| Research Abstract |
Naturally occurring humic substances, i, e., humic and fulvic acids, are the major and ubiquitous organic constituents of river, lake, pond and sea water. They interact with various heavy metal ions to form negatively charged humic complexes. They are also said to be precursors of trihalomethanes formed during water treatment with chlorine. Therefore, the characterization of humic and fulvic acids has been a topic of increasing research interest in geochemistry, environmental sciences and water treatment. In most cascs, however, the concentrations of humic substances are too low to study them directly. Therefore, large sample volumes should be treated for the collection of appreciable amounts of humic and fulvic acids.
Flotation in a flow system developed in our laboratory was a simple and powerful method, where aquatic humic substances at low ppm or ppb levels were continuously coprecipitated with metal hydroxide carrier (e.g., indium hydroxide) and separated by flotation on the solution surface. The proposed technique allows to concentrate semiautomatically milligram quantities of humic and fulvic acids from 10-100 1 of samples.
Further, the separation behavior of metal-humic complexes was studied in some preconcentra-tion steps, e.g., in coprecipitation with magnesium oxinale or collection on thermally reversible polymers. It was foumd that these complexes were completely separated and concentrated, together with metal ions. The dissociations of metal-humic complexes in slightly acidic solutions were examined by using sorption on a macroreticular anion exchanger Sephadex A-25 and inductively coupled plasma-mass spectrometry. The stability of metal-humic complexes were also discussed by using anodic stripping voltammetry.
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