Physics
Scientific paper
May 1983
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1983gecoa..47..947h&link_type=abstract
Geochimica et Cosmochimica Acta, vol. 47, Issue 5, pp.947-952
Physics
1
Scientific paper
Surface tension of sedimentary fulvic acid (FA) and humic acid (HA) with molecular weight from < 10,000 to > 300,000 was measured at 5°C and 25°C, over a wide range of concentrations (0.114-107.4 g/l) at pH 8. HA was in the form of sodium humate. Surface tension decreases with an increase in HA and FA concentration and both HA and FA were found to be surface active materials with FA exhibiting the lowest surface tension (31 dynes/cm). Plots of surface tension vs . log concentration gave two straight lines with a break at a certain concentration similar to surfactants. From the concentration at the break point, aggregation concentration (AGC) was determined. For HA with molecular weight above 10,000, the AGC decreased with an increase in molecular weight. The more hydrophobic the HA, the greater was the tendency to form aggregates. Surface excess (surface concentration) was determined (2.3 × 10 -10 -5.5 × 10 -10 mol / cn 2 ) from the slope of the plot of surface tension vs . log concentration for concentrations lower than the AGC. Adsorption of HA into the surface layer increased with increasing molecular weight of HA.
Hayase Kohji
Tsubota Hiroyuki
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