Permeable, robust and magnetic hydrogel beads: water droplet templating synthesis and utilization for heavy metal ions removal

By comprehensively utilizing interfacial tension and ultrafast radical polymerization as driving forces, we reported here a water droplet templating polymerization strategy to synthesize dithiocarbamate-decorated poly(vinyl amine) hydrogel beads (DTC-Fe3O4@PVAM) adsorbent material for heavy metal ions removal. The polymerization-induced rapid gelation behavior, being monitored by optical tracer microrheology, was achieved by using reactive monomers and low activation energy initiator. With this method, the monodisperse and size-controlled millimeter-scale DTC-Fe3O4@PVAM beads could be produced in mass. Different from traditional interfacially cross-linked hydrogel beads, the homogeneous polymeric network skeleton containing stable C–N cross-linkages was generated, which could withstand harsh chemical conditions and showed good fatigue resistance. Furthermore, the formed highly permeable macroporous structure is beneficial for mass transfer process and contributes to rapid adsorption equilibriums. Owing to the introduction of chelating DTC groups and Fe3O4 nanofillers, the reported adsorbent material also exhibits considerable adsorption capacities, good foreign ions resistance, convenient magnetic separation and efficient reusability. This work might contribute to the improved design and novel preparation strategy of millimeter-scale hydrogel beads adsorbent materials for water environment remediation.