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

School of Environmental and Municipal Engineering, Qingdao University of Technology, Qingdao 266033, China
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;
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.

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.

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.

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