Carbonaceous gold ore is widely recognized as the “hidden killer” in gold ore beneficiation and smelting.Many mine owners, upon receiving lab reports showing promising gold grades, are overjoyed and build carbon-in-pulp (CIP) plants. However, after production begins, they discover that leaching rates are only 50–60 percent, while chemical consumption is exorbitantly high—the problem often lies in the “carbon” present in the ore.Carbonaceous materials adsorb dissolved gold cyanide complexes, effectively “stealing” the gold that should have been recovered and returning it to the tailings—a phenomenon known in the industry as “preg-robbing.”When dealing with this type of ore, the CIL (carbon-in-leach) process—due to its characteristic of “simultaneous leaching and adsorption”—has become the mainstream choice for combating preg-robbing. However, there are many nuances involved in selecting the right CIL process, configuring the equipment, and choosing suppliers.Starting from the characteristics of carbonaceous gold ore, this article systematically analyzes the logic behind CIL process selection, complete equipment configuration, and supplier selection criteria to help you build a carbon-in-leach plant correctly and effectively.

I. Why Is “Gold Robbing” a Critical Concern for Carbon-Bearing Gold Ore?

The “carbon” in carbonaceous gold ore primarily refers to active carbonaceous substances such as organic carbon (humic acid, casein, etc.) and graphitized carbon. Their detrimental effects manifest on three levels:

1. Gold-scavenging effect: The surfaces of active carbonaceous materials possess adsorption activity, causing dissolved gold cyanide complexes to be re-adsorbed into the tailings, resulting in a precipitous drop in leaching recovery. For ores with severe gold scavenging, direct cyanide leaching recovery may drop from 90% to below 50%.

2. Soaring chemical consumption: Carbon-based materials continuously consume cyanide and oxygen, causing operating costs to spiral out of control.

3. Abnormal Grade of Gold-Loaded Carbon: Low gold concentration in the precious metal solution reduces the efficiency of subsequent adsorption and desorption, creating a vicious cycle in the system.

Key Consideration: A high “Total Carbon (TOC)” value on an analysis report does not necessarily indicate gold entrapment. Total carbon includes non-entrapping carbon sources such as carbonate carbon; the true determinants of the extent of gold entrapment are the active organic carbon content and gold entrapment rate tests. Therefore, the first step in selecting a processing method is always to conduct ore sample tests, rather than making decisions based solely on analysis reports.

II. Why Is CIL Preferred Over CIP for Carbonaceous Gold Ore?

Both CIP (Carbon-in-Pulp) and CIL (Carbon-in-Leach) are gold ore leaching and adsorption processes, but their core difference lies in:

• CIP: The leaching tank and adsorption tank are separate; the slurry first undergoes leaching before entering the adsorption tank to come into contact with activated carbon;

• CIL: Leaching and adsorption occur simultaneously in the same tank; once gold is dissolved, it is immediately captured by activated carbon.

For carbonaceous gold ores, the advantage of CIL lies in the “time window”: gold stripping is the process by which “dissolved gold is seized by carbonaceous material”; the longer gold remains in solution, the greater the risk of it being seized.CIL synchronizes leaching and adsorption, allowing activated carbon to “intercept” the gold immediately after it dissolves, thereby significantly shortening the window during which it can be scavenged by carbonaceous materials. As a result, CIL offers significantly stronger resistance to gold scavenging than CIP.

However, CIL is not a panacea. For ores with severe gold scavenging, relying solely on CIL is insufficient; it is usually necessary to combine the following measures:

• Addition of gold scavenging inhibitors (masking agents): kerosene, diesel, nonylphenol ethoxylate, etc., which preferentially occupy the active sites on the surface of carbonaceous materials;

• Flotation decarbonization: First, use flotation to remove carbonaceous matter, thereby reducing the carbon load on the leaching system;

• Pre-treatment: Roasting, bio-oxidation, or pressurized oxidation to disrupt the structure of carbonaceous matter.

Process Selection Conclusion: The CIL process for carbonaceous gold ores typically follows a “CIL as the core + a combination of masking agents/flotation decarbonization/pretreatment” approach. The specific combination must be determined through gold leaching rate tests on ore samples and leaching comparison tests; it is absolutely essential not to simply follow standard design specifications.

