Abstract
Recently, harmful ion, a large amount of phosphorus is contained in wastewater such as an agricultural effluent. The effluent standard is about determined as 10 ppm or less about phosphorus ion. It is, therefore, desired to develop the effective technology for removing phosphorus ion. Since O atom in phosphorus ion charge into minus, it is considered that these ions can be adsorbed by OH site by hydrogen bonding. From this viewpoint, we try to develop a new adsorbent that can remove the phosphoric acid by utilizing OH sites in FeOOH. We prepared various FeOOH adsorbents and examined the effect of the structure of FeOOH and the operation conditions on the removal performance of phosphorus ion. The FeOOH prepared by vacuum drying at 220°C had a high potential to remove the phosphorus ion below 2 or 3 ppm. Furthermore, it was found that the treatment at 320°C in 18 MPa enabled us recover phosphorus ion as a phosphorus iron composite of recycle material. By examining the structure change in the FeOOH during pretreatment and reaction with phosphorus ion by XRD and FTIR, it was clarified that the state of hydrogen bonding and pore development in FeOOH and the change in dielectric constant of water were a crucial factor for the removal of phosphorus ion. Thus, the proposed method gives a new route to recycle the phosphorus ion as well as to treat wastewater.
