Selective binding behavior of humic acid removal by aluminum coagulation

摘要

AbstractThe reactivity characteristics of humic acid (HA) with aluminium coagulants at different pH values was investigated. It revealed that the linear complexation reaction occurred between aluminum and humic acid at pH < 7, and the reaction rate increased as the pH increased from 2 to 6. While at pH = 7, most of the dosed aluminum existed in the form of free aluminum and remained unreacted in the presence of HA until the concentration reached to trigger Al(OH)3(s)formation. Differentiating the change of functional groups of HA by1H nuclear magnetic resonance spectroscopy and X-ray photoelectron spectra analysis, it elucidated that there was a selective complexation between HA and Al with lower Al dosage at pH 5, which was probably due to coordination of the activated functional groups onto aluminium. While almost all components were removed proportionally by sweep adsorption without selectivity at pH 7, as well as that with higher Al dosage at pH 5. This study provided a promising pathway to analyse the mechanism of the interaction between HA and metal coagulants in future.Graphical abstractDisplay OmittedHighlights•pH < 7, Al reacted with HA at a constant rate at given pH while it increased as pH rose.•pH = 7, dosed Al remained unreacted with HA until critical concentration was reached.•There was a selective complexation between HA and Al at a lower Al dosage at pH 5.•No selectivity occurred at higher Al dosage at pH 5 as well as that at pH 7.