Interactions between organic flocculant PAN-DCD and dyes

Organic flocculant polyacrylonitrile-dicyandiamide (PAN-DCD) was characteri zed by IR, H-1 NMR and C-13 NMR spectra. Polar groups, such as triazine, ca rboxyl, amidine, carbonamide and non-polar groups, such as methylene were i dentified in the macromolecular chain of PAN-DCD. The flocculant effectivel y decolorized the examined dyes in their aqueous solutions under acid condi tion. By comparing the IR spectra of dyes with that of PAN-DCD and that of flocs formed, weak chemical interactions between ainino in PAN-DCD side cha in and sulfonic acid group in the dye molecules were observed through the f ormation of -NH3SO3--, -NH2+SO3-- or/and =NH+SO3--. By using equilibrium di alysis technique, the hydrophobic interactions between PAN-DCD and the dyes in the binding process were also observed from the experimental results. T he binding extent of PAN-DCD to dye KN-R was greater than that of MO. The a ddition of urea into the binding system of KN-R by PAN-DCD reduced the firs t binding constant K from 12.2 x 10(5) (without urea) to 3.48 x 10(5) (with urea). (C) 2001 Elsevier Science Ltd. All rights reserved.