COPPER SULPHATE PENTAHYDRATE: THE VERSATILE BLUE CRYSTAL POWERING AGRICULTURE & INDUSTRY

Copper sulphate pentahydrate (CuSO₄·5H₂O), commonly recognized by its vibrant blue crystals, is one of the most important copper salts with diverse agricultural, industrial and chemical applications. With global production exceeding 300,000 metric tons annually, this compound serves critical functions from crop protection to electroplating, while requiring careful handling due to its toxicity.

Key Properties & Specifications

Physical & Chemical Characteristics

• Appearance: Bright blue triclinic crystals
• Molecular Weight: 249.68 g/mol
• Solubility:
  • 320 g/L (20°C water)
  • Insoluble in ethanol
• Decomposition: Loses water at 110°C (becomes anhydrous at 250°C)
• pH: 3.5-4.5 (10% solution)

Technical Grades

Major Applications

1. Agriculture (60% of global use)

• Fungicide:
  • Bordeaux mixture (1-3% solutions)
  • Controls mildew, blight (0.5-2 kg/ha)
• Fertilizer:
  • Corrects copper deficiency (5-10 kg/ha)
  • Chelated forms for alkaline soils

Case Study: Vineyards use 3-5 kg/ha annually to prevent downy mildew.

2. Animal Husbandry

• Foot Baths:
  • 5-10% solutions prevent hoof rot
• Feed Additive:
  • 15-25 mg/kg diet for swine/poultry

3. Industrial Processes

• Electroplating:
  • 200-250 g/L in acid copper baths
  • Essential for PCB manufacturing
• Wood Preservation:
  • CCA treatments (being phased out)
• Textile Dyes:
  • Mordant for vibrant colors

4. Chemical Synthesis

• Catalyst:
  • Organic reactions (e.g., oxidation of alcohols)
• Reagent:
  • Fehling’s solution for sugar detection

5. Educational & Specialty Uses

• Crystal Growing:
  • Classic chemistry demonstration
• Algicide:
  • Controls algae in pools (1 ppm Cu²⁺)

Production Methods

1. Copper Ore Processing

• Oxidized Ores:
  • Heap leaching with sulfuric acid
  • CuO + H₂SO₄ → CuSO₄ + H₂O
• Byproduct Recovery:
  • From copper refining electrolysis

2. Scrap Copper Dissolution

• Direct Reaction:
  • Cu + 2H₂SO₄ + O₂ → CuSO₄ + 2H₂O

3. Purification & Crystallization

• Evaporation:
  • Forms large monoclinic crystals
• Recrystallization:
  • For high-purity grades

Safety & Environmental Considerations

⚠ Toxicity:

• LD50 (oral, rat): 300 mg/kg
• Ecotoxicity:
  • LC50 (fish): 0.1-1 mg/L
  • Toxic to aquatic invertebrates at 0.01 mg/L

✅ Safe Handling:

• PPE: Gloves, goggles, dust masks
• Storage: Dry, sealed containers (hygroscopic)
• First Aid: Milk/water for ingestion

♻ Environmental Protection:

• Soil Binding:
  • Kd = 100-1,000 L/kg (reduces mobility)
• Precipitation:
  • Lime treatment for wastewater

Market Dynamics

Global Production

• Top Producers:
  • China (40%)
  • Chile, USA, Zambia
• Price Range:
  • $2.50-$4.00/kg (2024)

Emerging Trends

• Organic Farming:
  • Restricted use driving alternatives
• Nanoformulations:
  • Reduced-dose fungicides
• Recycling:
  • Recovery from industrial waste streams

Comparison to Other Copper Salts

Conclusion

Copper sulphate pentahydrate remains the most economically important copper compound worldwide, bridging agricultural needs with industrial processes. While facing increasing regulatory scrutiny, its unique combination of effectiveness, solubility and cost-efficiency ensures continued relevance. Sustainable use practices and precision application technologies are shaping its future across industries.