Adsorbents montmorillonite

Fig. 4.28 Isotherms for polar adsorbates on natural montmorillonite at 323 K. (Courtesy Barrer.) O, adsorption x, desorption.

Fig. 6. Pilot-scale kiln results for a fill fraction of 0.08% at 0.5 rpm and an initial toluene loading, on a dry, calcined, montmorillonite clay adsorbent, of 0.25 wt %, at A, 790°C B, 330°C and C, 190°C. The soHd lines are model fits using equation 24. The model simultaneously fits to all of the data (24).

Bentonite is a rock rich in montmorillonite that has usually resulted from the alteration of volcanic dust (ash) of the intermediate (latitic) siliceous types. In general, reUcts of partially unaltered feldspar, quartz, or volcanic glass shards offer evidence of the parent rock. Most adsorbent clays, bleaching clays, and many clay catalysts are smectites, although some are palygorskite [1337-76 ]. 

Loss of surfactant due to adsorption onto the rock surface can also be minimized by blending the AOS with DPOS. This is shown in Fig. 28 which is a plot of the amount of surfactant adsorbed onto montmorillonite clay vs. the percentage of AOS in the blend. Clearly, when there is more than about 30% DPOS in the blend, total adsorption of surfactant is suppressed. 

Alkyl aryl ketones can be converted to arylacetic acid derivatives in an entirely different manner. The reaction consists of treatment of the substrate with silver nitrate and I2 or Br2, ° or with thallium nitrate, MeOH, and trimethyl orthoformate adsorbed on Montmorillonite K-10 clay, an acidic clay. ... 

Five common desiccant materials are used to adsorb water vapor montmorillonite clay ([(Na,Cao.5)o.33(Al,Mg)2Si40io(OH)2 H20], silica gel, molecular sieves (synthetic zeolite), calcium sulfate (CaS04), and calcium oxide (CaO). These desiccants remove water by a variety of physical and chemical methods adsorption, a process whereby a layer or layers of water molecules adhere to the surface of the desiccant capillary condensation, a procedure whereby the small pores of the desiccant become filled with water and chemical action, a procedure whereby the desiccant undergoes a chemical reaction with water. 

The clay mineral montmorillonite, which is often used in different prebiotic syntheses, is probably now the most important mineral for experiments on prebiotic chemistry. It has shown its abilities in the area of simulation experiments on the formation of primitive cellular compartments montmorillonite accelerates the spontaneous conversion of fatty acid micelles to vesicles. Clay particles are often incorporated into the vesicle, just as is RNA, which is adsorbed at such clay particles. If the vesicles have been formed, they can continue to grow if fatty acids are fed to them via micelles. If the vesicles are pressed through 100 nm pore filters, they divide without dilution of their contents. 

The presence of hydroxyaluminum- and hydroxyaluminosilicate polymer in interlayered montmorillonite greatly promotes the adsorption of Cd, Zn, and Pb (Saha et al., 2001). The adsorption selectivity sequences of montmorillonite (Pb > Zn > Cd) and interlayered montmorillonite (Pb Zn Cd) resemble the metal selectivity on amorphous Fe and Al hydroxides (Saha et al., 2001). On montmorillonite, the metals are predominantly adsorbed on the permanent charge sites in an easily replaceable state. However, a substantial involvement of the edge OH" groups of montmorillonite in specific adsorption of the metals is also observed, especially at higher pH (Saha et al., 2001). 

Loupy and colleagues have prepared acetals of 1-galactono-l,4-lactone in excellent yields [31] by adsorbing the lactone and the aldehyde on montmorillonite K 10 or KSF clay followed by exposing the reaction mixture to microwave irradiation (Scheme 6.1). 

A solvent-free synthesis of flavones has been achieved that simply involves the MW irradiation of o-hydroxydibenzoylmethanes adsorbed on montmorillonite K 10 clay for 1-1.5 min. A rapid and exclusive formation of cyclized flavones occurs in good yields (Scheme 6.41) [140], The intramolecular Michael addition of o-hydroxy-... 

Microbial activity can also be stimulated by mineral colloids through their ability to sorb metabolites that would otherwise have an adverse effect on microbial growth (Filip et al. 1972 Filip and Hattori 1984) This may be due to the toxicity of metabolites, and their feed back repression and, encouraging competitors. Predictably, montmorillonite (CEC —100 cmol kg-1 and specific surface of 800 m g 1) is more effective than kaolinite and finely ground quarts. Other substances, such as antibiotics and pesticides that are toxic to some microorganisms, can also be adsorbed by the surfaces of mineral colloids (Theng and Orchard 1995 Dec et al. 2002). 

Nonionic cellulose ethers, hydroxyethyl(HE) and hydroxypropy1 (HP) cellulose, of variable molar substitution (M.S.) levels, were adsorbed on peptized sodium montmorillonite surfaces from fresh and saline (NaCl) aqueous solutions. The amounts adsorbed for 2 M.S. HEC and HPC and 4 M.S. HEC were insensitive to electrolyte concentration the 4 M.S. 

HPC exhibited a notable increase in adsorption with increasing NaCl concentration. Entrapment in the interlayer of recovered sodium montmorillonite did not vary with salinity the extent of entrapment was greater with the 4 M.S. HE and HP celluloses than either of the 2.0 M.S. polymers. Mixed ethers of HEC (2 M.S.) containing an anionic (carboxymethyl) or cationic (3-0-2-hydroxypropyltrimethylaramonium chloride) group at 0.4 M.S. levels did not adsorb from fresh water. Adsorption of these polar mixed ethers increased with increasing electrolyte until electrostatic and solvation effects were negated in 0.54N NaCl solutions and the adsorbed amounts typical of a 2 M.S. HEC were observed. Interlayer entrapments comparable to the equivalent M.S. HEC were observed at lower (0.18N) electrolyte concentrations. 

The effect of mineral and organic soil constituents on the mineralisation of LAS, AE, stearyl trimethylammonium chloride (STAC) and sodium stearate (main soap component) in soils was studied by Knaebel and co-workers [38]. The four 14C-labelled compounds were aseptically adsorbed to montmorillonite, kaolinite, illite, sand and humic acids and subsequently mixed with soil yielding surfactant concentrations of about 50 jig kg-1. The CO2 formation in the serum bottle respirometers was monitored over a period of 2 months indicating that the mineralisation extent was highest for LAS (49-75%). Somewhat lower amounts of produced CO2 were reported for AE and the stearate ranging from 34-58% and 29-47%, respectively. The mineralisation extent of the cationic surfactant did not exceed 21% (kaolinite) and achieved only 7% in the montmorillonite-modified soil. Associating the mineral type with the mineralisation kinetics showed that sand... 

Ulrich, H.-J., and C. Degueldre (1987), "The Sorption of 210Pb, 210Bi and 21°Po on Montmorillonite A Study with Emphasis on Reversibility Aspects and on the Effect of the Radioactive Decay of Adsorbed Nuclides", submitted. 

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