Alginate Composite Hydrogel Bead with Multilayer Flake Structure for Dye Adsorptions

With the rapid development of textile industry, a large amount of dye-contaminated effluents was produced and caused serious environmental problem. To remove the dye from effluents, adsorption materials have been applied because of their relatively cheap, high efficiency, and easy handling In this study, a novel composite hydrogel bead with unique multilayer flake structure was fabricated by alginate, acrylamide and attapulgite for dye adsorption. Acrylamide was grafted polymerization onto alginate to obtain alginate-g-poly(acrylamide). Then alginate-g-poly(acrylamide) was cross-linked by Ca2+ ions in present of attapulgite to form composite hydrogel bead. Scanning electron microscopy (SEM) results show that the freeze dried composite hydrogel bead has multilayer flake structure incorporating attapulgite. Fourier transform infrared spectroscopy (FTIR) and Thermo-gravimetric analysis (TGA) results indicate that acrylamide has been successfully grafted polymerization on sodium alginate. Grafting polymerization of acrylamide onto sodium alginate obviously enhances the swelling of hydrogel bead. Incorporating of attapulgite into hydrogel bead effectively enhances the adsorption capacity to methylene blue and the maximum adsorption capacity is 155.7 mg g(-1). Multilayer flake structure increases the adsorption area for methylene blue, but hinders the diffusion of methylene blue into the inner of composite hydrogel bead. High pH solution is beneficial to the adsorption. Pseudo-second order model and Fraundlinch model best describe the adsorption kinetic and isotherm, respectively. These results indicate that composite hydrogel bead is a promising adsorption material for dye-contaminated water treatment.