title: Phosphate adsorption on synthetic goethite and akaganeite.
abstract: Low crystalline iron hydroxides such as goethite (alpha-FeOOH) and akaganeite (beta-FeOOH) were synthesized, and the selective adsorption of phosphate ions from phosphate-enriched seawater was examined. The results of the distribution coefficients (K(d)) of oxoanions in mixed anion solutions at pH 8 follow the selectivity order Cl-, NO3-, SO4(2-) << CO3(2-), HPO4(2-) for goethite, and Cl-, CO3(2-) < NO3- < SO4(2) << HPO4(2-) for akaganeite. In seawater, both adsorbents show high selectivity for phosphate ions despite the presence of large amounts of major cations and anions in seawater. The adsorption isotherms fitted better with the Freundlich equation and the maximum uptake of phosphate from phosphate-enriched seawater was 10 mg P/g at an equilibrium phosphate concentration of 0.3 mg P/L on both adsorbents. The phosphate adsorption/desorption cycles show that akaganeite is an excellent adsorbent even after 10 cycles and its chemical stability is good.
authors.affiliation: Health Technology Research Center, National Institute of Advanced Industrial Science and Technology (AIST), 2217-14 Hayashi-cho, Takamatsu 761-0395, Japan. chitrakar-ramesh@aist.go.jp
authors.forename: Ramesh
authors.initials: R
authors.lastname: Chitrakar
authors.forename: Satoko
authors.initials: S
authors.lastname: Tezuka
authors.forename: Akinari
authors.initials: A
authors.lastname: Sonoda
authors.forename: Kohji
authors.initials: K
authors.lastname: Sakane
authors.forename: Kenta
authors.initials: K
authors.lastname: Ooi
authors.forename: Takahiro
authors.initials: T
authors.lastname: Hirotsu