Decolorization of anionic dye solutions using the hydrophobically modified polyelectrolytes containing beta-cyclodextrin moieties

• The hydrophobically modified polyelectrolyte with beta-cyclodextrin moieties was prepared.
• The beta-cyclodextrin derivative acts as a co-monomer as well as a solubilizer of styrene.
• The new polyelectrolyte had enhanced properties in the flocculated decolorization.
• The flocculated decolorization mechanism was further proposed.

Without using any surfactants, new hydrophobically modified polyelectrolytes containing beta-cyclodextrin (beta-CD) moieties were prepared by solution polymerization of styrene (St), maleic anhydride esterified beta-CD (beta-CD-MAH) and acryloyloxyethyl trimethyl ammonium chloride (AETAC). Introducing the St moieties as well as reducing the cationic AETAC moieties onto the backbone of copolymer was effective to obtain the polyelectrolyte with obviously improved hydrophobicity. Its chemical composition was confirmed by FT-IR and 1H NMR spectra. As a new flocculant, it had enhanced properties in decolorizing the C.I. reactive violet 5 solutions, i.e. faster decolorization speed, stronger resistance against inorganic salt, more flexibility of pH and wider flocculation window. For the given flocculant/dye solution system, apart from such roles as polymer bridging, electrostatic and covalent bonds, hydrophobic effect contributed to the flocculated decolorization mechanism. But their playing in role was dominated by the dye’s chemical structure and flocculation conditions, especially the temperature and pH.

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