A spectroelectrochemical investigation of the interaction of diisobutyldithiophosphinate with copper, silver and gold surfaces: II. Electrochemistry and Raman spectroscopy

The interaction of the sulphide mineral flotation collector, diisobutyldithiophosphinate (DIBDTPI), with silver, copper, and gold surfaces has been investigated by voltammetry and Raman scattering spectroscopy. Voltammetry showed that DIBDTPI is oxidised to its disulphide on gold whereas the metal-collector compounds are formed on silver and copper. Surface enhanced Raman spectra (SERS) were observed for silver in the presence of DIBDTPI over a wide potential range and demonstrated that charge transfer chemisorption of the collector takes place. At high potentials, Raman spectra from AgDIBDTPI were also detected. No SERS spectra were evident with copper electrodes, but the formation of CuDIBDTPI was confirmed from Raman spectra. Similar results were observed with diethyldithiophosphate on copper, and this indicates that copper metal does not behave in the same manner as copper sulphide minerals with regard to interaction with thiophosphate collectors. At high potentials on gold, Raman spectra were observed from the disulphide and AuDIBDTPI. SERS spectra were also found on gold under laser illumination that were characteristic of the development of layer of sulfur and this is explained in terms of photolysis of DIBDTPI radicals formed as intermediates in the oxidation of DIBDTPI to its disulphide.