A magnetic nanocomposite prepared from chelator-modified magnetite (Fe3O4) and HKUST-1 (MOF-199) for separation and preconcentration of mercury(II)

We describe a magnetic metal-organic framework for preconcentration of Hg(II). The material is obtained from magnetite (Fe3O4) nanoparticles that were modified with 4-(5)-imidazoledithiocarboxylic acid and then reacted with trimesic acid and Cu(II) acetate to form the metal-organic framework capable of extracting Hg(II). The sorption time, amount of the magnetic nanocomposite, and pH value of the sample were selected as the main affecting factors in sorption, and central composite design and response surface methodology were applied to optimize these parameters. Following sorption of Hg(II), the sorbent is removed by a magnet, Hg(II) is eluted with a solution of thiourea and then quantified by cold vapor AAS. The type, volume and concentration of the eluent, and the elution time were selected for the optimization of the elution. The results showed the sorption process to obey the Langmuir model. The maximum monolayer capacity is as high as 254 mg g(-1), and the Langmuir constant is 0.330 L mg(-1). The findings can be well described by pseudo second-order kinetics. High sorption capacity means that one needs less sorbent. Under the optimal conditions, the limit of detection and limit of quantification for Hg(II) were 10 ng L-1 and 40 ng L-1, respectively and the relative standard deviations are < 8.3 %. The nanocomposite was successfully applied to the rapid extraction of trace amounts of mercury ions from fish and canned tuna samples.