A selectivity-controlled adsorbent of molybdenum disulfide nanosheets armed with superparamagnetism for rapid capture of mercury ions

Abstract

Although the mercury pollution is declining in the Western and European parts of the world, it is still a widespread environmental concern because of its notorious toxic effects on aquatic ecosystems and human health. Selective and rapid enrichment is essential for timely monitoring and efficient removal of trace mercury contaminants, but has so far been a big challenge. In the current work, we report a superparamagnetic molybdenum disulfide (Fe3O4@MoS2) with an expanded interlayer spacing (1.0 nm) and high magnetic susceptibility for highly selective and rapid uptake of Hg2+ ions. Upon treatment by Fe3O4@MoS2, over 99% of 15 ppm Hg2+ can be removed in 2 min from aqueous solutions, with an initial adsorption rate as high as 52.62 g mg−1 min−1. Fe3O4@MoS2 also demonstrate capability to efficiently enrich Hg2+ from samples with ppb levels of Hg2+, resulting in an ultralow residual Hg2+ concentration (60 ppt), which is far below the acceptable limit for drinking water (2 ppb). Fe3O4@MoS2 also shows high selectivity for Hg2+versus other eight representative metal ions. Furthermore, the selectivity for heavy metal ions can be optionally tailored by simply controlling the contact time during the uptake. This new finding is in contrast to the previously reported selectivity enhancement strategies by searching for new materials and chemical modification of adsorbents, and would enable additional improvement of selectivity by kinetic process engineering.