PANDA Agent vs. Cyanide: Boosting Gold Recovery to 90% and Cutting Costs at Tianyang Mine
The first step in optimizing the leaching process was understanding the unique properties of the Tianyang ore. The mine processes a mixture of gold-bearing quartz veins and altered rock types. Key characteristics include:
Mineral Composition: Metal minerals account for 6.84% (mainly limonite, pyrrhotite, and pyrite), while gangue minerals (silicon-containing) make up 93.16%.
Gold Association: Approximately 81.59% of the gold is embedded within and wrapped by limonite particles. This close association with iron oxides presented a challenge for traditional methods.
Gold Fineness: The gold is finely disseminated, with 76.85% of particles sized between -0.037mm and +0.015mm.
Given that the primary recovered element is gold (2.61 g/t), a high-selectivity leaching agent was required to minimize environmental impact and maximize recovery.
The Transition from Cyanide to PANDA: Process & Results
Tianyang Gold Mine previously relied on sodium cyanide, which posed significant environmental risks due to toxic tailings. To address this, the mine conducted a phased transition involving small-scale tests and industrial trials.
1. PANDA Agent Composition & Mechanism
The FKN agent is a mixture containing thiosulfate and sodium polycyanamide. It operates in an alkaline medium (pH 11–12) and works through a dual-complexation mechanism:
Thiosulfate Action: Forms a stable complex ion Au(S2O3)23- with gold.
Sodium Polycyanamide Action: Decomposes to release N(CN)2- groups, which dissolve gold under aerobic conditions.
Unlike free cyanide (CN-), the polymeric cyanide N(CN)2- in the residue is significantly less toxic and easier to treat.
2. Small-Scale Testing
Initial laboratory tests compared PANDA directly against sodium cyanide under controlled conditions (grind fineness -0.074mm > 85%). The results, summarized below, showed PANDA's potential.
3. Industrial Application & Scale-Up
Following the successful small-scale tests, a 3-month industrial test was conducted on a 180 t/d production line. The results were compelling:
Reduced Dosage: The required dosage of PANDA was lower (0.55 kg/t vs 0.65 kg/t for cyanide).
Higher Recovery: The leaching rate increased from 85.5% to 88.7%.
Cost Savings: Sewage treatment costs were halved due to reduced toxicity.
Based on these results, Tianyang Mine converted all three series of its leaching process to use the PANDA agent. The current industrial leaching rate has stabilized at 90%.
Economic & Environmental Impact Analysis
The switch to PANDA proved that environmental compliance does not have to come at the expense of profitability. A comparative analysis of the economic indicators is shown below.
Cost Comparison: Sodium Cyanide vs. PANDA Agent
| Cost Indicator | Sodium Cyanide | PANDA Gold Extraction Agent |
|---|---|---|
| Gold Leaching Rate | 85.5% | 88.7% |
| Reagent Cost (CNY/t) | 10.4 | 10.45 |
| Sewage Treatment Cost (CNY/t) | 3.9 | 1.95 |
| Total Comprehensive Cost (CNY/t) | 14.3 | 12.4 |
By using the PANDA agent, the mine reduced its comprehensive processing cost by 1.90 CNY per ton while simultaneously improving gold recovery and meeting national environmental protection standards.
Conclusion
The successful application of the PANDA environmentally friendly gold extraction agent at Tianyang Gold Mine demonstrates a viable pathway for the industry. It effectively replaces toxic sodium cyanide, achieving a 90% leaching rate in full-scale production. This case study proves that mines can achieve superior economic efficiency and environmental safety simultaneously through innovative chemistry.
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FAQ for Replacing Cyanide with PANDA Agent at Tianyang Mine
1. Can the PANDA agent completely replace sodium cyanide in an existing CIP plant?
Yes. The industrial application at Tianyang Gold Mine proves that the PANDA agent can fully replace sodium cyanide. The operation method is simple and identical to using sodium cyanide on site, allowing for a seamless transition in existing Carbon-in-Pulp (CIP) or Carbon-slurry processes.
2. What is the leaching efficiency of the PANDA agent compared to traditional cyanide?
The PANDA agent outperforms sodium cyanide in leaching efficiency. Industrial tests showed the gold leaching rate increased from 85.5% (using cyanide) to 88.7% (using PANDA). In full-scale production, the leaching rate has reached 90%, which is 4.5 percentage points higher than the previous cyanide process.
3. Is the PANDA agent more expensive than cyanide?
While the unit price of the PANDA agent is slightly higher, the comprehensive processing cost is lower. The reagent cost is similar (~10.45 CNY/t vs 10.4 CNY/t), but the PANDA agent significantly reduces sewage treatment costs (by half, from 3.9 to 1.95 CNY/t). This results in a total saving of 1.90 CNY per ton of ore processed.
4. What are the environmental safety advantages of PANDA?
Unlike sodium cyanide, which produces highly toxic free cyanide (CN⁻) ions, the PANDA agent leaves behind polymeric cyanide N(CN)₂⁻ groups in the residue. These are less toxic and easier to manage. The residue from the PANDA process meets China's national environmental protection standards, eliminating the risk of severe environmental pollution from tailings.
5. What are the optimal technical parameters for using the PANDA agent?
Based on the industrial tests at Tianyang Mine, the optimal parameters are:
Grind Fineness: -0.074mm accounting for 85%.
Slurry Concentration: 40%.
Leaching Time: 42 hours.
pH Value: Maintained in the alkaline range of 11–12 using lime.