C - Lublin

The analysis of the specific surface area of the investigated preparations proved
that the addition of humic acids to the minerals caused an increase in their specific
surface area at all pH values both with and without aluminum. Observing the
impact of pH on the specific surface area there was noticed growing tendencies
with decreasing pH value from 7 to 3, which might have been caused by the
transformation of the crystal lattice of the used clay minerals during the elaboration
leading to formation of the synthetic bindings of minerals, humic acids and
aluminum ions. That gradual increase of the specific surface area might also be
related to the formation of amorphic silica of a great area in the processes of acid
mineral destruction [Drees et al.1989]. Therefore, at pH 3, the specific surface area
has the greatest value. The changes in the suspension of the organic-mineral
bindings may cause the destruction of the crystal lattice of clay minerals. Those
processes occur at the presence of hydrogen ions adsorbed exchangeably on the
mineral surface. The attack of protons in the case of montmorillonite takes place on
the face side, while in kaolinite – on the side of mineral plate, which has a great
impact on the specific surface area of the investigated minerals [Motowicka-
Terelak 1979; Milene et al. 1995; Józefaciuk 1995; Józefaciuk 1998].
Generally it can be stated that the degree of reaction of humic acids with
minerals depends most of all on the type of mineral, pH value, and the presence of
aluminum.
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temperature.
4. Józefaciuk, G. (1998). Changes of surface properties of soils and clay minerals in
acidification and alkalization processes. (in Polish). Acta Agrophysica, 15, Monograph.
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coverage by humic acids on surface free energy and wettability of quartz and kaolin.
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model. Geochemica et Cosmochimica Acta, 59, 1101-1112.
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