Gold Cyanidation Extraction: CIL/CIP Processes

gold heap leaching plant site

CIL (Carbon-In-Leach) and CIP (Carbon-In-Pulp) processes are the mainstream technologies in current hydrometallurgical gold extraction. Relying on the synergistic effect of cyanidation leaching and activated carbon adsorption, they achieve efficient leaching and enrichment of gold. With similar technical principles and strong process adaptability, these two processes are widely applied in gold extraction from various gold ores, boasting the technical advantages of high gold recovery rate, controllable operation and good industrial adaptability, and thus have become the core technical solutions for modern gold extraction.

1.Basic Principle

• Cyanidation is a method that uses aqueous solutions of alkali metal cyanides as leaching agents to extract gold and silver from gold and silver ores, followed by the recovery of gold and silver from the leach liquor containing gold and silver.

2.Process Steps

(1) Cyanidation Leaching

• Tank Leaching Cyanidation

• Heap Leaching Cyanidation

Heap leaching for gold ore refers to a process where low-grade gold ore is crushed to a certain particle size (or agglomerated) and stacked on an impermeable pad paved with materials such as asphalt, concrete or plastic. The ore heap is sprinkled with low-concentration cyanide solution, alkaline solution, non-toxic solvent or dilute sulfuric acid solution to dissolve gold. The gold-containing leach liquor percolates out of the ore heap and is then subjected to precipitation and extraction of gold.

(2) Precipitation and Recovery

This step involves converting gold and silver in aqueous solution into solid state through various methods, including:

• Zinc Cementation Process

• Activated Carbon Adsorption Process

• Ion Exchange Resin Process

• Electrowinning Process

• Magnetic Carbon Process

1.CIP (Carbon-In-Pulp) Process

(1) Basic Principle

• The whole-ore cyanidation carbon-in-pulp gold extraction process refers to a technological method in which gold ore is fully ground and pulped (with the content of -200 mesh particles accounting for more than 90-95%), followed by cyanidation leaching. Activated carbon is then used to directly adsorb the dissolved gold from the pulp to obtain gold-loaded carbon. Subsequently, gold mud is obtained through desorption and electrowinning of gold-loaded carbon, and finally gold is purified and smelted from the gold mud through direct separation.

(2) Process Steps

• Preparation of leached pulp

• Cyanidation leaching

• Activated carbon adsorption

• Desorption of gold-loaded carbon

• Gold mud recovery by electrowinning

• Regeneration and recycling of gold-stripped carbon

• Treatment of leached pulp

2.CIL (Carbon-In-Leach) Process

(1) Basic Principle

• Derived from the CIP process, the CIL process involves adding activated carbon to the pulp to realize simultaneous cyanidation leaching and gold adsorption in a single step. It combines the two steps of cyanidation leaching and activated carbon adsorption in the CIP process into one, which reduces material loss and lowers management costs simultaneously.

(2) Process Steps

• Crushing

• Grinding

• Simultaneous leaching and adsorption

• Desorption and electrowinning

• Tailings dewatering

3.Distinction

(1) CIP: Leaching followed by adsorption

• After the cyanidation process is basically complete, carbon is added for adsorption.

(2) CIL: Leaching and adsorption simultaneously

• Carbon is added shortly after the cyanidation process begins, allowing for simultaneous leaching and adsorption.

1.Grinding and Classification Equipment

（1）Ball Mill

（2）Spiral Classifier

（3）Hydrocyclone

2.Cyanidation Leaching Equipment

（1）Agitated Leaching Tank

（2）Cyanidation Tower

3.Solid-Liquid Separation and Concentration Equipment

（1）Thickener

（2）Filter (Vacuum Filter/Plate and Frame Filter)

（3）Filter Press

4.Gold Recovery Equipment

（1）Zinc Cementation Tank

（2）Desorption Column

（3）Electrowinning Cell

（4）Activated Carbon Adsorption Column/Tank

With the technical characteristics of cyanidation leaching and dynamic activated carbon adsorption, the CIL and CIP processes enable flexible application of simultaneous or stepwise leaching and adsorption in gold extraction, effectively improving the gold recovery efficiency and resource utilization rate, and are suitable for the industrial production of gold ores with different grades and types. These processes have the advantages of mature technology, convenient operation and controllable cost. Despite the need for proper environmental treatment of cyanide, they remain the preferred technologies for hydrometallurgical gold extraction. Moreover, with technological upgrading, their application level in green and intelligent production is continuously improved.