In-depth descriptive investigation of composite sorbent based self-assembled magnetic halloysite nanotube-graphene oxide: Actual use case study for rutin

In this study, a three-dimensional nanocomposite with magnetic features made of magnetic iron oxide nanoparticles (Fe3O4), graphene oxide (GO) and halloysite nanotube (Hal) was prepared and introduced for rutin separation from real sample based on magnetic solid phase extraction (MSPE) process. Hal was modified with chitosan (Hal-COS) and showed positive charge, which can combine with GO by electrostatic force self-assembly to fabricate Hal-GO. Based on this, in-situ growth of magnetic sphere on the surface of Hal-GO demonstrated high specific surface area, chemical and thermal stability, water solubility, and capacity of easy separation in aqueous solution. Several characterizations including FT-IR, HRTEM, TGA and XRD evidenced the successful synthesis of the nanocomposite. The results showed that the optimum adsorption pH was 6 and the optimum adsorption temperature was 25 °C. In addition, further experiments showed that the adsorption process conformed to the Langmuir adsorption model and pseudo-second-order kinetic model, which indicated that the maximum equilibrium adsorption capacity was 107.8 mg g−1 and the maximum equilibrium adsorption time was 120 min. With the optimized conditions, the methodological validation experiments showed that the linear range of MSPE based on Fe3O4@(Hal-GO) combined with HPLC was 10–100 μg mL−1, the correlation coefficient of the fitting equation was 0.9991, the LOD and LOQ reached 0.87 μg mL−1 and 2.9 μg mL−1 respectively. It was confirmed that prepared Fe3O4@(Hal-GO) supported efficient enrichment of rutin when the results were compared to those of other studies.