Adsorption of Ferrocenium Cation from Acidic Aqueous Solutions onto Humic Acids and Humin of Brown Coal

Abstract

Ferrocenium cation and methylene blue are shown to quantify and compare the specific surface area of humic acids and humin as alternative probes for the characterisation of adsorption properties. The isothermal adsorption of ferrocenium cation from acidic aqueous solutions onto initial and mechanochemically dispersed samples of humic acids and brown coal humin was investigated. It was found that the adsorption characteristic differs. For humic acids, the interaction is cation–π contact and π–π stacking between the ferrocenium cation and surface aromatic fragments of the sorbent supramolecule, as well as hydrophobic interaction. For humin, the porous structure gives rise to additional adsorption with multiple cation–π contacts with aromatic walls.