Retention of Humic Acid by Montmorillonite Saturated with Some Divalent Cations

The complexes formed by the interaction of humic acid (HA) with Cu-, Co-, In-, Ca- and Mg-montmorillonites were characterized by X-ray diffraction, transmission electron microscopy and differential thermal analysis. The amount of HA retained follows the order: Cu > Co > Zn > Ca > Mg. The X-ray diffractograms of complexes of HA with Cu, Zn and Co-montmorillonites indicate entry of some humic acid into the interlayers of minerals, supported by differential thermal analysis of Cu and In complexes. The external surface adsorption of humic acid with diffirent cationic forms of montmorillonite, and its role information of aggregates has been shown by electron microscopy.