COLLOIDS A AND Colloids and Surfaces SURFACES ELSEVIER A: Physicochemicaland Engineering Aspects94 (1995) 67-74 A spectroelectrochemical study of chemisorption of ethyl xanthate on gold R. Woods*, D. S. Kim, C. I. Basilio, R.-H. Yoon Virginia Center for Coal and Minerals Processing, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061 0258, USA Received 15 December 1993, accepted 2 June 1994 Abstract The species formed by the anodic oxidation of ethyl xanthate at gold electrodes has been investigated using an ex situ Fourier transform infrared (FTIR) spectroscopic technique to distinguish between chemisorbed ethyl xanthate and diethyl dixanthogen. Chemisorption of xanthate was found to commence about 0.15 V below the potential at which dixanthogen deposits and to reach a fractional surface coverage of about 0.2 at the reversible value of the xanthate/dixanthogen couple. The coverage increased in parallel with the anodic current arising from dixanthogen deposition. The significance of these findings on the mechanism of the flotation of gold with ethyl xanthate as collector is discussed. Keywords: Chemisorption; Dixanthogen; Ethyl xanthate; FTIR spectroscopy; Gold 1. Introduction red (FTIR) technique. They positively identified dixanthogen and silver xanthate as the oxidation The ethyl xanthate/gold system has been products on pure gold and silver, respectively, and regarded as a model for consideration of the elec- the presence of both species on the alloys. The trochemical aspects of the flotation of sulfide min- FTIR spectra also revealed the presence of erals [1]. Voltammetric studies showed [ 1-5] that "unknown surface species at low potentials", the dixanthogen is the major product of the anodic appearance of which did not correlate with the oxidation of xanthate on gold electrodes and potential at which a finite anodic current was [1,4,5] that the development of a finite contact observed. The spectrum of the "unknown" angle and the onset of flotation of gold particles was characterized by a dominant peak near occurred at a potential close to that of dixanthogen 1200 cm- 1, which is in the range expected for gold deposition. Leppinen et al. [6] studied the anodic and silver xanthates. However, the spectra failed oxidation of ethyl xanthate on silver, gold and to exhibit the other major bands characteristic silver/gold alloy electrodes and characterized the of gold or silver xanthates and, therefore, the products using an ex situ Fourier transform infra- "unknown" species was considered to be most likely a decomposition product of xanthate. Later electrochemical, UV-visible and FTIR * Corresponding author. Permanent address: CSIRO Division of Mineral Products, PO Box 124, Port Melbourne, V i c . spectroscopic studies of the anodic oxidation of 3207~ Australia. ethyl xanthate on silver electrodes established [ 7,8 ] 0927-7757/95/$09.50 © 1995 ElsevierScience B.V. All rights reserved SSDI 0927-7757(94)02964-T