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Environmental characteristics of clay and clay-based minerals

Environmental characteristics of clay and clay-based minerals GeoloGy, ecoloGy, and landscapes, 2017 Vol . 1, no . 3, 155–161 https://doi.org/10.1080/24749508.2017.1361128 INWASCON OPEN ACCESS a b c Suzanne Christine Aboudi Mana , Marlia Mohd Hanafiah and Ahmed Jalal Khan Chowdhury a b d epartment of Geology, Faculty of s cience, University of Malaya, Kuala l umpur, Malaysia; Faculty of s cience and Technology, s chool of environmental and natural Resource s ciences, national University of Malaysia, UKM, Bangi, Malaysia; Kulliyah of s cience, International Islamic University, Kuantan, Malaysia ABSTRACT ARTICLE HISTORY Received 6 February 2017 Clay is an inherently occurring material constituted with fined-grained mineral. The minerals a ccepted 13 July 2017 are generally less than 2 microns and occur to be plastic in water content which solidify when dried. In the earth surface, clay represents the most available mineral and forms rocks known KEYWORDS as shale and is the major component of sedimentary rocks. The small size of the particles and clay; environmental their unique crystal structures give clay materials special properties. These properties include: characteristics; clay-based cation exchange capabilities, plastic behaviour when wet, catalytic abilities, swelling behaviour, minerals and low permeability. They give to clay and clay-based minerals higher application in many industries and processes. To acknowledge all the features of clay and clay-based minerals, the understanding of their properties especially the cation exchange capability which affects the mechanical and physical properties of the clay is important, and also to acquire information about the crystal structure of clay mineral in general and montmorillonite especially. The purpose of this laboratory is to illustrate the importance of chemistry on the physical properties of montmorillonite, the clay mineral most often used to isolate dangerous waste materials from the environment. 1. Introduction clay and clay-based mineral varies dependently of the environment. Weathering of rocks and soil is the pri- Among the world’s most important and useful industrial mary way that clays and clay minerals form at the Earth’s minerals, clay minerals are of great significance. e Th y surface today. The weathering process involves physical are used in a number of geological applications such as disaggregation and chemical decomposition that change stratigraphic correlations, indicators of environments of original minerals to clay minerals. Clay and clay-based deposition and temperature for generation of hydrocar- minerals can be formed by the alteration of pre-existing bons. In agriculture, the clay minerals are a major com- mineral by weathering: for example, weathering boul- ponent of soils and determinants of soil properties. The ders on a hillside, sediments on sea or lake bottoms, clay minerals are important in construction where they deeply buried sediments containing pore water, and are a major constituent in brick and tile. The physical rocks in contact with water heated by magma (molten and chemical properties of clay minerals determine their rock) are to form relatively pure clay deposits that are utilization in the process industries (Table 1). of economic interest known as bentonites and primarily Up to date, clay and clay-based minerals need montmorillonite. improvement due to their utilization and demand. Immediately aer t ft heir formation, processes of Processing techniques need to be improved and new transport and deposition through gradual mechanisms equipment needs to be available so that improved clay of diagenesis excluding surficial alteration (which is mineral products are available. Pillared clays and nano- weathering) also favour in-place alteration of clay and composites will become important. Further develop- clay-based mineral to more stable forms, which occurs, ments in organoclay technology and surface treatments for example, when minerals stable in one depositional will provide new usage for these special clays. environment are exposed to another by burial and com- Clays and clay minerals occur under a fairly limited paction. Common silicate materials such as quartz, range of geologic conditions. e Th environments of for - feldspars, and volcanic glasses, as well as carbonates, mation include soil horizons, continental and marine non-crystalline iron oxides, and primary clay minerals, sediments, geothermal fields, volcanic deposits, and are transformed during diagenesis into more stable clay weathering rock formations. The cycle of formation of minerals mainly by dissolution and recrystallization. CONTACT suzanne christine aboudi Mana manachristina@siswa.um.edu.my © 2017 The a uthor(s). published by Informa UK limited, trading as Taylor & Francis Group. This is an open a ccess article distributed under the terms of the creative c ommons a ttribution license (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. 156 S. C. ABOUDI MANA ET AL. Table 1. physical properties of original clay in a native land of This may be the solid bedrock or a non-lithified super - Tanjung Beringin langkat by p anjaitan (2014). ficial layer such as boulder clay resting on bedrock. The clay mineral deposit is geochemically and biochemically No Nature of soil Unit The original clay 1 specific gravity (Gs) – 2.66 controlled in the environment in which it exists natu- 2 plastic limit (pl) % 20.78 rally. Hence, deposit of a given type of clay has similar 3 shrinkage limit (sl) % 54.47 geologic characteristics which also have similar envi- 4 liquid limit (ll) % 40.23 5 plastic index (pI) % 19.43 ronmental signature that can be quantified by pertinent 6 sieve analysis % 52.30 field and laboratory data and summarized in geoenvi- 7 dry weight contents (γd maks) gr/cm 1.363 8 optimum moisture content % 21.00 ronmental models for clay deposit type (Du Bray, 1995). (Wopt) 2. Clay and clay-based minerals properties Undoubtedly, clays and clay minerals are critical 2.1. Clay minerals as electron acceptors and/or components of both ancient and modern sedimentary donors in organic reactions environments. So the initial type of rock, factors governing rock e e Th lectron-accepting and the electron-donating sites weathering and soil formation, the ratio of water to rock, of clay can be explained by the fact the electron acceptor the temperature, the presence of organisms and organic sites are aluminium at crystal edges and transition met- als in the lower valency state. The catalysed polymeriza - material, and the amount of time play an important tions involve the conversion of the organic molecule to a role in the types of clay minerals found in weathering reactive intermediate; hence, the clay mineral accepts an rocks, and thus strongly control how the properties of electron from the vinyl monomer and a radical cation is the weathered rock will abound under various climatic formed, where the organic compound gains an electron conditions (such as humid-tropical, dry-tropical, and and forms a radical anion. temperate conditions). e in Th hibition of polymerization processes involves the In order to outline a simple but efficient classification, conversion of reactive organic intermediate, such as free Grim classification is the most useful. This classification radicals, which has been formed by heat or radical initi- gives a rough idea of the differences between various ators, to non-reactive entities. An