The reaction of ammonia with vermiculite and hydrobiotite

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Abstract
The reaction of ammonia with Mg-saturated vermiculite and hydrobiotite was studied by chemical analysis, X-ray diffraction, and differential thermal analysis, and the hydrobiotite also by infrared spectroscopy. The experimental evidence indicates that ammonia is adsorbed mainly as the ammonium ion, formed partly by reaction with interlayer water and partly by reaction with protons dissociated from octahedral layer hydroxyl groups, giving a single sheet of ions and molecules with irregular interlayer spacing. With large flakes (0.5–1.0 mm) the adsorbed ammonia is strongly retained on heating or on rehydration with water vapour: smaller flakes lose ammonia more readily. Ammonia uptake is related quantitatively to cation exchange capacity with two vermiculites and three hydrobiotites, and to the water content prior to adsorption.Na-saturated vermiculite adsorbs a similar amount of ammonia to the Mg form, but it is mostly desorbed on rehydration. Cu-saturated vermiculite displays intermediate behaviour, with much of the ammonia initially present as a Cu-ammine which slowly reacts to give more ammonium ion.