The Industry Standard for Gold Dissolution
Sodium cyanide (NaCN) has been the primary lixiviant in industrial gold extraction since the 1880s. Its ability to selectively dissolve gold from ore matrices at ambient temperatures and atmospheric pressure makes it the most cost-effective reagent for large-scale operations.
CHEMICAL ELEMENTS supplies industrial-grade sodium cyanide alongside our mercury and oxidative product lines, providing customers with a single-source reagent solution for their entire gold-recovery circuit.
How Cyanide Leaching Works
When a dilute NaCN solution contacts gold-bearing ore in the presence of dissolved oxygen, gold reacts to form the soluble aurocyanide complex:
4 Au + 8 NaCN + O₂ + 2 H₂O → 4 Na[Au(CN)₂] + 4 NaOH
The dissolved gold is then recovered from pregnant solution via activated carbon (CIL/CIP processes), zinc cementation (Merrill–Crowe process), or electrowinning.
Optimising Leach Performance
pH Management
Maintaining alkaline conditions (pH 10–11) is critical for two reasons: it maximises gold dissolution kinetics and prevents the formation of hydrogen cyanide gas (HCN), which is the primary safety hazard in cyanide operations.
Cyanide Concentration
Typical leach solutions contain 200–500 ppm NaCN, though optimal concentration depends on ore mineralogy. Over-dosing wastes reagent and increases detoxification cost; under-dosing leaves gold in the residue.
Oxygen Availability
Gold dissolution is an electrochemical reaction that requires dissolved oxygen. Forced-air injection or oxygen sparging in agitated tanks significantly improves leach rates compared to passive aeration.
Residence Time
CIL circuits typically require 24–48 hours of contact time; heap-leach cycles range from 60 to 120 days depending on ore permeability and gold grain size.
Safety Management
Sodium cyanide is classified as acutely toxic (GHS Category 1). CHEMICAL ELEMENTS provides the following guidance to all buyers:
- Storage: Keep in dry, ventilated areas away from acids. Moisture contact generates HCN gas.
- Handling: Use full-face respiratory protection, chemical-resistant suits, and emergency showers when working with solid briquettes or concentrated solutions.
- Spill response: Neutralise with sodium hypochlorite or ferrous sulphate solution. Never use acids.
- Medical readiness: Cyanide antidote kits (hydroxocobalamin or sodium thiosulphate) must be on-site at all operations handling NaCN.
Environmental Responsibility
Modern cyanide operations implement the International Cyanide Management Code (ICMC) framework:
- Detoxification: Barren solutions are treated with SO₂/air or hydrogen peroxide to reduce WAD cyanide below discharge limits
- Tailings management: Lined storage facilities prevent groundwater contamination
- Wildlife protection: Exclusion netting and solution monitoring protect migratory birds and mammals
Procurement
CHEMICAL ELEMENTS supplies sodium cyanide in solid briquette and solution form, with documentation including Certificate of Analysis, MSDS, and transport emergency cards. Contact info@chemicaleleements.com for specifications and lead times.