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Article

Surface Activity of Humic Acid and Its Sub-Fractions from Forest Soil

1
School of Environmental and Municipal Engineering, Qingdao University of Technology, Qingdao 266033, China
2
State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing 100012, China
*
Author to whom correspondence should be addressed.
Academic Editor: Chunjiang An
Sustainability 2021, 13(15), 8122; https://doi.org/10.3390/su13158122
Received: 9 May 2021 / Revised: 1 July 2021 / Accepted: 12 July 2021 / Published: 21 July 2021
(This article belongs to the Special Issue Environmental Behavior of Nanoparticles)
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 and its sub-fractions reduced from 72.4 mN·m−1 to 36.8 mN·m−1 in exponential model with the increasing concentration from 0 to 2000 mg·L−1. The critical micelle concentration (CMC) and Z-average particle size ranged from 216–1024 mg·L−1 and 108.2–186.9 nm for HA and its sub-fractions, respectively. The CMC have related with alkyl C, O-alkyl C, aromatic C, and carbonyl C (p < 0.05), respectively, and could be predicted with the multiple linear regression equation of CMC, CMC = 18896 − 6.9 × C-296 × alkyl C-331 × aromatic C-17019 × H/C + 4054 × HB/HI (p < 0.05). The maximum particle size was 5000 nm after filtered by a membrane with pore size of 450 nm, indicating HA and its sub-fractions could progressed self-assembly at pH 6.86. The aggregate sizes of number-base particle size distributions were mainly in six clusters including 2 ± 1 nm, 5 ± 2 nm, 10 ± 3 nm, 21 ± 8 nm, 40 ± 10 nm, and >50 nm analyzed by Gaussian model that maybe due to the inconsistency of the components and structures of the HA sub-fractions, requiring further study. It is significance to explore the surface activity of HA and its sub-fractions, which is helpful to clarify the environmental behavior of HA. View Full-Text
Keywords: humic acid; surface tension; CMC; gaussian model humic acid; surface tension; CMC; gaussian model
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MDPI and ACS Style

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. https://doi.org/10.3390/su13158122

AMA Style

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(15):8122. https://doi.org/10.3390/su13158122

Chicago/Turabian Style

Tian, Shijie, Weiqiang Tan, Xinyuan Wang, Tingting Li, Fanhao Song, Nannan Huang, and Yingchen Bai. 2021. "Surface Activity of Humic Acid and Its Sub-Fractions from Forest Soil" Sustainability 13, no. 15: 8122. https://doi.org/10.3390/su13158122

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