Aluminosilicate exchanged surface

In addition to stabilizing organic products by reaction with metal-exchanged clays, as indicated above, aluminosilicate minerals may enable the preparation of metal organic complexes that cannot be formed in solution. Thus a complex of Cu(II) with rubeanic acid (dithiooxamide) could be prepared by soaking Cu montmorillonite in an acetone solution of rubeanic acid (93). The intercalated complex was monomeric, aligned with Its molecular plane parallel to the interlamellar surfaces, and had a metal ligand ratio of 1 2 despite the tetradentate nature of the rubeanic acid. 

Humus/SOM enter into a wide variety of physical and chemical interactions, including sorption, ion exchange, free radical reactions, and solubilization. The water holding capacity and buffering capacity of solid surfaces and the availability of nutrients to plants are controlled to a large extent by the amount of humus in the solids. Humus also interacts with solid minerals to aid in the weathering and decomposition of silicate and aluminosilicate minerals. It is also adsorbed by some minerals. 

The molecular size and the cross-sectional area of coumarine 1 were calculated to be 3.2x10.4x7.5 (A) and 78 A, respectively. From the data of observed d-spacings and the calculated molecular size, three possibilities for the conformation of coumarine molecules could be proposed. In the dl-type [shown in Fig. 5(a)], since the thickness of one aluminosilicate layer was about 9.6 A, the full clearance space was estimated to be about 3.6 A. This value was almost equal to the thickness of the planar coumarine molecule. Therefore, it was considered that coumarine molecules were "flat" on the silicate surfaces and covered each exchangeable cation site without any overlap. In the dh-type [shown in Fig. 5(b,c)], the measured d-spacing was 18.5 A, so that the interlamellar spacing was evaluated to be about 8.9 A, in which the coumarine... 

The release of cations is interpreted to have resulted chiefly from two processes an initial release caused by rapid exchange of surface cations for hydrogen followed by a slow release due to structural attack and disintegration of the aluminosilicate lattice. Other processes which could complicate the form of the dissolution curves are adsorption of cations released by structural breakdown, ion exchange on interlayer sites of cations released by structural breakdown and surface exchange (shale only), precipitation of amorphous or crystalline material, and dissolution rate differences among the various crystalline phases. 

Two alternative explanations have been suggested which are both quite speculative. First, portions of mineral surfaces of intermediate polarity (e.g., siloxane regions, -Si-O-Si-) may permit some exchange of polar water and nonpolar organic sorbates (Hundal et al., 2001). Such surfaces occur in minerals like the faces of aluminosilicates. However, amorphous solids like silica (-Si-OH) and alumina (-A1-OH) have very hydrophilic exteriors when these inorganic materials are suspended in water. Yet these amorphous materials still clearly show sorption of apolar substances (e.g., Mills and Biggar, 1969a Schwarzenbach and Westall, 1981 Estes et al., 1988 Szecsody and Bales, 1989 Farrell et al., 1999). 

The determination of surface properties of particles is an important key to understanding interactions of trace elements and organic compounds between particulate and dissolved phases in estuarine and coastal systems. Specific surface area (SSA), cationic exchange capacity (CEC) and heat of immersion (AH) have been measured on native and treated suspended sediment and after oxidation with 15% H202- SSA and A H have also been measured on samples leached with NaOH and Na-dithionite in order to remove amorphous aluminosilicates. 

The use of surfactant-modified zeolite (SMZ) as a permeable barrier sorbent may offer several unique advantages when dealing with mixed contaminant plumes. Zeolites are hydrated aluminosilicate minerals characterized by cage-like structures, high internal and external surface areas, and high cation exchange capacities. Both natural and synthetic zeolites find use in industry as sorbents, soil amendments, ion exchangers,... 

Natural and synthetic zeolites, a family of aluminosilicates with pores and cavities in the range 0.4-1.5 nm, are well-known heterogeneous catalysts and sorbents. Zeolite-incorporated cellulosic fibers and membranes could be suitable for medical antibacterial materials, deodorizers, absorbent pads, sanitary napkins, gas separators, ion exchangers, and so forth however, the complete and continual use of the whole zeolite surface is not easy in the... 

However, the zeolite is not a unique substrate for this reaction, as is indicated in a recent patent (180), where it is shown that a Cu+-exchanged mont-morillonite clay and synthetic amorphous aluminosilicate will also catalyze butadiene cyclodimerization with high selectivities to VCH (>95%). Preexchange of these aluminosilicates with Cs+ ions was claimed to increase catalyst stability. This is most probably explained by a reduction in surface acidity resulting from the alkali metal ion exchange. 

Hydrogen ions participate in the cation-exchange processes of the interlayer space. As will be seen later (Section 2.7.1), they have a very large affinity for the layer charge. Hydrogen and hydroxide ions are potential-determining ions of the external surfaces via the protonation and deprotonation processes of aluminol and silanol sites. In acidic media, the degradation of aluminosilicates can be observed. 

The acidic destruction of montmorillonite results in the release of silicon and aluminum. The initial fast exchange of surface cations by hydrogen ions is followed by the release of aluminum and silicon. The dissolution rate of Si is higher than that of A1 and is influenced by the relative ratios of basal siloxane and edge surfaces. The shift of pH to more basic values by the ion-exchange processes and the hydrolysis of dissolved species induce the formation of secondary amorphous solids, initiating the formation of amorphous aluminosilicates (Sondi et al. 2008). 

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