Smectites distribution

Another feature of the process is that the sorption capacity of type II organoclays is inversely related to the aqueous solubility of the NOCs (Chiou 1989). For example, the affinity of HDTMA-smectite for various phenols increases in the order phenol < chlorophenol < dichlorophenol < trichlorophenol since phenol is the most water-soluble while trichlorophe-nol is the most hydrophobic (Mortland et al. 1986, Lo et al. 1998). The relationship between the distribution (partition) coefficient in a type II organoclay and water-solubility is illustrated in Fig. 5 for a range of nonionic organic pollutants. 

The size distribution of the kaolinite is quite variable and again the Kingston sample differed in that most of the kaolinite has sodium associated with it and could therefore be considered a smectite rather than kaolinite. Marcasite is commonly present as a replacement of original coal particles. The gypsum is present mainly in the -20 ym size range. Overall the mineral matter content of the lignites is of the order of 5%-10% (i.e. a medium distribution density). 

Therefore, based on available literature, the following sorption results were expected (l) as a result of the smectite minerals, the sorption capacity of the red clay would be primarily due to ion exchange associated with the smectites and would be on the order of 0.8 to I.5 mi Hi equivalents per gram (2) also as a result of the smectite minerals, the distribution coefficients for nuclides such as cesium, strontium, barium, and cerium would be between 10 and 100 ml/gm for solution-phase concentrations on the order of 10"3 mg-atom/ml (3) as a result of the hydrous oxides, the distribution coefficients for nuclides such as strontium, barium, and some transition metals would be on the order of 10 ml/gm or greater for solution-phase concentrations on the order of 10 7 mg-atom/ml and less (U) also as a result of the hydrous oxides, the solution-phase pH would strongly influence the distribution coefficients for most nuclides except the alkali metals (5) as a result of both smectites and hydrous oxides being present, the sorption equilibrium data would probably reflect the influence of multiple sorption mechanisms. As discussed below, the experimental results were indeed similar to those which were expected. 

The mineralogical composition of Sahara dust particles shows the predominance of aluminosilicates (clays). Illite is also present in many cases while quartz particles are rare. Scanning Electron Microscopy (SEM) results on dust composition transported over different regions in the Mediterranean Basin have shown that Al-rich clay minerals such as illite and kaolinite are very common in PM10 for Cypms and dominant for Crete. Dust particles are also very rich in calcium which is distributed between calcite, dolomite and sulphates and Ca-Si particles (e.g. smectites) whereas iron oxides are often detected [43]. 

Intact soil cores (6.7 cm i.d.) were taken with spilt spoon at depths of 1 to 2 meters from a field test site located approximately 50 km east of Cincinnati, Ohio. The soil in this interval consists mainly of quartz (60%) and clay minerals (35%) with minor amounts of plagioclase and potassium feldspar. The majority of clay is illite and smectite, with minor amount of kaolinite. Soil chemical properties were analyzed prior to, and after, electroosmosis, in order to evaluate the effects of electroosmosis on the distribution of elements within the soil column. Sampled cores were wrapped in aluminum foil and stored at 12°C until the EO cell was assembled. 

Octahedral Mg, Al, and Fe3+ for the dioctahedral clays were totalled and the relative proportion calculated (atomic percent). Octahedral Mg, Al, Fe3+ and Fe2 + were totalled and the percent Fe2+ calculated. The distribution values for the 2 1 minerals are summarized in Fig.25. For comparison purposes, values for attapulgite and some trioctahedral smectites are also shown. 

Skipper et al. [65, 66] and Refson et al. [67] have performed comparable investigations of water-smectite systems with bivalent and monovalent counterions. Hydrolysis in the case of Mg-montmorillonite is similar in that it was found in several experimental studies for Li-montmorillonite [42-44]. Calculations of the one- and two-layer hydrates of Mg-montmorillonite revealed an equilibrium distribution of counterions on the interlayer midplane, with each Mg2+ surrounded by an octahedral solvation shell. Extensive... 

The values of Dt of (1.89 0.09) and (1.94 0.10) reported by Van Damme and Fripiat (1985) for pillared clays were derived from the multilayer capacities of nitrogen and various organic adsorptives. The fact that Dt 2 appeared to confirm that the basal smectite surface was smooth and that the pillars were regularly distributed. It was argued by Van Damme and Fripiat that a random distribution of the pillars would necessarily lead to some localized molecular sieving and that this in turn would result in D% > 2. 

Note CEC = cation exchange capacity HISM = hydroxyinterlayered smectite HIV = hydroxyinterlayered vermiculite Kf = Freundlich metal distribution coefficients LSB = lime stabilized biosolids = total aluminosilicates. 

Several attempts were made to prepare pillared smectites with sufficient hydrothermal stability for use as active components in catalysts for catalytic cracking of heavy oil fractions. Although improvements were made, none of the attempts resulted in pillared materials stable enough to withstand the hydrothermal conditions found in the regenerator of a commercial FCC. One type of materials studied, i.e. alumina-montmorillonites, may be attractive alternatives to the active matrices, often alumina, currently used in FCC-catalysts designed for cracking of heavy oils. The alumina-montmorillonites can, perhaps, not be considered to be bona fide pillared smectites as they have considerably larger pores and a wider pore-size distribution than what is characteristic for pillared smectites. 

The pressure data from the Smprbukk field area shows that the top of the overpressure occurs at different depths in the different wells. This suggests that the permeability distribution is mainly controlled by the stratigraphy and mineralogy, and not by the developments of depth controlled pressure seals. The Eocene and Oligocene mudstones have low permeabilities and are poorly compacted, probably due to high amounts of smectite. 

By contrast, smectite clays develop in poorly drained sites. On the basaltic island of Hawaii, soil clay mineral type changes in the sequence smectite-kaoli-nite-gibbsite as rainfall amount increases (Fig. 4.18). A similar, generalized zona-tion has been proposed for clay mineral distribution with depth in soils, again based on the degree of leaching (Fig. 4.19). 

MudMaster MudMaster A program for calculating crystallite size distributions and strain from the shapes of X ray diffraction peaks. D. D. Eberl, V. Drits, J. Srodon, and R. Nuesch, U.S. Geological Survey Open File Report 96 171, (1996) 46 pp and XRD measurement of mean thickness, thickness distribution and strain for illite and illite/ smectite crystallites by the Bertaut Warren Averbach technique. 

What is the simplest adsorption model that can adequately define sorption in the system of interest for purposes of our study The simpler the model, the less information is needed to parameterize it. The distribution coefficient model requires only entry of the mass of sorbent in contact with a volume of water and a value for K,. Pesticide adsorption can often be modeled adequately using a simple K ) approach (cf. Lyman et al. 1982). For smectite and ver-miculite clays and zeolites that have dominantly pH-independent surface charge, ion-exchange or power-exchange models may accurately reproduce adsorption of the alkaline earths and alkali metals. If the system of interest experiences a wide range of pH and solution concentrations, and adsorption is of multivalent species by metal oxyhydroxides, then an electrostatic model may be most appropriate. 

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