A SERS spectroelectrochemical investigation of the interaction of flotation collectors with coinage metal surfaces.

Voltammetry and Raman spectroscopy were used to investigate the interaction of the sulphide mineral collectors diisobutyldithiophosphinate (DlBDTPI) and n-butylethoxycarbonylthiourea (BECTU) with Au, Ag and Cu metal surfaces. DIBDTPI is oxidised to its disulphide on Au whereas metal-collector compounds are formed on Ag and Cu. Surface enhanced Raman scattering (SERS) spectra observed from Ag in the presence of DIBDTPI showed that charge transfer chemisorption takes place over a wide potential range. At high potentials, spectra from AgDIBDTPI were also detected. No SERS spectra were evident with Cu electrodes, but the formation of CuDIBDTPI was confirmed from Raman spectra. Similar results were observed with diethyldithiophosphate. At high potentials on Au, Raman spectra were observed that corresponded to those of the disulphide and AuDIBDTPL. SERS spectra observed with Au under laser illumination, showed that S is formed by photolysis of intermediate DIBDTPI radicals. Raman spectra from the Cu(I) BECTU compound are consistent with the crystal structure of this compound which shows the organic molecule to be bonded to metal atoms through both S and N. SERS spectra showed that the major surface species on Cu was the BECTU compound at potentials greater than -0.4 V. The spectrum at about -0.5 V was indicative of charge transfer chemisorption of BECTD.
Voltammetry and Raman spectroscopy were used to investigate the interaction of the sulphide mineral collectors diisobutyldithiophosphinate (DlBDTPI) and n-butylethoxycarbonylthiourea (BECTU) with Au, Ag and Cu metal surfaces. DIBDTPI is oxidised to its disulphide on Au whereas metal-collector compounds are formed on Ag and Cu. Surface enhanced Raman scattering (SERS) spectra observed from Ag in the presence of DIBDTPI showed that charge transfer chemisorption takes place over a wide potential range. At high potentials, spectra from AgDIBDTPI were also detected. No SERS spectra were evident with Cu electrodes, but the formation of CuDIBDTPI was confirmed from Raman spectra. Similar results were observed with diethyldithiophosphate. At high potentials on Au, Raman spectra were observed that corresponded to those of the disulphide and AuDIBDTPL. SERS spectra observed with Au under laser illumination, showed that S is formed by photolysis of intermediate DIBDTPI radicals. Raman spectra from the Cu(I) BECTU compound are consistent with the crystal structure of this compound which shows the organic molecule to be bonded to metal atoms through both S and N. SERS spectra showed that the major surface species on Cu was the BECTU compound at potentials greater than -0.4 V. The spectrum at about -0.5 V was indicative of charge transfer chemisorption of BECTD.