Decoration of defective MoS2 nanosheets with Fe3O4 nanoparticles as superior magnetic adsorbent for highly selective and efficient mercury ions (Hg2+) removal

We report a facile approach to prepare a superior magnetic adsorbent towards Hg 2+ ions by decoration of defective MoS 2 (d-MoS 2 ) nanosheets with Fe 3 O 4 nanoparticles . The adsorption performance of the resulted d-MoS 2 /Fe 3 O 4 nanohybrids towards Hg 2+ ions was studied as a function of solution pH, contact time, and Hg 2+ ions concentration. The d-MoS 2 /Fe 3 O 4 nanohybrids simultaneously showed high adsorption capacity, outstanding selectivity, rapid adsorption rate, and excellent magnetic separation capability for the removal of Hg 2+ ions. Their adsorption capacities at the residual concentration of Hg 2+ ions 1 μg/L (drinking water regulation limit) and 2 μg/L (wastewater regulation limit) are 0.05 mg/g and 0.11 mg/g, respectively. With initial Hg 2+ ions concentration of 10 mg/L, the residual concentration of Hg 2+ ions decreased to as low as 1.7 μg/L after adsorption for only 20 min. The adsorption process can be well fitted by the pseudo-second-order kinetic model and Langmuir isotherm model, respectively. The maximum adsorption capacity of d-MoS 2 /Fe 3 O 4 nanohybrids can reach 425.5 mg/g, which is much higher than other reported magnetic adsorbents. Moreover, the Hg 2+ ions adsorbed d-MoS 2 /Fe 3 O 4 nanohybrids could be well regenerated in acid solution without obvious decline of removal efficiency.