Soils of the terrestrial planets form at the boundaries between lithosphere, atmosphere and hydrosphere. Biogenesis occurred in these zones; thus, it is axiomatic that some, perhaps many, stages of biogenesis occurred in intimate association with the mineral constituents of soils. Because of a high surface to mass ratio and, consequently, a high surface reactivity, the layer lattice clay minerals are the most important of these. According to the geological record, clay minerals appeared very early on the primordial Earth. Recent investigations have confirmed their presence in carbonaceous meteorites and have indicated their occurrence on Mars.

Soil and water and its relationship to the origin of life.

A study of the thermal transformation of alkylammonium cations adsorbed on the surface of a montmorillonite in various conditions of hydration has been carried out. The experimental conditions were: inert atmosphere, temperatures below 250°C and time periods up to 270 days. The reactions observed are mainly transalkylations, for which a mechanism of acid catalysis is proposed. A high degree of dissociation of the water remaining on the surface of the clay is required and is attained for an optimal, and rather low, water content of the clay.

Alkylammonium Decomposition on Montmorillonite Surfaces in an Inert Atmosphere

A B S T RAC T: Measurements of conductivity (dielectric losses) and real part of permittivity were performed, at variable frequency (103-107 Hz) and as a function of temperature (27-80~ in order to study the interaction between water vapour and kaolinite. The conductivity increased with frequency and temperature. The use of a conduction model involving proton hops between localized sites proved suitable. The law o'(co) Ao) ~ was verified. The development of parameter s as a function of water vapour pressure allowed determination of the mechanism of adsorption of water during monolayer formation on a solid. The real part of the permittivity decreased with frequency and increased with the water vapour pressure. A simple calculation led to the experimental law ~' ~ exp(K@P).

Etude de l'interaction eau-kaolinite par mesure des permittivites complexes

A B S T R A C T : Decomposition of decylammonium cations on vermiculite surfaces as a result of acidity has been studied. The vermiculite-decylammonium complex was treated with solutions of HC1 in water and butanol, and solutions of chlordimeform in butanol. X-ray powder diffraction and IR spectroscopy data showed the presence after treatment of ammonium cations in addition to aliphatic chain compounds in the interlamellar space. The ammonium cation is produced by breaking of the C-N bond of alkylammonium due to the low pH of the medium and, when using but/tool as solvent, to the dissociation of the scarce water molecules on the clay surface. The influence of the different solutions on the period of decomposition of alkylammonium cations is discussed. Vermiculite-decylammonium complex treated with HC1 solutions for a year released structural Mg z+ due to the acidity of the medium. This Mg 2+ partially displaced ammonium cations from the interlamellar space. The phenomenon of alkylammonium decomposition on montmorillonite surfaces has been studied by several workers. Calvet et al. (1964) showed that alkylammonium cations adsorbed on montmorillonite surfaces are decomposed at temperatures considerably below the corresponding theoretical decomposition temperatures of amines or their chlorhydrates. Above 100~ the adsorbed alkylammonium cations decompose into NHI (which remains on the clay), organic residues and hydrocarbons, as the result of the catalytic rupture of C-N bonds. The catalytic effect was attributed to protons in the water adsorbed on the montmorillonite surface. Durand et al. (1972) re-examined these experiments using an inert atmosphere and long reaction periods. They studied the thermal transformation of alkylammonium cations adsorbed on the surface of montmorillonite in various conditions of hydration. The reactions observed were mainly transalkylations, for which a mechanism of acid catalysis was proposed, requiring a high degree of dissociation of the water remaining on the surface of the clay. There are differences between the thermal transformation of alkylammonium montmorillonite in an inert atmosphere and the corresponding transformation in presence of oxygen. In the latter, a faster increase in the NH~ content was observed, and transalkylation processes did not operate. In a previous paper (P6rez-Rodriguez et al., 1985) we have observed the decomposition of interlamellar alkylammonium in vermiculite using butanol solutions of a pesticide, chlordimeform. The aim of this paper is to establish whether this decomposition was the result of the interlamellar acidity.

/pdf/decomposition-of-alkylammonium-cations-intercalated-in-2jxy4jnj1f.pdf

Decomposition of alkylammonium cations intercalated in vermiculite

We report the study of the dielectric relaxation mechanisms in the zeolite Na-X, “Faujasite”, by means of the method of Thermally Stimulated Depolarization Currents (TSDC), and polarization conductivity versus frequency. We give particular interest to the effect of adsorption on the evolution of dielectric parameters. Two distinct relaxation processes attributed to adsorbed water were found by TSDC measurements. Moreover, the polarization conductivity gives two sets of values of the potential barrier height. The evolution of the polarization conductivity as a function of the rate p/p° is comparable to the curve showing the isothermal water adsorption.

Process of polarization and analysis of the water adsorption on a zeolite

Protons de constitution, protons libres et eau adsorbée

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Protons de constitution, protons libres et eau adsorbée