Innovative Beneficiation Technology and High-Efficiency Gold Extraction Process for Carlin-Type Gold Ore

Introduction

With the gradual depletion of global easy-to-process gold resources, complex refractory gold ores have become a critical raw material for gold smelting. Carlin-type gold ore, a typical refractory ore, is characterized by finely disseminated gold particles, severe encapsulation by sulfides and silicates, and significant "gold-robbing" by organic carbon. Traditional extraction methods struggle to achieve efficient recovery. To address these challenges, this study proposes an innovative process: "Acid Pressure Oxidation Pretreatment-Jarosite Decomposition-Environmental Carbon Leaching," aiming to achieve high-efficiency and eco-friendly gold extraction while minimizing environmental risks.

Process Flow and Technological Breakthroughs

1. Process Mineralogy and Pretreatment Optimization

Systematic process mineralogy analysis clarified the physicochemical properties and gold occurrence in Carlin-type ore:

• Mineral Composition: Dominant phases include quartz (SiO₂), pyrite      (FeS₂), dolomite (CaMg(CO₃)₂), and muscovite (KAl₂Si₃AlO₁₀(OH)₂), with      over 95% of gold encapsulated in sulfides and silicates.

• Pretreatment: Sulfuric acid washing removed carbonate      minerals (98% efficiency), eliminating CO₂ interference during pressure      oxidation.

2. Acid Pressure Oxidation Pretreatment

Under high temperature (225°C), high oxygen pressure (1200 kPa), and acidic conditions (pH 1.2~1.5), sulfides were oxidized to release encapsulated gold:

• Sulfur Control: Optimized oxygen pressure and temperature      increased sulfide oxidation to 99%, significantly reducing elemental      sulfur residues.

• Iron Behavior: Ferric sulfate (Fe₂(SO₄)₃) formed jarosite      (e.g., KFe₃(SO₄)₂(OH)₆) under high temperatures. Post-cooling (6 hours)      dissolved basic iron sulfates, minimizing secondary encapsulation.

• 

3. Jarosite Decomposition and Eco-Leaching

• Alkaline Decomposition: Lime milk adjusted pH      to 10.5~11.5, decomposing jarosite into calcium sulfate and iron      hydroxide, increasing gold leaching efficiency to 80.7%.

• Carbon Adsorption: Coconut shell activated carbon (2~4 mm      diameter, surface area >1000 m²/g) achieved over 90% gold adsorption.

4. Deep Extraction Enhancement

• Ultrasonic Activation: At 90 kHz, micro-cracks formed on mineral      surfaces, boosting EP-1 system gold recovery to 93.1%.

• Super Energy Activation: 60 Hz activation for 4      minutes altered crystal structures, liberating silicate-encapsulated gold,      with leaching efficiency reaching 96.8%.

Results and Environmental Benefits

• Efficiency: The EP-1 system outperformed thiourea and      polysulfide systems in thermal stability, reagent consumption (30%      reduction), gold recovery (91.6%), and process continuity.

• Tailings Safety: All tailings passed HJ/T299-2007 toxicity      tests, with arsenic, cadmium, and lead levels below national standards (GB      5085.3-2007), enabling safe disposal.

• Circular Economy: EP-1 system enabled tailings liquid recycling,      reducing waste emissions by 40% and cutting production costs by 25%.

Conclusion

The developed "Pressure Oxidation-Jarosite Decomposition-Eco Carbon Leaching" process successfully addresses low efficiency and environmental concerns in Carlin-type gold extraction. Through sulfur regulation, jarosite decomposition optimization, and ultrasonic/super energy activation, gold recovery reached 96.8% with enhanced sustainability. This technology offers an innovative solution for refractory gold ores, demonstrating significant industrial potential.