Carbon-in-Pulp (CIP) Gold Extraction Method – Efficient Gold Recovery for Complex Ores | TuXingSun

The carbon-in-pulp (CIP) method, also known as the all-slime cyanidation method, is one of the main methods for gold extraction using cyanidation. In this process, all gold ores are ground into slurry, followed by cyanidation leaching. Activated carbon is then used to directly adsorb the dissolved gold from the slurry, and the gold is finally extracted by desorption and electrolysis of the loaded carbon, achieving gold recovery. The CIP method is suitable for low-grade, complex mineral composition, and finely disseminated gold ores, such as disseminated ores, mercury amalgamation residues, gravity separation tailings, and clay-type oxidized ores. This process is advantageous due to its low equipment requirements, short flow, and reduced labor and material costs, which significantly improve economic benefits. The CIP process is particularly effective for complex gold ores that are difficult to extract, making it a cost-efficient and high-recovery solution.

Slurry Preparation

The first step is to crush and grind the gold ore to the desired particle size. The ore undergoes closed-circuit crushing in two or three stages, achieving a final particle size of -12mm. The main crushing equipment used is jaw crushers. Next, the ore undergoes two-stage grinding in a ball mill, reaching a particle size of at least 80%-200 mesh. After crushing and grinding, the slurry concentration needs to meet the standard for cyanidation leaching. Therefore, the slurry undergoes thickening and dewatering using a high-efficiency thickener, bringing the concentration to between 40% and 45%, ready for cyanidation. This preparation ensures that the ore has the appropriate physical and chemical characteristics for cyanidation, leading to a smooth leaching process.

Cyanidation Leaching

The cyanide slurry is introduced into multiple leaching tanks where it undergoes leaching under appropriate temperature, pH, and oxygen conditions. Sodium cyanide reacts with the gold, forming a gold-cyanide complex. To ensure full reaction, the slurry is stirred continuously, typically in 5 to 8 tanks, similar to the traditional cyanidation method. Control over leaching time and reagent concentration is crucial to maximize the leaching rate. Optimizing these parameters ensures the full utilization of gold resources.

Activated Carbon Adsorption

After cyanidation, the slurry is introduced into adsorption tanks where activated carbon adsorbs the gold from the solution. Due to its highly developed pore structure and large surface area, activated carbon effectively captures gold ions. The process involves reverse-flow adsorption, facilitated by carbon screens and slurry lift pumps, which enhance adsorption efficiency. The quality of activated carbon is critical for maximum adsorption, and its unique pore structure enables rapid absorption of gold ions.

Loaded Carbon Desorption and Electrolysis

The loaded carbon is transferred to a desorption tank (or column), and a desorption solution is pumped into the system. The two primary desorption methods are ambient temperature and pressure desorption, and high-temperature and high-pressure desorption. These methods are highly efficient, automated, and do not require sodium cyanide. During desorption, anions are introduced to replace the gold-cyanide complex on the activated carbon, thereby achieving gold desorption. The desorbed gold solution is treated through electrolysis or replacement, recovering the gold.

Activated Carbon Regeneration and Reuse

To maintain the effectiveness of activated carbon, regeneration is essential. The pores of activated carbon may become clogged by inorganic substances such as calcium hydroxide, magnesium hydroxide, or organic materials such as lubricants and reagents. The commonly used regeneration methods include acid washing and thermal regeneration at 600°C to 800°C. Proper regeneration of the activated carbon not only improves its reuse but also reduces operational costs, aligning with environmental standards.

Tailings Slurry Treatment

Cyanide-containing slurry cannot be directly discharged due to its toxicity. Effective treatment methods must be used to ensure the slurry meets safety and environmental standards. Methods include sodium hypochlorite oxidation, chlorine gas oxidation, and alkaline absorption. Choosing the appropriate treatment method depends on the slurry’s composition and concentration, but the ultimate goal is to prevent environmental harm.