Synergism of Fe and Al salts for the coagulation of dissolved organic matter: Structural developments of Fe/Al-organic matter associations
Dissolved organic matter (DOM) is distributed ubiquitously in water bodies. Ferric ions can flocculate DOM to form stable coprecipitates; however, Al(III) may alter the structures and stability of Fe-DOM coprecipitates. This study aimed to examine the coprecipitation of Fe, Al, and DOM as well as st...
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Published in | Chemosphere (Oxford) Vol. 316; p. 137737 |
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Main Authors | , , , , |
Format | Journal Article |
Language | English |
Published |
England
Elsevier Ltd
01.03.2023
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Subjects | |
Online Access | Get full text |
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Summary: | Dissolved organic matter (DOM) is distributed ubiquitously in water bodies. Ferric ions can flocculate DOM to form stable coprecipitates; however, Al(III) may alter the structures and stability of Fe-DOM coprecipitates. This study aimed to examine the coprecipitation of Fe, Al, and DOM as well as structural developments of Fe-DOM coprecipitates in relation to changes in Fe/Al ratios and pHs. The results showed that the derived Fe/Al/DOM-coprecipitates could be classified into three categories: (1) at pH 3.0 and 4.5, the corner-sharing FeO6 octahedra associated with Fe–C bonds with Fe/(Fe + Al) ratios ≥0.5; (2) the Fe–C bonds along with single Fe octahedra having Fe/(Fe + Al) ratios of 0.25; (3) at pH 6.0, the ferrihydrite-like Fe domains associated with Fe–C bonds with Fe/(Fe + Al) ratios ≥0.5. At pH 3.0, the Fe and C stability of the coprecipitates increased with increasing Al proportions; nonetheless, pure Al-DOM coprecipitates were unstable even if they exhibited the maximum ability for DOM removal. The associations of Al-DOM complexes and/or DOM-adsorbed Al domains with external surfaces of Fe domain or Fe-DOM coprecipitates may stabilize DOM, leading to lower C solubilization at pH 4.5. Although the preferential formation of Fe/Al hydroxides decreased Fe/Al solubilization at pH 6.0, adsorption instead of coprecipitation of DOM with Fe/Al hydroxides may decrease C stabilization in the coprecipitates. Aluminum cations inhibit DOM releases from Fe/Al/DOM-coprecipitates, promoting the treatment and reuse efficiencies of wastewater and resolving water shortages. This study demonstrates that Al and solution pH greatly affect the structural changes of Fe-DOM coprecipitates and indirectly control the dynamics of Fe, Al, and C concentrations in water.
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•Solution pH and Al affect greatly the structural changes of Fe-DOM coprecipitates.•Al-DOM coprecipitates are unstable even if exhibit the maximum DOM removal at pH 3.•C associated with mixed and homogeneously distributed Fe/Al can form stable FAC.•Al is an important cation controlling the C dynamics in water systems with Fe. |
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Bibliography: | ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 |
ISSN: | 0045-6535 1879-1298 |
DOI: | 10.1016/j.chemosphere.2023.137737 |