Cation-exchange capacity effect

The main parameters that affect the cost-effectiveness of soil washing include the physicochemical parameters of the soil (grain size distribution, cation exchange capacity, percentage of silt, clay, or organic matter), and the type and concentration of contaminants. 

In a similar investigation Sastry and Fuerstenau (S4) used up to 1.5% Wyoming bentonite in a teconite feed with 48.4, 50.3, and 52.3% volume moisture. The water retention capacity was calculated as 0.47 0.11, independent of the water and bentonite contents. An evaluation of bentonites from three sources by Nicol and Adamiak (N3) indicates that the Wyoming bentonite has the highest cation exchange capacity and also the maximum retardation effect on the balling rate. 

Hedges, R.E.M. and McClennan, M. (1976). On the cation exchange capacity of fired clays and its effect on the chemical and radiometric analysis of pottery. Archaeometry 18 203-207. 

Another type of reaction that responds to WD cycles is the fixation of K and NH4 ions by smectite (3-7). The fixation of K in smectite has been studied extensively by soil scientists because of its effect on the availability of plant nutrients. The reaction also decreases smectite s ability to swell, decreases its cation exchange capacity (CEC), and modifies its BrjSnsted acidity. Therefore, an understanding of this phenomenon is applicable to many fields of study that are concerned with swelling clays, fields such as soil fertility, soil mechanics, waste disposal, clay catalysis, and the geochemistry of ground and surface waters. 

Effective cation exchange capacity (ECEC) the sum of the exchangeable cations (AF, H, Ca and Mg2+) extracted by 1 M potassium chloride... 

Method 5.3. Determination of effective cation exchange capacity (ECEC)... 

Temperature sensitivities can be a limiting factor when using surfactants in groundwater systems. Low temperatures can cause the surfactant concentration to drop below the cation exchange capacity (CMC), rendering the surfactant useless. This effect can be abated with surfactant engineering or by using a co-surfactant. 

Nitrification is limited in most soils by the supply rate of NH4+ (40, 41). Competition exists between nitrifiers and vegetation, which may both be limited by the availability of NH4 +. This microbial demand for NH4 +, coupled with the high cation-exchange capacity of most temperate forest soils, leads to surface-water NH4+ concentrations that are usually undetectable. Nitrification rates may also be limited by inadequate microbial populations, lack of water, allelopathic effects (toxic effects produced by inhibitors manufactured by vegetation), or by low soil pH. 

Most laboratory experiments demonstrating the utility of EO transport of organic compounds were conducted with kaolinite as the model clay-rich soil medium. Shapiro et al. (1989) used EO to transport phenol in kaolinite. Bruell et al. (1992) have shown that TCE can be transported down a slurry column by electroosmotic fluid flow, and more recently, Ho et al. (1995) demonstrated electroosmotic movement of p-nitrophenol in kaolinite. Kaolinite is a pure clay mineral, which has a very low cation exchange capacity and is generally a minor component of the silicate clay mineral fraction present in most natural soils. It is not, therefore, representative of most natural soil types, particularly those which are common in the midwestem United States. The clay content can impact the optimization and effectiveness of electroosmosis in field-scale applications, as has recently been discussed by Chen et al. (1999). 

Beneficial effects of compost addition to soil include increased pH and cation exchange capacity (CEC), higher N and P availability and improved soil structure. Applications of 5-10 t ha 1 of compost prepared from household refuses, farmyard manure, crop residues and ashes increased pH and CEC in the topsoil and boosted sorghum yields by factors of 1.5 to 3 in Burkina Faso (Ouedraogo et al.,... 

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