Sodium Cyanide Storage — NaCN Tank Selection for Gold Mining, CIP/CIL, Electroplating

Sodium Cyanide Storage — NaCN Tank Selection for Gold Mining Heap Leach, CIP / CIL Carbon Adsorption, Electroplating

Sodium cyanide (NaCN, CAS 143-33-9) is a white deliquescent crystalline solid or compacted briquette form supplied at 98%+ purity for industrial use, with aqueous solutions at 30% or 25% strength shipped via tank truck or rail tank car for mining-site delivery. The chemistry's signature toxicity makes it one of the most heavily-regulated industrial materials in commerce: oral lethal dose for adult human is approximately 200-300 mg as NaCN; cyanide blocks cytochrome-c-oxidase in the mitochondrial electron-transport chain producing rapid cellular asphyxiation independent of oxygen availability. Aqueous solutions are strongly alkaline (pH 11-12) due to cyanide hydrolysis CN^- + H₂O -> HCN + OH^-; the alkalinity is the engineering control that keeps the chemistry as cyanide-anion form rather than HCN volatile gas (HCN boils at 26°C). Storage discipline focuses obsessively on pH maintenance above 10.5 to suppress HCN evolution.

The dominant industrial use globally is gold + silver extraction via cyanide heap-leach + carbon-in-pulp (CIP) / carbon-in-leach (CIL) processes; an estimated 80-85% of global cyanide production feeds the precious-metals mining industry. Reaction: 4 Au + 8 NaCN + O₂ + 2 H₂O -> 4 Na[Au(CN)₂] + 4 NaOH (Elsner equation, late 1800s). Pregnant cyanide solution loads gold from the ore + heap; loaded cyanide solution is contacted with activated carbon which adsorbs the gold-cyanide complex; carbon is stripped + electrowinned to recover doré-bar gold. Operating cyanide concentration in heap-leach barren-solution recycle is typically 200-500 ppm; site-level cyanide inventory at major gold mines is 100-1,000 tonnes (220,000-2,200,000 pounds) of solid NaCN equivalent in 30%-solution storage.

The six sections below cite Draslovka A.S. (Czech Republic; Memphis Tennessee plant is the world's largest solid sodium cyanide plant since 1952; acquired Chemours Mining Solutions for $521 million 2021; March 2026 long-term Barrick Mining Nevada Gold Mines supply agreement), Orica Limited (Australia; acquired Cyanco February 2024 for $640 million with Winnemucca NV + Alvin TX + Mexicali plants), Cyplus GmbH (Evonik subsidiary, Germany), Australian Gold Reagents Pty Ltd (AGR; CSBP / Coogee Chemicals JV in Western Australia), Sasol (South Africa), and Tessenderlo Group spec sheets. Regulatory citations: EPA Risk Management Plan (RMP) listed under Clean Air Act Section 112(r) at 100-pound threshold quantity (40 CFR Part 68); OSHA Process Safety Management (PSM) listed at 100 pound threshold (29 CFR 1910.119 Appendix A); EPA TSCA Active Inventory; OSHA PEL 5 mg/m³ 8-hour TWA + skin notation (29 CFR 1910.1000 Table Z-1; cyanides as CN); ACGIH TLV-Ceiling 4.7 mg/m³ + skin notation; NIOSH IDLH 25 mg/m³ as cyanide; DOT UN 1689 Hazard Class 6.1 (Toxic) Packing Group I (highest toxicity tier in DOT system); RCRA P106 listed acute hazardous waste; SARA Title III Section 313 Toxic Release Inventory + EPCRA Section 304 emergency release notification; CWA Section 311 designated hazardous substance Reportable Quantity 10 pounds. International Cyanide Management Code (ICMC) industry-led voluntary compliance applies to gold mining + cyanide producer + transporter audits.

1. Material Compatibility Matrix

Sodium cyanide solution is moderately alkaline (pH 11-12) and chemically aggressive primarily toward acid-sensitive materials, copper alloys (cyanide complexes copper), and zinc. Material selection focuses on: (1) maintaining pH above 10.5 to suppress HCN evolution, (2) avoiding any acid contact (instantaneous HCN release reaction), (3) using alkali-resistant materials (HDPE, FRP, 304L / 316L stainless, mild steel with epoxy lining for solution service). Solid NaCN handling adds dust-control + moisture-exclusion considerations.

