title: A X-ray photoelectron spectroscopy study of HDTMAB distribution within organoclays.
abstract: X-ray photoelectron spectroscopy (XPS) in combination with X-ray diffraction (XRD) and high-resolution thermogravimetric analysis (HRTG) has been used to investigate the surfactant distribution within the organoclays prepared at different surfactant concentrations. This study demonstrates that the surfactant distribution within the organoclays depends strongly on the surfactant loadings. In the organoclays prepared at relative low surfactant concentrations, the surfactant cations mainly locate in the clay interlayer, whereas the surfactants occupy both the clay interlayer space and the interparticle pores in the organoclays prepared at high surfactant concentrations. This is in accordance with the dramatic pore volume decrease of organoclays compared to those of starting clays. XPS survey scans show that, at low surfactant concentration (<1.0CEC), the ion exchange between Na+ and HDTMA+ is dominant, whereas both cations and ion pairs occur in the organoclays prepared at high concentrations (>1.0CEC). High-resolution XPS spectra show that the modification of clay with surfactants has prominent influences on the binding energies of the atoms in both clays and surfactants, and nitrogen is the most sensitive to the surfactant distribution within the organoclays.
authors.affiliation: Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China. hehp@gig.ac.cn
authors.forename: Hongping
authors.initials: H
authors.lastname: He
authors.forename: Qin
authors.initials: Q
authors.lastname: Zhou
authors.forename: Ray L
authors.initials: RL
authors.lastname: Frost
authors.forename: Barry J
authors.initials: BJ
authors.lastname: Wood
authors.forename: Loc V
authors.initials: LV
authors.lastname: Duong
authors.forename: J Theo
authors.initials: JT
authors.lastname: Kloprogge
mesh_terms: D001546:Bentonite / Q000737:chemistry*; D000077286:Cetrimonium; D002593:Cetrimonium Compounds / Q000737:chemistry*; D013057:Spectrum Analysis / Q000379:methods*; D013501:Surface-Active Agents / Q000737:chemistry; D013818:Thermogravimetry; D014961:X-Ray Diffraction
chemical_list: D002593:Cetrimonium Compounds; D013501:Surface-Active Agents; D001546:Bentonite; D000077286:Cetrimonium