example of a thermal clay minerals and proposes their nomenclature. In this polymerization is illustrated by the loss of an electron from the free radical which gives a carbonium ion. classification, clay minerals are divided into four main groups: kaolinite group, illite group, smectite group, and In predicting the electron-accepting or electron-do- vermiculite. nating behaviour, colour reactions on clay minerals Geologic and geochemical information is necessary are useful for the reason that it similarly proceeds with mechanisms of polymerization reactions. For example, to establish environmental characteristics that ae ff ct the a blue reaction of benzidine: here there is one electron use of clays and clay minerals. Since clay minerals play transfer from the organic molecule to the electron-ac- important roles in environment protection, their envi- cepting sites in the mineral (aluminium edges, transi- ronmental characteristics allow them to be a barrier in tion metals in the higher valency state). the nature of inorganic contaminants distribution, such In order to understand the many abilities of electron as metals and metalloids like arsenic, iron, and lead, in exchange of clay minerals, masking the crystal edge clay-bearing rocks. These minerals have been used in the with polyphosphate destroys the electron-accepting disposal and storage of hazardous chemicals as well as properties of the crystal edges. This method is used to for remediation of polluted water. The use of clay min- assess the control of the reactivity of the mineral and erals as the adsorbents for the adsorption of various distinguish the crystal edge from the transition metal sites as electron-acceptor sites in the clay minerals. hazardous substances (heavy metals, dyes, antibiotics, (Solomon, 1968) biocide compounds, and other organic chemicals) has been widely studied by a large number of research- ers. So there is a need to reinforce information about 2.1.1. Ion exchange and cation exchange capacity current studies and discuss improvements that are to When erosion, transport, and deposition take place, being made to expand the knowledge of clay minerals clay minerals react to change in the environment. Ion and clay-based minerals. Certain clay minerals have the exchange, reconstruction of degraded mineral, and for- ability to catalyse the polymerization of some unsatu- mation of one type clay-based mineral from another or rated organic compounds and yet to inhibit polymer simpler substance appear as a result of those processes. formation from other closely related monomers. This Exchange reactions are dominated by physicochemical apparently contradictory behaviour of clay minerals is laws and depend upon the clay mineral, the nature, and known as electron-accepting and electron-donating sites ion population of the exchange sites and on the concentra- in the silicate layers. tion and the composition of the solution in which the clay e co Th mposition of clay is ae ff cted by the mineralog - mineral is found. However, the increase in salinity when ical and chemical compositions of the parent material. in a marine environment results in a decrease in the total GEOLOGY, ECOLOGY, AND LANDSCAPES 157 exchange capacities of clay mineral when clay enters the forces controlling the repulsive pressure are governed sea. So the crystal chemistry of clay mineral is considered by physicochemical swelling in clay minerals since the when exchange of cations takes place. Interlayer water cat- attractive forces by comparison are small within the ions and layer charge appear to be particularly important range of the external forces involved in the clay structure. in the understanding of selective adsorption and fixation Cations are attracted to external surfaces of clay minerals in the process of cation and ion exchange (Gillott, 2012). which are negatively charged and can also be drawn to internal surfaces of expandable minerals, so that clay 2.1.2. Swelling behaviour mineral properties and structure can be changed. e Th Clay mineral swelling is dependent on clay mineral type, sequence of replacement in clay minerals sites in nature the electrolyte concentration, and the nature of the cations of some principal cations is the same as their abundance in the solution. The swelling mechanism can be divided 2+ 2+ + + (Ca  > Mg  > K  > Na ). into mechanical and physicochemical processes. Through burial diagenesis, expandable layers are removed in the clay 3.1. Clay minerals classified by layer mineral structure such that inter and intralayer swelling of expandable clay mineral types can be expected to be at a Clay minerals can be described very simply by the stack- minimum in older rocks than in younger rocks. Mechanical ing of two kinds of layers: 1:1 layers and 2:1 layers. They swelling occurs in response to elastic and time-dependent are layered by silicate in which each layer in the structure stress unloading, which can be brought by man in digging in reality consists of two sublayers. e Th sublayer consists excavations or by nature in tectonic uplift and erosion because of octahedral coordinates and structural water in the the clay is free to expand in the vertical direction but not in form of hydroxyl groups. the horizontal direction. On the other side, physicochemical Anionic clays also known as layered double hydrox- swelling is governed by intrinsic effective stress which ides (LDHs) show a great example of the influence of clay commands the size disparity between larger, inter- layers on their cation–anion exchange capabilities. The aggregate voids and smaller intra-aggregate voids within clay intercalated structure and isomorphous replacement of mineral domains and between clay minerals themselves, all trivalent cations for a fraction of divalent cations leads those forces which exist in a clay–electrolyte system subject to positively charged host layers, where oxygen atoms to unloading aer wa ft ter had entered the system in response coordinate each metal cation, forming an octahedron. to mechanical cause (Taylor & Smith, 1986). Octahedra are composed of two-dimensional sheets formed by a wide range of interlayer anions, which then 2.1.3. Adsorptive and low permeability properties can constitute various kinds of anionic clay materials. As absorptive material, there are three ways clay minerals e co Th mputation model of anionic clay minerals by Yan and clay-based minerals can exert non-covalent adsorp- et al., 2008 in their layered double hydroxides (LDHs) tive power on various molecules from liquid to gaseous formula corroborated with previous work that the value states. Firstly, physical adsorption: there is non-ionic of the stoichiometry coefficient (X), the identities of the adsorption onto the surfaces of finely divided material n− interlayer anion (A ), and the intra-layer cation when (large surface areas of clay minerals are comprised in small they vary enable to produce a wide range of specific volumes), secondly ion exchange adsorption through tailor-made materials. To understand the electronic electrostatic interaction and exchange, and finally, the structure inside the LDHs is important for the stability inclusion of small molecules in pore or cavities, and par- formula of clay-based minerals. The electronic structure tial or complete exclusion of larger molecules by those of LDH materials is oen fir ft stly focused on proper - cavities through the zeolitic adsorption action. (Giese & ties related with the whole bulk of the LDHs crystal in van Oss, 2002). Permeability properties of clay miner- its