Water-based fractionation of a commercial humic acid. Solid-state and colloidal characterization of the solubility fractions

JOURNAL OF COLLOID AND INTERFACE SCIENCE

卷:508

Article

Swiech, Weronika M.¹  Hamerton, Ian^2,5  Zeng, Huang³  Watson, David J.²  Mason, Eleonore^4,6  Taylor, Spencer E.¹ 

[1] Univ Surrey, Fac Engn & Phys Sci, Ctr Petr & Surface Chem, Dept Chem, Guildford GU2 7XH, Surrey, England

[2] Univ Surrey, Fac Engn & Phys Sci, Dept Chem, Guildford GU2 7XH, Surrey, England

[3] BP Amer, Upstream Technol, 501 Westlake Blvd, Houston, TX 77079 USA

[4] Univ Reading, Dept Chem, Reading RG6 6AD, Berks, England

[5] Univ Bristol, Bristol Composites Inst ACCIS, Dept Aerosp Engn, Queens Bldg, Bristol BS8 1TR, Avon, England

[6] Univ Bath, Dept Chem, Bath BA2 7AY, Avon, England

关键词: AFM;    Colloidal properties;    Humic acid fractionation;    IR spectroscopy;    Solid-state NMR;    Surface tension;    SAXS;    TGA;   

DOI  :  10.1016/j.jcis.2017.08.031

来源: Elsevier

【 摘 要 】

Background and hypothesis: Humic acid (HA) is of considerable environmental significance, being a major component of soil, as well as being considered for application in other technological areas. However, its structure and colloidal properties continue to be the subject of debate, largely owing to its molecular complexity and association with other humic substances and mineral matter. As a class, HA is considered to comprise supramolecular assemblies of heterogeneous species, and herein we consider a simple route for the separation of some HA sub-fractions. Experiments: A commercial HA sample from Sigma-Aldrich has been fractionated into two soluble(S1, S2) and two insoluble (I1, I2) fractions by successive dissolution in deionized water at near-neutral pH. These sub-fractions have been characterized by solution and solid-state approaches. Findings: Using this simple approach, the HA has been shown to contain non-covalently bonded species with different polarity and water solubility. The soluble and insoluble fractions have very different chemical structures, as revealed particularly by their solid-state properties (C-13 NMR and IR spectroscopy, and TGA); in particular, S1 and S2 are characterized by higher carbonyl and aromatic contents, compared with I1 and I2. As shown by solution SAXS measurements and AFM, the soluble fractions behave as hydrophilic colloidal aggregates of at least 50 nm diameter. (C) 2017 Elsevier Inc. All rights reserved.

【 授权许可】

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