Application of a new N,S-containing silica-coated nanomagnetic sorbent for the trace quantification of Hg(II) ions in aquatic samples: evaluation of adsorption mechanism

Herein, an effective µ-dispersive solid-phase extraction (µ-dSPE) for the adsorption of Hg(II) ions from various water samples was implemented using a N,S-containing silica-coated nanomagnetic sorbent (Fe3O4@SiO2-N/S). Initially, the sorbent was synthesized via N-substituted amide reaction followed by the characterization by several analytical techniques such as scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), vibrating sample magnetometer (VSM) and X-ray diffraction (XRD). After that, Hg(II) ions interacted with the dentate (N,S) of the dispersed sorbent, which seems to be the cornerstone of the extraction concept. Then, Hg(II) ions were desorbed off the sorbent and quantified by a cold vapor atomic absorption spectrometer (CV-AAS). A number of influential factors impacting the analyte extraction/desorption efficiency were fully investigated, and subsequently, the optimal conditions were established. Under the optimal conditions, the calibration curve was linear over the concentration range of 0.1�5.0 µg L�1, and based on a signal-to-noise ratio of 3 (S/N = 3), the method detection limit was determined to be 0.05 µg L�1 for the analyte of interest. The µ-dSPE method was applied for the determination of Hg(II) in various fortified real aquatic samples to test its performance. The average relative recoveries obtained from the fortified water samples varied in the range of 93�107 with the relative standard deviations of 2.8�6.4. In addition, an investigatory approach regarding the equilibrium adsorption isotherms of the target ion was performed which fitted best to the Langmuir isotherm model. Finally, the method is assumed to have a great potential to be implemented in environmental/other laboratories for the monitoring trace level of Hg(II) ions. © 2020, Iranian Chemical Society