entire extension in the periodicity coupled with ab als can be explained by the type and distribution of the initio plane-wave density functional theory or linear clay minerals within the pore system. Generally, in rocks combination of atomic orbitals methods and secondly which are predominantly argillaceous, permeability is low. to predict the geometry of layer structure and the struc- e min Th eralogy of different types of rocks semi-perme- tural and chemical properties are investigated through able in nature gives a noticeably different set of chemical semi-empirical molecular orbital method. So Hong Yan parameters, whereas low to medium permeability can be et al. (2008) concluded in their work that the distorsion assimilated to a closed system where rocks and uid a fl re angle of an octahedral coordinated hexahydrated cat- effectively part of the same physicochemical unit. ion plays a significant role in the formation of anionic clay layers. Also, the structural properties of the hex- 3. Clay mineral classified by its structure and ahydrated cations such as metal–oxygen bond length, layer type O–M–O bond angle distorsion, binding energy, and e in Th teraction between clay minerals depends on their valence electronic configuration ligand field are in great structure. This structure controls the behaviour of clay agreement with the construction of anionic clay layers. 2+ minerals’ double layer which is the primary generator Therefore, metal cations with similar ion size to Mg of repulsive pressure in the double layer model. The are able to form the canonical hexahydrated structure 158 S. C. ABOUDI MANA ET AL. with the distorsion angle θ smaller than 1° which are transformations taking place in the surface structure of easily integrated into LDH layers on the basis of DFT clay minerals. theoretical calculation results. Adding ion size rule to 3.2.2. Layer charge this precept can give more insight into the application Either electrically neutral or negatively charged structure of layered double hydroxides (Yan, Wei, Ma, Evans, & of clay mineral may occur as a result of the tetrahedral Duan, 2010) (Figure 1). and octahedral sheets’ junction in clay. The electrical neutral charge exists if the octahedral sheet contains tri- 3.2. Clay minerals classified by the structure valent cations in two octahedral sites, with a vacancy in 3.2.1. Adsorption the third octahedron, or with the divalent cation occu- Weathering and precipitation at the mineral–water pying all the octahedral site, secondly in the lower charge 3+ 2+ interface are of interest in mineral structure separation cation where all the octahedral sites Al and Mg are processes such as flotation, sedimentation, adsorption, substituted, and thirdly when there is presence of vacan- scavenging of trace element, and transport of nuclear or cies. This aspect of the layer charge is the most important other materials in groundwater (Batley, 1988). Chemical feature of 2:1 clay minerals because it influences occu- reactivity of the mineral–water interface is influenced by pancy of the interlayer space by exchangeable cations properties which can be electrically charged at the surface (Figure 2). of the mineral leading to the formation of an electrical double layer, less mobility of ions and water molecules. 3.2.3. Polytypism However, effects of the perturbed layer of water and the This feature of clay minerals structure is mentioned in electrical double layer on chemical reactions at the inter- several diverse structural modifications in which layers face play an important role. Understanding mechanism of identical structure and composition are stacked in reactions of sorption is valuable and their kinetic inter- different ways. The normal periodicity to layers varies pretation explains the rate of attachment between an ion with stacking sequence between polytypes according to and the surface mineral. So the arrangement of group the number of layers involved. sites on mineral surface may influence the adsorption; 3.2.4. Mixed layers structures however, under certain conditions, the formation of a Mixed layer structures or inter-stratified layers can be monolayer of adsorbing ions may be less favourable than built by two or more than two different components. the formation of multi-layers or precipitated material; This clay minerals can have ordered or regular-mixed such a process plays a critical role in accelerating the rate layer structures if different layers alternate along the of redox reactions, polymerization, hydrolysis, and other Figure 1. s tructure of clay showing two layers of the stacked sheets of kaolinite. GEOLOGY, ECOLOGY, AND LANDSCAPES 159 Figure 2. exchangeable cation in clay minerals. direction in a periodic pattern and disordered or irreg- minerals’ surface bound for example to organic matter ular mixed layers structures if the stacking along the compounds determines the organo–clay interaction and direction of the type of layer is random (Brigatti, Poppi, influence of the sorption capacity at the solid aqueous & Medici, 2002). e Th interfaces between clay particles interface (Baldock & Skjemstad, 2000). are capable of adsorbing water or organic molecules so Many mechanisms of biological protection in envi- that the adjacent layers are perceived as interstratified ronment containing clay minerals and clay-based min- with non-expanding silicates layers, thus having impor- eral particles operating from the smallest to the largest tant geochemical consequences. In addition, illitization scale depend on the chemical properties and the dimen- is ae ff cted by the abundance of water in the system. sional arrangement of layers in the mineral. As a result, This conversion phenomenon can actually involve diverse mechanisms of protection can be attributed to inter-stratified clays like illite-smectite (Whitney, 1990). clay minerals in some matrix-like soil for example. Due This conversion may involve smectite dissolution and to firstly the physical nature of the mineral fraction, thin illite precipitation or growth. When major amounts especially the presence of surfaces capable of adsorbing of smectite are not no more present, either elementary organic materials, and secondly the architecture of lay- or possibly thicker, illite particles become dominant ers in the clay surface, there are multiple applications and will yield interstratified illite-smectite and as the of clay minerals because of their versatile arrangements thickness of the illite particles increases, the diagenesis (Baldock & Skjemstad, 2000). Surface reactive phases increases. This interstratification also has implications to of clay minerals and clay-based minerals also play an clay chemistry and their stability in the environment to important role in the regulation of contaminant fate some extent (Nadeau, Wilson, McHardy, & Tait, 1984). and transport in surface and subsurface of the environ- Indeed, the versatile structures of clay minerals are ment because these surfaces are the primary controllers key factors responsible for clay minerals’ behaviours of sorption processes in soils, thus acting as important and use for a wide range of applications both as colloid regulators of contaminant transport. The modification of stabilizers, catalysts, catalytic and chemicals supports, surface charge of clay minerals by organic constituents coagulants, sorbents, coating, and perhaps in many more is responsible for dispersion/flocculation mechanisms areas. of clay assemblage in the surface as well as the transport of mineral colloidal phases through soil. This