Dithiophosphinate-pyrite interaction: Voltammetry and DRIFT spectroscopy investigations at oxidizing potentials

The electrochemistry of dithiophosphinate (DTPI) adsorption on pyrite was investigated by cyclic voltammetry (CV) and diffuse reflectance infrared Fourier transformation (DRIFT) spectroscopy at oxidizing potentials under acid, neutral, and alkaline conditions. CV study showed that the mineral surface was covered by porous ferric oxyhydroxide species. Irreversible DTPI adsorption on the pyrite surface and inhibition of electron transfer to some extent were also observed from electrochemical work. Major collector species were determined from DRIFT spectroscopy study as adsorbed collector compound, DTPI°, and dimer of dithiophosphinate, (DTPI)2. Maximum adsorption density of DTPI was obtained in acid solution. It decreased sharply under neutral and alkaline conditions due to heavy surface oxidation at higher pH.