Free radical polymerization of polyvinyl butyral/polyethylene glycol diacrylate copolymer for removing organic dyes from waste water

Copolymers of polyvinyl butyral (PVB)/polyethylene glycol diacrylate (PEGDA) were prepared by free radical polymerization using gamma irradiation. The physical properties such as gelation, swelling and the thermal behavior of the prepared PVB/PEGDA copolymer were investigated as a function of molecular weight of PEGDA. The thermal behavior of blank PVB (PVB/PEGDA)-575 and (PVB/PEGDA)-750 copolymers as a function of absorbed dose up to 100 kGy was determined using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The thermal stability of the prepared copolymers was improved by gamma irradiation, PEGDA and the increasing of PEGDA molecular weight. Two textile dyes, Diamine Fast Scarlet GG and Direct Pink 3B, were used as model anionic dyes. The adsorption of PVB/PEGDA hydrogels of different molecular weights was investigated towards the two anionic dyes by the batch equilibrium method. The adsorption capacity of the copolymers was evaluated as a function of initial dye concentration, different molecular weight, and time. The equilibrium data obtained in batch experiments were correlated to Langmuir and Freundlich isotherm equations. Results showed that the adsorption of Direct Pink 3B fitted well to the Langmuir model, while the adsorption pattern of Diamine Fast Scarlet GG followed the Freundlich isotherm, which suggests heterogeneity of the adsorption sites on the copolymer. Thermodynamic data revealed spontaneous exothermic processes and was a physisorption reaction. Our results demonstrate that the PVB/PEGDA copolymer is very promising for removing organic dyes from waste water.