BLEACHING EARTH: THE ESSENTIAL PURIFICATION AGENT FOR OILS & FATS

Bleaching earth (activated clay) is a specially processed clay used to remove impurities from edible oils, mineral oils, and biofuels. With global consumption exceeding 2 million metric tons annually, this versatile adsorbent plays a critical role in producing clear, stable, and high-quality oils through its unique combination of physical and chemical adsorption properties.

Key Properties & Composition

Physical Characteristics

• Appearance: Fine tan/gray powder
• Particle Size: 10-100 μm (95% passing 200 mesh)
• Bulk Density: 0.6-0.9 g/cm³
• Surface Area: 100-300 m²/g
• Oil Retention: 30-50% by weight

Chemical Composition

Activation Process

1. Natural vs. Activated Bleaching Earth

2. Activation Steps

1. Mining: Select high-smectite clays
2. Drying: Reduce moisture to <15%
3. Acid Treatment: Sulfuric/hydrochloric acid (20-35%)
4. Washing: Remove residual acid
5. Drying/Milling: Optimize particle size

Major Industrial Applications

1. Edible Oil Refining (75% of use)

• Impurity Removal:
  • Chlorophyll (90-98% reduction)
  • Peroxides (70-85% reduction)
  • Soaps (complete removal)
• Dosage:
  • Palm oil: 0.5-2%
  • Soybean oil: 0.3-1.5%
• Case Study: A Malaysian palm oil plant achieved 30% longer frying stability through optimized bleaching

2. Mineral Oil Processing

• Lubricant Purification:
  • Removes asphaltenes
  • Improves color (200% lighter)
• Wax Bleaching:
  • Food-grade paraffin production

3. Biodiesel Treatment

• Soap Removal: 0.5-1.0% dosage
• Phospholipid Adsorption: Critical for ASTM specs

4. Emerging Applications

• Waste Oil Recycling:
  • Regenerator for used cooking oils
• Water Treatment:
  • Heavy metal removal (Pb²⁺, Cd²⁺)

Performance Metrics

Adsorption Efficiency

Quality Parameters

Market Dynamics

Global Production

• Leading Producers:
  • China (35%)
  • Clariant, Taiko Group, Musim Mas
• Price Range:
  • $200-600/ton (2024)

Sustainability Trends

• Regeneration:
  • Solvent extraction of spent earth
  • 3-5 reuse cycles possible
• Low-Acid Activation:
  • Reducing wastewater load

Comparison to Alternatives

Conclusion

Bleaching earth remains the most cost-effective solution for oil purification, combining superior adsorption capacity with low operational costs. As the food industry demands higher quality standards and sustainable practices, innovations in regeneration technologies and activation methods are extending its dominance in oil processing worldwide.