Humic acids were divided into several fractions using buffer solutions as extraction agents with different pH values. Two methods of fractionation were used. The first one was subsequent dissolution of bulk humic acids in buffers adjusted to different pH. The second one was sequential dissolution in buffers with increasing pH values. Experimental data were compared with hypothesis of partial solubility of humic acids in aqueous solutions. Behaviour of humic fractions obtained by sequential dissolution, original bulk sample and residual fractions obtained by subsequent dissolution at pH 10 and 12 agrees with the hypothesis. Results demonstrated that regardless the common mechanism, solubility and dissociation degree of various humic fractions may be very different and can be estimated using parameters of the model based on the proposed mechanism. Presented results suggest that dissolving of solid humic acids in water environment is more complex than conventional solubility behaviour of sparingly soluble solids.

Faculty of Chemistry Materials Research Centre Brno University of Technology Purkyňova 464 118 612 00 Brno Czech Republic

Zobrazit více v PubMed

Chemosphere. 2014 Mar;99:239-47 PubMed

Environ Sci Technol. 2009 May 15;43(10):3626-31 PubMed

Talanta. 2006 Jul 15;69(5):1234-9 PubMed

Environ Int. 2006 Jan;32(1):101-5 PubMed

Anal Chem. 2002 Jun 1;74(11):326A-333A PubMed

Chemosphere. 2008 Sep;73(4):557-63 PubMed

Functional Hydrogels for Agricultural Application

Mean Activity Coefficients of Humic Acids as Physicochemical Characteristics of Their Behavior in Water Environment

Size and Charge Evaluation of Standard Humic and Fulvic Acids as Crucial Factors to Determine Their Environmental Behavior and Impact