How to select the optimal CIP, CIL, or RIP process based on ore characteristics?

Cyanidation, as a vital branch of hydrometallurgy, has been extensively employed since the last century for extracting precious metals such as gold and silver. This method utilises dilute cyanide solutions to leach gold and silver from ore in air, followed by recovery through activated carbon, ion exchange resins, or zinc displacement. With technological advancements, traditional tank leaching processes have gradually been superseded by more efficient methods such as heap leaching, carbon-in-pulp (CIP), carbon-in-leach (CIL), and resin-in-pulp (RIP), significantly enhancing processing capacity and economic viability.

Carbon-in-Pulp (CIP) involves adding activated carbon (approximately 20g/t) to the pulp during cyanide leaching, extracting gold through adsorption. The gold-loaded carbon is subsequently desorbed and treated via electrowinning. This method replaces the multi-step process of traditional cyanidation with a single leaching-adsorption-desorption cycle, offering high adaptability, excellent recovery rates, and favourable economic benefits.

Carbon-in-Leach (CIL) integrates leaching and adsorption within a single tank, enabling simultaneous leaching and adsorption. Its advantages include lower investment, reduced footprint, and minimal energy consumption, coupled with rapid gold dissolution, making it suitable for easily leachable or low-grade ores. However, CIL faces challenges such as short leaching times, substantial carbon inventory within the process, and significant carbon wear.

Resin-in-Pulp (RIP) technology has gradually supplemented activated carbon due to the latter's limitations, including slow adsorption rates, susceptibility to breakage, and the requirement for high-temperature activation. Resin outperforms activated carbon in adsorption rate, capacity, and desorption efficiency, significantly reducing both capital and operational costs. For instance, after adopting the RIP process at South Africa's Golden Jubilee mine, gold recovery rates increased from 65% to 85%, production capacity rose by 200%, and costs were substantially reduced.

Heap leaching is suitable for processing large volumes of low-grade ore or waste rock. Gold is leached by spraying cyanide solution, with the leachate then cycled and concentrated before gold recovery via activated carbon, resin, or zinc replacement. This method features a straightforward process, is suitable for native gold deposits, handles large volumes, and operates at relatively low cost.

Overall, the cyanidation process offers mature technology, high recovery rates, strong adaptability, and low operating costs, demonstrating clear advantages in extracting fine-grained gold. When selecting specific processes, comprehensive consideration must be given to ore properties, grade, investment budget, and operational costs to determine the most suitable gold extraction pathway.