Nontronite clays

Codeine Nontronite clay-modified SPCE 0.625 pM 15 pM Human urine (96.8-105.9) by square-wave stripping voltammetry 20 nM Flow injection analysis and square-wave stripping voltammetry Shih et al. [132]... 

In glauconites, octahedral A1 ranges from 0.00 to 1.28 and Fe3+ from 0.35 to 1.77 (11 out of 82 samples have more octahedral A1 than Fe3+). Within these limits, there is a continuous isomorphous series between A1 and Fe3+. The composition of the basic unit cell of many glauconites is within the range of composition of the nontronite clays however, on the average, glauconites have more Fe2 + and Mg and less tetrahedral A1 than the average nontronite. The most variable components within the layer are the Al3+ and Fe3+ ions in the octahedral sheet. Fe3+ increases as A1 decreases. 

Lear, P.R. and Stucki, J.W., 1989. Effects of iron oxidation state on the specific surface area of nontronite. Clays and Clay Minerals, 37 547-552. 

Gates WP, Slade PG, Manceau A, Lanson (2002) Site occupancies by iron in nontronites. Clays Clay Minerals 50 223-239... 

Transmission electron micrographs show hectorite and nontronite as elongated, lath-shaped units, whereas the other smectite clays appear more nearly equidimensional. A broken surface of smectite clays typically shows a "com flakes" or "oak leaf surface texture (54). High temperature minerals formed upon heating smectites vary considerably with the compositions of the clays. Spinels commonly appear at 800—1000°C, and dissolve at higher temperatures. Quartz, especially cristobalite, appears and mullite forms if the content of aluminum is adequate (38). 

Halmann and Aurian-Blajeni115 also examined C02 reduction by irradiation either with sunlight or a high-pressure Hg lamp of aqueous suspensions of various oxide semiconductors (i.e., Ti02, Fe203, W03, ZnO, and nontronite, an ion-containing clay mineral). 

Wang MC, Huang PM (1986) Humic macromolecular interlayering in nontronite through interaction with phenol monomers. Nature (London) 323 529-531 Wang MC, Huang PM (1988) Catalytic power of nontronite, kaolinite, and quartz and their reaction sites in the formation of hydroquinone-derived polymers. Appl Clay Sci 4 43-57... 

The palagonite is thermodynamically unstable and, hence, reacts with seawater to form various clay minerals, including smectites (montmorillonite, nontronite, and saponite), micas (celadonite), and zeolites (phillipsite). This chemical weathering involves uptake of Si, Al, Mg, Ca, Na, and K and the release of water, reversing to some extent, the elemental effect of palagonitization. These mineral alterations tend to proceed progressively from the outer margin of the pillow basalts to their interior. 

Komadel P, Madejova J, Stuck JW. 1995. Reduction and reoxidation of nontronite questions of reversibility. Clays and Clay Minerals 43 105-110. 

Organophosphate esters Hydrolysis Cu- and Mg-montmo-rillonite, Cu-BeideUite Cu-Nontronite Cu-mont. better catalyst than other Cu-clays or Mg-mont. 

In a further test of the clustering procedure, analyses of particles of standard clay minerals, ripidolite, montmorillonite, nontronite as well as muscovite mica, were clustered. The procedure easily identified the different minerals, giving rise to well... 

A quartz-free nontronite sample (6) was expanded by reacting a slurry containing 0.0075 g clay/g water with an excess of ChlorhydrolA pillared product was obtained that after drying at -100 C had a d(OOl) spacing of 19.4A. Calcination in air at 400 C/10h reduced the d(OOl) value to 16.9A the calcined ACH-Nontronite had BET surface area of 310 m /g and contained 31.9% FegOj. All powder diffraction measurements were obtained with a Siemens D-500 diffractometer at a scan of r/min using monochromatic Cu-Ka radiation. 

