Gold and Silver Ore Carbon-in-Pulp Beneficiation Process

1. Process Overview

The Carbon-in-Pulp (CIP) process is a key technology widely used in gold and silver ore beneficiation. Its core is to adsorb gold and silver ions after cyanide leaching using activated carbon, achieving the separation of precious metals from pulp. It features high efficiency, strong adaptability, and controllable environmental protection. This process is particularly suitable for treating fine-grained disseminated gold and silver ores, effectively improving resource utilization, and is one of the mainstream technologies for precious metal extraction.

2. Basic Principles and Processes

1. Ore Pretreatment
   Raw ore is crushed and ground to a reasonable particle size (usually -200 mesh accounting for over 80%) to fully dissociate gold and silver minerals. The pretreatment stage must strictly control particle size distribution to avoid increased pulp viscosity due to over-grinding or mineral encapsulation caused by under-grinding, which affects subsequent leaching efficiency.

2. Cyanide Leaching
   The pulp enters the leaching tank, and cyanide (such as sodium cyanide) is added as a leaching agent. Under aerated and stirred conditions, gold and silver minerals react with cyanide ions to form soluble gold and silver cyanide complexes (e.g., [Au(CN)₂]⁻, [Ag(CN)₂]⁻). During leaching, pH (usually adjusted to 10-11 with lime), cyanide concentration, and stirring intensity must be controlled to ensure stable leaching efficiency.

3. Activated Carbon Adsorption
   The leached pulp enters the CIP tank, and uniformly sized activated carbon (usually 8-30 mesh) is added. Through physical and chemical adsorption on the surface of activated carbon, gold and silver cyanide complexes are transferred from the solution to the carbon particle surface. The adsorption process requires optimizing activated carbon dosage, pulp flow rate, and contact time to ensure an adsorption rate of over 95%.

4. Gold-Loaded Carbon Treatment
   Gold-loaded carbon with saturated adsorption is desorbed (e.g., high-temperature high-pressure sodium cyanide desorption or zinc powder replacement) to recover gold and silver. The desorbed activated carbon can be recycled after regeneration (acid washing, roasting), reducing costs and solid waste generation.

5. Tail Liquid and Tailings Treatment
   The tail liquid after adsorption is treated to destroy cyanide (e.g., acidification, hydrogen peroxide oxidation) to meet standards before reuse or discharge. Tailings are concentrated, filtered, and stockpiled, and some can be further processed through secondary recovery processes to extract residual gold and silver, maximizing resource utilization.

3. Key Influencing Factors

1. Ore Properties

• Ore type (sulfide ore, oxide ore) determines leaching conditions: sulfide ores require pre-desulfurization, while oxide ores have faster leaching rates but are easily interfered by clay minerals.

• Particle size distribution: fine-grained minerals leach fully but tend to agglomerate, requiring dispersants (e.g., water glass) to improve pulp fluidity.

2. Process Parameters

• Leaching stage: cyanide concentration (0.02%-0.1%), pH value, and stirring speed (200-400r/min) directly affect leaching efficiency.

• Adsorption stage: activated carbon dosage (5-15g/L), pulp temperature (20-40℃), and contact time (1-3 hours) determine adsorption saturation.

3. Reagent Performance
   The stability of cyanide, adsorption capacity of activated carbon (usually 10-30g/kg), and regeneration efficiency are core indicators. The development of new low-toxicity leaching agents (e.g., thiosulfate) and high-efficiency activated carbon is gradually addressing the environmental pain points of traditional processes.

4. Process Optimization and Development Trends

1. Precise Parameter Regulation
   Real-time monitoring of pulp concentration, pH value, and cyanide concentration through intelligent control systems, and dynamic adjustment of stirring speed and reagent dosage can increase gold and silver recovery rates by 3%-5%.

2. Environmental Protection Technology Upgrades

• Promote cyanide-free leaching processes (e.g., thiosulfate-copper ammonia system) to reduce cyanide pollution.

• Tailings resource utilization: biological oxidation is used to treat tailings, recovering residual gold and silver while converting waste residues into building materials.

3. Intelligence and Automation
   Introduce AI algorithms to optimize the leaching-adsorption process, combined with real-time feedback data from sensors, to achieve full-process unmanned operation, reducing labor costs and improving stability.

5. Application Value

Through continuous optimization, the CIP process has been industrially applied in many large gold and silver mines worldwide, such as Beiya Gold Mine in Yunnan, China, and Kalgoorlie Gold Mine in Australia, with beneficiation recovery rates generally reaching 85%-95%. While improving economic benefits, the process gradually meets the standards of "green mines" through environmental transformation, providing technical support for the sustainable development of the precious metal mining industry.