Tian, S.; Tan, W.; Wang, X.; Li, T.; Song, F.; Huang, N.; Bai, Y. Surface Activity of Humic Acid and Its Sub-Fractions from Forest Soil. Sustainability2021, 13, 8122.
Tian, S.; Tan, W.; Wang, X.; Li, T.; Song, F.; Huang, N.; Bai, Y. Surface Activity of Humic Acid and Its Sub-Fractions from Forest Soil. Sustainability 2021, 13, 8122.
Surface activity of humic acid (HA) and its six sub-fractions isolated from forest soil were characterized by surface tension measurements, dynamic light scattering, and laser doppler electrophoresis. The surface tension of HA sub-fractions decreased from 72.4 mN·m-1 to 36.8 mN·m-1 with the increasing concentration from 0 to 20000 mg·L-1. The critical micelle concentration (CMC) of HA and its sub-fractions ranged from 216 to 1024 mg·L-1 with the multiple linear regression equation of CMC = 18896–6.9×C–296×alkyl-C–331×aromatic-C–17019×H/C+4054×HB/HI (p < 0.05). The Z-average particle size ranges from 108.2 nm to 186.9 nm. The maximum particle size was 5000 nm after filtered with a membrane of 0.45 μm, indicating HA and its sub-fractions progressed self-assembly during 2000 mg·L-1, pH = 6.86. The number-base particle size distribution of HA sub-fractions was identified as four peaks by Gaussian model, and the aggregate sizes were mainly in six clusters including 2 ± 1 nm, 5 ± 2 nm, 10 ± 3 nm, 21 ± 8 nm, 40 ± 10 nm, and > 50 nm indicating multiple aggregations of different particle sizes in the HA fractions solution.
Humic acid; Surface tension; CMC; Gaussian model
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.