Preparation of neutral red functionalized Fe3O4@SiO2 and its application to the magnetic solid phase extraction of trace Hg(II) from environmental water samples

In this work, for the first time, neutral red functionalized Fe3O4@SiO2 was prepared, characterized and subsequently used for magnetic solid phase extraction of Hg(II) from environmental water samples followed by inductively coupled plasma-mass spectrometry determination. TEM images shows uniform decoration of SiO2 on the Fe3O4 surface (with a typical particle size of 220 nm). The FT-IR analysis indicates that neutral red was combined with the SiO2 surface by chemical bonds. Trace levels of Hg(II) can be extracted efficiently and selectively due to the electrostatic and coordinate interactions of Hg(II) and neutral red. Parameters affecting the quantitative recovery of Hg(II) were investigated, and the optimized values were 6.0, 25 mg, 60 min, and 5 mL of 1.0 mol L-1 HNO3 for pH value of the solution, amount of the extractant, equilibration time and volume, concentration of eluent, respectively. Under the optimized conditions, at Hg(II) concentrations as low as 2 ng mL(-1), the recovery is >85%, and the enrichment factor is as high as 100. The commonly encountered ions show no interference with the extraction process. The material can be regenerated and reused at least ten times without loss of adsorption capacity (84 mg g(-1)). In addition, magnetic separation greatly simplifies the extraction procedure and filtration and/or centrifugation processes were avoided. The material was successfully applied for the separation and pre-concentration of low levels of Hg(II) in environmental water samples with satisfactory results.