A SERS spectroelectrochemical investigation of the interaction of butylethoxycarbonylthiourea with copper surfaces

The interaction of the sulfide mineral flotation collector, n-butylethoxycarbonylthiourea (BECTU), with copper surfaces at pH 9.2 has been investigated by voltammetry and Raman scattering spectroscopy, NMR, Raman and FTIR spectroscopies have been applied to characterise BECTU and its copper(I) compound to provide a basis for interpreting the spectroelectrochemical data. In the copper compound, the organic molecule is bonded to metal atoms through both its sulfur atom and the nitrogen of the NHCO group of BECTU with the release of the proton. Voltammetry showed that the copper compound is formed above approximately −0.4 V and its presence on the surface inhibits oxide formation. Surface enhanced Raman scattering (SERS) spectra from copper electrodes in the presence of BECTU showed that the major surface species was the copper compound at potentials more than or equal to –0.4 V. The SERS spectrum at approximately −0.5 V was significantly different to that observed from for the bulk compound. This spectrum is interpreted in terms of charge transfer chemisorption of BECTU onto copper atoms in the metal surface.