Preparation of a porous graphene oxide/alkali lignin aerogel composite and its adsorption properties for methylene blue.

Herein, a three-dimensional porous graphene oxide/alkali lignin aerogel composite was prepared by a simple green method, and its adsorption performance for methylene blue (MB) in water was studied. The graphene oxide/alkali lignin aerogel composite (GO-AL aerogel) was characterized by scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy and the BET surface area. The adsorption kinetics study showed that the adsorption process conformed to the second-order kinetic model and this process was chemical adsorption. It was also found that intraparticle diffusion was not the only rate control step in the adsorption process. The adsorption isotherm study showed that the adsorption process conforms to the Langmuir isotherm adsorption model and the process was a single layer adsorption. The maximum adsorption capacity of MB on GO-AL aerogel was 1185.98 mg/g, at 303 K. Adsorption thermodynamics studies showed that adsorption process was a spontaneous endothermic process and the disorder increased during the adsorption process. Overall, this study indicated the GO-AL aerogel could be an eco-friendly, cost-effective and recyclable adsorbent for the removal of dyes from water.