2 research outputs found
Chitosan-multilayered graphene oxide hybrid beads for Zn 2 + and metoprolol adsorption
International audienc
Chitosan-multilayered graphene oxide hybrid beads for \protect \text{Zn}^{2+} and metoprolol adsorption
Chitosan (CS) hydrogel beads and hybrid beads made of a blending of CS hydrogels and Multilayer Graphene Oxide (MGO) were synthesized. The hybrid beads were prepared by gelation in NaOH solution of a 1 wt% CS acid solution with addition of MGO at either 1.5 wt% or 3 wt% loading rates. Prepared beads were characterized by infrared spectroscopy, thermogravimetric analysis (TGA), scanning electron cryo-microscopy and Brunauer–Emmett–Teller (BET) specific surface area measurements. and Metoprolol (MTP) adsorption kinetics and isotherms were studied on the pristine and hybrid CS hydrogel beads. The adsorption kinetics of and MTP in hybrid beads is limited by the diffusion to the MGO sites depending on their accessibility. While pure CS is not efficient for the MTP adsorption, the Langmuir-type isotherms of the 3 wt% MGO hydrogel beads (dose: 5 mg/100 mL) show 163 mgg maximum adsorption uptake. The MTP adsorption kinetics and isotherm suggest a MTP trapping on the MGO anionic sites (carboxylate groups) by electrostatic interactions. The adsorption capacities are the highest for the 3 wt% MGO hydrogel beads (236 mgg), and only of 40 mgg for the pure CS beads. The presence of adsorption sites in the hybrid bead, such as MGO carboxylate groups giving electrostatic interactions, and CS amine groups leading to complexation, provides synergic adsorption effects. The competitive adsorption of with respect to MTP in equimolar mixture was observed on hybrid beads (dose: 200 mg/100 mL) at 2 mmolL initial total concentration. At pollutant initial total concentration lower than 1.5 mmolL, no competition occurs. The regeneration at pH 4 of the hybrid beads toward MTP or adsorption was found to be 35–40% of the initial adsorption uptake for five adsorption/regeneration cycles