Investigation of the adsorption of dithiophosphate and dithiophosphinate on chalcopyrite as a function of pulp potential and pH

Güler, Taki
Pulp potential and pH play important roles on flotation of sulphide ores. These parameters define the redox products formed on sulphide mineral surface. Therefore, it is essential to investigate electrochemical behaviour of sulphide minerals under different conditions. In this research, electrochemical behaviour of chalcopyrite from Artvin- Murgul deposit were investigated in the presence and absence of dithiophosphate (DTP) and dithiophosphinate (DTPI) by cyclic voltammetry and Diffuse Reflectance Infrared Fourier Transform (DRIFT) spectroscopy. Microflotation tests were performed by using a modified Hallimond tube to determine the effect of pulp potential (Eh), pH and collectors. Cyclic voltammetry studies showed that iron preferentially dissolves from chalcopyrite surface and would cause iron-deficient, S°-rich surface in acid iiisolution, and iron-hydroxide precipitation on chalcopyrite in neutral and alkaline solutions. DTP and DTPI caused surface passivation and did not form any redox peak on voltammograms. Compounds, which adsorbed on the surface of chalcopyrite electrode, were identified by DRIFT spectroscopy: Adsorbed dithiophosphate (DTP0) would be the major surface compound of chalcopyrite at reducing and mildly oxidising potentials, whereas at oxidising potentials, CuDTP+(DTP)2 may be in acid solutions in DTP induced condition. However, hydrophobic DTP species could not be defined in neutral and alkaline pH. On the other hand, in DTPI induced condition, CuDTPI formed in acid and neutral solutions. In alkaline conditions, CuDTPI formation at reducing potentials and Cu(DTPI)2 and/or (DTPI)2 formation on mineral surface at oxidising potentials would be possible. Microflotation tests demonstrated that maximum recovery could be obtained in acid solutions possibly due to iron-deficient surface. It decreased with increasing pH because of hydrophilic surface hydroxides. Recovery increased up to mildly oxidising potentials (100-300 mV) and then decreased. Recovery was low in reducing (<0 mV) and highly oxidising potentials (>300 mV) possibly due to unoxidised surface and surface coverage by hydrophilic oxy/hydroxy species, respectively. Although DTP and DTPI improved flotation recovery, their effect decreased at higher pH values. DTPI displayed higher recoveries than DTP.
Citation Formats
T. Güler, “Investigation of the adsorption of dithiophosphate and dithiophosphinate on chalcopyrite as a function of pulp potential and pH,” Ph.D. - Doctoral Program, Middle East Technical University, 2002.