Removal of dyes from water by poly(vinyl pyrrolidone) hydrogel

The interaction between polymer and dye leading to polymer-dye complex formation exhibits many interesting and important practical features. For this purpose, a hydrogel was prepared by cross-linking copolymerization of vinyl pyrrolidone with tetraallyl ammonium bromide in aqueous solution, using K₂S₂O₈ as a radical initiator. Dye extraction experiments were carried out simply by contacting wetted gel samples with aqueous dye solutions at room temperature. Capacities were determined by colorimetric analysis of the residual dye contents. The hydrogel swelled in water showing that reasonable high dye sorption capacity (0.71-1.13 g per gram of gel) was achieved. This material is also able to remove the anionic dyes completely even from highly diluted aqueous dye solutions. No trace absorbance was detected in the visible range, after processing.