Magnetic graphitic carbon nitride nano-composite for ultrasound-assisted dispersive micro-solid-phase extraction of Hg(II) prior to quantitation by atomic fluorescence spectroscopy

A nanosheet structure of Fe3O4/g-C3N4 magnetic composite has been prepared and utilized as adsorbent for the ultrasound-assisted dispersive magnetic micro-solid-phase extraction of the ultra-trace inorganic mercury [Hg(II)]. Scanning electron microscopy, transmission electron microscopy, X-ray diffraction and Fouries transform infrared spectroscopy images manifested that the hydrothermal systhesis promoted the binding of Fe3O4 particles with g-C3N4. The enrichment performance of composites depended on their compositions, and the recovery of Hg(II) on C-m30 (with Fe3O4/g-C3N4 mass ratio 2:3) was higher than that on other ratios. Recorded data showed that ultrasound wave was an effective method for reducing the agglomeration of magnetic materials and enhancing their adsorption properties. The Hg signal obtained by 80% power input is 3.2 times stronger than the signal by strring mode. X-ray diffraction characterization of the recovered adsorbent showed that g-C3N4 needed to be updated after repeated use for four times. In addition, competitive adsorption may be main factor affecting the inhibitory effect of high concentration methylmercury on inorganic mercury. Under the optimized conditions, the detection limit of the proposed method was 1.4 ng L-1 and relative standard deviation of 4.6% for 0.05 mu g L-1 Hg(II) was obtained. The linear calibration range was 0.005-0.4 mu g L. The accuracy of the method was verified through analysis of the certificated reference materials. The proposed method has been applied in the determination of inorganic Hg in natural water samples. (C) 2019 Elsevier B.V. All rights reserved.