Preparation of κ-carrageenan/graphene oxide gel beads and their efficient adsorption for methylene blue

A series of environmental-friendly adsorbents, κ-carrageenan/graphene oxide gel beads (κ-Car/GO GBs), were synthesized from κ-carrageenan and graphene oxide via a simple method. The composition and morphology of these gel bead adsorbents were characterized by Fourier transform infrared spectroscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, thermogravimetric analysis, scanning electron microscopy, etc. The adsorption ability of κ-Car/GO GBs was investigated by measuring the removal of methylene blue (MB) from aqueous solutions. The effects of the initial dye concentration, adsorption time, temperature and pH value were evaluated. The results of the adsorption experiments were consistent with the Langmuir model, while the adsorption kinetic data were fit with a pseudo-second-order model. The maximum adsorption capacity of κ-Car/GO GBs for MB is 658.4mg/g at 25°C, which barely declined even after five cycles. Hence, the κ-Car/GO GBs are outstanding adsorbents with high adsorption capacity and excellent regeneration ability. Furthermore, the gel bead adsorbents could be easily separated from aqueous solutions after adsorption using a simple filtration method.