Oxidation of chalcopyrite in air-equilibrated acidic solution: Inhibition with phenacyl derivatives
(1. Department of Chemistry, University of Craiova, Calea Bucuresti 107I, 200478, Craiova, Romania;
2. Department of Chemistry, Physics and Environment, ‘‘Dunarea de Jos” University of Galati, 111 Domneasca Street, Galati 800201, Romania;
3. Department of Chemistry, “Al. I. Cuza” University of Iasi, 11 Carol I Blv., Iasi 700506, Romania;
4. Lab. Optical Processes in Nanostructured Materials, National Institute of Materials Physics, P. O. Box MG-7, Bucharest, R077125, Romania)
2. Department of Chemistry, Physics and Environment, ‘‘Dunarea de Jos” University of Galati, 111 Domneasca Street, Galati 800201, Romania;
3. Department of Chemistry, “Al. I. Cuza” University of Iasi, 11 Carol I Blv., Iasi 700506, Romania;
4. Lab. Optical Processes in Nanostructured Materials, National Institute of Materials Physics, P. O. Box MG-7, Bucharest, R077125, Romania)
Abstract: The effects of 4-(2-hydroxyphenyl)-2-(morpholin-4-yl)-1,3-thiazole (Pr02), 1-(3,5-dibromo-2-hydroxyphenyl)- 1-oxoethan-2-yl-N,N-diethyldithiocarbamate (Pr04) and 1-(5-bromo-2-hydroxy-3-methylphenyl)-1-oxoethan-2-yl-O- ethyl xanthate (Pr06) on the aqueous oxidation of chalcopyrite (CuFeS2) in air-equilibrated solution at a temperature of 25 °C and a pH of 2.5 were studied. The effects were investigated by using potentiodynamic polarization, electro- chemical impedance spectroscopy (EIS), scanning electron microscopy coupled with energy dispersive X-ray (SEM/EDX) analysis, aqueous batch experiments, Fourier transform infrared (FTIR) spectroscopy, Raman scattering and quantum chemical calculations. It is found that the anodic current densities decrease in the order of EtOH > Pr02 > Pr04 > Pr06. These results, along with those of the EIS measurements, show that Pr02, Pr04 and Pr06 are effective anodic inhibitors of chalcopyrite aqueous oxidation. Both Raman scattering and FTIR spectroscopy indicate that the elemental sulfur, polysulfide and ferric oxyhydroxides that form on the surface of the mineral are not responsible when it comes to the aqueous oxidation inhibition of chalcopyrite. Quantum chemical calculations show that the adsorption of the tested compounds on the chalcopyrite surface is energetically favorable and so, it can explain the inhibiting effects that were observed.
Key words: chalcopyrite oxidation; phenacyl derivatives; inhibition; potentiodynamic polarization; quantum chemical calculation