surface charge is manifested by a significant retention of anions 4. Importance of clays and clay-based which assure that complex chemical properties have a minerals in the environmental aspect of their number of important implications for solute and con- characteristics taminant transport (Bertsch & Seaman, 1999). Clay mineral particles’ aggregation and dispersion take Mutations and transformations of clays and clay- place under changing conditions in naturals systems. based minerals respond to their chemical and thermal u Th s, the structure of clays particles is inherently influ- environments, their properties and species change at enced by the mineral matrix and the different fractions each step from the origin, weathering, through their bound to it since properties of clays and clay-based min- transportation, sedimentation, burial diagenesis, and erals play an important role in the clay mineral assem- metamorphism. blage, nature, structure, and ionic strength related to Another transformation through the bounding mech- the interrelation between the surface of clay and the anism between the organic cation and the charged clay surrounding environment. The chemical nature of clay layers is essentially electrostatic. Through ion exchange 160 S. C. ABOUDI MANA ET AL. Figure 3. examples of structural transformation of clay to nanoparticle clays. Figure 4. classification of silicates by Bailey (1980). reactions, the inorganic exchangeable cation of layered clays with quaternary ammonium salts producing silicates belonging to clay minerals can be replaced by organophilic solids which can be used as paint thicken- organic cations (Figure 3). ers and for other industrial uses and similar applications. e io Th ns used for this purpose result in the formation es Th e transformations make organo-clay prepared for - of organophillic clay minerals which may greatly adsorb mulations suitable for environmental applications since a wide variety of organic compounds. These materials they are generally based on the (i) substrate: due to its are known as organoclays. Their properties and applica - unique mineralogical structure, it oer ff s several binding tions strongly depend on the nano and micro-structural sites to different types of molecules, (ii) the modifier: arrangement of hybrid materials and from the mecha- the organic molecule bound to the clay mineral allows nisms involved in the clay–organic interactions. Hence, the modification of the substrate surface to increase the diverse applications can be derived from the character- affinity of the hybrid nanomaterial obtained, and (iii) the istics of organoclay minerals. For example in the prepa- molecule of interest: the organoclay is prepared either ration of polymer-clay nano composites, organophillic to remove contaminants by adsorption, to avoid the polymers and clays acting as nanofillers are also used to leaching or decomposition, or to enhance the activity develop inorganic heterostructures and inorganic pol- of an organic molecule. So organophylic clay minerals ymer clay nano-composites that generates porous silica as mentioned above like clay modifiers have the capa- acting as pillared materials. Another use of organoclay is bility to ec ffi iently sorb organic compounds and remove the preparation of sepiolite or palygorskite microb fi rous them from water or effluents, reaching high capacity of GEOLOGY, ECOLOGY, AND LANDSCAPES 161 materials against biological attack. Organic Geochemistry, adsorption at high pollutant concentrations allowing the 31, 697–710. use or reuse of water that before treatment would be Bertsch, P. M., & Seaman, J. C. (1999). Characterization considered unusable (Ruiz-Hitzky, Aranda, Darder, & of complex mineral assemblages: Implications for Rytwo, 2010) (Figure 4). contaminant transport and environmental remediation. Proceedings of the National Academy of Sciences, 96, 3350– 5. Conclusion Brigatti, M. F., Poppi, L., & Medici, L. (2002). Effect of ionic solutions on clay mineral crystal chemistry. In C. Di Maio, Clay is abundant and the clay-based minerals are derived T. Hueckel, & B. Loret (Eds.), Chemo-mechanical coupling from versatile raw materials from a small to a wide in clays (pp. 29–46). Lisse: Balkema Publishers. range of composites which make it suitable for envi- Du Bray, E. A. (1995). Preliminary compilation of descriptive ronmental applications and purposes. Nanostructured geoenvironmental mineral deposit models. Denver, CO: US hybrid materials resulting from ion exchange to cova- Geological Survey. Giese, R. F., & van Oss, C. J. (2002). Colloid and surface lent bonding explain organoclays’ preparation and its properties of clays and related minerals (Vol. 105). Boca feasible environmentally friendly use, like removal of Raton, FL: CRC Press. pollutants and pesticides formulations. Although there Gillott, J. E. (2012). Clay in engineering geology. Amsterdam: is improvement in the use of clay minerals and hybrid Elsevier. materials based on clay minerals and organic molecules Nadeau, P. H., Wilson, M. J., McHardy, W. J., & Tait, J. M. for the removal of pollutants, several problems remain (1984). Interparticle diffraction: A new concept for interstratified clays. Clay Minerals, 19(5), 757. unsolved. The regeneration of the polluted sorbent and Panjaitan, S. R. N. (2014). The effect of lime content on the the low hydraulic conductivity are some of the issues bearing capacity and swelling potential of expansive soil. among others in the removal of contaminants which are Journal of Civil Engineering Research, 4, 89–95. still unresolved and may be of great interest for future Ruiz-Hitzky, E., Aranda, P., Darder, M., & Rytwo, G. (2010). research aiming to improve the mechanical behaviour Hybrid materials based on clays for environmental and biomedical applications. Journal of Materials Chemistry, in order to enhance structural features of organoclay as 20, 9306–9321. far better functionally useful materials for environment Solomon, D. H. (1968). Clay minerals as electron acceptors among others applications. and/or electron donors in organic reactions. Clays and Clay Minerals, 16, 31–39. Taylor, R. K., & Smith, T. J. (1986). The engineering geology of clay minerals: Swelling, shrinking and mudrock Disclosure statement breakdown. Clay Minerals, 21, 235–260. No potential conflict of interest was reported by the authors. Whitney, G. E. N. E. (1990). Role of water in the smectite-to- illite reaction. Clays and Clay Minerals, 38, 343–350. Yan, H., Lu, J., Wei, M., Ma, J., Li, H., He, J., … Duan, X. References (2008). Theoretical study of the hexahydrated metal Bailey, S. W. (1980). Structures of layer silicates. In G. W. cations for the understanding of their template effects in Brindley & G. Brown (Eds.), Crystal structures of clay the construction of layered double hydroxides. Journal of minerals and their x-ray identicfi ation, 5 (pp. 1–123). Molecular Structure: THEOCHEM, 866, 34–45. London: The Mineralogical Society. Yan, H., Wei, M., Ma, J., Evans, D. G., & Duan, X. (2010). Bailey, S. W. (1988). Hydrous phyllosilicates. Washington, DC: Plane-wave density functional theory study on the American Mineralogical Society. structural and energetic properties of cation-disordered Baldock, J. A., & Skjemstad, J. O. (2000). Role of the soil Mg–Al layered double hydroxides. e J Th ournal of Physical matrix and minerals in protecting natural organic Chemistry A, 114, 7369–7376. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Geology Ecology and Landscapes Taylor & Francis

