A biomimetic strategy for improving activity of nano zero-valent iron based on the adhesive behavior of polydopamine on PVDF·Al2O3 film

To enhance the activity and dispersibility of nano zero-valent iron particles (NZVI), PVDF·Al 2 O 3 film is innovatively modified by an environmentally friendly reagent, polydopamine (PDA), via one-step grafting with an in situ simultaneous self-polymerization of PDA onto PVDF·Al 2 O 3 film surface before immobilization of NZVI in the PVDF·Al 2 O 3 film. The resultant PDA/PVDF·Al 2 O 3 –NZVI (PPAN) hybrid exhibits high activity and reusability for metronidazole (MNZ) removal. Investigation on mechanical strength of PDA/PVDF·Al 2 O 3 film indicates that the tensile strengh and modulus of elasticity of the film are significantly improved. Compared with unimmobilized NZVI, the removal efficiency of MNZ by PPAN-2 hybrid synthesized under optimized conditions is increased by 40.2%. Such excellent performance can be attributed to –OH and/or –NH groups in PDA polymer structure that facilitate the interaction and coordination between the precursor of NZVI and functional groups coating on PVDF·Al 2 O 3 film, resulting in the enhanced loading amount, dispersion, and activity of NZVI on PPAN-2 hybrid. Kinetics of MNZ removal by PPAN-2 are found to follow a two-parameter pseudo-first-order model. The presence of humic acid (HA) slightly inhibits the activity of PPAN-2 for MNZ removal. This research suggests that PPAN hybrid may be a promising functional composite for antibiotic wastewater treatment.