Chitosan cross-linked graphene oxide/lignosulfonate composite aerogel for enhanced adsorption of methylene blue in water

Abstract

Graphene oxide (GO)/polymer composites have received wide interests in adsorption of pollutants in water. However, the use of synthetic polymers and toxic cross-linking agents impacts the environment. Herein, a new GO/lignosulfonate aerogel (GLCA) cross-linked by chitosan was prepared without using any toxic chemicals. Characterizations by scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, and X-ray diffraction confirmed the three-dimensional porous structure and diverse functionalities of GLCA. The adsorption performance of GLCA to methylene blue (MB) was investigated by varying pH, dosage, contacting time, temperature and initial concentration. The obtained GLCA could capture MB molecules efficiently and over 99% MB could be removed from a MB solution (100 mg/L). The maximum adsorption capacity of MB onto GLCA was 1023.9 mg/g, higher than other reported GO/polymer composites and activated carbon. Adsorption thermodynamic analysis revealed the adsorption of MB on GLCA was spontaneous and endothermic. The interaction mechanisms involved electrostatic attraction, π-π interaction and hydrogen bond between GLCA and MB. Moreover, GLCA could be regenerated by washing with HCl solution and ethanol for multiple usage. Overall, this study indicated the GLCA could be an eco-friendly, cost-effective and recyclable adsorbent for the removal of dyes from water.