Cation exchange and it’s role on soil behaviour

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Cation Exchange And It’s Role On Soil Behavior

Autumn ,1391

Presented by Sh.Maghami Instructor : Dr.Nikoodel

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

What expect you to know

Cation

Cation Exchange & Cation Echange Capacity (CEC)

What is the relation of surface properties

of the soil

CEC Agents and whatIs their relationship

to soil

How CEC effecton soil properties ?

What properties affected ?

Describing the clay structures and the differences between those .

Cation Exchange

How the soil propertiescould related to each other

INTRODUCTION Definitions

Cation ExchangeCation Exchange Capacity

Why do soils have CEC

Chapter 1

23

4

Chapter 1

Definitions

Soil colloids will attract and hold positivelycharged ions to their surface Replacementof 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 capable of holding, at a given pH value, available for exchange with the soil solution (meq+/100g)

Cation Exchange

Cation Exchange Capacity (CEC)

Chapter 1

23

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)

much greater capacity to hold

cations .

Low CEC

Chapter 1

23

4

Sand Clay

No charge. Negative charge. Does not retain cations Attracts and retains

cations

Si2O4 SiAlO4-

Clay & Humus : Cation warehouse or reservoir of the soil

CLAY STRUCTUREHow do clays Have a CECIsomorphous substitutionFoundations and differences of Clays structures

1:1 Clays2:1 Clays

Some properties of clay minerals

1

Chapter 23

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

1

Chapter 23

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

Tetrahedron - SiO4 Octahedron - Al(OH)6

Figure 2)

1

Chapter 23

4

How clays are forming basically ?

(a) Tetrahedral sheet (b) Octahedral sheet

Si Al

Figure 3) Sheets Formation

Sheets and unit layers

Sharing of O or OH groups

1

Chapter 23

4

How clays are forming basically ?

Si

Al

Exposed Oxygen

Shared OxygenHydrogen

Balance Oxygen Charge

Figure 4) Clays unit structure

1

Chapter 23

4

Clay Types

A) 1:1 Type Minerals Mostly Kaolinite

Si

Al

Si

Al

Hydrogen bonding between layers. This gives 1:1 type minerals a very rigid structure .

7Ao

Fixed lattice type No interlayer activity No shrink-swell Only external surface

Well crystallizedLow cation adsorption Little isomorphous substitutionLarger particle size (0.1 - 5 m m)

Figure 5) 1:1 clays

1

Chapter 23

4

Clay Types

B) 2:1 Type Minerals1. Expanding lattice

Smectite group Mostly Montmorillonite

Si

Al

Si

Si

Al

Si

Ca H2O

18Ao

Mg Freely expanding Water in interlayer Large shrink-swell Small size Poorly crystallizedLarge internal surfaceIsomorphous substitution Large cation adsorption Adsorbed cations in interlayer Figure 6) 2:1 expanding clays

1

Chapter 23

4

Clay Types

2. Non-expanding lattice Fine-grained micas or illite

Some distribution of Al for Si in the tetrahedral layers leads to permanent net negative charge Al+3 and K+ substitute for Si+4 (tetrahedral

sheet)

weathering at edges = release of K+

very limited expansionmedium cation adsorption limited internal surfaceproperties between kaolinite and

vermiculite

Si

Al

SiSi

Al

Si

K- - - - - - -- - - - - - -

- - - - - - -

- - - - - - -

10Ao

KKKKKK

Figure 7) 2:1 non expanding clays

1

Chapter 23

4

Clay Types

Figure 8) Clays comparison

Chlorites : Mg replace K+ of illite Similar to illite

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

adsorption

1

Chapter 23

4

Table 1) Summary of Properties :

  Size (um)Surface Area (m2/g)

External Internal

InterlayerSpacing

(nm)

CationSorption

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

Major Clay particles properties differences

1

Chapter 23

4

R-H+

R-H+

R-H+

R-H+

+ 4 Na+

R-Na+

R-Na+

R-Na+

R-Na+

+ 4 H+

Figure 9) what happens in soil

What happens in soil1

Chapter 23

4

Conclusion

CEC , Shrinkage & Swelling

Montmorillonite Illite

Kaolinite

Non Clays

From the previous discussion , it is obvious that the amount and type 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:

Figure 10) CEC comparison

1

Chapter 23

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

1

Chapter 23

4

SURFACE PROPERTIESSurface Properties Relations

1

2Chapter 3

4

Chapter 3

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

1

2Chapter 3

4

Reason of differences

Figure 11)

Area : 6 m2Area : 18 m2

1 m

Montmorillonite

1

2Chapter 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 .

