Mg-smectite

The interlayer configuration in two-layer hydrate of Mg-beidelite [74] is consistent with results of previous simulations of Mg-smectites [66, 67], The Mg2+ cations are situated at the midplane solvated by three water molecules each above and below in agreement with a number of experimental studies [15, 34], Nonsolvating water molecules form H-bonds with surface O atoms of beidelite. However, water molecules in Mg-beidelite show a greater tendency to occupy ditrigonal cavities in the siloxane surface than in the case of Mg-montmorillonite. 

Torii, K. and Iwasaki, T. 1986. Synthesis of new trioctahedral Mg-smectite. Chemical Letters 2021-24. 

Slightly higher 5 0 values of hydrothermal solution than seawater value are caused by seawater-basalt interaction. Some elements (Mg, S04 ) remove from circulating seawater to basalt by the formation of minerals (Mg-smectite, Mg-chlorite and anhydrite), but most of elements (base metals. Si etc.) are leached out from basalt. 

Lentz et al. (1985) Experiment Mg smectite NaOH Brucite Permeability drop... 

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. 

Smectites (Montmorillonites). Smectites are the 2 1 clay minerals that carry a lattice charge and characteristically expand when solvated with water and alcohols, notably ethylene glycol and glycerol. In earUer Uterature, the term montmorillonite was used for both the group (now smectite) and the particular member of the group in which Mg is a significant substituent for Al in the octahedral layer. Typical formulas are shown in Table 2. Less common smectites include volkhonskoite [12286-87-2] hich. contains Cr " medmontite [12419-74-8], Cu " andpimeUte [12420-74-5], (12). 

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). 

Chlorite is abundant in Cu-Pb-Zn-rich deposits but is scarce in Au-Ag-rich deposits. Fe chlorite is the most common and Fe-Mg chlorite is subordinate (Shirozu, 1969). Almost all of the chlorite is classified as orthochlorite which can be regarded as part of the clinochlore-daphnite solid solution series. In general, chlorite is intimately associated with sulfide minerals such as sphalerite, galena, pyrite, chalcopyrite, and pyrrhotite. A 7 A septechlorite was reported from the Toyoha Pb-Zn deposits (Sawai, 1980). Interstratified chlorite-smectite and vermiculite-saponite are rather common minerals in Au-Ag deposits (e.g., Yoneda and Watanabe, 1981), but they have not yet been reported from other deposits. 

The Mg content of hydrothermally altered volcanic rocks is reflected by the extent of seawater-volcanic rock interaction at elevated temperatures, because it has been experimentally and thermodynamically determined that nearly all of the Mg in seawater transfer to volcanic rocks, owing to the reaction of the cycled seawater with volcanic rocks at elevated temperatures (Bischoff and Dickson, 1975 Mottl and Holland, 1978 Wolery, 1979 Hajash and Chandler, 1981 Reed, 1983 Seyfried, 1987). It has been shown that the CaO content of hydrothermally altered midoceanic ridge basalt is inversely correlated with the MgO content with a slope of approximately — 1 on a molar basis (Mottl, 1983). This indicates that Ca of basalt is removed to seawater and Mg is taken up from seawater by the formation of chlorite and smectite during the seawater-basalt interaction. This type of reaction is simply written as ... 

Smectite-high-Fe-Mg Na.1Ca.025K.2Mg1.15Fe.7- Ali.25Si3.5Oio(OH)2 smectite... 

The elemental compositions in weight percent of the four samples coded Brine Surge 1, Brine Surge 2, MBL-1A and MBL-1B collected from brine surge tank and MBL-1 sampling points were determined by EDX analysis. The clays are composed dominantly of 02 ( 70-80 wt. %) and Si ( 10-15 wt. %), and minor amounts of Na, Mg, and Al (below 5 wt.%). Trace to nil K, Ca, Fe, Mn, Zn, and Cl are also present. In MBL-1 B, however, significant amounts of Fe ( 6.5 wt. %) is present in the sample. These elemental compositions are consistent with the general formula of smectite as will be discussed later. 

Aromatic polycarbonates are currently manufactured either by the interfacial polycondensation of the sodium salt of diphenols such as bisphenol A with phosgene (Reaction 1, Scheme 22) or by transesterification of diphenyl carbonate (DPC) with diphenols in the presence of homogeneous catalysts (Reaction 2, Scheme 22). DPC is made by the oxidative carbonylation of dimethyl carbonate. If DPC can be made from cyclic carbonates by transesterification with solid catalysts, then an environmentally friendlier route to polycarbonates using C02 (instead of COCl2/CO) can be established. Transesterifications are catalyzed by a variety of materials K2C03, KOH, Mg-containing smectites, and oxides supported on silica (250). Recently, Ma et al. (251) reported the transesterification of dimethyl oxalate with phenol catalyzed by Sn-TS-1 samples calcined at various temperatures. The activity was related to the weak Lewis acidity of Sn-TS-1 (251). 

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