As shown in Fig. 5, the raw iron was mainly composed of zerovalent
iron based on the XRD analysis. After hermetically
storing in water for a period, the iron particles used had been
covered with a significant amount of magnetite, presenting a
dense surface with cracks from the SEM image. Under the
anoxic condition, both suspended precipitates and surface
coatings were identified as magnetite (Fe3O4), which was
showed as black partly rounded crystals