Azo-Phenol ligand surface-active magnetic graphene oxide nanosheets as solid-phase adsorbents for extraction of cadmium in food samples

A sensitive and simple method using azo-phenol ligand functionalized magnetic graphene oxide nanosheets, as an adsorbent, has been successfully developed for extraction and preconcentration trace amounts of cadmium. The prepared nanosheets were confirmed by Fourier transform infrared spectra, X-ray diffraction, vibrating sample magnetometry and transmission electron microscopy. The main factors affecting the recovery such as the sample pH, adsorbent amount, eluent concentration, time of sonication and coexisting ions have been investigated and established. The adsorption equilibrium data obeyed the Freundlich model and the kinetic data were well fitted to the pseudo-second-order model. Thermodynamic studies revealed the feasibility and endothermic nature of the system. Under the optimum conditions, linear calibration curves were established between 1-10000 μg L-1. Detection limit obtained in this way is 0.4 μg L-1. The relative standard deviation (RSD%) was found to be less than 3.32 %. Accuracy of the method was evaluated by the analysis of different food samples; rice, barley, milk and fish. These results demonstrated that the functionalized magnetic graphene oxide nanosheets can be a potential adsorbent for cadmium removal.