Mussel-inspired Fe3O4@Polydopamine(PDA)-MoS2 core–shell nanosphere as a promising adsorbent for removal of Pb2+ from water

Because of the easy-separation, high specific surface areas and rich binding sites, magnetic MoS2 with nanoscale architectures showed great potential in working as adsorbents for heavy metal ions. However, the general composites of nanoscale MoS2 and Fe3O4 suffered from the poor stability in acidic solution due to their entire exposures of Fe3O4 to H+, which made it difficult to regenerate the used adsorbents by the general acid treatment. This work reported a facile approach to prepare Fe3O4@Polydopamine (PDA)-MoS2 nanospheres via in-situ growth of MoS2 on the PDA modified Fe3O4 nanospheres. Fe3O4@PDA-MoS2 nanospheres possessed a fast adsorption of 2.4076 g/mg·min (Initial concentration of Pb2+: 200 mg/L) and high adsorption capacity of 508.9 mg/g at 298 K to Pb2+. This was because the specific surface area of MoS2 grown in-situ on Fe3O4@PDA was 7.6 times that of the pure MoS2, which significantly increased the binding sites of MoS2 for heavy metal ions. In addition, the as-prepared nanocomposites exhibited not only easy-separation within 120 s by an external magnet, but also long-term stability in strong acid solutions as well as facile regeneration by general acid treatment. The tight PDA layers outside the Fe3O4 nanospheres could work as not only a template for the formation of MoS2 nanoflowers but also an efficient protective coating for the improvement of the stability of nanocomposites. The findings might open up the possibility of expanding the practical application of nanoadsorbent in environmental remediation.