Using Fe3O4-graphene oxide-modified chitosan with melamine magnetic nanocomposite in the removal and magnetic dispersive solid-phase microextraction of Cr (VI) ion in aquatic samples

An eco-friendly magnetic nanoparticle (MNPs)-based stir rod-assisted dispersive solid-phase extraction (SRMDSPE) method was proposed for the removal and extraction of Cr (VI) preceding its spectrophotometric determination. The magnetic melamine‐functionalized chitosan-modified graphene oxide (MCMGO) nanocomposites were synthesized as a biocompatible, effective adsorbent with admirable adsorption capacity, great magnetic property and excellent dispersion ability for the adsorption of the Cr (VI) ion. The prepared adsorbent was characterized by XRD, FTIR, TGA, VSM, EDX, and SEM. Different parameters affecting removal and microextraction efficiencies such as sample volume, pH, interferences, volume and type of eluent, and adsorbent dosage were investigated and optimized. The result of isotherm shows that Cr (VI) adsorption followed the Freundlich model. Thermodynamic parameters (i.e., change in the free energy (ΔG0), the enthalpy (ΔH0), and the entropy (ΔS0)) were also evaluated. The overall adsorption process was endothermic and spontaneous. The sorbent elution with ability and reusability was used in dispersive solid-phase extraction. Under optimal conditions, the extraction efficiency was 78.0%, and the enrichment factor was 31.19. The SRMDSPE was successfully quantified in the 0.05–0.5 mg L−1 (R2 = 0.9993) with a detection limit of 0.015 mg L−1. The proposed method was applied to leather wastewater, Tabriz, and some surface waters. The percentage of recoveries for spiked real samples were in the range of 91–101%, and the percentage of relative standard deviations were 2–6%.