Characteristics of phosphate aluminum oxide hydroxide for ion adsorption-desorption onto preventing eutrophication

Human and industrial activities have recently lead to problems in regard to the eutrofication of isolated bodies of water due to influx of phosphate ions from industrial and domestic wastewater. Various methods have been developed for the removal of phosphate ions. And in particular, adsorption allows efficient and inexpensive recovery of phosphate ions in which the adsorbant and adsorbate are regenerable. In this study, investigations were carried out regarding the production of aluminum oxide hydroxide and granular aluminum oxide hydroxide, the adsorption and desorption capacities of these substances with respect to phosphate ion, and desorption efficiency and phosphate ion recovery levels obtained using sodium hydroxide and sodium carbonate. Adsorption and desorption were repeated 50 times in order to evaluate the effectiveness of aluminum oxide hydroxide, and it was determined that the adsorption performance of aluminum oxide hydroxide and granular aluminum oxide hydroxide with respect to phosphate ions is highly relative to aluminum oxide. The quantity of phosphate ions adsorbed was seen to decrease with repeated use of aluminum oxide hydroxide. The adsorption mechanism for phosphate ions onto aluminum oxide is conjectured as involving the presence of active hydroxyl groups contributing to ion exchange at the surface of the aluminum oxide hydroxide, ion exchange with phosphate ions, and the chemical bonding of hydroxyl groups with phosphate ions. It was thus clarified that aluminum oxide hydroxide is suitable for use as an adsorbant for the recovery of phosphate ions. Moreover, the investigations suggested that this material would be useful for preserving phosphate ion resources by recovering phosphate, a cause of eutrophication, as a value-added sodium phosphate product.