Gold Cyanidation: Key Processes and Solution Selection

In gold mineral processing, cyanidation stands as a mature and highly efficient hydrometallurgical technique, occupying a central position due to its exceptional recovery capability for fine-grained disseminated gold. This method selectively dissolves gold from ore using a cyanide solution, followed by subsequent processes to recover the metal from the solution. Based on processing methods, cyanidation is primarily categorized into stirred cyanidation and leaching cyanidation to accommodate ores with varying properties.

Agitated Cyanidation: Efficient Processing of Gold Concentrates and Slurries

Agitated cyanidation is suitable for treating finely ground flotation gold concentrates or whole-mine slurries. By ensuring thorough contact between the slurry and cyanide solution in agitated tanks, it achieves rapid gold leaching with high and stable recovery rates. Mainstream processes include Cyanide-in-Pulp (CIP) and Cyanide-in-Leach (CIL).

Cyanidation-in-Pulp (CIP): This process first performs cyanide leaching. After gold is fully dissolved, activated carbon is added to the pulp for countercurrent adsorption. Gold-loaded carbon undergoes desorption, electrowinning, and smelting to produce refined gold, while the activated carbon can be regenerated and reused. CIP achieves recovery rates exceeding 90%, offers relatively simple operation, but involves higher investment and operational costs, requiring strict management of environmental and safety risks.

Carbon-in-Leach (CIL): An optimized variant of CIP, CIL integrates gold leaching and activated carbon adsorption within a single series of tanks for simultaneous processing. This “leach-and-adsorb concurrently” approach reduces equipment requirements, lowers infrastructure and production costs, and improves gold dissolution kinetics by promptly removing dissolved gold from the solution, thereby enhancing leaching rates.

Leach Cyanidation: Economical Processing for Low-Grade Ore

Leach cyanidation primarily treats low-grade, easily leachable oxidized ores or waste rock. Gold is dissolved through cyanide solution permeating fixed ore piles, offering advantages of high throughput and low operating costs. Main methods include tank leaching and heap leaching.

Tank Leaching: Crushed ore is placed in leak-proof leaching tanks and saturated with circulating cyanide solution. After leaching, the precious liquid is collected for gold recovery through replacement. This method suits ores with low clay content, typically achieving 50%-70% recovery rates. While cost-effective, it requires substantial upfront investment, has extended leaching cycles, and efficiency is significantly affected by material permeability.

Heap Leaching: This is an economically viable method for processing low-grade ores (0.5-3 g/t). Crushed ore is piled, and cyanide solution is sprayed onto the heap top. Gold dissolves as the solution percolates through the heap. Enriched solution is collected from the heap base, and gold is recovered via activated carbon adsorption or zinc replacement. Heap leaching features a simple process, low investment, and minimal costs, enabling utilization of vast low-grade resources. Gold recovery rates reach 50%-90%, with tailings discharged after harmless treatment.

Conclusion: Pilot Testing First, Optimize Solutions

Gold ore properties vary greatly, and no universal “best” cyanidation scheme exists. Therefore, conducting systematic mineral processing tests before constructing a processing plant is crucial. Testing enables precise evaluation of ore leachability and determination of optimal parameters—including grinding fineness, cyanide concentration, pH, and leaching time—to tailor a technically efficient and economically viable process flow. Only through this approach can gold recovery rates be maximized, investment and operational costs controlled, and ultimately, an ideal return on investment achieved.