Molecular insights into the impacts of iron(III) ions on membrane fouling by alginate. (March 2020)

• Record Type: Journal Article
• Authors: Chen, Yifeng; Teng, Jiaheng; Liao, Bao-Qiang; Li, Renjie; Lin, Hongjun
• Is Part Of: Chemosphere. Volume 242(2020)
• Publication Date: 2020-03
• Subjects: Gel layer -- Membrane fouling -- Flory-Huggins theory -- Density functional theory -- Filtration resistance; Pollution -- Periodicals; Pollution -- Physiological effect -- Periodicals; Environmental sciences -- Periodicals; Atmospheric chemistry -- Periodicals; 551.511
• DOI: 10.1016/j.chemosphere.2019.125232
• Languages: English
• ISSNs: 0045-6535

Abstract

Abstract: Molecular mechanisms responsible for the filtration behaviors of sodium alginate (SA) in presence of different iron(III) ion concentration were explored in this study. It was found that specific filtration resistance (SFR) of alginate mixtures (1.0 gSA/L) firstly increased and then decreased to a trough with iron(III) concentration increase from 0 to 2.5 mM. Alginate mixture interacting with 0.1 mM iron(III) possessed an SFR as high as 1.65 × 10 14 m kg −1, which could be explained by Flory-Huggins lattice theory related with gel filtration. Optical observation showed significant morphology transition (from gel to granular solids) of foulant layers with iron(III) concentration increase. A series of characterizations indicated the change of microstructure, pH and surface charge of alginate mixture with iron(III) concentration. Density functional theory (DFT) simulation suggested that iron(III) ion preferentially forms coordination bonds with three terminal carboxyl groups of alginate chains, facilitating elongation and cross-linking of alginate chains. Such a coordination mode induces formation of a slime and homogeneous gel, corresponding to high SFR. Continuous increase in iron(III) concentration leads to non-terminal coordination, which makes alginate chains more clustered and coiled. This effect, together with effects of the reduced surface charge and electric double layer compression, significantly decrease SFR of alginate mixtures. This study provided deep molecular insights into effects of iron(III) ions on alginate fouling. Graphical abstract: Image 10993 Highlights: Alginate specific filtration resistance (SFR) unimodally changed with Fe 3+ content. Alginate interacting with 0.1 mM Fe 3+ possessed an SFR as high as 1.65 × 10 14 m kg −1 Fe 3+ preferentially coordinated with terminal –COOH to form slime gel with high SFR. High Fe 3+ content led to non-terminal coordination and coiled clusters with low SFR. High gel SFR could be explained by Flory–Huggins lattice theory.