Kaolin, Calcined Kaolin, Aluminum Silicate Dihydroxide, Aluminum Silicate Hydroxide, Kaolinite, Porcelain Clay, 1332-58-7, 52624-41-6, 92704-41-1

Kaolin, Calcined Kaolin, Aluminum Silicate Dihydroxide, Aluminum Silicate Hydroxide, Kaolinite, Porcelain Clay, 1332-58-7, 52624-41-6, 92704-41-1

KAOLIN (KAOLIN CLAY / CHINA CLAY)

Kaolin / Calcined Kaolin / Kaolin Clay / Aluminum Silicate Dihydroxide / Aluminum Silicate Hydroxide / Porcelain Clay
CAS Numbers: 1332-58-7, 52624-41-6, 92704-41-1
EC Number: 310-194-1

1. IDENTIFICATION INFORMATION

2. PHYSICAL PROPERTIES

3. CHEMICAL PROPERTIES

Thermal Decomposition (Calcination):

Al₂Si₂O₅(OH)₄  —[500-600°C]—> Al₂Si₂O₇ (Metakaolin) + 2 H₂O↑
Al₂Si₂O₇  —[900-1000°C]—> Al₂O₃·SiO₂ (Spinel)

Mineral Composition (Typical):

4. PRODUCTION PROCESS

Processing Routes:

5. AVAILABLE GRADES AND SPECIFICATIONS

Typical Specifications (Water-Washed Hydrous Kaolin):

Typical Specifications (Calcined Kaolin):

6. APPLICATIONS

6.1. Ceramics Industry – Largest Use

6.2. Paper and Packaging Industry

6.3. Paints and Coatings Industry

6.4. Plastics and Rubber Industry

6.5. Construction and Building Materials

6.6. Cosmetics and Personal Care

6.7. Pharmaceutical Industry

6.8. Agriculture

6.9. Adhesives and Sealants

6.10. Fiberglass Industry

6.11. Wastewater Treatment

6.12. Other Applications

7. CALCINED KAOLIN VS HYDROUS KAOLIN

8. STORAGE AND HANDLING

Handling Notes:

• Kaolin dust can be irritating to respiratory tract

• Use dust mask when handling significant quantities

• Avoid generating dust (static electricity hazard for organic dust mixtures)

• Wash hands after handling

• In case of spill, sweep up or vacuum to minimize dust

9. SAFETY AND HEALTH INFORMATION (GHS CLASSIFICATION)

Note: Kaolin is generally recognized as safe (GRAS) for food and pharmaceutical applications. Inhalation of large amounts of dust may cause mechanical irritation. Prolonged heavy exposure may cause kaolinosis (benign pneumoconiosis).

10. HAZARD STATEMENTS (H-CODES)

11. SAFETY STATEMENTS (P-CODES)

12. TOXICOLOGICAL INFORMATION

Health Effects:

Regulatory Status:

13. FIRST AID MEASURES

14. FIRE FIGHTING MEASURES

15. ENVIRONMENTAL INFORMATION

16. TRANSPORT INFORMATION

17. REGULATORY INFORMATION

FDA Compliance: GRAS (21 CFR 182.2729) for food contact and pharmaceutical use

EU Compliance: Food additive E559 (anti-caking agent)

18. OTHER NAMES AND SYNONYMS

Database Identifiers:

19. PHYSICAL AND CHEMICAL NOTES

Kaolinite Crystal Structure:

• 1:1 layer silicate (one tetrahedral silica sheet + one octahedral alumina sheet)

• No interlayer swelling (hydrogen bonding between layers)

• Hexagonal platelet morphology (0.1-10 µm diameter, 0.05-0.2 µm thickness)

• Low cation exchange capacity (3-15 meq/100g)

Calcination Effects:

• At 500-600°C: Dehydroxylation → Metakaolin (amorphous)

• At 900-1000°C: Spinel phase formation

• At >1000°C: Mullite formation

• Calcination increases hardness, brightness, oil absorption, and electrical resistivity

Major Global Deposits:

• USA (Georgia, South Carolina)

• Brazil

• United Kingdom (Cornwall)

• China

• Germany

• Czech Republic

• Australia

20. SUMMARY AND IMPORTANT WARNINGS

SUMMARY:

