Electrochemical dissolution of roasted gold ore in cyanide solutions

A study of the electrochemical dissolution and passivation phenomenon of roasted gold ore in cyanide solutions

“…At the end of polarization test, a 5-fold higher current density was obtained at 0.1 M to that of 0.01 M NaCN suggesting more dissolution behaviour at high cyanide concentration. For comparison, Bas et al (2015a) did not obtain any passive peak but lower current densities were observed for roasted gold ore electrode alone polarization. Then, it can be deduced that magnetite and hematite have significant and dominating effects on gold leaching and this should be examined case by case.…”

“…Then, corrosion rates of pure gold of 8.60 × 10 −7 ± 4.56% mol m − 2 s − 1 and 10.57 × 10 − 7 ± 1.33% mol m −2 s −1 were found to be for cathodic Tafel slope only and cyanide leaching, respectively. Similarly, authors have found more representative corrosion rates of gold from roasted gold ore considering only cathodic Tafel curve by extrapolating to open circuit potential (3.30 × 10 − 8 ± 3.27% mol m −2 s − 1 ) if compared to that of cyanide leaching (3.07 × 10 − 8 ± 7.03% mol m − 2 s −1 ) (Bas et al, 2015a). Since Tafel curves are generally accepted for an estimation of the corrosion rates of a tested specimen, then the difference in corrosion rates of gold (~25%), which is compatible with the findings of Dai and Breuer (2013), could be considered reasonable.…”

“…Microscopic analysis showed that gold is mainly associated with iron oxides. Metal analysis by atomic absorption spectroscopy (AAS, Perkin Elmer AAnalyst 800) has shown that gold and silver contents are~8 and~5 g/t, respectively (Bas et al, 2015a).…”

“…13), whereas~50 rpm rotation speed is generally used for industrial tank leaching processes (Xianhai Mining, 2015). Authors have recently reported 250 rpm agitation as optimal speed with no indication of passive peak for roasted gold ore polarization (Bas et al, 2015a). It has generally been accepted that the leaching rate of gold increases with increasing agitation speed (Jeffrey and Ritchie, 2001).…”