Graphene/chitosan composite aerogels towards methyl orange and copper ions

The composite of graphene oxide (GO) and chitosan (CS) effectively addresses the issues of GO aggregation, difficult recovery, and the poor mechanical properties and small surface area of CS, while significantly improving the adsorption performance of CS. However, during the composite process, the active sites of GO and CS may react, which reduces the number of available adsorption sites and thereby impacts overall adsorption efficiency. In this study, a composite aerogel (GCG) was prepared using glutamine-modified CS and GO, and its adsorption performance for methyl orange and Cu2+ was investigated. The results show that GCG exhibits significantly better adsorption performance than the unmodified composite aerogel (GC). Under conditions of pH = 3 and 25°C, the maximum adsorption capacity of GCG for methyl orange reached 261.78 mg/g; at pH = 6 and 25°C, the maximum adsorption capacity for Cu2+ was 74.79 mg/g. The adsorption process follows pseudo-second-order kinetics and the Langmuir adsorption isotherm model. After six cycles of adsorption–desorption, the adsorption capacity remained above 85% of the initial value. This study provides important insights for the development of efficient and renewable nanoadsorbents.