Chapter 3 Surface Properties Relations 1 24
Surface Properties
Surface Properties Relations

21. Surface Properties Relations1 2
Chapter 3 4
Surface Properties Relations
There are some important correlations between some surface properties of soil ,that have to be obvious .
This Properties are :
Clay Fractures Content
Clay Mineral Type
Specific Surface Area
Cation Exchange Capacity

22. Reason of differences Montmorillonite Area : 6 m2 Area : 18 m2 1 m
Chapter 3 4
Reason of differences
Montmorillonite
Area : 6 m2
Area : 18 m2
1 m
Figure 11)

23. Surface Area to relate closely to Cation Exchange Capacity of soils. 1 2
Chapter 3 4
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 .

24. Table 2) Equations between CEC and SSA1 2
Chapter 3 4
Table 2) Equations between CEC and SSA
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)
Correlation Equations for Relationships Between CEC and Surface Area .

25. 1 2
Chapter 3 4
Figure 12) SSA versus CEC
Correlation Between CEC and SSA for Osaka Bay Clay.
(after Tanaka 1999)
Correlation Between CEC and SSA for Clay Soils of Israel.
(after Banin and Amiel 1970)

26. Relationship Between Cation Exchange Capacity and Clay Fraction.1 2
Chapter 3 4
Figure 13) CF versus CEC
Relationship between Surface Area and Clay Fraction for Sensitive
Canadian Clays. (after Locat et al. 1984)
Relationship Between Cation Exchange Capacity and Clay Fraction.
(after Davidson et al. 1952)
Relationship between Surface Area and Clay Fraction for Sensitive Canadian Clays. (after Locat et al. 1984)

27. Total surface area of different clays1 2
Chapter 3 4
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 .
M2/g
Figure 16) Surface area of clays

28. Figure 14) Cation activity chart2
Chapter 3 4
Figure 14) Cation activity chart
Cation Activity Chart (after Kolbuszewski et al. 1965)

29. Engineering Properties
Chapter 4 1 2 3
Chapter 4
Engineering Properties
How the surface properties affect on soil physical properties

30. 1 2
Chapter 3 4
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)

31. Soil Engineering Properties1 2 3
Chapter 4
Diagram
Following previous session ,some soil engineering properties changes that found to be related ,directly or not ,with Cation Exchange process are discussed
1: Atterberg Limits
2: Dispersion
3: Hydraulic conductivity
Soil Engineering Properties
4: Swelling Potential
5: Compressibility
6: Consoildation

32. 1 2 3
Chapter 4
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)

33. Relationship Between Cation Exchange Capacity and Liquid Limit.1 2 3
Chapter 4
Figure 16) LL versus CEC
Relationship Between Cation Exchange Capacity and Liquid Limit.
(after Davidson et al. 1952)

34. This Slide Removed For More Reviews…1 2 3
Chapter 4
Figure 17) PL versus CEC
This Slide Removed For More Reviews…

35. Relationship Between Cation Exchange Capacity and Plasticity Index1 2 3
Chapter 4
Figure 18) IP versus CEC
Relationship Between Cation Exchange Capacity and Plasticity Index
(after Davidson et al. 1952)

36. Relationship Between Cation Exchange Capacity and Shrinkage Limit.1 2 3
Chapter 4
Figure 19) SL versus CEC
Relationship Between Cation Exchange Capacity and Shrinkage Limit.
(after Davidson et al. 1952)

37. Montmorillonitic soils = high water adsorption = high shrinkage 1 2 3
Chapter 4
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 % SL
optimum clay content (Sridharan 1998).
30 and 50 %.

38. Table 3) Equations between PL , LL & SA1 2 3
Chapter 4
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 .
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
PL=0.43SAext
African/Georgia/Missoury
Hammel et al. (1983)
PL=0.064SA+16.60
Correlation Equations for Relationships Between PL ,LL ,and SA

39. Sodic soils are typically highly dispersive.1 2 3
Chapter 4
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.

40. 3: Hydraulic conductivity1 2 3
Chapter 4
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

41. As the surface area increases, the swelling potential increases1 2 3
Chapter 4
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) .

42. Figure 21) Swelling versus SSA3
Chapter 4
Figure 21) Swelling versus SSA
Swelling
Specific Surface Area
(De Bruyn et al ,1957)

43. 1 2 3
Chapter 4
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).

44. 1 2 3
Chapter 4
Figure 22)Cc versus SSA
(De Bruyn et al ,1957)

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

46. Thanks For Your Attention .
Engineering Geology Department , Tarbiat Modares University ,Tehran Iran .