Solid illite

Cs NMR results for Cs on the surfaces of illite, kaolinite, boehmite and silica gel (Figure 3) show that for this large, low charge cation the surface behavior is quite similar to the interlayer behavior. They also illustrate the capabilities of NMR methods to probe surface species and the effects of RH on the structural environments and dynamical behavior of the Cs. The samples were prepared by immersing 0.5 gm of powdered solid in 50 ml of O.IM CsCl solution at 2 5°C for 5 days. Final pHs were between 4.60 and 7.77, greater than the zero point of charge, except for boehmite, which has a ZPC... 

The recovery of M2D-C3-0-(E0)n-CH3 after exposure to various solid media has been investigated by API-MS, high performance liquid chromatography light scattering mass detection (HPLC-LSD) and HPLC-APCI-MS methods [10]. Recoveries with extraction immediately following application were determined (surfactant concentration 0.1%, surfactant/solid lOmgg-1) with complete recoveries obtained on all media other than the clays illite and montmorillonite (Table 5.5.2) [10]. 

The behaviour of M2D-C3-0-(E0)ra-CH3 over time (4 weeks) has been monitored by FIA-APCI-MS in the presence of Al(OH)3, CaC03 (calcite), FeO(OH) (goethite), Fe203 (hematite), halloysite, illite, kaolinite, sand, pumice, talc and Ti02 (anatase), and provides some useful comparative information regarding silicone surfactant behaviour in the presence of various solid media [10]. In general, the results indicated a dependence of parent molecule recovery on pH, with lower recoveries obtained with more extreme pH values (i.e. halloysite and sand, pH 3.7 and 4.8, respectively), consistent with the known pH instability of trisiloxanes under aqueous conditions [3,11,12,16]. In particular, the loss of the parent molecule was most rapid in the presence of the clay, halloysite, and is consistent with other reports of acceleration of silicone hydrolysis in the presence of acid clays [23-25]. Comparison of the recovery of M2D-C3-0-(E0) -CH3 in the presence of halloysite, kaolinite and illite clays (0.1%, 10 mg g-1) by FIA-APCI-MS is presented in Fig. 5.5.1 [10],... 

Figure 8. Percentage illite layers versus equivalents of fixed interlayer cations (Na + K) per illite layer [based on 01o(0H)2]. Solid circles = aluminous smectites with 1 Sr-exchange. Open circles = aluminous smectites with 2 or 3 Sr-exchanges. X = iron-rich smectites with 1 Sr-exchange. Points calculated from data in Tables III, IV, VI, and VIII.

This information is reported as the percentage that each of the clay mineral type contributes to total identifiable clay mineral content of the noncarbonate clay-sized fraction of the surface sediments. These percentages were determined by x-ray diffraction, which is luiable to identify noncrystalline solids. Using this technique, clay minerals were found to comprise about 60% of the mass of carbonate-free fine-grained fraction. Most of the noncrystalline soUds are probably mixed-layer clay minerals. Carbonate was removed to facilitate the x-ray diffraction characterization of the clay minerals. In some cases, roimd off errors cause the sum of the percentages of kaolinite, illite, montmorillonite, and chlorite to deviate slightly from 100%. 

Ca (aq), Mg (aq), and HCOjCaq). Silicate weathering is an incongruent process. The most important of these reactions involves the weathering of the feldspar minerals, ortho-clase, albite, and anorthite. The dissolved products are K (aq), Na (aq), and Ca (aq), and the solid products are the clay minerals, illite, kaolinite, and montmorillonite. The weathering of kaolinite to gibbsite and the partial dissolution of quartz and chert also produces some DSi,... 

The kinetic mass transfer model developed to take into consideration the geochemical evolution of the Cigar Lake ore deposit was mainly done by simulating the evolution of the Al-Si system in the Cigar Lake ore deposit system. To this aim the system formed by kaoli-nite, gibbsite and illite as main aluminosilicate solid phases was considered and kinetics for the dissolution-precipitation processes were taken from the open scientific literature (Nagy et al. 

The general character of low charge and high Si-content of illites can be attributed to solid solution with a chemical component such as pyrophyllite in the aluminous system or chlorite in an Fe-Mg system. 

Figure 11 indicates the necessary change in composition which a muscovite would need to become stable under conditions in a sedimentary rock where chlorite is present (x to y). The solid solution for mica-illites is delimited by the shaded area which represents a much larger variation than is possible under metamorphic or igneous conditions. The detrital muscovite (composition x) is in itself stable if the bulk composition of the sediment as projected into the coordinates is found at x. 

Figure XI. Representation of the phase relations near the illite compositions in the MR - 2R - 3R coordinates. M = muscovite y = illite solid...

The most important observation which can be made after the analysis of the chemical and phase equilibria information is that illite and glauconite mineral series, do not overlap. Solid solution is not continuous, neither in the mica-like phase alone nor in mixed layering between mica and expanding layers. Glauconite is not a subspecies of illite. 

