XPS study of the hematite-aqueous solution interface

Journal Article · Tue Apr 01 04:00:00 EDT 2008 · Surface and Interface Analysis, 40(3-4):349-353

DOI:https://doi.org/10.1002/sia.2657· OSTI ID:934885

Shchukarev, Andrei; Boily, Jean F

The electric double layer at the surface of micrometer-sized hematite platelets dominated by the basal {001} and the edge {012} planes was investigated using the cryogenic XPS technique. Thoroughly dialysed hematite suspensions revealed the presence of surface-bound sodium (2.2 at. %) and chloride (0.4 at. %). Suspensions in 10 mM and 100 mM NaCl revealed additional uptake of sodium and chloride. The Na/Cl atomic ratio follows the pH dependence found with previous studies of goethite, manganite and gibbsite. An excess of Cl- was demonstrated at positively charged hematite surface, and Na+ at negatively charged surfaces. The surface coverage of electrolyte ions was also shown to play an important role on the presence of water at the interface. At low ionic strength the water content was about of 10 at. %, yielding a water/counter-ions atomic ratio of about 3-6, depending on pH. At 100 mM NaCl, however, the large atomic concentrations of sodium and chloride resulted in a water content of about 25 at. %, nonetheless yielding a water/counter-ion atomic ratio about 1. The presence of 100 mM CsCl, on the other hand, yielded the same amount of surface-bound water as in 10 mM NaCl due to a lower surface coverage for Cs and to its weaker affinity for water. Finally, a non-equilibrated hematite sample at pH 4 enabled a description the formation of the electric double layer upon addition of 100 mM NaCl to an electrolyte-free suspension

• Research Organization: Pacific Northwest National Laboratory (PNNL), Richland, WA (US)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC05-76RL01830
• OSTI ID: 934885
• Report Number(s): PNNL-SA-47767; KC0303020
• Journal Information: Surface and Interface Analysis, 40(3-4):349-353, Journal Name: Surface and Interface Analysis, 40(3-4):349-353 Journal Issue: 3-4 Vol. 40; ISSN SIANDQ; ISSN 0142-2421
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
58 GEOSCIENCES
EDL.
HEMATITE
INTERFACES
IONIC CONDUCTIVITY
PH VALUE
SURFACE PROPERTIES
WATER
X-RAY PHOTOELECTRON SPECTROSCOPY
XPS
adsorption
hematite
salt