The dominant industrial pattern at gold-mining sites is HDPE rotomolded vertical bulk tank (5,000-30,000 gallon range, 1.9 SG rating for 30% solution density) with PVC or PP piping + PP / PVDF pump body + EPDM gasket sets. Mid-volume + high-temperature electroplating use 316L stainless tanks. Carbon-steel tanks with epoxy lining are common at large mine sites with 50,000-200,000 gallon central solution storage. Plastic-mart-type vertical HDPE storage tanks are the operational standard for the small to mid mine sites and for satellite distribution at large operations.

2. Real-World Industrial Use Cases

Gold + Silver Mining Heap Leach (Dominant Use, ~80% of Global Volume). Heap-leach operations apply 100-1,000 tonne / day of solid NaCN equivalent (typically delivered as 30% aqueous solution by tank truck or rail) to the leach-pad sprinkler system. Pregnant cyanide solution percolates through the crushed-ore heap, dissolving gold + silver as cyanide complexes [Au(CN)₂]^- + [Ag(CN)₂]^-; pregnant solution drains to the pregnant-pond, is contacted with activated-carbon columns that adsorb the gold-cyanide complex, barren solution recycles back to the heap. Site-level cyanide inventory is typically 100-1,000 tonnes (1-2 weeks of operating consumption) in 5,000-30,000 gallon HDPE bulk-storage tanks. Major US sites: Nevada Gold Mines (Barrick / Newmont JV; Cortez, Carlin, Goldstrike, Phoenix); Round Mountain (Kinross); Marigold (SSR Mining); Long Canyon (Newmont). Major international sites: Olimpiada (Polyus Russia), Lihir (Newcrest PNG), Boddington (Newmont Australia), Veladero (Barrick Argentina). March 2026 Draslovka announced multi-year supply agreement with Barrick Mining for 100% US-produced sodium cyanide from Memphis to Nevada Gold Mines + Carlin terminal expansion.

Carbon-in-Pulp / Carbon-in-Leach (CIP / CIL) Processing. Tank-leach operations use CIP / CIL configuration: ground-ore pulp is contacted with cyanide solution + activated carbon in agitated tanks at 50-60% solids density. Cyanide-gold complex adsorbs onto carbon as it forms; carbon is screened out, transferred to elution / electrowinning, and barren pulp goes to tailings. CIL operations consume 50-500 tonne / day NaCN at major sites. Tank-leach is preferred over heap-leach for higher-grade ores + complex sulfide mineralogy where heap-leach kinetics are too slow. Site cyanide inventory similar scale to heap-leach (5,000-30,000 gallon HDPE bulk-storage tanks at the leach-circuit feed point).

Electroplating + Case-Hardening of Steel. Cyanide-based plating baths are the historical standard for gold, silver, copper, zinc, and cadmium electroplating + case-hardening (carbonitriding) of steel. Modern plating-shop trends move toward non-cyanide alternatives (acid copper, alkaline copper, cyanide-free zinc) due to wastewater treatment + worker-safety considerations, but cyanide baths remain in service for: high-quality gold electronics plating (printed circuit board hard-gold contacts), silver decorative + industrial plating, hard-chrome + cadmium specialty applications. Plating-shop NaCN inventory is typically 500-5,000 lb in solid-drum form at the bath-makeup station. Bath operating concentration 30-60 g/L NaCN.

Organic Chemical Synthesis Intermediate. Cyanide is a critical intermediate in: cyanohydrin chemistry (acetone + HCN -> acetone cyanohydrin, the methyl-methacrylate precursor), nitrile synthesis (RX + NaCN -> RCN), Strecker amino acid synthesis (aldehyde + NH₃ + HCN -> alpha-amino acid), pharmaceutical-intermediate manufacturing (multiple beta-blocker + sympathomimetic drug syntheses), and adiponitrile manufacturing (precursor to nylon-66). Specialty chemical sites maintain 1,000-50,000 lb solid NaCN inventory or aqueous-solution storage at the chemical-feed point.

Specialty Mining Reagent. Cyanide is also used in: copper-molybdenum flotation depressant chemistry (suppresses copper flotation in molybdenum concentrate cleaning), electrolytic copper refining (anode-mud noble-metal recovery), specialty mineral leaching (silver + platinum-group metals from secondary materials).

