Magnetic Graphene Oxide/Chitin Nanocomposites for Efficient Adsorption of Methylene Blue and Crystal Violet from Aqueous Solutions

The present study is focused on the synthesis of prominent magnetic graphene oxide/chitin nanocomposites, which behaves as an adsorbent for organic dyes under visible light. The nanocomposites were characterized using physicochemical techniques such as X-ray diffraction, Fourier transform infrared spectroscopy, Raman spectroscopy, vibrating-sample magnetometer, scanning electron microscopy, and transmission electron microscopy. A band gap energy of 2.01 eV was evaluated from Tauc and Davis-Mott plots. Batch adsorption studies were performed on crystal violet and methylene blue dyes with varying parameters such as time, pH, concentration, dosage, and temperature, which resulted to excellent adsorption activities of 403.78 mg/g for crystal violet and 332.61 mg/g for methylene blue. The as-synthesized nanocomposite showed excellent recovery capability, retaining its adsorption efficiency even after nine cycles of regeneration. The adsorption equilibrium data fitted well into the pseudo-second-order model and Langmuir isotherm model, while the spontaneity and exothermic nature of the adsorption phenomenon are demonstrated by thermodynamic studies. A comparative adsorption study results to a selective adsorption of cationic dyes over anionic ones, which goes in conformity with the high negative value of zeta potential obtained at neutral pH.