title: A Fourier transform infrared spectroscopic study of Mg-rich, Mg-poor and acid leached palygorskites.
abstract: The FTIR spectra of pure magnesium-rich (Mg-rich) and magnesium-poor (Mg-poor) palygorskites, before and after short-term (<7 h) and long-term (360 h) acid leaching are presented here. Comparison of decomposition spectra of Mg-rich and Mg-poor palygorskites clearly shows that the absorption peaks related to pairs of octahedral cation differ depending on the octahedral site occupancy. Short-term acid leaching of palygorskites results in significant changes to FTIR absorption bands near 1200 and 790 cm-1. As the acid attack progresses, the band at 1200 cm-1 shifts to lower wavenumbers, whilst the band at 790 cm-1, which here is assigned to SiU-O-SiD symmetrical stretching vibration, shifts to higher wavelengths. Longer-term leaching of palygorskites results in the disappearance of 900-1200 cm-1 absorption bands, showing that the palygorskite has largely decomposed to amorphous silica. Assignments of several other bands have been made as follows: several vibrations relate to OH, i.e. 847 cm-1, hygroscopic water (1635 cm-1), Si-O vibrations 1100, 611-621, 470-481 cm-1, etc. appear in the FTIR spectra of 360 h acid leached palygorskite. Three bands near 1100, 611-621 and 470-481 cm-1 relate to Si-O vibration of an ideal hexagonal (Si2O5)n sheet.
authors.affiliation: Department of Earth Sciences, Nanjing University, Nanjing 210093, Peoples Republic of China. caiyf@nju.edu.cn
authors.forename: Yuanfeng
authors.initials: Y
authors.lastname: Cai
authors.forename: Jiyue
authors.initials: J
authors.lastname: Xue
authors.forename: D A
authors.initials: DA
authors.lastname: Polya
mesh_terms: D000143:Acids / Q000737:chemistry; D008274:Magnesium / Q000737:chemistry*; D017616:Magnesium Compounds / Q000737:chemistry*; D017655:Silicon Compounds / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared
chemical_list: D000143:Acids; D017616:Magnesium Compounds; D017655:Silicon Compounds; D008274:Magnesium; C026325:attapulgite