Interaction between Al3+ and Poly(acrylic acid) (PAA) in Aqueous Solution—Formation Modes for the Al–PAA Complexes

Mayumi Etou, Kotaro Yonezu, Takanori Inoue, Takushi Yokoyama

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The interaction between Al3+ and poly(acrylic acid) (PAA) which is a polyelectrolyte was investigated under various conditions. It was revealed that PAA has a strong binding ability with Al3+ not only in liquid phase but also in solid phase. Even when no hydrolysis of Al3+ occur at pH 3, the Al3+ was deposited together with PAA under various COOH/Al ratios and formed an insoluble Al–PAA complex. It was found that the hydrolysis of Al3+ was strongly retarded due to the complexation with PAA even under neutral and alkaline conditions. An excess amount of PAA in mixed solution retarded the precipitation of Al3+ at pH 4.5–8. The soluble Al–PAA complex suppressed the formation of the Al13 polycation in solution. Moreover, an insoluble Al–PAA complex was also formed under COOH/Al ratio of 1. The molar ratio of COOH/Al in precipitates was dependent on the pH of the reaction solution. The type of chemical bond involved in the Al–PAA complex was affected by the Al3+ hydrolysis and dissociation of H+ from the carboxyl groups in PAA. At pH 3, one Al3+ combined with three carboxyl groups by substitution reaction with H+. Above pH 3, one Al(OH)2+ or one Al(OH)+2 combined ionically with two or one COO groups, respectively. The results of this study can be potentially applied to formulate a method to remove Al3+ from various wastewater environments in a wide pH range.

Original languageEnglish
Pages (from-to)275-280
Number of pages6
Issue number8
Publication statusPublished - Aug 20 2022

All Science Journal Classification (ASJC) codes

  • General Chemistry
  • General Chemical Engineering


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