3. Regulatory Hazard Communication

EPA RMP and OSHA PSM Listed Substance. Sodium cyanide solution at concentrations above 30% and the equivalent solid in storage above 100 pounds threshold quantity is a Listed Toxic Substance under EPA Risk Management Plan (RMP) regulations 40 CFR Part 68 Section 112(r) of the Clean Air Act. RMP-covered facilities must develop + submit + update a Risk Management Plan including: hazard assessment (worst-case + alternative-case offsite consequence analysis), prevention program (process safety management elements equivalent to OSHA PSM), emergency response program (coordination with local emergency planning committee LEPC), and management system. EPA RMP*Comp software supports the offsite-consequence analysis (atmospheric dispersion modeling for HCN release scenarios). OSHA Process Safety Management (PSM) under 29 CFR 1910.119 Appendix A lists hydrogen cyanide above 1,000 pound + sodium cyanide at the same threshold; PSM-covered processes require: process safety information, process hazard analysis, operating procedures, employee training, contractor management, pre-startup safety review, mechanical integrity, hot work permit, management of change, incident investigation, emergency planning, and compliance audits.

OSHA, ACGIH, NIOSH Exposure Limits. OSHA PEL is 5 mg/m³ 8-hour TWA as cyanide with skin notation (29 CFR 1910.1000 Table Z-1). ACGIH TLV is a Ceiling value of 4.7 mg/m³ as cyanide with skin notation; the ceiling-value designation reflects the rapid acute toxicity (no time-weighted-average concept applies because exposures above the limit produce immediate effects). NIOSH IDLH is 25 mg/m³. Skin notation reflects significant dermal absorption of cyanide especially from solid + dust exposure on damp skin. Acute toxicity targets: cytochrome-c-oxidase blockade in mitochondrial electron-transport chain producing cellular asphyxiation; loss of consciousness within minutes at 100-200 ppm HCN inhalation, fatal within 30 minutes at 50 ppm + minutes at 100 ppm. Antidote kit (sodium nitrite + sodium thiosulfate IV; or hydroxocobalamin / Cyanokit IV) must be pre-positioned at any cyanide-handling site; medical surveillance includes urinary thiocyanate biological-monitoring as a metabolic marker of chronic exposure.

EPA TSCA, TRI, RCRA. Sodium cyanide is on EPA TSCA Active Inventory. SARA Title III Section 313 Toxic Release Inventory: cyanide compounds reportable above 25,000 lb/yr manufacturing or 10,000 lb/yr otherwise-using. EPCRA Section 304 emergency release notification + Section 311/312 Tier II reporting at 500 pound threshold quantity. CWA Section 311 designated hazardous substance with 10-pound Reportable Quantity. RCRA P106 listed acute hazardous waste (P-codes are the most heavily regulated waste category, lower threshold quantities than U-codes); land disposal restrictions, permitted incineration is the typical disposal route, generators of even small quantities are large-quantity-generator regulated.

DOT and Shipping. Solid sodium cyanide ships under UN 1689, Hazard Class 6.1 (Toxic), Packing Group I (highest toxicity tier; PG I status drives the most restrictive packaging + handling + driver-qualification requirements in DOT system). Aqueous solution ships under UN 3414 (cyanide solutions) Class 6.1 PG I or PG II depending on concentration. Bulk shipping: rail tank car (DOT-105 specification with thermal protection + head-shield), tank truck (MC-307 / DOT-407 specification with safety-trained driver), 1-tonne supersack for solid product (with overpack drum for international shipment), 55-gallon DOT-rated drum, or specialty 1,000-pound briquette container. Hazmat training requirements stricter than standard hazmat under 49 CFR Part 172 + 173; emergency response phone number on shipping papers (CHEMTREC 800-424-9300 typical). International Cyanide Management Code (ICMC) certification of producer + transporter is industry-standard practice for gold-mining-supply chain.

NFPA 704 Diamond. Sodium cyanide rates NFPA Health 4 (highest health-hazard rating), Flammability 0, Instability 0, special hazard not assigned (HCN release on acid contact is the dominant hazard mode but is implicitly covered by Health 4). The Health 4 designation is shared with very few other industrial chemicals (HF, HCN gas, anhydrous ammonia, phosgene); the NFPA 704 placard alone communicates the immediate-life-threatening nature of any release.

