Heap bioleaching of secondary sulfides in acidic sulfate media requires supply of oxygen to sustain bacterial activities, which are responsible for converting ferrous to ferric ions that act as the oxidant for sulfides oxidation. An alternative water source that is being increasingly explored is seawater for heap leaching, taking advantage of faster leaching kinetics in chloride media. For heap leaching in acidic chloride media, oxygen is required to oxidize cuprous to cupric ions, which are the oxidant for sulfide mineral dissolution. In either leaching media, oxygen mass transfer from the gaseous phase (air) to the liquid phase (leaching solution) is a fundamental process that may limit the kinetics of copper extraction from the minerals. This paper reports the calculations of oxygen mass transfer rate in leaching solutions with high ionic strength and at low oxygen partial pressure, which are relevant to some heap leach operations using seawater and located at high altitude in Chile. Oxygen mass transfer rate is influenced by oxygen mass transfer coefficient and oxygen solubility. We calculated the oxygen mass transfer coefficient as a function of temperature as reported for the sulfate system. Oxygen solubility is a function of temperature, ionic strength, and oxygen partial pressure. The effects of these parameters were quantified using the Tromans' model. The results show that even though oxygen solubility decreases with increasing temperature, oxygen mass transfer rate does not significantly respond to temperature because the oxygen mass transfer coefficient increases with increasing temperature. However, higher ionic strength, relevant to the application of seawater, results in a lower oxygen mass transfer rate. Low oxygen partial pressure at high altitude significantly lowers the oxygen mass transfer rate.
展开▼
