Precious metals—such as gold, silver, platinum group metals, and base metals like copper and zinc—are often locked within sulfide ore deposits. While these deposits can be low‑grade, rising market prices and advanced recovery techniques make them economically viable.
Locate ore bodies with sufficient metal content for profitable recovery. Induced polarization (IP) surveys are invaluable for detecting sulfide‑rich zones, as these minerals store electrical energy when charged and release it slowly, allowing geologists to estimate deposit size.
Extract ore and feed it to a gyratory crusher to produce ~6‑inch fragments. Subsequent wet grinding—via ball mills or semi‑autogenous grinders—reduces particles to 5–50 µm, the optimal size for effective froth flotation.
Transport the finely ground ore into flotation cells where it is pulped with water. Add a collector (an organic reagent that selectively binds precious metals) and aerate the pulp to introduce fine air bubbles. The metal‑laden bubbles rise, forming a froth that is skimmed off for further processing.
Introduce alkyl alcohol to the frother cell to stabilize the froth layer. Once the froth is thickened, filter, dry, and package the concentrate. Water is typically recycled within the circuit to minimize environmental impact.
For metals like zinc, copper, and nickel, bioleaching can be employed. Bacteria such as Acidithiobacillus ferrooxidans oxidize the sulfides, liberating metals into an acidic solution. The solution is then treated to recover the metals. This method is also effective for enhancing gold and silver extraction from complex ores. Proper handling of the acid solution is essential to prevent acid mine drainage.