If we now consider the bulk compositions of the mixed-layered minerals which contain both expandable and non-expandable layers, two series are apparent, one between theoretical beidellite and illite and one between theoretical montmorillonite and illite (Figure 25). The intersection of the lines joining muscovite-montmorillonite and beidellite-celadonite (i.e., expandable mineral to mica), is a point which delimits, roughly, the apparent compositional fields of the two montmorillonite-illite compositional trends for the natural mixed layered minerals (Figure 26). That is, the natural minerals appear to show a compositional distribution due to solid solutions between each one of the two montmorillonite types and the two mica types—muscovite and celadonite. There is no apparent solid solution between the two highly expandable (80% montmorillonite) beidellitic and montmorillonitic end members. The point of intersection of the theoretical substitutional series beidellite = celadonite and muscovite-montmorillonite is located at about 30-40% expandable layers— 70-60% illite. This interlayering is similar to the "mineral" allevardite as defined previously. It appears that as the expandability of the mixed... 

As we have seen in the previous section, the bulk chemical compositions of montmorillonites taken from the literature are dispersed over the field of fully expandable, mixed layered and even extreme illite compositions. Just what the limits of true montmorillonite composition are cannot be established at present. We can, nevertheless, as a basis for discussion, assume that the ideal composition of beidellite with 0.25 charge per 10 oxygens and of montmorillonite with the same structural charge do exist in nature and that they form the end-members of montmorillonite solid solutions. Using this assumption one can suppose either solid solution between these two points or intimate mixtures of these two theoretical end-member fully expandable minerals. In either case the observable phase relations will be similar, since it is very difficult if not impossible to distinguish between the two species by physical or chemical methods should they be mixed together. As the bulk chemistry of the expandable phases suggests a mixture of two phases, we will use this hypothesis and it will be assumed here that the two montmorillonite... 

Once the illite-chlorite zone is entered, i.e., the facies where dioctahedral mica-montmorillonite mineral solid-solutions are no longer stable, how does the assemblage change into muscovite-chlorite The major... 

A common way to determine Kid values is to measure sorption isotherms in batch experiments. To this end, the equilibrium concentrations of a given compound in the solid phase (Cis) and in the aqueous phase (CIW) are determined at various compound concentrations and/or solid-water ratios. Consider now the sorption of 1,4-dinitrobenzene (1,4-DNB) to the homoionic clay mineral, K+-illite, at pH 7.0 and 20°C. 1,4-DNB forms electron donor-acceptor (EDA) complexes with clay minerals (see Chapter 11). In a series of batch experiments, Haderlein et al. (1996) measured the data at 20°C given in the margin. 

Fig. 2. Logarithmic activity diagram depicting equilibrium phase relations among aluminosilicates and sea water in an idealized nine-component model of tire ocean system at the noted temperatures, one atmosphere total pressure, and unit activity of H20. The shaded area represents (lie composition range of sea water at the specified temperature, and the dot-dash lines indicate the composition of sea water saturated with quartz, amotphous silica, and sepiolite, respectively. The scale to the left of the diagram refers to calcite saturation foi different fugacities of CO2. The dashed contours designate the composition (in % illite) of a mixed-layer illitcmontmorillonitc solid solution phase in equilibrium with sea water (from Helgesun, H, C. and Mackenzie, F T.. 1970. Silicate-sea water equilibria in the ocean system Deep Sea Res.).

From HemleyJs work on the potassium system (11) one may infer that kaolinite, quartz, and K-mica ( illite) may be stable together, and the equilibrium constant [K+]/[H+] may be extrapolated, (from 200°C.) to 106 at 25°C.—e.g., Hollands (15) value of 10,50 O5. Hem-ley s work on the sodium system (12) in the same way indicates that quartz, Na-montmorillonite, and kaolinite can form a stable assemblage, and a somewhat risky extrapolation of the equilibrium ratio [Na+]/[H+] from 300° to 25°C. gives 107° (15). These ratios are not far from the corresponding ratios in sea water. One could not expect them to be exactly the same since the hydromica and montmorillonite phases in sea water are solid solutions, containing more components than the phases in Hemley s experiments. His experiments surely do not contradict the idea that the previously mentioned phases could exist together at equilibrium. 

Suspended solid surfaces (particles or colloids) in waters play a prominent role in controlling the concentration of dissolved trace elements. Most of these elements are eliminated by sedimentation after incorporation on to or into particles, generally by complexation with the surface sites. The most common inorganic particles and colloids are non-clay silicates (quartz, potash feldspar, plagioclase, opaline silica (diatoms)) clays (illite, smectite) carbonates (calcite, dolomite) Fe-Mn oxides (goethite, magnetite) phosphates (apatite) sulfides (mackinawite). Particles and colloids in a water body may be classified as a function of their origin ... 

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