1

2Chapter 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 .

1

2Chapter 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)

1

2Chapter 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)

1

2Chapter 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 .

Montmorillonite

Illite

Kaolinite

0100

200300

400500

600700

800900

700

600

0

150

100

50

Internal ExternalFigure 16) Surface area of clays

1

2Chapter 3

4

M2/g

Figure 14) Cation activity chart

Cation Activity Chart (after Kolbuszewski et al. 1965)

1

2Chapter 3

4

ENGINEERING PROPERTIESHow the surface properties affect on soil physical properties

1

23

Chapter 4

Chapter 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.

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)

Figure 11) Lime Stabilization

1

2Chapter 3

4

Diagram

4: Swelling Potential

3: Hydraulic conductivity

Following previous session ,some soil engineering properties changes that found to be related ,directly or not ,with Cation Exchange process are discussed

5: Compressibility

6: Consoildation

1: Atterberg Limits

Soil Engineering Properties

2: Dispersion

1

23

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.

CEC

LL%

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

1

23

Chapter 4

Figure 16) LL versus CEC

Relationship Between Cation Exchange Capacity and Liquid Limit.

(after Davidson et al. 1952)

1

23

Chapter 4

Figure 17) PL versus CEC1

23

Chapter 4

This Slide Removed For More Reviews…

Figure 18) IP versus CEC

Relationship Between Cation Exchange Capacity and Plasticity Index

(after Davidson et al. 1952)

1

23

Chapter 4

Figure 19) SL versus CEC

Relationship Between Cation Exchange Capacity and Shrinkage Limit.

(after Davidson et al. 1952)

1

23

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)

optimum clay content (Sridharan 1998).Clay %

SL

30 and 50 %.

1

23

Chapter 4

Table 3) Equations between PL , LL & 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)

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

1

23

Chapter 4

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+

2: Dispersion1

23

Chapter 4

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

3: Hydraulic conductivity 1

23

Chapter 4

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) .

4: Swelling Potential1

23

Chapter 4

Figure 21) Swelling versus SSA

Specific Surface Area

Sw

ellin

g

(De Bruyn et al ,1957)

1

23

Chapter 4

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).

5: Compressibility 1

23

Chapter 4

Figure 22)Cc versus SSA

1

23

Chapter 4

(De Bruyn et al ,1957)

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. 1975. Mechanisms Controlling the Liquid Limits of Clays.

Locat, J. Lefebvre, G, and Ballivy, G., 1984. 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. 1982. 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. 1974. Shrinkage of Clay Soils: A Statistical Correlation with Other Soil Properties .

Smith R.M. 1959. Some Structural Relationships of Texas Blackland Soils with Special Attention to Shrinkage and Swelling .

Sridharan, A. and Prakash, K. 1998. Mechanism Controlling the Shrinkage Limit of Soils.

Sridharan, A., and Nagaraj, H.B. 2000. Compressibility Behaviour of Remoulded, Fine-Grained Soils and Correlation With Index Properties .

Smith, C.W., Hadas, A., Dan, J., and Koyumdjisky, H., 1985. Shrinkage and Atterberg Limits Relation to Other Properties of Principle Soil Types in Israel.

Grabowska-Olszewska, B. 1970. Physical Properties of Clay Soils as a Function of Their Specific Surface.

Heinzen, R.T. and Arulanandan, K., 1977. Factors Influencing Dispersive Clays and Methods of Identification.

Tanaka, H. and Locat J. 1999. A Microstructural Investigation of Osaka Bay Clay .

Banin, A., and Amiel, A. 1970. 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., 1952. 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

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