Study On Preparation, Characterization And Adsorption Properties Of Oxidized Graphene Composites

Methylene blue(MB) is an important organic dye widely used in textile, dyeing, printing, pesticide, and coating for paper stock. Because of its aromatic ring, MB is highly toxic and very difficult to degrade. Consequently, MB must be removed from wastewater before discharging. Many treatment methods, including adsorption,chemical coagulation, membrane separation, photo-catalytic degradation, biological treatmenthave been developed for the removal of dyes from aquatic environment. Among these methods, adsorption was proved to be an effective method due to its cost-effective, high efficiency, and simple operation. Therefore, preparing an efficienctive and recycled adsorbent is becoming a hotspot.With the rapid development in nanotechnology, nanomaterials have been investigated in water treatment, such as, the carbon nanotubes, and grapheme. Graphene is an ideal two-dimensional sheet of hexagonally arrayed sp2-bonded carbon atoms, has drawn tense attentions due to its unique electronic, thermal, and mechanical properties. As a derivative of graphene, graphene oxide(GO) have some amazing properties, such as abundant oxygen containing functional groups, and large surface area. Futhermore, it can be easily chemical modified and compound, which is of great significance for the applications of nanomaterials.In this paper, cellulose/graphene oxide(CGO) fiber and three-dimensional(3D) agar/graphene oxide(AGO) composite aerogel have been prepared and be used to study the adsorption properties and mechanism for methylene blue.A novel and efficient CGO composite fiber biosorbent was prepared by a wet-spinning technique. The equilibrium adsorption data were well fitted to the Langmuir models, and the adsorption capacity calculated by the Langmuir model reached 480.77 mg/g at 318 K. The thermodynamic parameters indicated that the adsorption was an endothermic and spontaneous process.3D AGO composite aerogel was prepared by a vacuum freeze drying method. The AGO aerogel was tested for its adsorption capacity of 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 pseudo-second-order model best describe the adsorption kinetic data. The thermodynamic parameters calculated from the Van’t Hoff equation indicated 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.