Environmental characteristics of clay and clay-based minerals

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GeoloGy, ecoloGy, and landscapes, 2017 Vol . 1, no . 3, 155–161 https://doi.org/10.1080/24749508.2017.1361128 INWASCON OPEN ACCESS a b c Suzanne Christine Aboudi Mana , Marlia Mohd Hanafiah and Ahmed Jalal Khan Chowdhury a b d epartment of Geology, Faculty of s cience, University of Malaya, Kuala l umpur, Malaysia; Faculty of s cience and Technology, s chool of environmental and natural Resource s ciences, national University of Malaysia, UKM, Bangi, Malaysia; Kulliyah of s cience, International Islamic University, Kuantan, Malaysia ABSTRACT ARTICLE HISTORY Received 6 February 2017 Clay is an inherently occurring material constituted with fined-grained mineral. The minerals a ccepted 13 July 2017 are generally less than 2 microns and occur to be plastic in water content which solidify when dried. In the earth surface, clay represents the most available mineral and forms rocks known KEYWORDS as shale and is the major component of sedimentary rocks. The small size of the particles and clay; environmental their unique crystal structures give clay materials special properties. These properties include: characteristics; clay-based cation exchange capabilities, plastic behaviour when wet, catalytic abilities, swelling behaviour, minerals and low permeability. They give to clay and clay-based minerals higher application in many industries and processes. To acknowledge all the features of clay and clay-based minerals, the understanding of their properties especially the cation exchange capability which affects the mechanical and physical properties of the clay is important, and also to acquire information about the crystal structure of clay mineral in general and montmorillonite especially. The purpose of this laboratory is to illustrate the importance of chemistry on the physical properties of montmorillonite, the clay mineral most often used to isolate dangerous waste materials from the environment. 1. Introduction clay and clay-based mineral varies dependently of the environment. Weathering of rocks and soil is the pri- Among the world’s most important and useful industrial mary way that clays and clay minerals form at the Earth’s minerals, clay minerals are of great significance. e Th y surface today. The weathering process involves physical are used in a number of geological applications such as disaggregation and chemical decomposition that change stratigraphic correlations, indicators of environments of original minerals to clay minerals. Clay and clay-based deposition and temperature for generation of hydrocar- minerals can be formed by the alteration of pre-existing bons. In agriculture, the clay minerals are a major com- mineral by weathering: for example, weathering boul- ponent of soils and determinants of soil properties. The ders on a hillside, sediments on sea or lake bottoms, clay minerals are important in construction where they deeply buried sediments containing pore water, and are a major constituent in brick and tile. The physical rocks in contact with water heated by magma (molten and chemical properties of clay minerals determine their rock) are to form relatively pure clay deposits that are utilization in the process industries (Table 1). of economic interest known as bentonites and primarily Up to date, clay and clay-based minerals need montmorillonite. improvement due to their utilization and demand. Immediately aer t ft heir formation, processes of Processing techniques need to be improved and new transport and deposition through gradual mechanisms equipment needs to be available so that improved clay of diagenesis excluding surficial alteration (which is mineral products are available. Pillared clays and nano- weathering) also favour in-place alteration of clay and composites will become important. Further develop- clay-based mineral to more stable forms, which occurs, ments in organoclay technology and surface treatments for example, when minerals stable in one depositional will provide new usage for these special clays. environment are exposed to another by burial and com- Clays and clay minerals occur under a fairly limited paction. Common silicate materials such as quartz, range of geologic conditions. e Th environments of for - feldspars, and volcanic glasses, as well as carbonates, mation include soil horizons, continental and marine non-crystalline iron oxides, and primary clay minerals, sediments, geothermal fields, volcanic deposits, and are transformed during diagenesis into more stable clay weathering rock formations. The cycle of formation of minerals mainly by dissolution and recrystallization. CONTACT suzanne christine aboudi Mana manachristina@siswa.um.edu.my © 2017 The a uthor(s). published by Informa UK limited, trading as Taylor & Francis Group. This is an open a ccess article distributed under the terms of the creative c ommons a ttribution license (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. 156 S. C. ABOUDI MANA ET AL. Table 1. physical properties of original clay in a native land of This may be the solid bedrock or a non-lithified super - Tanjung Beringin langkat by p anjaitan (2014). ficial layer such as boulder clay resting on bedrock. The clay mineral deposit is geochemically and biochemically No Nature of soil Unit The original clay 1 specific gravity (Gs) – 2.66 controlled in the environment in which it exists natu- 2 plastic limit (pl) % 20.78 rally. Hence, deposit of a given type of clay has similar 3 shrinkage limit (sl) % 54.47 geologic characteristics which also have similar envi- 4 liquid limit (ll) % 40.23 5 plastic index (pI) % 19.43 ronmental signature that can be quantified by pertinent 6 sieve analysis % 52.30 field and laboratory data and summarized in geoenvi- 7 dry weight contents (γd maks) gr/cm 1.363 8 optimum moisture content % 21.00 ronmental models for clay deposit type (Du Bray, 1995). (Wopt) 2. Clay and clay-based minerals properties Undoubtedly, clays and clay minerals are critical 2.1. Clay minerals as electron acceptors and/or components of both ancient and modern sedimentary donors in organic reactions environments. So the initial type of rock, factors governing rock e e Th lectron-accepting and the electron-donating sites weathering and soil formation, the ratio of water to rock, of clay can be explained by the fact the electron acceptor the temperature, the presence of organisms and organic sites are aluminium at crystal edges and transition met- als in the lower valency state. The catalysed polymeriza - material, and the amount of time play an important tions involve the conversion of the organic molecule to a role in the types of clay minerals found in weathering reactive intermediate; hence, the clay mineral accepts an rocks, and thus strongly control how the properties of electron from the vinyl monomer and a radical cation is the weathered rock will abound under various climatic formed, where the organic compound gains an electron conditions (such as humid-tropical, dry-tropical, and and forms a radical anion. temperate conditions). e in Th hibition of polymerization processes involves the In order to outline a simple but efficient classification, conversion of reactive organic intermediate, such as free Grim classification is the most useful. This classification radicals, which has been formed by heat or radical initi- gives a rough idea of the differences between various ators, to non-reactive entities. An example of a thermal clay minerals and proposes their nomenclature. In this polymerization