The interaction of N-butoxypropyl-N′-ethoxycarbonylthiourea with sulfide minerals: Scanning electrochemical microscopy, diffuse reflectance infrared Fourier transform spectroscopy, and thermodynamics

The adsorption mechanism of N-butoxypropyl-N′-ethoxycarbonyl thiourea (BOPECTU) on chalcopyrite surfaces was investigated by thermodynamics, scanning electrochemical microscopy (SECM), and diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy. The thermodynamic results demonstrated that the adsorption agreed well with the Langmuir or Freundlich isotherm and the adsorption parameters of thermodynamics were ΔG (303 K) = −31.02 kJ mol−1, ΔS = 10.92 J mol−1 K−1 and ΔH = −27.71 kJ mol−1. It inferred the adsorption of BOPECTU on chalcopyrite was a spontaneously exothermic chemisorption process. The in situ SECM images indicated the adsorption of BOPECTU on chalcopyrite resulted in the decrease of the current response. DRIFT spectra exhibited that after BOPECTU treatment, the characteristic peaks of copper–BOPECTU complex appeared on chalcopyrite surfaces, while on pyrite or sphalerite surfaces, no new peaks appeared. UV–vis and FTIR spectra elucidated that BOPECTU showed more affinities to Cu2+ ions than to Zn2+, Fe3+ or Fe2+ ions, and might bond copper atoms with its sulfur and nitrogen atoms. The results of flotation and adsorption experiments further demonstrated BOPECTU owned stronger collecting ability to chalcopyrite than to sphalerite or pyrite.