An ESCA study of lunar and terrestrial materials

Abstract--X-ray photoelectron spectroscopy (XPS) has been used to characterize the bonding state of Cu 2 § Si 4+, A13 § and 02 ions in structural (octahedral and interlamellar) or adsorbed position in phyllosilicates. Five smectites, 5 kaolinites, and 1 chrysocolla with Cu(II) in known positions (octahedral, interlamellar, or surface adsorbed) have been investigated. Their spectra were compared with those of pure Cu metal and of pure Cu(I) and Cu(II) oxides.The line for Cu 2p3/2 (binding energy of 935.4 eV) and well-defined shake-up lines (binding energy of about 943 eV) observed after 1 hr of X-ray irradiation are characteristic of Cu(II) in phyllosilicate octahedral sites. But due to the photoreduction effect, they show Cu(I) oxidation states (Cu 2P3/2, binding energy of 933.2 eV and near absence of shake-up lines) for the phyllosilicates with adsorbed Cu or in interlamellar positions. The kinetics of photoreduction distinguishes octahedral from interlamellar positions, and the latter from a surface adsorbed position. The enlargement of the FWHM (full width at half maximum) of XPS lines has been used to describe crystallochemical parameters linked to local ordering around the probe cations. Crystallization produces decreasing O 1 s and Cu 2p (octahedral cation) line widths but has no effect on the Si 2p (tetrahedral cation) line width. The enlargement of FWHM for all ion lines of the lattice is linked to the nature (Cu > Mg > AI) and the number and amount of structural cations in the phyllosilicates.

Section: Structural and Oxidation State Effectsmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

Natural and Synthetic Copper Phyllosilicates Studied by XPS

Mosser

Roméo

et al. 1992

“…Studies of the chemical nature of metal ions in minerals using XPS have been successful in identifying the oxidation state of iron in lunar materials (Huntress and Wilson, 1972). Measurements of the binding energies of aluminum in a variety of materials have revealed that binding energies are affected by stoichiometric changes in composition (Lindsay et al, 1973), but are not affected by alterations in coordination geometry (Anderson and Swartz, 1974).…”

Section: Introductionmentioning

confidence: 99%

A Study of the Adsorption of Ni(II) and Cu(II) by Clay Minerals

Koppelman

Dillard

1977

Abstract--The adsorption of Ni(II) and Cu(II) on to the clay minerMs kaolinite, chlorite, and illite has been investigated. The quantity of Ni(II) at pH 6 and Cu(II) at pH 5 adsorbed has been found to vary in the manner chlorite > illite > kaolinite. Examination of the mode of bonding of the metal ions to the clay minerals using X-ray photoelectron spectroscopy (XPS) has been carried out. Comparison of the binding energies for metal ions in octahedral sites in selected minerals (reference minerals) and in simple nickel and copper containing compounds with values for Ni(II) and Cu(II) adsorbed on chlorite indicate that nickel(II) is probably bound as the aquo ion while copper(II) may be adsorbed as Cu(OH) § INTRODUCTION

“…Core binding energies for Fe, Mg, A1, Si, and O electrons in ten well-characterized silicate minerals (none of them clays) were determined by Adams et al (1972). ESCA spectra of lunar samples reported by Huntress and Wilson (1972) revealed chemical shifts of the Fe (2p) line which are characteristic of Fe 2 +. A difference in core binding energies of bridging and non-bridging oxygen atoms in the silicate tetrahedra of olivines and pyroxenes has been observed (Yin et al, 1971).…”

Section: Introductionmentioning

confidence: 99%

Analysis of Iron-Bearing Clay Minerals by Electron Spectroscopy for Chemical Analysis (ESCA)

Stucki

Roth

Baitinger

1976

Abstract--Nontronite and biotite were analyzed by Electron Spectroscopy for Chemical Analysis (ESCA). Both minerals yielded ESCA spectra with well-defined peaks and the elements identified by the ESCA spectra were in good agreement with the molecular formulas. High resolution scans were made of the iron (2p3/2) and oxygen (ls) electron binding energies for oxidized and reduced forms of nontronite and biotite. Binding energies for Fe 3 § were observed at 711.8 eV in dithionite-reduced nontronite and in oxidized biotite. Peaks for Fe 2 § occurred at 710.0 eV for unaltered biotite, at 709 eV for oxidized biotite and at 708.6 eV for hydrazine-reduced and dithionite-reduced nontronite. The oxygen (Is) peak for unaltered nontronite was skewed to the high energy side of the 530.6 eV maximum, but became more symmetrical as the Fe 2 § content increased.