is illustrated by the loss of an electron from the free radical which gives a carbonium ion. classification, clay minerals are divided into four main groups: kaolinite group, illite group, smectite group, and In predicting the electron-accepting or electron-do- vermiculite. nating behaviour, colour reactions on clay minerals Geologic and geochemical information is necessary are useful for the reason that it similarly proceeds with mechanisms of polymerization reactions. For example, to establish environmental characteristics that ae ff ct the a blue reaction of benzidine: here there is one electron use of clays and clay minerals. Since clay minerals play transfer from the organic molecule to the electron-ac- important roles in environment protection, their envi- cepting sites in the mineral (aluminium edges, transi- ronmental characteristics allow them to be a barrier in tion metals in the higher valency state). the nature of inorganic contaminants distribution, such In order to understand the many abilities of electron as metals and metalloids like arsenic, iron, and lead, in exchange of clay minerals, masking the crystal edge clay-bearing rocks. These minerals have been used in the with polyphosphate destroys the electron-accepting disposal and storage of hazardous chemicals as well as properties of the crystal edges. This method is used to for remediation of polluted water. The use of clay min- assess the control of the reactivity of the mineral and erals as the adsorbents for the adsorption of various distinguish the crystal edge from the transition metal sites as electron-acceptor sites in the clay minerals. hazardous substances (heavy metals, dyes, antibiotics, (Solomon, 1968) biocide compounds, and other organic chemicals) has been widely studied by a large number of research- ers. So there is a need to reinforce information about 2.1.1. Ion exchange and cation exchange capacity current studies and discuss improvements that are to When erosion, transport, and deposition take place, being made to expand the knowledge of clay minerals clay minerals react to change in the environment. Ion and clay-based minerals. Certain clay minerals have the exchange, reconstruction of degraded mineral, and for- ability to catalyse the polymerization of some unsatu- mation of one type clay-based mineral from another or rated organic compounds and yet to inhibit polymer simpler substance appear as a result of those processes. formation from other closely related monomers. This Exchange reactions are dominated by physicochemical apparently contradictory behaviour of clay minerals is laws and depend upon the clay mineral, the nature, and known as electron-accepting and electron-donating sites ion population of the exchange sites and on the concentra- in the silicate layers. tion and the composition of the solution in which the clay e co Th mposition of clay is ae ff cted by the mineralog - mineral is found. However, the increase in salinity when ical and chemical compositions of the parent material. in a marine environment results in a decrease in the total GEOLOGY, ECOLOGY, AND LANDSCAPES 157 exchange capacities of clay mineral when clay enters the forces controlling the repulsive pressure are governed sea. So the crystal chemistry of clay mineral is considered by physicochemical swelling in clay minerals since the when exchange of cations takes place. Interlayer water cat- attractive forces by comparison are small within the ions and layer charge appear to be particularly important range of the external forces involved in the clay structure. in the understanding of selective adsorption and fixation Cations are attracted to external surfaces of clay minerals in the process of cation and ion exchange (Gillott, 2012). which are negatively charged and can also be drawn to internal surfaces of expandable minerals, so that clay 2.1.2. Swelling behaviour mineral properties and structure can be changed. e Th Clay mineral swelling is dependent on clay mineral type, sequence of replacement in clay minerals sites in nature the electrolyte concentration, and the nature of the cations of some principal cations is the same as their abundance in the solution. The swelling mechanism can be divided 2+ 2+ + + (Ca  > Mg  > K  > Na ). into mechanical and physicochemical processes. Through burial diagenesis, expandable layers are removed in the clay 3.1. Clay minerals classified by layer mineral structure such that inter and intralayer swelling of expandable clay mineral types can be expected to be at a Clay minerals can be described very simply by the stack- minimum in older rocks than in younger rocks. Mechanical ing of two kinds of layers: 1:1 layers and 2:1 layers. They swelling occurs in response to elastic and time-dependent are layered by silicate in which each layer in the structure stress unloading, which can be brought by man in digging in reality consists of two sublayers. e Th sublayer consists excavations or by nature in tectonic uplift and erosion because of octahedral coordinates and structural water in the the clay is free to expand in the vertical direction but not in form of hydroxyl groups. the horizontal direction. On the other side, physicochemical Anionic clays also known as layered double hydrox- swelling is governed by intrinsic effective stress which ides (LDHs) show a great example of the influence of clay commands the size disparity between larger, inter- layers on their cation–anion exchange capabilities. The aggregate voids and smaller intra-aggregate voids within clay intercalated structure and isomorphous replacement of mineral domains and between clay minerals themselves, all trivalent cations for a fraction of divalent cations leads those forces which exist in a clay–electrolyte system subject to positively charged host layers, where oxygen atoms to unloading aer wa ft ter had entered the system in response coordinate each metal cation, forming an octahedron. to mechanical cause (Taylor & Smith, 1986). Octahedra are composed of two-dimensional sheets formed by a wide range of interlayer anions, which then 2.1.3. Adsorptive and low permeability properties can constitute various kinds of anionic clay materials. As absorptive material, there are three ways clay minerals e co Th mputation model of anionic clay minerals by Yan and clay-based minerals can exert non-covalent adsorp- et al., 2008 in their layered double hydroxides (LDHs) tive power on various molecules from liquid to gaseous formula corroborated with previous work that the value states. Firstly, physical adsorption: there is non-ionic of the stoichiometry coefficient (X), the identities of the adsorption onto the surfaces of finely divided material n− interlayer anion (A ), and the intra-layer cation when (large surface areas of clay minerals are comprised in small they vary enable to produce a wide range of specific volumes), secondly ion exchange adsorption through tailor-made materials. To understand the electronic electrostatic interaction and exchange, and finally, the structure inside the LDHs is important for the stability inclusion of small molecules in pore or cavities, and par- formula of clay-based minerals. The electronic structure tial or complete exclusion of larger molecules by those of LDH materials is oen fir ft stly focused on proper - cavities through the zeolitic adsorption action. (Giese & ties related with the whole bulk of the LDHs crystal in van Oss, 2002). Permeability properties of clay miner- its entire extension in the periodicity coupled with ab als can be explained by the type