7 Practical Operational Guidelines for CIP/CIL/CIC Circuits

Author: Yicarb Engineering Specialist 

Technical Whitepaper — Field Solutions 

Date: June 11, 2026 | Version: 1.0

In precious metal recovery, activated carbon 'poisoning' or fouling represents a silent, multi-million dollar leak. Fouling agents physically and chemically mask active adsorption sites, impeding gold dicyanoaurate [Au(CN)2]- mass transfer. This document presents a comprehensive analysis of organic and inorganic fouling and provides 7 field-proven recommendations for prevention and high-efficiency regeneration.

1. Understanding Carbon 'Poisoning' & Fouling /

During CIP (Carbon-in-Pulp) and CIL (Carbon-in-Leach) cycles, activated carbon is exposed to a harsh chemical slurry. Over time, competitive organic compounds and mineral salts deposit into the carbon pore structure, causing progressive deactivation. This process, technically termed 'fouling' or 'poisoning', blocks the pathways (mesopores) and anchoring spots (micropores) needed to bind gold complexes.

Fouling species are broadly classified into two categories: inorganic scaling (which forms a physical crust over pore openings) and organic poisoning (which strongly binds and blocks microporous surface area). The following matrix contrasts their characteristics:

2. Seven Practical Recommendations to Prevent Failure and Regenerate Effectively

Recommendation 1: Implement Strict Upstream Oil & Grease Control

Organic oils (such as lubricating greases from ball mills, crushers, and pump packings) are the most lethal poisons for gold carbon. Even a trace oil concentration (< 5 ppm) in the slurry can cause a catastrophic drop in adsorption rate (R-value). Companies should implement mechanical oil-skimmers in thickeners and run regular maintenance on ball mill seals to completely eliminate leakage into the leaching tanks.

Recommendation 2: Optimize Pre-screening and Wood Fiber Capture

Wood fibers and organic debris originating from timber supports, cardboard packaging, or vegetation can enter the milling circuit. These fibers clog safety screens, leading to carbon loss, and adhere to the active outer surface of carbon particles, blocking passage. High-frequency, dual-deck trash screens must be operated prior to CIL tanks to extract these fibers.

Recommendation 3: Standardize the Acid Wash Protocol

Calcium carbonate scaling is inevitable due to lime addition for pH control. Before thermal regeneration, carbon must undergo acid washing with a 3%-5% hydrochloric acid (HCl) solution. Acid wash dissolves the mineral crust and unclogs transport pores. Failing to acid wash before heating causes the calcium salts to fuse permanently into the carbon grid during kiln firing, causing irreversible surface sintering.

Recommendation 4: Fine-tune Thermal Kiln Parameters

Effective organic regeneration requires a strictly controlled environment inside the rotary kiln. The temperature must be maintained at 650°C to 750°C, with a slight negative pressure, complete oxygen exclusion, and superheated steam injection (0.2 to 0.5 kg steam per kg of carbon). Insufficient temperature fails to crack heavy organics, while excess temperature (> 850°C) without steam causes severe microstructural sintering, destroying micropores.

Recommendation 5: Optimize Quenching and Hydraulic Transfer

When regenerated carbon exits the rotary kiln at > 650°C, it must be instantly quenched in cold water. This thermal shock strengthens the pore walls, but excessive physical impact during this phase will fracture fragile grains. Quench water must be clean and cold, and the carbon must be transferred using gentle water-eductors or recess-impeller slurry pumps rather than abrasive centrifugal pumps.

Recommendation 6: Establish Regular Carbon Activity Audits

To catch deactivation before gold loss occurs, metallurgical labs must run weekly activity audits. This includes testing the ASTM Iodine Number (for total microporosity) and running 30-minute gold adsorption rate (R-value) benchmarking. Comparing regenerated carbon with fresh carbon allows the team to adjust kiln speed, acid strength, or screen sizes dynamically.

Recommendation 7: Prevent Post-Regeneration Storage Contamination

Regenerated carbon is highly active and highly vulnerable. Storing open bags near diesel generators, mining truck parking bays, or oil stores leads to rapid gas-phase poisoning from VOCs (volatile organic compounds) and exhaust fumes. Regenerated carbon must be stored in heavy-duty, sealed woven bags in a clean, isolated dry warehouse with dedicated vapor barriers.

3. Summary & Systematic QA Checklist

An active carbon management strategy is not a separate operation—it is a continuous loop that directly dictates CIL gold recovery efficiency. To implement these 7 recommendations, gold mining companies should adopt the following weekly QA checklist:

• Acid-washed Carbon Calcium Content: Must be maintained at < 1.0% (dry weight). Anything higher indicates insufficient acid wash time or low acid concentration.

• Regenerated Carbon CTC Recovery : Should be restored to $ge 90%$ of the fresh carbon baseline. This ensures transport pores are clear.

 Attrition/Fines Generation : Monitor screen undersize carbon volume. Fines generation exceeding 1.5% per cycle indicates thermal shock damage or over-activation (low hardness).