Rapid separation of humic acid in fresh waters by coprecipitation and flotation

After removal of suspended matter in 1 liter of water by flotation with a cationic surfactant, humic acid at theg/l level is separated from fulvic acid by coprecipitation with milligram quantities of iron(III) hydroxide at pH 7 followed by flotation with anionic surfactants. The iron(III) hydroxide is dissolved in 2M hydrochloric acid, and the acid-insoluble humic acid is filtered off on an ultrafilter and then dissolved in 10 ml of 0.1M potassium hydroxide solution for measurements of absorption spectra, molecular weight distribution and complexing ability. The time required for the separation is ca. 1 h.