Brandenburg University of Technology Cottbus-Senftenberg, Faculty of Environment, Process Engineering, Biotechnology and Chemistry, Department of Soil Protection and Recultivation, Konrad-Wachsmann-Allee 6, 03046 Cottbus, Germany.
Brandenburg University of Technology Cottbus-Senftenberg, Faculty of Environment, Process Engineering, Biotechnology and Chemistry, Department of Geopedology and Landscape Development, Siemens-Halske-Ring 8, 03046 Cottbus, Germany.
J Environ Sci (China). 2018 Aug;70:175-189. doi: 10.1016/j.jes.2017.12.001. Epub 2017 Dec 12.
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 PO vibrational bands can shift depending on reaction conditions, pH or adsorbed phosphate content. Adsorption 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 AlHPO and AlHPO can be assumed, while for ferrihydrite, a FeHPO or FePO complex and the precipitation of FePO with longer equilibration time were proposed. FeHPO or a FePO surface complex was deduced for Fe-hydroxides, an AlHPO 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, FePO 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.
傅里叶变换红外（FT-IR）光谱实验在高结晶水铝石、低结晶度 2 线水铁矿和无定形铁铝水合混合物吸附磷酸盐时进行，摩尔比为 1:0、10:1、5:1、1:1、1:5、1:10 和 0:1。利用 OH 伸缩振动带分析吸附过程中结构和表面 OH 基团的变化，因为特征 PO 振动带的位置可能因反应条件、pH 值或吸附磷酸盐含量而异。在 pH6 和不同初始磷酸盐浓度下研究吸附和解吸动力学，以实现矿物表面不同的磷酸盐覆盖率。对于水铝石，可以假设形成 AlHPO 和 AlHPO，而对于水铁矿，则提出了 FeHPO 或 FePO 配合物和更长平衡时间下的 FePO 沉淀。对于铁水合氧化物，推断出 FeHPO 或 FePO 表面配合物，对于氢氧化铝，鉴定出 AlHPO 表面配合物，两者都显示出与相邻羟基的氢键或与外部配合物的氢键。高铝比的 Fe-Al 水合混合物显示出低的磷酸盐解吸速率，而高铁比的水铁矿和 Fe-Al 水合混合物几乎没有解吸速率。得出的结论是，在弱缔合的无定形 FeO(OH)材料中，沉淀出 FePO，它由外部氢键结合。高铝比时，解吸增加，这表明内球和外球配合物的磷酸盐结合较弱，因此沉淀量很少或没有。与无定形铁水合氧化物相比，水铁矿具有更刚性的结构和更低的沉淀程度。
