Acid mine drainage includes arsenic. Arsenic is toxic for human body. Therefore, it is necessary to treat arsenic in solutions with adsorbents before discharge. Recently, porous iron oxide is reported as an adsorbent of arsenic acid (As(V)) in acidic condition. Porous iron oxide is aggregate of fine maghemite(γ-Fe2O3) particles and it is synthesized using alkaline treatment of scorodite(FeAsO4·2H2O) or strengite(FePO4·2H2O). The porous iron oxide keeps original particle's shape and size after alkaline treatment. Thus, the material synthesized using large raw material will show good sedimentation property and large specific surface area. On the other hand, spherical is desirable figure to use the material in column. In this study, we synthesized amorphous iron phosphate dihydrate with large and spherical particle using ultrasound oxidation. The ultrasound irradiation advanced particle growth with continuous oxidation and the particle size was 1 μm for 4 h sonication. The porous iron oxide synthesized from amorphous dihydrate iron oxide showed good adsorption capacity of As(V).
