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

Swiech, Weronika, Hamerton, Ian, Zeng, Huang, Watson, David J., Mason, Eleonore and Taylor, Spencer (2017) Water-based fractionation of a commercial humic acid. Solid-state and colloidal characterization of the solubility fractions Journal of Colloid and Interface Science, 508. pp. 28-38.

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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 (13C 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.

Item Type: Article
Divisions : Faculty of Engineering and Physical Sciences > Chemistry
Authors :
Hamerton, Ian
Zeng, Huang
Watson, David J.
Mason, Eleonore
Date : 12 August 2017
DOI : 10.1016/j.jcis.2017.08.031
Copyright Disclaimer : © 2017 Elsevier Inc. All rights reserved.
Uncontrolled Keywords : AFM; Colloidal properties; Humic acid fractionation; IR spectroscopy; Solid-state NMR; Surface tension; SAXS; TGA; Zeta potential
Depositing User : Clive Harris
Date Deposited : 15 Aug 2017 11:01
Last Modified : 10 Aug 2019 02:08

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