III. Complete Process Stages and Equipment Configuration for CIL Plants Processing Carbonaceous Gold Ore

A complete CIL processing line for carbonaceous gold ore typically consists of seven process stages:

1. Crushing and Screening Stage

The ore is crushed to the feed size required for grinding (typically ≤15–25 mm), following the principle of “more crushing, less grinding.” Core equipment: jaw crusher, cone crusher (or impact crusher), vibrating screen, feeder, and belt conveyor.

2. Grinding and Classification Stage

The ore is ground to the fineness required for single-particle liberation of gold (as determined by testing), while avoiding overgrinding and slagging. Core equipment: ball mill, spiral classifier or hydrocyclone, slurry pump.

3. Flotation Decarbonization Section (if determined necessary by testing)

First, carbon-bearing materials (and some sulfides) are removed via flotation to reduce the carbon load entering the leaching system. Core equipment: agitation tanks, dosing systems, SF/BF-type flotation cells, thickeners, and filter presses.

4. Leaching and Adsorption Section (CIL Core)

Leaching and adsorption occur in the same tank; gold is leached with sodium cyanide under alkaline conditions (pH 10–11), while activated carbon adsorbs the gold simultaneously.Core equipment: High-efficiency dual-impeller carbon-in-leach tanks (typically 4–6 stages in series), carbon-separating screens, carbon-extraction pumps (air lifters), sodium cyanide and lime dosing systems, inhibitor dosing system, blowers, and online monitoring of pH and chemical concentration.

Key Configuration Points: The volume and number of stages of the carbon leaching tanks are calculated based on the processing capacity and leaching time; the mesh size of the carbon retention screen must precisely match the particle size of the activated carbon to prevent carbon loss; the addition points for the masking agent must be precise and controllable, as excessive amounts will affect activated carbon adsorption.

5. Desorption, Electrolysis, and Smelting Section

Gold-laden carbon is subjected to desorption to remove gold, followed by electrolysis to produce gold slime, which is then smelted into refined gold. Core Equipment: Desorption and electrolysis equipment (desorption rate up to 96% or higher, electrolysis rate exceeding 99%), gold smelting furnace, and carbon regeneration/acid washing equipment.

6. Tailings and Environmental Protection Section

Cyanide-containing tailings are treated to meet regulatory standards, and tailings are safely stockpiled or dry-discharged. Core equipment: high-efficiency thickeners, filter presses, cyanide removal/neutralization treatment systems, and emergency ponds.

7. Auxiliary and Automation Section

Slurry pumps, carbon-extraction pumps, water pumps, agitation tanks, electrical control systems, and online monitoring systems.

It should be emphasized again: The above represents a typical framework; actual equipment models, quantities, and specifications must be customized based on ore characteristics, processing capacity, gold recovery rate, and site conditions, with the mineral processing test report serving as the definitive reference.

IV. Five Common Misconceptions in CIL Process Selection

Misconception 1: Assuming severe gold leaching simply because the total carbon content is high, and blindly proceeding with pretreatment
. Total carbon includes non-leachable carbon; a gold leaching rate test must be conducted first. Correct Approach: Laboratory analysis + gold leaching rate test + leaching comparison test; make decisions based on data.

Misconception 2: Choosing Between CIP and CIL Arbitrarily.
Carbonaceous gold ores have a strong tendency for gold entrapment, and CIL\'s resistance to gold entrapment is significantly superior to that of CIP. Correct Approach: Verify the difference in recovery rates between CIL and CIP through leaching comparison tests, and give priority to CIL.

Misconception 3: Relying solely on CIL without adding masking agents or decarbonization
. CIL narrows the gold leaching window, but combined measures are still required for ores with severe gold leaching. Correct approach: Conduct tests to evaluate the types and dosages of masking agents, as well as the feasibility of flotation decarbonization, to develop a combined solution.

Misconception 4: Neglecting Gold Losses
from Flotation Decarbonization. Flotation decarbonization removes some gold; recovery rates must be comprehensively evaluated. Correct Approach: Conduct tests to compare the overall recovery rates and economic viability of “decarbonization + tailings CIL” versus “direct CIL + masking agent.”

