Facile synthesis of cysteine functionalized magnetic graphene oxide nanosheets: Application in solid phase extraction of cadmium from environmental sample

A facile method for synthesis of cysteine functionalized magnetic graphene oxide nanosheets is introduced. In comparison with other metal ions, cysteine has more affinity to coordinate with cadmium, therefore, the modified graphene oxide nanosheets were used as a selective sorbent for solid-phase extraction and determination of trace cadmium in different food samples (rice, wheat, milk and shrimp). Satisfactory recoveries were obtained by using 0.8 mg mL^-1 of sorbent in a pH range of 5-9. The results showed good adsorption capacities (24.39-30.30 mg g^-1 at 298-328 K) of the adsorbent with the high selectivity toward cadmium ions. The process was relatively fast and the equilibrium was established within 5 min and its kinetics followed the pseudo-second order mechanism. The best interpretation for the equilibrium data was given by Langmuir isotherm and the thermodynamic parameters showed that the adsorption process was spontaneous, endothermic and chemical in nature.