Adsorbed Cr(III) on Chlorite, Illite, and Kaolinite: An X-Ray Photoelectron Spectroscopic Study

Abstract

The adsorption of Cr(III) was studied at pH 1, 2, 3, 4, 6, 8, and 10 on chlorite and kaolinite and at pH l, 2, 3, and 6 on illite. The amount of chromium adsorbed on chlorite varied from 3.1 • l0 -5 mole/ g at pH 1 to 16.6 • 10 -3 mole/g at pH 4, and on illite from 4.9 • 10 -5 mole/g to 9.2 • 10 5 mole/g at pH 1 and 3, respectively. Kaolinite adsorbed 3.7 • 10 -5 mole Cr/g at pH 1, 2, and 3 and 5.5 • 10 -5 mole Cr/ g at pH 4. Measurements of the Cr 2p core-level binding energies indicate that chromium is probably adsorbed as a Cr(III) aqua ion at pH values below 4. The binding energies for the Cr 2p level for samples prepared above pH 4 compare favorably with the value determined for chromium hydroxide and lead to the conclusion that the chromium species present at pH 6, 8, and l0 is chromium hydroxide.

Molecular Structure and Binding Sites of Cobalt(II) Surface Complexes on Kaolinite from X-Ray Absorption Spectroscopy

“…In all sorption samples, a low degree of distortion around sorbed Co is indicated by EXAFS analysis o f the ligating oxygen shell and by the small amplitude of pre-edge feature in the X-ray abs o r p t i o n edges, similar to that o f Co in both Co(NO3)2(aq) and Co(OH)2(s ). The XAS results are in agreement with XPS studies of metal ions on clays that indicate a local electronic environment similar to aquo solution complexes Dillard, 1975, 1977;Koppelman et al, 1980;Dillard and Koppelman, 1982;Schenk et al, 1983). In the lowest uptake samples, backscattering from A1/Si is weak and variable among the different kaolinite samples.…”

“…In a series of investigations, metal ions (Co(II), Ni(II), Cr(III), Fe(III)) sorbed to clays and oxides (kaolinite, illite, chlorite, goethite) as a function of increasing pH were studied by XPS Dillard, 1975, 1977;Koppelman et al, 1980;Dillard and Koppelman, 1982;Schenk et al, 1983). Based on changes in binding energies and peak intensities, these studies concluded that the bonding environment of the metal cation becomes "more ionic" with increasing pH.…”

Adsorption of Cr(NH3)63+ and Cr(en)33+ on Clay Minerals and the Characterization of Chromium by X-Ray Photoelectron Spectroscopy

“…The measured binding energy (BE) for the Cr 2p3/2 level of each chromium complex-clay sample is 577.3 -+ (Table 3) for chromium complexes adsorbed on the three clays are equal, within experimental error, to the Cr 2p binding energies for adsorbed chromium aqua ions (Koppelman et al, 1980). In addition, the N/Cr atom ratio is less than that expected if the complexes were adsorbed as Cr(NH3)~ 3+ or Cr(en)33+.…”

“…It is not likely that Cr(III) is reduced to Cr(II). The equivalence of the binding energies for adsorbed Cr(H.zO)n 3+ (Koppelman et al, 1980) and the hydrolysis products of Cr(en)33+ and Cr(NH3), 3+ suggests that the hydrolysis products are Cr(III) species. Of particular significance is the fact that for Cr(NH3)~ 3+ adsorption, the change in pH is greatest and fastest for chlorite and illite and slowest for kaolinite.…”

Sorption studies of Cs+ and Ba2+ cations on magnesite

“…Many studies of the interactions between radionuclides and dierent mineral matrices have used this powerful tool *To whom all correspondence should be addressed. (Koppelman et al, 1980;Dillard and Koppelman, 1992). In this study the sorption anities of magnesite towards cesium and barium ions are examined.…”