title: Spectroscopic Characterization of Azo Dyes Aggregation Induced by DABCO-Based Ionene Polymers and Dye Removal Efficiency as a Function of Ionene Structure.
abstract: The aggregation mode of three azo dyes, methyl orange (MO), ponceau SS (PSS), and direct blue 1 (DB1) induced by three 1,4-diazabicyclo[2.2.2]octane (DABCO)-based ionene polymers having different topologies (i.e., 1,2-ionene, 1,3-ionene, and 1,4-ionene) was investigated in this work. Metachromatic behavior of the dyes in the presence of ionenes, and the stability of the ionene/dye complex were discussed as a function of ionene structure. It was demonstrated that the association of the dye molecules with the ionenes and the metachromasy were strongly influenced by both the dye structure and the ionene topology. Thus, MO, having one -SO3Na group per molecule, was almost stoichiometrically bound to all ionenes regardless of their topology, showing also a metachromatic effect. In sharp contrast, the interaction of PSS and DB1 molecules with ionenes was strongly dependent on the polymer topology. It was found that PSS having two -SO3Na groups per molecule was preferentially bound onto both 1,2-ionene and 1,3-ionene, but DB1, having four -SO3Na groups per molecule and a more complex structure, was efficiently bound only onto 1,2-ionene. The dye removal efficiency with each ionene was evaluated in batch mode taking into account the affinity of ionenes for azo dyes. The experimental isotherms of the dye sorption were fitted with four isotherm models, i.e., Langmuir, Freundlich, Sips, and Dubinin-Radushkevich. It was found that the best fitting of the experimental data was given by the Langmuir, Sips, and Dubinin-Radushkevich isotherm models. The maximum equilibrium sorption capacity, qm, evaluated by the Langmuir model, at 35 °C, was as follows: 985.71 mg MO/g 1,3-ionene, 483.71 mg PSS/g 1,3-ionene, 1010.49 mg PSS/g 1,2-ionene, and 976.7 mg DB1/g 1,2-ionene. Kinetic study of the dye removal indicated chemisorption as the main mechanism of sorption.
authors: "Petru Poni" Institute of Macromolecular Chemistry , Grigore Ghica Voda Alley 41 A, Iasi 700487, Romania.
authors: Ecaterina Stela
authors: ES
authors: Dragan
authors: Institut für Organische Chemie, Universität Regensburg , Universitätsstraße 31, 93053 Regensburg, Germany.
authors: Judith
authors: J
authors: Mayr
authors: Institut für Organische Chemie, Universität Regensburg , Universitätsstraße 31, 93053 Regensburg, Germany.
authors: Marleen
authors: M
authors: Häring
authors: "Petru Poni" Institute of Macromolecular Chemistry , Grigore Ghica Voda Alley 41 A, Iasi 700487, Romania.
authors: Ana Irina
authors: AI
authors: Cocarta
authors: Institut für Organische Chemie, Universität Regensburg , Universitätsstraße 31, 93053 Regensburg, Germany.|IQAC-CSIC , Jordi Girona 18-26, 08034 Barcelona, Spain.
authors: David Díaz
authors: DD
authors: Díaz
keywords: direct blue 1; ionene; metachromasy; methyl orange; ponceau SS; sorption