Misconception 5: Piecing Together Equipment, Leading to Incompatibility in the Leaching and Adsorption System. When
carbon leaching tanks, carbon separation screens, carbon lift pumps, and desorption electrolysis units are sourced from different manufacturers, issues such as carbon carryover, blockages, and mismatched production capacity frequently occur. Correct Approach: Select a turnkey equipment supplier with in-house manufacturing capabilities for core equipment and experience in system integration.

V. Why Choose a Turnkey Equipment Supplier + EPC Model?

CIL projects for carbonaceous gold ore involve multiple stages, including gold recovery testing, process combination evaluation, equipment manufacturing, installation, and commissioning, presenting high technical barriers and complex lines of responsibility.Under the traditional fragmented model—where “design institutes draw up plans, equipment manufacturers sell machines, and construction teams build plant facilities”—multiple parties shift blame when performance targets are not met, forcing mine owners to act as “referees.”

Advantages of choosing a turnkey equipment supplier + EPC model:

• Closed-loop accountability: A single team takes full responsibility for the final outcome, coordinating the entire process from pilot testing to production launch;

• Customized Integration: Processes are tailored based on test data from ore samples, and in-house equipment manufacturing capabilities ensure seamless integration between hardware and process;

• Proactive Anti-Extortion Measures: CIL/CIP selection, suppressant solutions, and flotation decarbonization feasibility are comprehensively planned during the design phase;

• Cost Reduction and Efficiency Improvement: Eliminates hidden costs associated with coordinating multiple parties and shortens the plant construction timeline;

• Reduced Design Costs: Core design phases are completed by our in-house team, saving hundreds of thousands of dollars in design fees for medium- to large-scale projects.

VI. OreSolution\'s Turnkey Equipment Supply Solution for CIL Carbon-in-Leach Plants for Carbonaceous Gold Ore

OreSolution specializes in mining equipment and mineral processing solutions, with operations spanning five major sectors: metal ores, non-metal ores, precious metal ores, alluvial deposits, and tailings/solid waste. The company operates three modern manufacturing bases(Shahe Industrial Park, Zhanggong District, Ganzhou, Jiangxi; Guzhang Industrial Park, Shicheng County, Ganzhou, Jiangxi; and Weifang Heavy Industry Park, Shandong). With 20 years of experience in mining equipment manufacturing and solution integration, our products are exported to more than 80 countries and regions worldwide.As a supplier of complete mineral processing equipment for CIL (carbon-in-leach) plants processing carbonaceous gold ore, we provide comprehensive EPC turnkey services from ore sample testing to production commencement and compliance with standards:

Step 1: Requirements Discussion and Preliminary Assessment
—We assess the ore type, gold grade, total carbon/organic carbon content, sulfur content, processing capacity, and site conditions to propose a preliminary process direction and feasibility assessment.

Step 2: Ore Sample Analysis and Mineral Processing Tests
: Conduct chemical composition analysis, phase analysis, gold recovery rate tests, and leaching comparison tests (CIL vs. CIP; with vs. without masking agents; flotation decarbonization vs. no decarbonization) on representative ore samples, and issue an authoritative “Mineral Processing Test Report,”recommend a process route, parameters, equipment selection, and expected performance indicators. This serves as the scientific foundation for the entire project.

Step 3: Customized Solution Design and Quotation
Based on the test report, we complete the Process Flow Diagram (PFD), equipment configuration list, plant layout plan, 3D layout proposal, and civil engineering requirements drawings, and provide a transparent EPC (Engineering, Procurement, and Construction) budget. All core design work is completed by our in-house team, eliminating the need for you to engage a separate design firm.

Step 4: Equipment Manufacturing and Quality Inspection
Core equipment (crushers, ball mills, flotation cells, high-efficiency twin-impeller carbon-in-leach tanks, carbon separation screens, carbon-extraction pumps, desorption and electrolysis equipment, gold smelting furnaces, thickeners, filter presses, etc.) is manufactured strictly in accordance with drawings and standards, and undergoes rigorous quality inspection prior to shipment.

Step 5: On-Site Installation Guidance and Commissioning
We dispatch senior engineers to the site to guide equipment installation, piping connections, and electrical layout; complete individual unit commissioning and full-process integrated testing; and conduct commissioning with water and feed material until the production line operates stably and meets the contractually agreed-upon performance metrics.Civil engineering work is organized and carried out by the client according to the drawings; we provide technical briefings. Installation workers are sourced locally by the client, with our engineers providing on-site guidance—resulting in lower labor costs and greater flexibility.

