Synthesis of large porous particles of iron oxide and their arsenic adsorption characteristics in aqueous solution

A novel method has been developed for the synthesis of large porous particles of iron oxide. In this synthesis, large particles of phosphosiderite (FePO ₄2H2 _O)were first prepared by coprecipitation from an Fe(II) and P(V) aqueous solution by oxygen injection at about 368 K. Porous particles of iron oxide were then obtained by removing the phosphorus in the particles in an alkaline solution. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) were used to characterize formation of the porous particles of iron oxide. The extended X-ray absorption fine structure (EXAFS) in the range of the Fe K absorption edge was investigated to characterize the local structure of the porous particles. The characteristics of As adsorption onto the porous particles of iron oxide were examined by analyzing the As concentration in aqueous solution. For comparison, the As adsorption characteristics of y-Fe ₂O ₃ particles, which were prepared from y-FeOOH, were also studied. The results showed that the porous particles of iron oxide prepared from large phosphosiderite particles had superior As adsorption characteristics compared to those of y-Fe ₂O ₃ particles prepared from y-FeOOH. It was shown that large porous particles of iron oxide with high filterability in water are promising for use as As adsorbents in aqueous solution.