Color removal from model dye effluent using PVA-GA hydrogel beads

A low cost polyvinyl alcohol-glutaraldehyde cross-linked hydrogel beads were prepared and used for color removal from model industrial effluent containing Congo Red dye, using adsorption technique. The adsorption studies were performed using batch and fixed-bed reactor. Developed adsorbent, achieved adsorption capacity as high as ~34 mg of dye per gram of bead (condition: pH 6 and 45 °C). These beads were re-used for 7 times (many more runs possible) to remove the color from model dye effluent, without much loss in removal efficiency. Batch studies revealed a multi-layer adsorption governed by Harkins Jura model. Whereas the adsorption kinetics followed fractal like pseudo second order model, controlled by intraparticle diffusion phenomena. The fixed bed studies revealed steeper break through curves during adsorption operation when high dye influent rates and low bed height were used. This behaviour by the fixed bed reactor was best explained by the Thomas mathematical model. Studies further demonstrated that an external and internal mass diffusion become no more rate limiting during these experiments.