and distribution of the initio plane-wave density functional theory or linear clay minerals within the pore system. Generally, in rocks combination of atomic orbitals methods and secondly which are predominantly argillaceous, permeability is low. to predict the geometry of layer structure and the struc- e min Th eralogy of different types of rocks semi-perme- tural and chemical properties are investigated through able in nature gives a noticeably different set of chemical semi-empirical molecular orbital method. So Hong Yan parameters, whereas low to medium permeability can be et al. (2008) concluded in their work that the distorsion assimilated to a closed system where rocks and uid a fl re angle of an octahedral coordinated hexahydrated cat- effectively part of the same physicochemical unit. ion plays a significant role in the formation of anionic clay layers. Also, the structural properties of the hex- 3. Clay mineral classified by its structure and ahydrated cations such as metal–oxygen bond length, layer type O–M–O bond angle distorsion, binding energy, and e in Th teraction between clay minerals depends on their valence electronic configuration ligand field are in great structure. This structure controls the behaviour of clay agreement with the construction of anionic clay layers. 2+ minerals’ double layer which is the primary generator Therefore, metal cations with similar ion size to Mg of repulsive pressure in the double layer model. The are able to form the canonical hexahydrated structure 158 S. C. ABOUDI MANA ET AL. with the distorsion angle θ smaller than 1° which are transformations taking place in the surface structure of easily integrated into LDH layers on the basis of DFT clay minerals. theoretical calculation results. Adding ion size rule to 3.2.2. Layer charge this precept can give more insight into the application Either electrically neutral or negatively charged structure of layered double hydroxides (Yan, Wei, Ma, Evans, & of clay mineral may occur as a result of the tetrahedral Duan, 2010) (Figure 1). and octahedral sheets’ junction in clay. The electrical neutral charge exists if the octahedral sheet contains tri- 3.2. Clay minerals classified by the structure valent cations in two octahedral sites, with a vacancy in 3.2.1. Adsorption the third octahedron, or with the divalent cation occu- Weathering and precipitation at the mineral–water pying all the octahedral site, secondly in the lower charge 3+ 2+ interface are of interest in mineral structure separation cation where all the octahedral sites Al and Mg are processes such as flotation, sedimentation, adsorption, substituted, and thirdly when there is presence of vacan- scavenging of trace element, and transport of nuclear or cies. This aspect of the layer charge is the most important other materials in groundwater (Batley, 1988). Chemical feature of 2:1 clay minerals because it influences occu- reactivity of the mineral–water interface is influenced by pancy of the interlayer space by exchangeable cations properties which can be electrically charged at the surface (Figure 2). of the mineral leading to the formation of an electrical double layer, less mobility of ions and water molecules. 3.2.3. Polytypism However, effects of the perturbed layer of water and the This feature of clay minerals structure is mentioned in electrical double layer on chemical reactions at the inter- several diverse structural modifications in which layers face play an important role. Understanding mechanism of identical structure and composition are stacked in reactions of sorption is valuable and their kinetic inter- different ways. The normal periodicity to layers varies pretation explains the rate of attachment between an ion with stacking sequence between polytypes according to and the surface mineral. So the arrangement of group the number of layers involved. sites on mineral surface may influence the adsorption; 3.2.4. Mixed layers structures however, under certain conditions, the formation of a Mixed layer structures or inter-stratified layers can be monolayer of adsorbing ions may be less favourable than built by two or more than two different components. the formation of multi-layers or precipitated material; This clay minerals can have ordered or regular-mixed such a process plays a critical role in accelerating the rate layer structures if different layers alternate along the of redox reactions, polymerization, hydrolysis, and other Figure 1. s tructure of clay showing two layers of the stacked sheets of kaolinite. GEOLOGY, ECOLOGY, AND LANDSCAPES 159 Figure 2. exchangeable cation in clay minerals. direction in a periodic pattern and disordered or irreg- minerals’ surface bound for example to organic matter ular mixed layers structures if the stacking along the compounds determines the organo–clay interaction and direction of the type of layer is random (Brigatti, Poppi, influence of the sorption capacity at the solid aqueous & Medici, 2002). e Th interfaces between clay particles interface (Baldock & Skjemstad, 2000). are capable of adsorbing water or organic molecules so Many mechanisms of biological protection in envi- that the adjacent layers are perceived as interstratified ronment containing clay minerals and clay-based min- with non-expanding silicates layers, thus having impor- eral particles operating from the smallest to the largest tant geochemical consequences. In addition, illitization scale depend on the chemical properties and the dimen- is ae ff cted by the abundance of water in the system. sional arrangement of layers in the mineral. As a result, This conversion phenomenon can actually involve diverse mechanisms of protection can be attributed to inter-stratified clays like illite-smectite (Whitney, 1990). clay minerals in some matrix-like soil for example. Due This conversion may involve smectite dissolution and to firstly the physical nature of the mineral fraction, thin illite precipitation or growth. When major amounts especially the presence of surfaces capable of adsorbing of smectite are not no more present, either elementary organic materials, and secondly the architecture of lay- or possibly thicker, illite particles become dominant ers in the clay surface, there are multiple applications and will yield interstratified illite-smectite and as the of clay minerals because of their versatile arrangements thickness of the illite particles increases, the diagenesis (Baldock & Skjemstad, 2000). Surface reactive phases increases. This interstratification also has implications to of clay minerals and clay-based minerals also play an clay chemistry and their stability in the environment to important role in the regulation of contaminant fate some extent (Nadeau, Wilson, McHardy, & Tait, 1984). and transport in surface and subsurface of the environ- Indeed, the versatile structures of clay minerals are ment because these surfaces are the primary controllers key factors responsible for clay minerals’ behaviours of sorption processes in soils, thus acting as important and use for a wide range of applications both as colloid regulators of contaminant transport. The modification of stabilizers, catalysts, catalytic and chemicals supports, surface charge of clay minerals by organic constituents coagulants, sorbents, coating, and perhaps in many more is responsible for dispersion/flocculation mechanisms areas. of clay assemblage in the surface as well as the transport of mineral colloidal phases through soil. This surface charge is manifested by a significant retention of anions 4. Importance