Abstract: Expanded graphite was prepared by natural flake graphite as raw material, phosphoric acid and nitric acid as intercalating agent, potassium permanganate as oxidant.  The chitosan/expanded graphite composite adsorbent was prepared by expanded graphite and chitosan in a certain proportion. The chitosan/expanded graphite was characterized by Fourier transform infrared spectroscopy(FT-IR), scanning electron microscopy(SEM), X-ray diffraction(XRD). The effects of adsorption conditions such as the mass ratio of chitosan and expanded graphite, the dosage of adsorbent, the mass concentration of Congo red, and the adsorption time on the adsorption performance of Congo red wastewater by chitosan/expanded graphite were investigated.  The experimental results show that chitosan is successfully combined with expanded graphite, the adsorption performance is best when the mass ratio of chitosan and expanded graphite is 3∶1, the dosage of adsorbent is 1.75 g/L, the mass concentration of Congo red is 250 mg/L, and the adsorption time is 40 min at room temperature. The adsorption process is more in line with Lagergren pseudo-second-order kinetic equation. The experimental data fit well with the Langmuir isotherm adsorption model. The adsorption process of Congo red on chitosan/expanded graphite is monolayer adsorption.

Key words: chitosan, expanded graphite, adsorption, Congo red, kinetics