Vermiculite clay mineral

Bradley, W.F. and Weaver, C.E., 1956. A regularly interstratified chlorite-vermiculite clay mineral. Am. Mineralogist, 41 497-504. 

Brown, G., 1953. The dioctahedral analoque of vermiculite. Clay Miner., 2 64-70. 

The amount of plagioclase (Na and Ca) and smectite-vermiculite clay minerals decreases downstream, to the benefit of quartz and kaolinite. 

Brown, G. (1953). The dioctahedral analogue of vermiculite. Clay Miner. Bull. 2, 64-70. Buffle, J. (1988). Complexation Reactions in Aquatic Systems An Analytical Approach. 

Svegl IG, Kolar M, Ogorevc B, Pihlar B (1998) Vermiculite clay mineral as an effective carbon paste electrode modifier for the preconcentration and voltammetric determination of Hg(II) and Ag(I) ions. Fresenius J Anal Chem 361 358-362... 

Silicates with layer. structures include some of the most familiar and important minerals known to man, partieularly the clay minerals [such as kaolinite (china clay), montmorillonite (bentonite, fuller s earth), and vermiculite], the micas (e.g. muscovite, phlogopite, and biotite), and others such as chrysotile (white asbestos). 

Other studies use soil or sediment samples for a more accurate indication of microbial activity in natural environments. In these samples, organic matter and clay particles play a role in metal toxicity.76112113 Both organic material and clay particles in soil can bind metals and reduce their bioavailability. For example, Pardue et al.87 demonstrated that much less solution-phase cadmium was required to inhibit trichloroaniline (TCA) dechlorination in a mineral-based soil than in a soil containing a higher concentration of organic matter. Other studies have shown that adding clay minerals to a medium mitigates toxicity. Clay minerals, such as kaolinite, montmorillonite, bentonite, and vermiculite, can bind to metals to decrease the amount that is bioavailable.112 115... 

Ericsson T.J., Linares, Lotse E.A. Mossbauer study of the effect of dithionite-citrate-bicarbonate treatment on a vermiculite, a smectite and a soil. Clay Miner 1984 19 85-91. 

Lagaly G (1982) Layer charge heterogeneity in vermiculites. Clays Clay Miner 30 215-222... 

The two types of clay mineral structures which are of interest in the present discussion are the expanding 2 1 structures (the smectites and vermiculites) and the 1 1 structures (the kaolins). 

In view of the problems associated with the expanding 2 1 clays, the smectites and vermiculites, it seemed desirable to use a different clay mineral system, one in which the interactions of surface adsorbed water are more easily studied. An obvious candidate is the hydrated form of halloysite, but studies of this mineral have shown that halloysites also suffer from an equally intractable set of difficulties (JO.). These are principally the poor crystallinity, the necessity to maintain the clay in liquid water in order to prevent loss of the surface adsorbed (intercalated) water, and the highly variable morphology of the crystallites. It seemed to us preferable to start with a chemically pure, well-crystallized, and well-known clay mineral (kaolinite) and to increase the normally small surface area by inserting water molecules between the layers through chemical treatment. Thus, the water would be in contact with both surfaces of every clay layer in the crystallites resulting in an effective surface area for water adsorption of approximately 1000 tor g. The synthetic kaolinite hydrates that resulted from this work are nearly ideal materials for studies of water adsorbed on silicate surfaces. 

Our approach has been to study a very simple clay-water system in which the majority of the water present is adsorbed on the clay surfaces. By appropriate chemical treatment, the clay mineral kao-linite will expand and incorporate water molecules between the layers, yielding an effective surface area of approximately 1000 m2 g . Synthetic kaolinite hydrates have several advantages compared to the expanding clays, the smectites and vermiculites they have very few impurity ions in their structure, few, if any, interlayer cations, the structure of the surfaces is reasonably well known, and the majority of the water present is directly adsorbed on the kaolinite surfaces. 

Rather small selectivity differences are observed for homovalent-and heterovalent exchanges involving alkali, alkaline earth, bivalent transition metal ions, aluminium and rare earth cations, as is amply evidenced from the extensive compilation by Bruggenwert and Kamphorst (16). This compilation includes various clay minerals illite, montmorillonite, vermiculite and kaolinlte. 

Roth CB, Jackson ML, Syers JK. 1969. Deferration effect on structural ferrous-ferric iron ration and CEC of vermiculites and soils. Clays and Clay Minerals 17 253-264. 

MgOn(OH)j -] units (Fig. 7.5), and the illite type in which the octahedral sheet is sandwiched between two layers of tetrahedra (cf. micas such as muscovite, Fig. 7.4). Many important clay minerals such as vermiculite, biotite, and smectites (notably montmorillonite and beidellite, the princi-... 

Chlorite and Vermiculite. Chlorite is a 1,4-nm (14 A) clay mineral that cannot be expanded or collapsed by traditional laboratory procedures. Structurally, the unit layer of chloride is composed of a 2 I layer combined with a ().4-nin Mg or Al interlayer or hydroxide sheet. 

Figure 7.37 Comparison of the X-ray crystal structure of (a) / -sulfonatocalix[4]arene with (b) the naturally occurring clay mineral sodium vermiculite. (Reproduced with permission from [49]).

Figure 5.5. Adsorption of cesium (Cs) by Ca-saturated clay minerals with time.Ill, illite Mt. montmorillonite Vr, vermiculite. [From Sawhney (1966), with permission.]...

Rates of exchange on vermiculite and micaceous minerals, particularly involving ions such as K+, NH, and Cs+, are usually quite slow. These are 2 1 clay minerals with peripheral spaces that impede many ion exchange reactions. Micaceous minerals typically have a more restrictive interlayer space than vermiculite, since the area between layer silicates of micas is selective for certain types of cations such as K+, Cs+, NH4, and H30+ (Sparks and Huang, 1985 Sparks, 1987a). 

There is a large number of clays which are not pure mineral types but consist of interstratified units of different chemical composition. (In detail, this may include nearly all the 2 1 layer minerals.) These are called mixed-layer clays. The two or possibly three different units can be regularly interstratified ABABAB or more commonly randomly interstratified AABABBABA. The most common regularly interstratified clay mineral, corrensite (Lippman, 1954), consists of alternate layers of chlorite and vermiculite or chlorite and montmorillonite. 

Bassett, W.A., 1963. The geology of vermiculite occurrences. Clays Clay Miner., Proc., 10 61-69. 

Curtis, C.D., Brown, P.E. and Somogyi, V.A., 1969. A naturally occurring sodium vermiculite from Unst, Shetland. Clay Miner., 8 15-19. 

Gjems, O., 1963. A swelling dioctahedral clay mineral of a vermiculite-smectite type in the weathering horizons of podzols. Clay Miner., 5 183-193. 

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