title: Effects of Al(3+) doping on the structure and properties of goethite and its adsorption behavior towards phosphate.
abstract: Al substitution in goethite is common in soils, and has strong influence on the structure and physicochemical properties of goethite. In this research, a series of Al-doped goethites were synthesized, and characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR) and extended X-ray absorption fine structure (EXAFS) spectroscopy. The adsorption behavior of these samples towards PO4(3-) was also investigated. Characterization results demonstrated that increasing Al content in goethite led to a reduction in crystallinity, increase in specific surface area (SSA), and morphology change from needle-like to granular. Rietveld structure refinement revealed that the lattice parameter a remained almost constant and b slightly decreased, but c was significantly reduced, and the calculated crystal density increased. EXAFS analysis demonstrated that the Fe(Al)-O distance in the structure of the doped goethites was almost the same, but the Fe-Fe(Al) distance decreased with increasing Al content. Surface analysis showed that, with increasing Al content, the content of OH groups on the mineral surface increased. The adsorption of phosphate per unit mass of Al-doped goethite increased, while adsorption per unit area decreased owing to the decrease of the relative proportion of (110) facets in the total surface area of the minerals. The results of this research facilitate better understanding of the effect of Al substitution on the structure and properties of goethite and the cycling of phosphate in the environment.
authors.affiliation: Key Laboratory of Arable Land Conservation (Middle and Lower Reaches of Yangtse River) Ministry of Agriculture, College of Resources and Environment, Huazhong Agricultural University, Wuhan 430070, China.
authors.forename: Wei
authors.initials: W
authors.lastname: Li
authors.affiliation: Key Laboratory of Arable Land Conservation (Middle and Lower Reaches of Yangtse River) Ministry of Agriculture, College of Resources and Environment, Huazhong Agricultural University, Wuhan 430070, China.
authors.forename: Longjun
authors.initials: L
authors.lastname: Wang
authors.affiliation: Key Laboratory of Arable Land Conservation (Middle and Lower Reaches of Yangtse River) Ministry of Agriculture, College of Resources and Environment, Huazhong Agricultural University, Wuhan 430070, China.
authors.forename: Fan
authors.initials: F
authors.lastname: Liu
authors.affiliation: CAS Key Laboratory of Mineralogy and Metallogeny, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China.
authors.forename: Xiaoliang
authors.initials: X
authors.lastname: Liang
authors.affiliation: Key Laboratory of Arable Land Conservation (Middle and Lower Reaches of Yangtse River) Ministry of Agriculture, College of Resources and Environment, Huazhong Agricultural University, Wuhan 430070, China.
authors.forename: Xionghan
authors.initials: X
authors.lastname: Feng
authors.affiliation: Key Laboratory of Arable Land Conservation (Middle and Lower Reaches of Yangtse River) Ministry of Agriculture, College of Resources and Environment, Huazhong Agricultural University, Wuhan 430070, China.
authors.forename: Wenfeng
authors.initials: W
authors.lastname: Tan
authors.affiliation: Beijing Synchrotron Radiation Facility, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100039, China.
authors.forename: Lirong
authors.initials: L
authors.lastname: Zheng
authors.affiliation: Key Laboratory of Arable Land Conservation (Middle and Lower Reaches of Yangtse River) Ministry of Agriculture, College of Resources and Environment, Huazhong Agricultural University, Wuhan 430070, China; CAS Key Laboratory of Mineralogy and Metallogeny, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China. Electronic address: yinhui666@mail.hzau.edu.cn.
authors.forename: Hui
authors.initials: H
authors.lastname: Yin
mesh_terms: D065966:Absorption, Physicochemical; D000535:Aluminum / Q000737:chemistry*; D058085:Iron Compounds / Q000737:chemistry*; D046529:Microscopy, Electron, Transmission; D008903:Minerals / Q000737:chemistry*; D008956:Models, Chemical; D010710:Phosphates / Q000737:chemistry*; D056951:Photoelectron Spectroscopy; D017550:Spectroscopy, Fourier Transform Infrared; D013499:Surface Properties; D014961:X-Ray Diffraction
chemical_list: D058085:Iron Compounds; D008903:Minerals; D010710:Phosphates; C094886:goethite; D000535:Aluminum
keywords: Adsorption; Al substitution; Goethite; XAFS; XRD