Study on a novel polyampholyte nanocomposite superabsorbent hydrogels: Synthesis, characterization and investigation of removal of indigo carmine from aqueous solution

The aim of this study was to synthesize and characterize the novel polyampholyte nanocomposite hydrogels (NH) and to investigate the efficiency in the removal of the indigo carmine from the aqueous solutions. Acrylic acid (AA), 2-(diethylamino)ethyl methacrylate (2-DEAEMA) and montmorillonite (MMT) were used as ionic monomers and inorganic component, respectively. In the preparation of NH, in-situ free radical addition polymerization technique was used in the aqueous media. The formation of NH was confirmed by FTIR and XRD analyses. All NH are sensitive to pH and they have zwitter ion characteristics at pH 7.21. The diffusion of water into these gel systems is assumed to be a non-Fickian behavior. The indigo carmine adsorption rate of NH is faster than that of hydrogel. The kinetic studies for indigo carmine adsorption onto NH show that the pseudo-first-order adsorption mechanism is predominant. The adsorption isotherm data indicate that the BET model is the best fit model. It was concluded that the NH synthesized in this study being an adsorbent with the best mechanical properties might be suitable alternative for the removal of indigo carmine from textile aqueous effluents. (C) 2011 Elsevier B.V. All rights reserved.