4. Storage System Specification

Mine-Site Bulk Solution Storage. The dominant industrial cyanide inventory is at gold + silver mining sites in 5,000-30,000 gallon HDPE rotomolded vertical bulk tanks (1.9 SG rating for 30% NaCN solution density 1.16 kg/L) or epoxy-lined carbon-steel API 650 atmospheric tanks at major sites in the 50,000-200,000 gallon range. Outdoor location is the standard at mine sites; indoor-location at electroplating + chemical-synthesis sites uses additional engineering controls (room-level HCN monitor + ventilation interlock).

Solid Sodium Cyanide Bulk Storage. Solid NaCN supplied as 1-tonne supersack or briquette in DOT-rated overpack at integrated mining + electroplating + chemical-synthesis sites typically maintains 30-90 day inventory. Typical bag-tip station feeds an under-floor solution-makedown tank (5,000-15,000 gallon HDPE with mixer) for batch dilution to 30% solution.

Solution Makedown + Day-Tank. Plant-scale operations dissolve solid NaCN into water at the bag-tip / supersack-discharge station to produce 30% solution; makedown tank is typically 5,000-15,000 gallon HDPE with top-mounted mixer (15-30 minute mixing time). Day-tank for continuous dosing is 1,000-5,000 gallon HDPE with level control + caustic-soda pH-trim dosing + bottom outlet to metering pump suction.

Pump and Piping Selection. Centrifugal pumps with mechanical seals or magnetic-drive pumps (zero-leak option) are standard for cyanide-solution transfer. Diaphragm metering pumps (PTFE diaphragm + EPDM check valves + PVDF or 316L head) for precise dosing. Carbon-steel pipe is acceptable for short runs at mine sites; PVC or HDPE pipe for longer runs + chemically-aggressive service. Always EPDM gaskets, never copper-bronze or galvanized fittings.

Secondary Containment + Engineered Barriers. Per RMP + ICMC + state mining permit requirements, all cyanide-containing tankage requires secondary containment sized to 110-150% of largest tank capacity with: (1) double-liner construction with leak-detection between liners, (2) engineered drainage to a designated catchment basin with sampling port for verification of release-or-no-release, (3) impervious liner verified for cyanide-solution service (typically HDPE primary liner + GCL geosynthetic clay secondary liner), (4) above-ground tank arrangement (no buried cyanide-containing piping or vessels per ICMC).

HCN Monitoring + Emergency Systems. All cyanide handling areas require: (1) area-monitor HCN gas detection at 1-5 ppm action level + 10 ppm alarm + audible / visual alarm + ventilation interlock, (2) emergency eyewash + safety shower within 10-second travel per ANSI Z358.1, (3) cyanide-antidote kit (sodium nitrite + sodium thiosulfate IV; or hydroxocobalamin / Cyanokit IV) at the medical / first-responder station, (4) self-contained breathing apparatus (SCBA) at access-control points for emergency response, (5) coordination with local fire department + emergency medical services on cyanide-incident response protocol per RMP + EPCRA.

5. Field Handling Reality

The Acid-Contact Catastrophe. The single most-critical engineering control for cyanide handling is total prevention of any acid contact with cyanide solution or solid. Even mild acids (citric, carbonic) drive HCN evolution; pH below 9.5 generates measurable HCN; pH below 7 produces immediate gas-phase HCN at lethal levels. Operating discipline at cyanide-handling sites includes: (1) absolute physical segregation of acid + cyanide storage (separate buildings or 50+ foot isolation distances), (2) dedicated transfer equipment (no shared pumps, hoses, or piping between acid + cyanide service), (3) operator training emphasizing "no acid near cyanide ever" as foundational safety rule, (4) emergency response procedures for accidental acid spill into cyanide-storage area (immediate evacuation + emergency response team SCBA entry only).

pH Maintenance Above 10.5. The engineering control that keeps cyanide as the relatively stable cyanide anion (CN^-) rather than volatile HCN gas is solution pH above 10.5. Operating cyanide solutions are dosed with caustic soda (NaOH) on continuous level-trim or pH-trim cycle to maintain pH 11.0-12.0. Loss of pH control through: caustic-soda reagent depletion, pump failure, instrumentation fault, operator error, or acid-spill contamination is a top-tier safety incident that triggers immediate emergency response. Operators monitor pH continuously at multiple points (storage tank, makedown tank, day tank, leach-circuit feed) with alarm at 10.5 + emergency action at 10.0.

