Consignes de sécurité Gold EW

This document examines critical health, safety, and environmental (HSE) risks associated with gold electro-extraction using cyanide and proposes non-negotiable control measures. It first analyses the CN⁻/HCN equilibrium, emphasizing that any local pH decrease can shift cyanide to volatile HCN, creating a severe toxic gas hazard. Using the Henderson–Hasselbalch relationship, the document quantifies the fraction of HCN as a function of pH and establishes rigorous pH setpoints (typically ≥10.5–11) as the primary HSE barrier, supported by continuous pH monitoring, alarms, prohibition of acid use, and operator training. The second focus is on electrolytic gas generation (H₂ at the cathode, O₂ at the anode), for which Faraday-based calculations provide order-of-magnitude flowrates in industrial cells. These data underpin ventilation design and ATEX prevention, given hydrogen’s wide flammability range (4–75% vol.). Detailed operational guidance is provided for managing high-H₂ atmospheres, including electrical isolation, access control, inert gas purging, controlled venting, ignition source exclusion, and continuous gas monitoring. Finally, the document addresses effluent management (barren solutions, wash waters, sludges), advocating source reduction, internal recycling, solid–liquid separation, and cyanide detoxification via peroxide, INCO, or alkaline chlorination. Key monitoring parameters (pH, free CN, WAD CN, total CN, metals, ORP) and kinetic considerations for complexed cyanides are highlighted to ensure robust environmental performance.