Highly efficient removal of aqueous Hg(II) by FeS micro-flakes

FeS (mackinawite) is known to be effective in the sorption of aqueous Hg(II). However, FeS nanoparticles are apt to aggregate and easy to be oxidized, which limits their wide applications. Here, we have synthesized FeS micro-flakes which can be uniformly dispersed in water without aggregation. Owing to the good stability and dispersibility, FeS micro-flakes exhibit high efficiency in the removal of Hg(II) from water. The sorption of Hg(II) on the FeS micro-flakes is more consistent with the pseudo-second-order kinetic model and Langmuir model, indicating that the sorption of Hg(II) is mainly monolayer sorption dominated by chemical sorption. The maximum sorption capacity is 2680 mg/g at pH 5.6 and 30 °C, significantly higher than those of FeS nanoparticles and other Hg(II) scavengers. The pH studies indicate that FeS (0.31 g/L) can effectively remove >97.6 % of 200 mg/L Hg(II) in the pH range of 2-12 at 30 °C. Powder X-ray diffraction, elemental and sorption analyses suggest that Hg(II) is removed via chemical precipitation and surface adsorption. This study demonstrates the potential and viability of FeS micro-flakes for efficient removal of aqueous Hg(II).