Organic clay interactions

Naidja A, Huang PM, Bollag J-M (2000) Enzyme-clay interactions and their impact on transformations of natural and anthropogenic organic compounds in soils. J Environ Qual 29 677-691... 

The carboxyl group (-COOH) of organic acids interacts either directly with the interlayer cation or by forming a hydrogen bond with the water molecules coordinated to the exchangeable cation on the soil-solid and sediment-solid clay... 

As a function of their structural properties, clays interact differently with organic and inorganic contaminants. Two major groups of clay minerals are selected for discussion here (a) kaolinite, with a 1 1 layered structured aluminosilicate and a surface area ranging from 6 to 39 m g" (Schofield and Samson 1954) and (b) smectites with a 2 1 silicate layer and a total surface area of about 800m g" (Borchardt 1989). 

Surface-catalyzed degradation of pesticides has been examined in the context of research on contaminant-clay interactions. Such interactions were observed initially when clay minerals were used as carriers and diluents in the crop protection industry (Fowker et al. 1960). Later specific studies on the persistence of potential organic contaminants in the subsurface defined the mechanism of clay-induced transformation of organophosphate insecticides (Saltzman et al. 1974 Mingelgrin and Saltzman 1977) and s-triazine herbicides (Brown and White 1969). In both cases, contaminant degradation was attributed to the surface acidity of clay minerals, controlled by the hydration status of the system. 

The HSs and other aquatic and soil organic compounds interact with other components of the environmental system. Various kinds of clay organic intercalation compounds have been described, which are able to initiate unique photochemical reactivities characteristic of their specific molecular arrangements these differ considerably from solution photochemistry [18]. 

The water-rock/soil and organic matter-minerals (including soil organic matter-clay), interactions can also be studied by infrared spectroscopy (Chapter 2, Section 2.1.2). 

Organic-clay nanohybrids can be roughly grouped into two different types by crystalline property, that is, lattice regularity. Depending on the interaction... 

Fernandez, F. Quigley R. M. 1991. Controlling the destructive effect of clay-organic liquid interactions by application of effective stresses. Can. Geotech. J. 28 pp. 388-398. 

EFFECTS OF ORGANIC MATTER-CLAY INTERACTIONS IN SOILS... 

Different types of fillers are utilized, the most common is a nanoclay material called montmorillonite—a layered smectite clay. Clays, in a natural state, are hydrophilic while polymers are hydrophobic. To make the two compatible, the clay s polarity must be modified to be more "organic" to interact successfully with polymers (Hay Shaw, 2000 Ryan, 2003). One way to modify clay is by exchanging organic ammonium cations for... 

McGILL W.B, and PAUL E.A. 1976. Fractionation of soil and N nitrogen to separate the organic and clay interactions of immobilized N. 

Many factors affect the mechanisms and kinetics of sorption and transport processes. For instance, differences in the chemical stmcture and properties, ie, ionizahility, solubiUty in water, vapor pressure, and polarity, between pesticides affect their behavior in the environment through effects on sorption and transport processes. Differences in soil properties, ie, pH and percentage of organic carbon and clay contents, and soil conditions, ie, moisture content and landscape position climatic conditions, ie, temperature, precipitation, and radiation and cultural practices, ie, crop and tillage, can all modify the behavior of the pesticide in soils. Persistence of a pesticide in soil is a consequence of a complex interaction of processes. Because the persistence of a pesticide can govern its availabiUty and efficacy for pest control, as weU as its potential for adverse environmental impacts, knowledge of the basic processes is necessary if the benefits of the pesticide ate to be maximized. 

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