Step 6: Personnel Training and After-Sales Support We provide systematic theoretical and hands-on training
for operators and maintenance teams (including equipment start-up and shutdown, parameter adjustment, daily inspections, and troubleshooting). We offer a 12-month warranty period, during which replacement parts are provided free of charge for quality-related issues. After the warranty period, we provide lifetime technical support at cost.

Estimated Timeline: From ore sample testing to final commissioning,the overall timeline is typically 8–12 months (ore beneficiation testing: 30–45 days; engineering design: approximately 30 days; equipment manufacturing: approximately 60 days; logistics and transportation: approximately 60 days; installation and commissioning: 60–150 days). For projects involving carbon-containing ores that are difficult to process, the timeline may be extended slightly due to the complexity of gold recovery testing and process comparison.

VII. Frequently Asked Questions (FAQ)

Q: My gold ore has high total carbon content. Does this necessarily mean gold leaching will be compromised?
A: Not necessarily. Total carbon includes non-leaching carbon such as carbonate carbon; a gold leaching rate test must be conducted to determine this. For ores with low gold leaching rates, conventional CIL is sufficient; only ores with high gold leaching rates require a combination of masking agents, flotation decarbonization, or pretreatment.

Q: What exactly is the difference between CIL and CIP? Why is CIL preferred for carbon-bearing ores?
A: In CIL, leaching and adsorption occur simultaneously in the same tank; gold is captured by activated carbon immediately after dissolution, shortening the window during which it can be leached out by carbonaceous material;CIP is carried out in stages, resulting in a longer residence time for gold in the solution and a higher risk of gold leaching. CIL is the preferred method for carbonaceous gold ores, though this must be verified through comparative leaching tests.

Q: Do masking agents affect activated carbon adsorption?
A: Yes. Excessive amounts of masking agents can occupy surface sites on the activated carbon, reducing the gold loading capacity. Therefore, the type, dosage, and addition point of masking agents must be optimized through testing.

Q: What recovery rate can you guarantee?
A: The recovery rate depends on the characteristics of the ore itself (gold occurrence, degree of gold leaching, grain size, etc.).We do not promise fabricated figures; what we do promise is this: through rigorous mineral processing tests, we will design a process that achieves the highest possible recovery rate under the conditions of your ore, and we will strive for excellence in equipment selection and process control to ensure that actual production results closely match the test expectations.

Q: My mine is overseas. Can you provide on-site support?
A: Yes. We export equipment to over 80 countries and offer technical coordination in English or bilingual formats. Our expert engineers can travel to the site to guide installation, conduct commissioning with actual ore, and provide staff training. We are familiar with logistics routes in Africa, Southeast Asia, South America, Central Asia, and the Middle East.

Q: Are there fees for testing and design?
A: We charge a modest basic service fee; however, upon signing an equipment or EPC contract, the initial testing and design fees can be fully offset against the equipment cost. Testing services can also be purchased separately without any obligation to enter into subsequent cooperation.

VIII. Carbon Is Not a Terminal Illness—Choosing the Right CIL Solution Is the Key

Carbon-bearing gold ores are challenging because carbon-rich materials “steal” gold, chemical consumption is high, and recovery rates remain low.However, there are proven technical approaches within the industry to address these challenges—including CIL simultaneous leaching and adsorption, masking agents, flotation decarbonization, and combined pretreatment methods. The key is to select the right approach based on your ore sample\'s gold leaching rate test data and to implement the process through the closed-loop EPC responsibility of a turnkey equipment supplier.

As a supplier of complete mineral processing equipment for CIL carbon-in-leach plants processing carbon-bearing gold ore, OreSolution has a clear approach: testing first, design second. A single team takes full responsibility for the final outcome, providing end-to-end EPC turnkey delivery—from ore sample testing, process design, equipment manufacturing, installation, and commissioning to personnel training.Conventional processes ensure the minimum yield, while proprietary technologies maximize it—whether your carbon-bearing gold ore suffers from moderate or severe gold loss, we have tailored solutions to address it.

Contact OreSolution and turn your carbon-bearing gold ore from a “gold recovery challenge” into “gold extraction profits.”