A novel hierarchical nanobiocomposite of graphene oxide–magnetic chitosan grafted with mercapto as a solid phase extraction sorbent for the determination of mercury ions in environmental water samples

• New mercapto-grafted graphene oxide–magnetic chitosan (GO–MC) has been synthesized.
• A novel biosorbent for the preconcentration of Hg+2 was developed.
• GO–MC was thiol functionalized to prepare a high efficient sorbent for Hg2+.
• A facile and ecofriendly procedure was used for modification of GO–MC.

New mercapto-grafted graphene oxide–magnetic chitosan (GO–MC) has been developed as a novel biosorbent for the preconcentration and extraction of mercury ion from water samples. A facile and ecofriendly synthesis procedure was also developed for modification of GO–MC with 3-mercaptopropyltrimethoxysilane. The prepared nanocomposite material (mercapto/GO–MC) was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR) and energy-dispersive X-ray spectroscopy (EDX). The mercury analysis was performed by continuous-flow cold vapor atomic absorption spectrometry. The parameters affecting the extraction and preconcentration processes were carried out. The optimum conditions were found to be 60 mg of sorbent, pH of 6.5, 10 min for adsorption time, 3 mL of HCl (0.1 mol L−1)/thiourea (2% w/v) as the eluent and 250 mL for breakthrough volume. An excellent linearity was achieved in the range of 0.12–80 ng mL−1 (R2 = 0.999) at a preconcentration factor of 80. The limit of detection and quantification were achieved as 0.06 ng mL−1 and 0.12 ng mL−1, respectively. A good repeatability was obtained with the relative standard deviation (RSD) of 4.7%. Furthermore, real water samples were analyzed and good recoveries were obtained from 95 to 100%.

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