Cyanide Antidote Kits and Medical Response. Industrial cyanide-handling sites maintain pre-positioned cyanide-antidote kits at the medical / first-aid station + emergency-response location. Two antidote regimens are in current use: (1) Eli Lilly Cyanide Antidote Kit (sodium nitrite + sodium thiosulfate IV + amyl nitrite inhalation; classic regimen), (2) Cyanokit / hydroxocobalamin (5g vial IV; modern preferred regimen with simpler administration + reduced methemoglobin-induction risk). Medical surveillance for cyanide-handling workforce includes: pre-employment + periodic urinary thiocyanate biological monitoring (cyanide metabolite excreted as thiocyanate; ACGIH BEI 5 mg/g creatinine end-of-shift increase from pre-shift), thyroid function testing (cyanide chronic exposure is a thyroid antagonist), neurological exam.

Spill Response and Decontamination. Cyanide spill response is fundamentally different from most chemical spills due to the catastrophic acid-contact hazard + extreme toxicity. Industrial spill response: (1) immediate evacuation of all unprotected personnel from the spill area + downwind zone (HCN density is 0.94 vs air, slightly lighter; vapor disperses with wind), (2) emergency response entry with SCBA + Level A or Level B PPE only, (3) characterize spill (solid vs solution, contained vs spreading), (4) raise + maintain pH of spill area with caustic soda or sodium hypochlorite (hypochlorite oxidizes cyanide to cyanate + then to CO₂ + N₂; standard cyanide-destruction chemistry), (5) absorb + recover treated material to drum for hazardous-waste disposal under RCRA P106. CERCLA Reportable Quantity is 10 pounds; spills above RQ require National Response Center notification at 800-424-8802 + EPCRA Section 304 emergency release notification to LEPC + State Emergency Response Commission within 15 minutes.

Cyanide Destruction Chemistry. Engineered cyanide destruction at mining + electroplating + chemical-synthesis sites uses: (1) alkaline chlorination (sodium hypochlorite + NaOH at pH 11.5; CN^- + OCl^- -> CNO^- + Cl^-; then CNO^- + further OCl^- -> CO₂ + N₂), (2) hydrogen-peroxide + copper-catalyst (INCO process, lower-cost alternative for tailings treatment), (3) SO₂ / air + copper catalyst (INCO SO₂ / Air Process for tailings cyanide destruction), (4) UV / hydrogen-peroxide advanced oxidation for low-concentration polishing. Tailings cyanide destruction is required to achieve under 50 ppm WAD (weak-acid-dissociable) cyanide before discharge to tailings storage facility per ICMC + state mining-permit requirements.

ICMC Audit + Certification. The International Cyanide Management Code is a voluntary industry program with mandatory triennial third-party audit certification for: cyanide producers (Draslovka, Cyanco, Cyplus, AGR, Sasol all ICMC certified), cyanide transporters (rail + tank truck + ocean), cyanide consumers (gold-mining sites). ICMC compliance demonstrates: secure handling, transport, storage, use, decommissioning, emergency response, financial assurance, dialogue + disclosure. Most major insurers + financiers require ICMC certification of suppliers + customers as a precondition of coverage / financing.

Related Chemistries in the Severe-Hazard Specialty Cluster

Related chemistries in the severe-hazard specialty cluster (HF-related + Cr(VI) + heavy-metal + reactive amine + cyanide + hydrosulfide + reactive monomer + chlorinated acid + aromatic-amine intermediate + carbonyl-toxin):

• Sodium Hydrosulfide (NaHS) — Mining flotation specialty companion
• Sodium Dichromate (Cr(VI)) — Severe-hazard heavy-metal companion
• Sodium Hydroxide (NaOH) — Caustic stabilizer companion (HCN suppression)
• Hydroxylamine (NH2OH) — Specialty reducing-agent companion
• Hydrazine (N2H4) — Severe-hazard reducing-agent companion

Related Hub Pillars

For broader chemistry context, see the OneSource Plastics high-traffic chemical-compatibility hub pillars:

• Sodium Hydroxide (NaOH / caustic soda)
• Sodium Hypochlorite (NaOCl / bleach)
• Sulfuric Acid (H₂SO₄)