Humic acid extraction

F-l, F-4, F-7, and F-9 are the first, fourth, seventh, and nineth extracted humic acids, respectively. 

Fig. 5. Relationship between the log Koc for phenanthrene sorption and the aliphaticity of humic acids, sequentially extracted from a soil. F-l, F-4, F-7, and F-9 are the first, fourth, seventh, and nineth extracted humic acids, respectively. 0.005, 0.05, and 0.5 pg mL are selected liquid-phase equilbrium concentrations of phenanthrene (Kang and Xing 2005).

Kang S, Amarasiriwardena D, Veneman P, Xing B (2003) Characterization of ten sequentially extracted humic acids and a humin from a soil in western Massachusetts. Soil Sci 168 880-887... 

Extraction. Humic acids were extracted from their sources with IN sodium hydroxide. The solution was acidified with sulfuric acid, and the resulting precipitate was dried under vacuum at room temperature. Fulvic acid was obtained by evaporating to dryness the neutral filtrate from the humic acid mixture. 

Veeken, A., Nierop, K., De Wilde, V., and Hamelers, B. (2000). Characterisation of NaOH-extracted humic acids during composting of a biowaste. Bioresource Technol. 72, 33 U. Wilson, M. A. (1987). NMR Techniques and Applications in Geochemistry and Soil Chemistry. Pergamon Press, Oxford, UK. 

The variation in the weight percentage of tqtal solvent extractable (TSE) material (extraction with chloroform/methanol/toluene) and solvent extractable humic acid (SEHA) for the coal samples is... 

Surface Activity Measurements. The surface activity displayed by solutions of humic substances and raw foam samples from Como Creek and Suwannee River stream and foam samples was compared to the surface activity of an impure standard of commercial surfactant sodium dodecyl sulfate (SDS) and surface-tension measurements for both sites are shown in Figures 3a and 3b. Como Creek raw foam and foam-extract humic acid showed the greatest surface activity, with foam humic acid contributing to a lesser extent (Figure 3a). In contrast, Como Creek foam and foam-extract fulvic acid and stream humic substances showed little surface activity. Fulvic and humic acids from Suwannee River foam and foam extract showed comparable surface activity to the raw foam, and all samples were less surface active than the SDS (Figure 3b). Stream humic substances showed little surface activity and were comparable to Como Creek stream humic substances. 

The similarities in surface activity between raw foam and the foam-extract humic acid from Como Creek and Suwannee River indicate that the foam-extract humic acid is the main foaming agent. The low carboxyl content of the humic-acid extract, the increased aliphaticity, and the increased contribution of ester/lactone bonds to the carbonyl content indicate that this fraction of the DOC may contain lipids and other hydrophobic substances, which have undergone minimal oxidative degradation. This fraction, therefore, may represent fresh plant material that has encountered limited degradation. 

Fatty acid Stream fulvic acid Foam fulvic acid Foam humic acid Foam-extract humic acid raw foam... 

For metal-humic acids complexes solubilization, 5 g of finely powdered sediment dried at 45°C are shaken with 0.1 M acetic acid and the treatment is repeated until the carbonates are completely removed. After centrifugation and washing with water, 0.5 M NaOH (degassed with N2) is added and shaken for 24 hr in order to extract the complexes. The extraction is repeated with a fresh 0.5 M NaOH solution and the two extracts are combined. The resulting alkaline solution is filtered through a 0.45 pm Millipore filter and analyzed by ICP-AES. After purification of the extracted humic acids by precipitation and redissolution, they are extracted into chloroform by means of cetylpiridinium chloride and NaCl. The absorbance of the chloroform extract at 450 nm is then measured to determine the concentration of humic acids (51). 

Although the definitions of humic acid and of other fractions were initially based on extraction of soil with alkaline reagents, the same terminology is used when the extractants are neutral, acidic, or organic. In these cases the term humin means not extracted, humic acid means soluble in the ex-... 

Fig. 4.3. Hg-release curves of samples I 73.1 and I 84.2 compared with their extracted humic acids...

The comparison of the samples I 73.1 and I 84.2 with their extracted humic acids (Fig. 4.3) shows that the Hg-release curves of the humic acids are very similar to the first peak of their original samples. In contrast, the thermal release characteristics of natural crystalline cinnabar correspond to the second peak of sample I 74 (Fig. 4.4). The Hg-release curve of the incubated clay mineral standard (Fig. 4.4) displays a very wide irregular release curve in the temperature range from 30° to about 610°C. The curve rises up to a first maximum at about 110°C and continues with some changes to the maximum extinction at about 240°C. 

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