Cation exchange and it’s role on soil behaviour
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  • charges from broken edges and hydroxyls are variable and pH-dependent charges from isomorphous substitution are permanent and do not vary with pH
  • +4Na+
  • 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.
  • Relationship between Surface Area and Clay Fraction for Sensitive Canadian Clays. (after Locat et al. 1984)

Cation exchange and it’s role on soil behaviour Cation exchange and it’s role on soil behaviour Presentation Transcript

  • LOGOCation Exchange And It’s Role On Soil BehaviorPresented by Sh.MaghamiInstructor : 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
  • DefinitionsSoil colloids will attract and hold positivelycharged ions to their surface Replacement Cation Exchangeof 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 bythe amount of clay and/or humus that is present . Clay & Humus : Cation warehouse or reservoir of the soilSandy soils with very little OM Low CECClay 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 andoxygen (Quartz), the particle wouldnot 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 chargeFigure 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 ChargeFigure 4) Clays unit structure
  • Clay Types A) 1:1 Type Minerals Si Mostly Kaolinite Al 7Ao Si AlHydrogen bonding between layers. This gives 1:1 Figure 5) 1:1 claystype 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 SiSome distribution of Al for Si in the tetrahedrallayers 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 Clayparticles Surface Area (m2/g) Interlayer Cationproperties Size (um) External Internal Spacing (nm) SorptiondifferencesKaolinite 0.1-5.0 10-50 - 0.7 5-15Smectite <1.0 70-150 500-700 1.0-2.0 85-110Vermiculite 0.1- 5.0 50-100 450-600 1.0-1.4 100-120Illite 0.1-2.0 50-100 5-100 1.0 15-40Humus 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 MontmorilloniteFigure 10) CEC comparison
  • How tight an ion is held .1) Ion’s hydrated radius  • Smaller radius = tighter hold2) 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 adsorptionHigh 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 claysAccording 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/gFigure 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. (after Davidson et al. 1952)
  • Figure 17) PL versus CEC  This Slide Removed For More Reviews…
  • Figure 18) IP versus CEC Relationship Between Cation Exchange Capacity and Plasticity Index (after Davidson et al. 1952)
  • Figure 19) SL versus CEC Relationship Between Cation Exchange Capacity and Shrinkage Limit. (after Davidson et al. 1952)
  • 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 & SAThe Plastic and Liquid limit has been highly correlated with CEC andSpecific Surface Area (Smith et al. 1985; Gill and Reaves 1957; Farrar andColeman 1967; Odell et al. 1960), as seen in Table 3 . Correlation Equations for Relationships Between PL ,LL ,and SACEC=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
  • LOGOEngineering Geology Department, Tarbiat Modares University,Tehran Iran .Shahram.maghami@modares.ac.ir