Application of magnetic graphene-based bucky gel as an efficient green sorbent for determination of mercury in fish and water samples

In this article, a highly efficient method based on coupling magnetic solid-phase extraction and dispersive microsolid-phase extraction was proposed to preconcentrate Hg2+. In this technique, extraction of Hg2+ was carried out by magnetic graphene-based bucky gel (MGBG). MGBG was prepared by dispersing magnetic graphene (MG) in a [Hmim][BF4]. Utilization of [Hmim][BF4] led to better dispersion of MG in aqueous solution and decreased the extraction time. In addition, MG was separable by an external magnet so filtration steps were omitted. The sorbent was characterized by X-ray diffraction, scanning electron microscopy, alternating gradient force magnetometer and Fourier transform infrared spectroscopy. The preconcentration conditions were optimized as pH value of 1 ± 0.2, dithizone concentration of 8 × 10−6 mol L−1, [Hmim][BF4] volume of 50 µL, MG amount of 5 mg, n-hexane volume of 200 µL and elution time of 5 min. The quantification of Hg2+ was carried out by UV–visible spectroscopy. Under the optimized conditions, limit of detection (2.11 μg L−1), relative standard deviation (2.59%), preconcentration factor (150) and linearity of dynamic range (7–100 μg L−1) were calculated which showed high reliability of sorbent to preconcentrate Hg2+. The effect of interference ions was investigated. The method was successfully applied to preconcentrate Hg2+ in fish and water samples. To better understand the adsorption of Hg2+ onto MGBG, thermodynamic of adsorption is reported.