Heap Leaching for Low-Grade Gold Ore: Efficient Gold Extraction | Zhengzhou Jinquan Mining
Zhengzhou Jinquan Mining Equipment Co., Ltd. is a professional mining equipment manufacturer. We provide efficient, economical and eco-friendly solutions for low-grade gold ore processing. Low-grade gold ore is widely distributed in nature and has great development value. However, its low gold content makes traditional extraction methods difficult. We introduce the heap leaching method—a mature, reliable technology for low-grade gold ore. It boosts gold recovery rates, cuts production costs, and brings substantial economic benefits to global mining enterprises.
Heap leaching is a hydrometallurgical process: we dissolve gold from ore via chemical reactions, then recover it through adsorption and refining. It is one of the most economical gold extraction methods and offers irreplaceable advantages for utilizing low-grade gold resources. Additionally, it features simple processes, low investment, low energy consumption, and strong scalability. Below are its detailed operation steps:
Step 1: Low-Grade Gold Ore Pretreatment
First, clean raw low-grade gold ore to remove surface impurities like clay, sand, and gravel. This prevents interference with the leaching agent’s contact with gold later. Next, use professional crushing and screening equipment to process the ore, and select ore with a particle size of less than 70mm for further treatment.
This particle size ensures sufficient contact between ore and leaching agent while avoiding ore heap blockage and ensuring smooth leaching agent penetration. After that, add slaked lime (calcium hydroxide) to the screened ore in a reasonable ratio and stir well to form a uniform mixture.
Slaked lime not only adjusts the ore heap’s pH value but also inhibits cyanide hydrolysis in subsequent leaching and reduces reagent loss. Finally, pile the mixture into a regular ore heap on a professional anti-seepage leaching pad, which prepares for the subsequent spray leaching process.
Step 2: Leaching Agent Preparation
Preparing a high-performance leaching agent is key to better gold leaching. First, adjust the solvent to an alkaline solution with a pH value of 10-12, as this alkaline environment prevents sodium cyanide decomposition and enhances the leaching agent’s stability.
Subsequently, add sodium cyanide (NaCN) to the alkaline solution in an appropriate ratio and stir thoroughly to get a uniform leaching agent. As a common reagent in cyanidation, sodium cyanide selectively dissolves gold in ore to form soluble gold cyanide complexes, thereby laying the foundation for gold recovery.
It is crucial to strictly control sodium cyanide concentration and leaching agent pH. Specifically, adjust them according to the ore’s actual characteristics to ensure both leaching effect and production safety.
Step 3: Continuous Spray Leaching
Once the ore heap is built and the leaching agent is ready, immediately start continuous spray operations. Specifically, use a professional spray system to evenly spray the prepared leaching agent onto the ore heap surface.
During spraying, the leaching agent slowly penetrates the ore heap and fully reacts with gold in the ore, dissolving the gold to form a gold-containing solution—known as "pregnant solution" in the industry. Importantly, continuous spraying keeps the ore heap wet.
This wet environment ensures full reaction between the leaching agent and gold, effectively improving the gold leaching rate. Afterward, the leached pregnant solution flows through the anti-seepage pad into a special collection tank for subsequent treatment.
Step 4: Preparation of Gold-Loaded Carbon
First, use a professional pump to transfer the collected pregnant solution into an adsorption column filled with activated carbon. Notably, activated carbon has strong adsorption capacity for gold cyanide complexes in the pregnant solution.
It effectively adsorbs these complexes onto its surface, producing gold-loaded carbon. After adsorption, the remaining solution—with low gold content—is called "barren solution." To save resources and cut costs, we recycle and treat the barren solution until it meets standards.
We then reuse it in leaching agent preparation (Step 2), spray leaching (Step 3), and gold-loaded carbon preparation (Step 4), which forms a closed-loop production cycle. This cycle not only reduces solvent and reagent consumption but also minimizes environmental pollution, aligning with green, sustainable development.
Step 5: Extraction of Elemental Gold
Process the gold-loaded carbon from Step 4 through professional desorption, electrolysis, and refining to extract high-purity elemental gold. To begin with, desorb the gold-loaded carbon under high temperature and pressure.
This process separates gold from activated carbon, forming a high-concentration gold-containing solution. Next, electrolyze the solution to deposit gold mud and further refine the gold mud (e.g., acid washing, smelting) to remove impurities.
This final step yields high-purity elemental gold (usually over 99.9% purity). Additionally, regenerate the desorbed activated carbon for reuse to further reduce production costs.
Advantages of the Heap Leaching Method for Low-Grade Gold Ore
Compared with traditional gold extraction methods, heap leaching for low-grade gold ore has distinct advantages. For instance, it suits low-grade ore with low gold content, enabling the use of resources hard to develop traditionally. Besides, it has simple processes and easy operation, with low requirements for equipment and operators.
It is highly scalable, adjustable to mine scale, and suitable for both small and large gold extraction projects. Furthermore, it features low investment and operation costs, delivering significant economic benefits. Moreover, the closed-loop recycling of barren solution makes it energy-efficient and eco-friendly, meeting global environmental standards.
Zhengzhou Jinquan Mining Equipment Co., Ltd. has rich experience in R&D, production, and application of low-grade gold ore heap leaching equipment. Specifically, we provide customers with complete sets of heap leaching equipment and customized solutions.
We tailor these solutions to the ore’s actual characteristics and project needs. Our offerings include key equipment such as crushing equipment, screening equipment, spray systems, adsorption columns, and pumps. In addition, our equipment is efficient, stable, durable, and energy-saving, helping customers improve gold extraction efficiency and cut production costs.
If you need a reliable low-grade gold ore extraction method and supporting equipment, contact Zhengzhou Jinquan Mining Equipment Co., Ltd. We not only offer professional technical support but also provide high-quality after-sales service to help you achieve efficient development and utilization of low-grade gold resources.
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