High performance agar/graphene oxide composite aerogel for methylene blue removal

• A novel 3D AGO composite aerogel was prepared by a simple vacuum freeze drying method.
• The aerogel had an excellent adsorption performance for the removal of methylene blue.
• The adsorption process was characterized by kinetics and isotherm analysis.
• The aerogel can be effectively regenerated with a dilute NaOH solution.

A novel three-dimensional (3D) agar/graphene oxide (AGO) composite aerogel was prepared by a vacuum freeze drying method. The AGO aerogel was tested for its adsorption capacity of methylene blue (MB) and was found to have a maximum adsorption capacity of 578 mg/g, as determined from the Langmuir isotherm. The adsorption kinetic studies revealed that adsorption followed pseudo-second-order model. The thermodynamic parameters calculated from the Van’t Hoff equation indicate that the adsorption was an endothermic and spontaneous process. The adsorption mechanism may be attributed to electrostatic interaction between MB and AGO aerogel. Furthermore, the AGO aerogel can easily be recycled with a dilute NaOH solution wash, retaining over 91% of the adsorption capacity after recycling three times.