Surface chemistry and flotation of au containing pyrite

Gold occurrence in ore deposits exhibits a wide distribution, ranging from coarse grains to fine particles encapsulated within sulfide minerals. Pyrite is the most common host mineral associated with gold. Flotation is a widely applied method in cases where fine gold particles are present as inclusions within pyrite or where gold is chemically bonded to the mineral. Gold ores contain various types of pyrite with differing gold concentrations, typically ranging from a few ppm to thousands of ppm. This thesis focuses on the surface chemistry and flotation of gold-bearing (AuPy) and barren (BPy) pyrite minerals. Difficulties in the selective flotation of gold-bearing pyrite from barren pyrite lead to industrial challenges such as low gold grades and high smelting costs. The objective of this study is to compare the surface properties of AuPy and BPy using mineral electrodes produced from real ore samples, determine industrially applicable flotation parameters to achieve selective gold-pyrite flotation, and correlate the obtained findings. Within the scope of experimental studies, flotation tests, SEM-EDS (Scanning Electron Microscopy-Energy Dispersive X-Ray Spectroscopy), open circuit potential (OCP), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS) analyses were conducted. Laboratory-scale flotation experiments performed on four different gold-pyrite samples demonstrated that gold-bearing pyrite can be selectively separated from barren pyrite through the use of strong pyrite depressants and selective collectors. Sodium metabisulfite (MBS), identified as the optimum depressant, proved to be an effective and selective pyrite depressant for ores where both gold-bearing and barren pyrite minerals coexist. The results reveal a direct correlation between cyanide-soluble gold (CNSolAu) values and gold recovery, highlighting the role of surface-exposed gold in selective flotation. Electrochemical studies conducted with AuPy and BPy electrodes prepared from natural ore samples showed that the presence of gold increases the oxidation tendency on the pyrite surface through galvanic interactions. Furthermore, it was observed that surface gold is less affected by MBS and other depressants, allowing for the subsequent adsorption of selective collectors. These findings demonstrate that the combined use of appropriate depressants and selective gold collectors enables the effective selective flotation of gold-bearing pyrite.