IR spectra for the pillared bentonites in the OH-stretching region show an intense and broad OH-band centered near 3640 cm this band is shifted to near 3600 cm for the ACH-nontronite sample under study, Fig. 1. After pyridine sorption, only minor changes were observed in these spectra, indicating little reaction of the hydroxyl groups present with pyridine. As the degassing temperature is increased from 200 C to 500 C, OH bands decrease in intensity due to dehydroxylation reactions of the clay lattice. Fig. 1. Dehydroxylation is more facile in the iron-containing ACH-nontronite sample. Fig. IF. 

Wang, M. C., and Huang, P. M. (1989c). Pyrogallol transformations as catalyzed by nontronite, bentonite and kaolinite. Clays Clay Miner. 37, 525-531. 

Wang, M.C. (1991). Catalysis on nontronite in phenols and glycine transformations. Clays Clay Min., 39 202-210. 

The cation population of the octahedral sheet of glauconite includes a wider range of values than is found for most other 2 1 clays, with possible exception of the beidellites and nontronites. The average for the 82 samples is 2.054 and 77% of the values are larger than 2.00. The values range from 1.94 to 2.31. Some of these high... 

Nontronite apparently forms under the same general environmental conditions as the low-iron montmorillonites. It is formed by hydrothermal alteration and as vein fillings. It is commonly formed by both the hydrothermal alteration and surface weathering of basalt. Nontronite is the dominant clay in some soils (Ross and Hendricks, 1945). Arrhenius (1963) found that much of the authigenic montmoril-lonite in the pelagic muds of the Pacific Ocean has a relatively high iron content. 

In Fig.30, the dividing line between predominantly octahedral charge and predominantly tetrahedral charge approximately coincides with the boundaries separating the A1 and Fe clays (illite-glauconite and montmorillonite-nontronite). Actually a simplified division (Fig.31) based on the 0.7 charge boundary and the boundary between predominantly octahedral and predominantly tetrahedral charge coincides well with the divisions based on the plotted data. 

Present data indicate that Fe3+-rich low-charge clays increase their layer charge by increasing the Mg and Fe2+ content of the octahedral sheet at the expense of Fe3 + more so than of Al. The average Al content of glauconite and celadonite is similar to that of nontronite, but the Fe3+ values are lower. With increased octahedral charge there is an increase anion-anion repulsion and the octahedral sheet increases relatively more in the c direction than the 6 direction, which also favors the large cations. Thus, relatively less tetrahedral Al is required to afford the sheet size differential to allow sufficient tetrahedral rotation to lock the K into place. 

Osthaus, B.B., 1954. Chemical determination of tetrahedral ions in nontronite and montmoril-lonite. Proc. Natl. Conf. Clays Clay Miner. 2nd-Natl. Acad. Sci. Natl. Res. Counc., Publ., 327 404 417. 

A small fraction of iron may enter the tetrahedral sites in 2 1 clays. In nontronite, there is often enough tetrahedral iron (ca. 5 %) to be detectable using Mossbauer spectra. The Mossbauer spectra in Figure 3, for example, shows a weak quadrupole doublet due to tetrahedral Fe3. Optical spectra of nontronites in the visible region also show an absorption band that is assigned to tetrahedrally coordinated Fe3+. This is discussed in more detail below. 

Iron may also occur as an interlayer species. Mossbauer spectra show the presence of an Fe2+ aquo complex in the interlayer of montmorillonite (13). The labile nature of this Fe2+ is suggested by the large temperature dependence of its recoil-free-fraction. In contrast, Fe3+ aquo complexes are unlikely to occur as discrete species in a clay interlayer. Instead, Fe(0H)2(H20)4 complexes will condense to form ferric hydroxy polymers which, in a clay interlayer, might form two-dimensional sheets or three-dimensional pillars. Such pillars in nontronite have been characterized by Gangas et al. (14). 

Electronic Structure of Fe3 in Tetrahedral Coordination. As mentioned earlier, some Fe3 in clays may substitute for Si in the tetrahedral sheet. In the case of nontronite, the fraction of tetrahedrally coordinated iron is only a few percent. Other phyl-losilicates (such as cronstedite) can have a considerable fraction of iron in tetrahedral coordination. 

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