Hierarchical zero-valent iron fabricated from microfluidic reactor for the removal of organic dyes from aqueous media

Microfluidic devices have been extensively applied for many applications including, but not limited to bio-chemical sensors, micro fuel cell, micro controllable lens, micro cell sorting and chapping devices and microreactors. In this study, microfluidic devices were designed, fabricated and used as a microreactor for synthesis of zero-valent iron nanosheets (ZVIns) by reducing Fe(II) ions in ethanol solution with a reducing agent. The Computational Fluid Dynamics simulation using Ansys Fluent Software was employed to study the mixing process for optimization of ZVIns synthesis conditions via microfluidic device. The prepared ZVIns was characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) mapping, X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR) and magnetic measurements. The ZVIns showed a top layer of the structural flower-like ZVIns clusters with average diameter of 1 µm and a beneath layer of uniform petal-like nanosheets with the thickness of < 50 nm. The removal performance of the resultant ZVIns toward methylene blue (MB) and methyl orange (MO) dyes in the aqueous solution and the influencing factors were investigated. Finally, the possible simultaneous absorption and reduction mechanism of the ZVIns for MB and MO removals were also discussed.