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Cation exchange and it’s role on soil behaviour
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Transcript of Cation exchange and it’s role on soil behaviour
LOGO
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
LOGO
Engineering Geology Department , Tarbiat Modares University ,Tehran Iran . [email protected]