Efficient flocculation of an anionic dye from aqueous solutions using a cellulose-based flocculant

In this current work, a series of cellulose-based flocculants, carboxymethyl cellulose-graft-poly[(2-methacryloyloxyethyl) trimethyl ammonium chloride] (CMC-g-PDMC) with different grafting ratios were successfully synthesized. CMC-g-PDMC bears high flocculation performance in removal of an anionic dye, Acid Green 25 (AG25), at various pH conditions, which is due to improvement of both positive charge and molecular weight after modification. Moreover, the dye removal efficiency is mostly improved with the increase of grafting ratio. Among the four tested salt additives, CMC-g-PDMC exhibits good salt resistance except for sodium chloride in the measured salt concentration range. Furthermore, the image analysis in combination with fractal theory has been employed to investigate the flocs properties including floc size and fractal structure for studying the flocculation mechanism in detail. It is confirmed that charge neutralization and bridging flocculation effects both play important roles in removal of AG25 from water.