Hectorites

Clays and Other Sources. Sedimentary deposits, especially hthium-bearing clays found in the western United States, offer an additional source of lithium. These clays contain lithium-hearing trioctahedral smectites, of which hectorite [12173-47-6] NaQ23(Mg,Li)2Si402Q(F,0H)2, is one mineral. 

Hectorite usually contains 0.3—0.6% Li or 0.7—1.3% Li20. Deposits are found in Nevada, California, Utah, Oregon, Wyoming, Ari2ona, and New Mexico. 

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). 

Camphor, dibutyl phthalate [84-74-2], and other Hpidic solvents are common plastici2ers. Nad lacquers requite the presence of a suspending agent because pigments have a tendency to settle. Most tinted lacquers contain a suitable flocculating agent, such as stearalkonium hectorite, a reaction product of hectorite [12173 6-6] and stearalkonium chloride [122-19-0],... 

We have done our experiments with hectorite, which is a 2 1 smectite that develops negative layer charge by substitution of Li for Mg in the octahedral sheet.Samples were prepared by multiple exchange in 1.0 and 0.1 M CsCl solutions until essentially complete Cs-exchange was reached (97% of the interlayer cations). Temperature dependent data are essential to interpret the results, because there is rapid exchange of Cs among different interlayer sites at room temperature (RT). 

At temperatures greater than -10°C, the Cs NMR spectrum of a Cs-exchanged hectorite in contact with l.OM CsCl solution (a slurry sample) consists of two peaks, one between 3.5 and... 

Figure 1. MAS NMR spectra of cs-exchanged hectorite in a 1,0 M CsCl slurry at temperatures betwee.. 50 and -100°C. The H field strength was 8.45 T. After reference 22.

Figure 2. Cs MAS NMR spectra of Cs-exchanged hectorite sample dehydrated at 500°C before analysis at temperatures from 80 to -80°C. The labeled peaks near -120 and +30 ppm are true center bands, and the other peaks are spinning sidebands. After reference 22.

Many varieties of clay are aluminosilicates with a layered structure which consists of silica (SiOa" ) tetrahedral sheets bonded to alumina (AlOg ) octahedral ones. These sheets can be arranged in a variety of ways in smectite clays, a 2 1 ratio of the tetrahedral to the octahedral is observed. MMT and hectorite are the most common of smectite clays. 

This is the most widely used naturally occurring rubber. The literature search shows that many research groups have prepared nanocomposites based on this rubber [29-32]. Varghese and Karger-Kocsis have prepared natural rubber (NR)-based nanocomposites by melt-intercalation method, which is very useful for practical application. In their study, they have found increase in stiffness, elongation, mechanical strength, and storage modulus. Various minerals like MMT, bentonite, and hectorite have been used. 

FIG. 4 Experimental (vertical bars) and simulated (symbols) values of the d-spacings for aUcy-lammonium-exchanged clay at three different cation exchange capacities (CECs) (a) SWy2 mont-morillonite, CEC = 0.8 meq/g (b) AMS montmorillonite (Nanocor), CEC = 1.0 meq/g (c) fluoro-hectorite (Dow-Corning), CEC = 1.5 meq/g. (Erom Ref. 30.)... 

Polyimide-clay nanocomposites constitute another example of the synthesis of nanocomposite from polymer solution [70-76]. Polyimide-clay nanocomposite films were produced via polymerization of 4,4 -diaminodiphenyl ether and pyromellitic dianhydride in dimethylacetamide (DMAC) solvent, followed by mixing of the poly(amic acid) solution with organoclay dispersed in DMAC. Synthetic mica and MMT produced primarily exfoliated nanocomposites, while saponite and hectorite led to only monolayer intercalation in the clay galleries [71]. Dramatic improvements in barrier properties, thermal stability, and modulus were observed for these nanocomposites. Polyimide-clay nanocomposites containing only a small fraction of clay exhibited a several-fold reduction in the... 

FIG. 13 Reduction of the relative permeability coefficient is dependent on the clay platelet aspect ratio in the system of polyimide-clay hybrid with water vapor as the permeate. Each hybrid contains 2 wt% clay. The aspect ratios for hectorite, saponite, montmorillonite, and synthetic mica are 46, 165, 218, and 1230, respectively. (From Ref. 71.)... 

R. B. Carpenter, J. B. Bloys, and D. L. Johnson. Cement composition containing synthetic hectorite clay. Patent WO 9902464,1999. 

Chiral recognition of A-[Co(phen)3]3+ has been observed in a modified /3-cyclodextrin.772 Chiral discrimination has also been seen in photoinduced energy transfer from luminescent chiral lanthanoid complexes773 to [Co(phen)3]3+ and between photoexcited [Ru(bpy)3]2+ and [Co(phen)3]3+ co-adsorbed on smectite clays.774 The [Co(bpy)3]3+ ion has been incorporated into clays to generate ordered assemblies and also functional catalysts. When adsorbed onto hectorite, [Co(bpy)3]3+ catalyzes the reduction of nitrobenzene to aniline.775 The ability of [Co(phen)3]3+ to bind to DNA has been intensively studied, and discussion of this feature is deferred until Section 6.1.3.1.4. 

The positively charged phosphonium ligand was intercalated in the hectorite and was used to catalyze olefin hydroformylation.156 Cu(II)-exchanged clays were tested as catalysts in the cyclopropanation reaction of styrene with... 

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