Heap leach pads in mining operations demand exceptionally chemical-resistant liners to withstand pH extremes (0.5–13) and metal-laden solutions. This analysis compares HDPE, LLDPE, and PVC geomembranes through:
✔ pH-dependent degradation curves
✔ $2.3M cost-saving case study
✔ Vendor qualification checklist
1. Material Performance Under Extreme pH Conditions
Accelerated Aging Test Results (ASTM D5322)
| Material | pH 0.5 (Sulfuric Acid) | pH 4 (Copper Leachate) | pH 13 (Cyanide Solution) |
| 1.5mm HDPE | 12% tensile loss (6 months) | 8% loss | 15% loss (alkali hydrolysis) |
| 2.0mm LLDPE | 5% loss | 3% loss | 22% loss |
| PVC | FAILS (dissolves in 3 weeks) | 18% loss | 35% loss |
Key Findings:
- HDPE outperforms LLDPE in strong acids (pH<2) due to higher crystallinity
- LLDPE resists copper/cyanide solutions better (lower metal ion absorption)
- PVC fails completely in sulfuric acid environments
2. Case Study: Chilean Copper Mine Saves $2.3M
Project Background
- Location: Atacama Desert, Chile
- Problem: 1.2mm PVC liner failed after 8 months in pH 1.5 heap leach pad
- Solution: Upgraded to 1.8mm HDPE with antioxidant package
Cost Comparison Over 5 Years
| Cost Factor | PVC Liner | HDPE Liner | Savings |
| Initial Installation | $1.2M | $1.8M | -$600K |
| Repairs (Year 1–2) | $950K | $0 | +$950K |
| Production Downtime | $1.1M | $0 | +$1.1M |
| Total (5 Years) | $3.25M | $1.8M | $2.3M |
Operational Bonus: HDPE allowed higher (10%) acid concentrations, improving copper recovery rates.
3. Vendor Selection Checklist for Acid-Resistant Liners
Mandatory Requirements
✅ Third-Party Certifications:
- ASTM D1693 (Environmental Stress Crack Resistance)
- ISO 9080 (Hydrostatic Design Basis)
✅ Material Specifications:
- ≥2% carbon black for UV protection (critical for heap pads)
- High-density (>0.94 g/cm³) HDPE for acid resistance
✅ Quality Control Documents:
- Mill test reports (MTRs) for every roll
- Seam welding validation samples
Red Flags:
❌ Vendors unable to provide long-term (10+ year) acid exposure data
❌ No on-site welding certification program
4. Recommended Specifications by Ore Type
| Ore Type | Best Geomembrane | Thickness | Special Additives |
| Copper (pH 1–2) | HDPE | 1.8–2.5mm | Antioxidant package |
| Gold (Cyanide) | LLDPE | 2.0mm | Cyanide-resistant stabilizers |
| Nickel (pH 3–4) | Reinforced HDPE | 2.2mm | Anti-UV masterbatch |
Key Takeaways
- HDPE is optimal for extreme acids (pH<3), while LLDPE suits moderate pH/cyanide solutions
- 1.8mm HDPE reduces life-cycle costs by 40%+ vs thinner/PVC liners
- Require vendors to provide ASTM G26/G155 accelerated aging reports
Need help specifying your heap leach liner? Get a free ore compatibility analysis
