Scanning force microscopy study of etch pits formed during dissolution of a barite (001) surface in CDTA and EDTA solutions

Kang Shi Wang, Roland Resch, Kai Dunn, Patrick Shuler, Yongchun Tang, Bruce E. Koel, Teh Fu Yen

Research output: Contribution to journalArticle

19 Scopus citations

Abstract

Dissolution of the barite (001) surface in aqueous solutions of 0.18 M CDTA (trans-1,2-cyclohexylene-diaminetetraacetic acid) and 0.18 M EDTA (ethylenediaminetetraacetic acid) at pH 12 was investigated using ex situ scanning force microscopy. In both solutions, triangular and trapezoidal etch pits developed on the (001) surface and became deeper and longer with increasing dissolution time. The orientation of the etch pits in CDTA and EDTA solutions was elongated along the crystallographic b axis. Furthermore, dissolution of the (001) surface in a layer-by-layer fashion was observed. This resulted in the formation of `alternating' etch pits with heights of one half-unit cell (about 3.6 angstroms), with the orientations of any two consecutive etch pits pointing oppositely to each other. In CDTA, etch pits within the half-unit cell were frequently bounded along the 〈120〉 and 〈010〉 directions. However, in EDTA, etch pits within the half-unit cell were bounded along the 〈110〉 and 〈010〉 directions. The dissolution behavior of barite in these two solutions is different based on the observed differences in the etch pits geometries as an assay for specific interactions between the crystal surface and organic molecules. Thus, we suggest that CDTA molecules bind to one Ba2+ cation along the 〈120〉 and/or 〈010〉 directions and EDTA molecules bind along the 〈110〉 directions to two Ba2+ cations exposed on the (001) surface.

Original languageEnglish (US)
Pages (from-to)649-655
Number of pages7
JournalLangmuir
Volume16
Issue number2
DOIs
StatePublished - Jan 25 2000
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Materials Science(all)
  • Condensed Matter Physics
  • Surfaces and Interfaces
  • Spectroscopy
  • Electrochemistry

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