Sodium Cyanide Safety and Handling Guidelines for Mining Operations

Understanding Sodium Cyanide in Gold Mining

Sodium cyanide (NaCN) is the most widely used reagent in gold extraction, accounting for approximately 90% of gold produced worldwide. The cyanidation process dissolves gold from ore using a dilute sodium cyanide solution, after which gold is recovered through carbon-in-pulp (CIP), carbon-in-leach (CIL), or Merrill-Crowe processes.

While highly effective, sodium cyanide is extremely toxic and requires rigorous safety protocols throughout its lifecycle—from transport and storage to use and disposal. This guide covers essential safety practices for mining operations handling sodium cyanide.

Chemical Properties and Hazards

Personal Protective Equipment (PPE)

All personnel handling sodium cyanide must wear appropriate PPE:

• Respiratory protection: Full-face respirator with cyanide-specific cartridge (B-class) or supplied-air respirator in confined spaces
• Chemical-resistant gloves: Butyl rubber or nitrile (minimum 0.5mm thickness)
• Protective clothing: Chemical-resistant coveralls, apron, and boots
• Eye protection: Chemical splash goggles (full-face respirator provides combined protection)
• Personal HCN monitor: Wearable gas detector with audible/visual alarm, calibrated to alarm at 4.7 ppm (TLV) and 10 ppm

Storage Requirements

1. Location: Store in a dedicated, locked, well-ventilated area away from acids, oxidizers, and food products
2. Temperature control: Keep storage area cool and dry; avoid temperatures above 30°C
3. Container integrity: Store in original UN-approved drums or IBCs with intact seals
4. Segregation: Maintain minimum 3-meter separation from acids and other incompatible materials
5. Signage: Post prominent hazard signs (toxic, no unauthorized entry, no eating/drinking/smoking)
6. Inventory control: Maintain accurate inventory records with batch numbers and quantities
7. Spill kit availability: Keep a cyanide-specific spill kit (alkaline hypochlorite solution, absorbent material) near storage area

Safe Handling During Gold Leaching Operations

Solution Preparation

• Maintain solution pH above 10.5 using lime (CaO) or sodium hydroxide (NaOH) to prevent HCN gas formation
• Use automated dosing systems to minimize manual handling
• Prepare solutions in designated mixing areas with emergency eyewash and safety showers within 10 seconds' travel
• Monitor cyanide concentration regularly using titration or photometric methods

Leach Circuit Operations

• Enclose leach tanks and vats with vapor extraction systems
• Monitor ambient HCN levels continuously in process areas
• Implement interlock systems to shut down operations if HCN exceeds alarm thresholds
• Restrict access to leach circuit areas to trained, authorized personnel only

Tailings Management

Cyanide-containing tailings must be treated before disposal to meet environmental standards:

• SO2/air process: Most common destruction method, reducing WAD cyanide to <1 mg/L
• Hydrogen peroxide process: Alternative for sites with lower cyanide concentrations
• Biological treatment: Uses bacteria to degrade cyanide complexes
• Natural degradation: UV photolysis and volatilization in tailings ponds (slower, climate-dependent)

Emergency Response and Spill Management

Every cyanide-handling facility must have a written emergency response plan that includes:

Spill Response

1. Evacuate: Clear the area and move upwind of the spill
2. Alert: Activate emergency response team and notify site management
3. Don PPE: Only trained responders in full PPE and SCBA approach the spill
4. Contain: Prevent spill from entering drains or waterways
5. Treat: Apply alkaline hypochlorite solution (decontaminant) to the spill area
6. Clean up: Collect treated residue in sealed containers for proper disposal
7. Decontaminate: Wash the area thoroughly with alkaline water

Exposure Response

International Cyanide Management Code

The International Cyanide Management Code (ICMC) is a voluntary industry program for gold mining companies. It provides standards for:

• Cyanide production, transport, and handling
• Operating practices and emergency response
• Worker safety and training
• Environmental protection and monitoring
• Decommissioning and financial assurance

Compliance with the Code demonstrates a mine's commitment to responsible cyanide management and is increasingly required by investors, regulators, and communities.

Sourcing Sodium Cyanide Responsibly

When sourcing sodium cyanide for mining operations, ensure the supplier:

• Holds a valid hazardous chemicals business license
• Provides complete documentation (COA, MSDS, transport permits)
• Uses UN-approved packaging (drums or IBCs for solid briquettes; isotanks for solution)
• Has experience with international dangerous goods shipping (Class 6.1)
• Can provide technical support for safe handling and dosing optimization
• Complies with the International Cyanide Management Code supply chain requirements