Clay colloids, properties

Cerpa, A. Garcia-Gonzalez, M.T. Tartaj, P. Re-quena, J. Garcell, L. Serna, C.J. (1999) Mineral-content and particle-size effects on the colloidal properties of concentrated lateri-tic suspensions. Clays Clay Min. 47 515-521 Cervini-Silva, J. Sposito, G. (2002) Steady-state dissolution kinetics of aluminum-goethite in the presence of desferrioxamine-B and oxalate. Environ. Sci. Technol. 36 337-342 Cesco, S. Rdmheld.V. Varanini, Z. Pinton,... 

Clay Minerals and Clay Colloids. The literature on clays and clay colloids is expansive, but there remains a degree of uncertainty in many areas of their study due to their inherent heterogeneity. Descriptions of the structures and properties of clay minerals can be found in Grim (1968), Brindley and Brown (1980), Newman and Brown (1987), Sposito et al. (1999), and Giese and van Oss (2002). 

Clay minerals and clay colloids are the products of the advanced weathering of primary silicates. They are comprised mainly of silica and alumina, often with appreciable amounts of alkali and alkaline earth metals and iron. Most also have varying amounts of water bound to their surfaces and can take on a variety of different chemical and physical properties depending on the amount of water adsorbed. They have the ability to exchange or bind cations and anions and are capable of complex formation with a wide variety of organic molecules. 

Keren, R. and I. Shainberg. 1984. Colloid properties of clay minerals in saline and sodic solution. In I. Shainberg and J. Shelhevet, Eds. Soil Salinity Under Irrigation—Processes and Management. Springer-Verlag, Berlin, pp. 32-47. 

Cerpa, A. et al.. Mineral-content and particle-size effects on the colloidal properties of concentrated lateritic suspensions. Clays Clay Miner, 47, 515, 1999. 

The complexity of ion interactions with the soil s solid phase is greatly increased by the colloidal properties of the soil s clay and organic fractions. Colloids are substances of about 1- to 1000-nm particle size that form unique mixtures when sus-... 

The important colloidal properties that clays impart to soils include ion and molecular retention and exchange and water and gas adsorption. The colloidal properties of day create the intimate mixture of solids, liquids, and gases in the soil that is essential to life. 

Soil organic matter also has a strongly pH-dependent charge. The charge develops mostly by H+ dissociation from carboxylic and phenolic groups. Table 5.5 summarizes the colloidal properties of the major components of the soil s clay fraction. 

The petroleum industry suspension applications and problems have in common the same basic principles of colloid science that govern the nature, stability, and properties of suspensions. The widespread importance of suspensions in general and scientific interest in their formation, stability, and properties have precipitated a wealth of published literature on the subject. This chapter provides an introduction intended to complement the other chapters on suspensions in this book. A good starting point for further basic information, although focused on clays, is van Olphen s classic book, An Introduction to Clay Colloid Chemistry (I). There are several other good books on suspensions (2, 3), and most good colloid chemistry texts contain introductions to suspensions and some of their properties (4-8). 

In the ceramic industry the rheology of clay suspensions plays a major role. Their colloidal properties are of especial significance in the process of slip-casting, in which a clay slurry is put in contact with a porous plaster mould, which sucks up the water to leave a solid form ready for firing, Here the suction provided by the porous mould in relation to the rate of flow of water through the clay matrix is important. The structure of the clay slurry, as determined by its degree of dispersion, has also to be controlled by suitable additives. 

There have been a number of studies reported that have examined the effect of the presence or absence of humic materials and NOM on the fractal properties of other colloidal materials such as hematite, clays, colloidal hydrous oxides and similar materials [e.g. 45-48]. However, since the focus of this chapter is on the use of a fractal approach to explore the unique nature of humic materials, these studies are not discussed in this chapter. 

Arable lands containing high percentages of clay when flooded by seawater will usually be severely damaged in terms of porosity and productivity. Suggest some logical explanation based on colloidal properties and the theories discussed in the text. 

Soil Colloids Properties and Ion Binding examines soil colloidal components and their interactions with ionic species, irrtegrating soil science and colloid chemistry and considering the latest advances in this active research area. Part I covers the fundamentals of colloid science for readers not familiar with these principles. It discrrsses all the important concepts, without excessive detail such as extensive mathematical derivations. Part II deals with soil and its components, especially clay and oxide minerals and humic substances. It covers their composition and characteristics, with an emphasis on colloidal properties and ion sorption on colloids. 

Deflocculation. — This is a term employed to indicate an increase in the colloidal properties, and usually involves a lowering in the value of n. The principal defloculants for clays are alkalis, or salts that by hydrolysis give alkaline reactions. Chiefly among the latter are sodium, potassium, and ammonium carbonates, oxalates and phosphates. According to Ashley sodium carbonate may react as follows ... 

Due to the high retention capacities, swelling and colloidal properties, clays and clay minerals have been proposed as useful materials to modify drug-delivery systems (Datta and Kaur, 2014). The interactions of ibuprofen (Zheng et al., 2007), nicotine, timolol and donepezil (Park et al., 2008), a well-known drug for Alzheimer s disease. 

The uses of clay minerals and other colloidal materials are numerous. In this diapter, we review the major uses and try to indicate how the surface and interfacial pro(>erties of these materials influence the utility of the materi d in question. FWther, we attempt to indicate how knowledge of the colloidal properties of these materials can be modified or how the surface properties might be better utilized. 

In addition to the paving grades of emulsions, a variety of products are available that are suitable for industrial uses, for paper sidings, and for use in the roofing appHcation field. Asphalts emulsified with colloidal clays are especially suitable for outdoor appHcations because of their exceUent weathering properties. Some of these products have been adapted for use with roofing systems, either with bmsh or spray appHcation. 

The possible content of hydrated alumina and iron. Hydrated alumina minerals like gibbsite [14762-49-3] Al(OH)2, boehmite [1318-23-6] AlOOH, and diaspore [14457-84-2] AlOOH, occur ia bauxitic clays. Bauxites grade chemically iato hydrated fermgiaous and manganiferous laterites. Hence, finely divided M2O2, usually hydrated, may be a significant constituent of a clay where M may be A1 or Fe. Hydrated colloidal s ica may play a role ia the sHppery and sticky properties of certain clays. 

J) The extreme fineness of iadividual clay particles, which may be of colloidal size ia at least one dimension. Clay minerals are usually platy ia shape, and less often lathlike and tubular or scroU shaped (13). Because of this fineness clays exhibit the surface chemical properties of coUoids (qv) (14). Some clays possess relatively open crystal lattices and show internal surface colloidal effects. Other minerals and rock particles, which are not hydrous aluminosihcates but which also show colloidal dimensions and characteristics, may occur intimately intermixed with the clay minerals and play an essential role. 

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