of clays and clay-based which assure that complex chemical properties have a minerals in the environmental aspect of their number of important implications for solute and con- characteristics taminant transport (Bertsch & Seaman, 1999). Clay mineral particles’ aggregation and dispersion take Mutations and transformations of clays and clay- place under changing conditions in naturals systems. based minerals respond to their chemical and thermal u Th s, the structure of clays particles is inherently influ- environments, their properties and species change at enced by the mineral matrix and the different fractions each step from the origin, weathering, through their bound to it since properties of clays and clay-based min- transportation, sedimentation, burial diagenesis, and erals play an important role in the clay mineral assem- metamorphism. blage, nature, structure, and ionic strength related to Another transformation through the bounding mech- the interrelation between the surface of clay and the anism between the organic cation and the charged clay surrounding environment. The chemical nature of clay layers is essentially electrostatic. Through ion exchange 160 S. C. ABOUDI MANA ET AL. Figure 3. examples of structural transformation of clay to nanoparticle clays. Figure 4. classification of silicates by Bailey (1980). reactions, the inorganic exchangeable cation of layered clays with quaternary ammonium salts producing silicates belonging to clay minerals can be replaced by organophilic solids which can be used as paint thicken- organic cations (Figure 3). ers and for other industrial uses and similar applications. e io Th ns used for this purpose result in the formation es Th e transformations make organo-clay prepared for - of organophillic clay minerals which may greatly adsorb mulations suitable for environmental applications since a wide variety of organic compounds. These materials they are generally based on the (i) substrate: due to its are known as organoclays. Their properties and applica - unique mineralogical structure, it oer ff s several binding tions strongly depend on the nano and micro-structural sites to different types of molecules, (ii) the modifier: arrangement of hybrid materials and from the mecha- the organic molecule bound to the clay mineral allows nisms involved in the clay–organic interactions. Hence, the modification of the substrate surface to increase the diverse applications can be derived from the character- affinity of the hybrid nanomaterial obtained, and (iii) the istics of organoclay minerals. For example in the prepa- molecule of interest: the organoclay is prepared either ration of polymer-clay nano composites, organophillic to remove contaminants by adsorption, to avoid the polymers and clays acting as nanofillers are also used to leaching or decomposition, or to enhance the activity develop inorganic heterostructures and inorganic pol- of an organic molecule. So organophylic clay minerals ymer clay nano-composites that generates porous silica as mentioned above like clay modifiers have the capa- acting as pillared materials. Another use of organoclay is bility to ec ffi iently sorb organic compounds and remove the preparation of sepiolite or palygorskite microb fi rous them from water or effluents, reaching high capacity of GEOLOGY, ECOLOGY, AND LANDSCAPES 161 materials against biological attack. Organic Geochemistry, adsorption at high pollutant concentrations allowing the 31, 697–710. use or reuse of water that before treatment would be Bertsch, P. M., & Seaman, J. C. (1999). Characterization considered unusable (Ruiz-Hitzky, Aranda, Darder, & of complex mineral assemblages: Implications for Rytwo, 2010) (Figure 4). contaminant transport and environmental remediation. Proceedings of the National Academy of Sciences, 96, 3350– 5. Conclusion Brigatti, M. F., Poppi, L., & Medici, L. (2002). Effect of ionic solutions on clay mineral crystal chemistry. In C. Di Maio, Clay is abundant and the clay-based minerals are derived T. Hueckel, & B. Loret (Eds.), Chemo-mechanical coupling from versatile raw materials from a small to a wide in clays (pp. 29–46). Lisse: Balkema Publishers. range of composites which make it suitable for envi- Du Bray, E. A. (1995). Preliminary compilation of descriptive ronmental applications and purposes. Nanostructured geoenvironmental mineral deposit models. Denver, CO: US hybrid materials resulting from ion exchange to cova- Geological Survey. Giese, R. F., & van Oss, C. J. (2002). Colloid and surface lent bonding explain organoclays’ preparation and its properties of clays and related minerals (Vol. 105). Boca feasible environmentally friendly use, like removal of Raton, FL: CRC Press. pollutants and pesticides formulations. Although there Gillott, J. E. (2012). Clay in engineering geology. Amsterdam: is improvement in the use of clay minerals and hybrid Elsevier. materials based on clay minerals and organic molecules Nadeau, P. H., Wilson, M. J., McHardy, W. J., & Tait, J. M. for the removal of pollutants, several problems remain (1984). Interparticle diffraction: A new concept for interstratified clays. Clay Minerals, 19(5), 757. unsolved. The regeneration of the polluted sorbent and Panjaitan, S. R. N. (2014). The effect of lime content on the the low hydraulic conductivity are some of the issues bearing capacity and swelling potential of expansive soil. among others in the removal of contaminants which are Journal of Civil Engineering Research, 4, 89–95. still unresolved and may be of great interest for future Ruiz-Hitzky, E., Aranda, P., Darder, M., & Rytwo, G. (2010). research aiming to improve the mechanical behaviour Hybrid materials based on clays for environmental and biomedical applications. Journal of Materials Chemistry, in order to enhance structural features of organoclay as 20, 9306–9321. far better functionally useful materials for environment Solomon, D. H. (1968). Clay minerals as electron acceptors among others applications. and/or electron donors in organic reactions. Clays and Clay Minerals, 16, 31–39. Taylor, R. K., & Smith, T. J. (1986). The engineering geology of clay minerals: Swelling, shrinking and mudrock Disclosure statement breakdown. Clay Minerals, 21, 235–260. No potential conflict of interest was reported by the authors. Whitney, G. E. N. E. (1990). Role of water in the smectite-to- illite reaction. Clays and Clay Minerals, 38, 343–350. Yan, H., Lu, J., Wei, M., Ma, J., Li, H., He, J., … Duan, X. References (2008). Theoretical study of the hexahydrated metal Bailey, S. W. (1980). Structures of layer silicates. In G. W. cations for the understanding of their template effects in Brindley & G. Brown (Eds.), Crystal structures of clay the construction of layered double hydroxides. Journal of minerals and their x-ray identicfi ation, 5 (pp. 1–123). Molecular Structure: THEOCHEM, 866, 34–45. London: The Mineralogical Society. Yan, H., Wei, M., Ma, J., Evans, D. G., & Duan, X. (2010). Bailey, S. W. (1988). Hydrous phyllosilicates. Washington, DC: Plane-wave density functional theory study on the American Mineralogical Society. structural and energetic properties of cation-disordered Baldock, J. A., & Skjemstad, J. O. (2000). Role of the soil Mg–Al layered double hydroxides. e J Th ournal of Physical matrix and minerals in protecting natural organic Chemistry A, 114, 7369–7376.

Journal

Geology Ecology and Landscapes – Taylor & Francis

Published: Jul 3, 2017

Keywords: Clay; environmental characteristics; clay-based minerals

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