Impact of crystalline and amorphous iron-and aluminum hydroxides on mechanisms of phosphate adsorption and desorption

作     者：Stella Gypser Florian Hirsch Anja M.Schleicher Dirk Freese 

作者机构：Brandenburg University of Technology Cottbus-Senftenberg Faculty of Environment Process Engineering Biotechnology and Chemistry Department of Soil Protection and Recultivation Brandenburg University of Technology Cottbus-Senftenberg Faculty of Environment Process Engineering Biotechnology and Chemistry Department of Geopedology and Landscape Development German Research Centre for Geosciences Section 3.1 Inorganic and Isotope Geochchemistry 

出 版 物：《Journal of Environmental Sciences》 (环境科学学报（英文版）)

年 卷 期：2018年第30卷第8期

页      面：175-189页

核心收录：

学科分类：0710[理学-生物学] 0830[工学-环境科学与工程（可授工学、理学、农学学位）] 07[理学] 09[农学] 

基　　金：the German Federal Ministry of Education and Research (BMBF) for funding the BonaR es project InnoS oil Phos (No. 031A558) 

主　　题：Phosphate Adsorption Desorption Surface complexation Precipitation FT-IR 

摘      要：Fourier-transform infrared（FT-IR） spectroscopic experiments were carried out during phosphate adsorption on highly crystalline gibbsite, poorly crystalline 2-line-ferrihydrite and amorphous iron–aluminum–hydroxide mixtures in the molar ratio 1：0, 10：1, 5：1, 1：1, 1：5, 1：10 and 0：1. The OH stretching vibrational bands were utilized to analyze changes in structural and surface OH groups during adsorption, because the position of characteristic P／O vibrational bands can shift depending on reaction conditions, pH or adsorbed phosphate *** and desorption kinetics were studied at pH6 and different initial phosphate concentrations to achieve varying phosphate coverage on the mineral surfaces. For gibbsite the formation of AlHPO4 and Al2HPO4 can be assumed, while for ferrihydrite, a FeHPO4 or Fe2PO4 complex and the precipitation of FePO4 with longer equilibration time were ***2HPO4 or a Fe2PO4 surface complex was deduced for Fe-hydroxides, an AlH2PO4 surface complex was identified for Al-hydroxide, and both displayed either hydrogen bonds to neighboring hydroxyl groups or hydrogen bonds to outer-sphere complexes. Fe：Al-hydroxide mixtures with high Al ratios showed a low phosphate desorption rate, while ferrihydrite and the Fe：Al-hydroxide mixtures with high Fe ratios had almost negligible desorption rates. It was concluded that within the weakly associated amorphous FeO（OH） materials, FePO4 precipitated, which was bound by outer-sphere hydrogen bonds. With high Al ratios, desorption increased, which indicated weaker phosphate binding of both inner-sphere and outer-sphere complexes and hence, either no or minor quantities of precipitate. Ferrihydrite showed a more rigid structure and a lower extent of precipitation compared to amorphous Fe-hydroxide.