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

Shijie Tian, Weiqiang Tan, Xinyuan Wang, Tingting Li, Fanhao Song, Nannan Huang and Yingchen Bai
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Shijie Tian: School of Environmental and Municipal Engineering, Qingdao University of Technology, Qingdao 266033, China
Weiqiang Tan: School of Environmental and Municipal Engineering, Qingdao University of Technology, Qingdao 266033, China
Xinyuan Wang: School of Environmental and Municipal Engineering, Qingdao University of Technology, Qingdao 266033, China
Tingting Li: State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing 100012, China
Fanhao Song: State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing 100012, China
Nannan Huang: State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing 100012, China
Yingchen Bai: State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing 100012, China

Sustainability, 2021, vol. 13, issue 15, 1-14

Abstract: 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.

Keywords: humic acid; surface tension; CMC; gaussian model (search for similar items in EconPapers)
JEL-codes: O13 Q Q0 Q2 Q3 Q5 Q56 (search for similar items in EconPapers)
Date: 2021
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