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·Al2O3 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·Al2O3 film surface before immobilization of NZVI in the PVDF·Al2O3 film. The resultant PDA/PVDF·Al2O3–NZVI (PPAN) hybrid exhibits high activity and reusability for metronidazole (MNZ) removal. Investigation on mechanical strength of PDA/PVDF·Al2O3 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·Al2O3 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.