Kaolin (Al₂Si₂O₅(OH)₄, CAS 1332-58-7) is a naturally occurring white clay mineral primarily composed of kaolinite, a 1:1 layered aluminosilicate. It is a soft, fine white powder with a density of approximately 2.6 g/cm³ and a Mohs hardness of 2-2.5. Kaolin is chemically inert, has a neutral pH, does not swell in water, and has good adsorption properties. It is produced by open-pit mining followed by beneficiation processes including blunging, degritting, classification, bleaching, dewatering, and drying. Dry-processed (air-floated), wet-processed (water-washed), calcined, delaminated, and surface-modified grades are available. Kaolin is one of the most widely used industrial minerals with applications across numerous industries: ceramics (porcelain, tiles, sanitary ware), paper and packaging (coating and filler), paints and coatings (extender pigment), plastics and rubber (reinforcing filler), construction (cement additive), cosmetics (absorbent), pharmaceuticals (excipient), agriculture (crop protection), adhesives, fiberglass, and wastewater treatment.

Key Properties:

Main Application Areas:

Key Safety Points:

• LOW TOXICITY: Oral LD50 >5,000 mg/kg; FDA GRAS status

• MECHANICAL IRRITANT: Dust may cause mechanical irritation to eyes and respiratory tract

• NON-FLAMMABLE: Does not burn; use appropriate extinguishing media for surrounding fire

• DUST CONTROL: Avoid generating dust; use local exhaust ventilation

• USE PPE: Dust mask for dusty operations, safety goggles, gloves

• STORAGE: Cool, dry area; protect from moisture (caking)

• ENVIRONMENT: Low environmental impact; non-hazardous

IMPORTANT WARNINGS:

Kaolin Mining and Processing: Kaolin is mined from natural deposits using open-pit methods. Major global deposits are found in the United States (Georgia - the "kaolin capital of the world"), Brazil, the United Kingdom (Cornwall), China, Germany, Czech Republic, and Australia. Processing includes dry processing (crushing, pulverizing, air classification) for applications such as rubber and plastics, and wet processing (blunging, degritting, centrifugation, bleaching, filtering, drying) for high-grade applications such as paper coating and paints.

Calcination Benefits: Calcined kaolin (heat-treated at 500-1000°C) has enhanced properties including higher brightness (90-95%), higher oil absorption (50-80 g/100g), higher hardness, and higher electrical resistivity. Calcined kaolin is preferred for paper coatings (improved opacity and printability), paints (better hiding power), plastics (improved electrical properties), and refractories (high-temperature resistance).

Chemical Inertness: Kaolin is chemically inert and has a neutral pH (6-8), making it ideal for use in pharmaceuticals, cosmetics, and food applications where it will not alter product chemistry or promote bacterial growth. It is approved as a food additive (E559) and is GRAS (Generally Recognized as Safe) by the FDA.

Non-Swelling Property: Unlike other clay minerals (such as bentonite), kaolin does not swell in water. Hydrogen bonds between kaolinite layers prevent water molecules from penetrating the crystal structure. This non-swelling property is valuable in applications where dimensional stability is required.

Adsorption Capacity: Kaolin has excellent adsorption properties due to its high surface area (10-25 m²/g) and platelet structure. It is effective at adsorbing metal ions (copper, lead, zinc, cadmium), organic compounds, dyes, and bacteria. This property makes kaolin useful in wastewater treatment, gastrointestinal protectants, and facial masks.

Paper Industry Significance: The paper and paperboard industry is a major consumer of kaolin, particularly water-washed and calcined grades. Kaolin improves paper brightness, gloss, smoothness, opacity, and printability. As a filler, it extends wood fibers and reduces production costs. As a coating pigment, it provides a smooth, high-quality surface for printing.

Pozzolanic Activity in Cement: Kaolin, particularly metakaolin (calcined at 500-600°C), has high pozzolanic activity, meaning it reacts with Portland cement hydration products to improve concrete strength and durability. Metakaolin also improves concrete's resistance to chemical attack and reduces permeability.

Fiberglass Applications: Kaolin is a critical raw material in fiberglass production, providing the necessary alumina (Al₂O₃) for glass formulation. It improves surface durability, reduces weight while maintaining strength, and enhances thermal insulation properties.

Kaolinosis (Benign Pneumoconiosis): Prolonged, heavy inhalation exposure to kaolin dust may cause kaolinosis, a benign form of pneumoconiosis (dust-induced lung disease). This condition is rare and typically only occurs with massive, long-term occupational exposure without dust controls. Using proper dust control measures (ventilation, dust masks) prevents this risk. Typical commercial grades contain very low levels of respirable crystalline silica (<0.5%).

Agricultural Applications: Kaolin-based crop protectants form a barrier film on plant surfaces that controls damage from insects, mites, and fungal pathogens. Kaolin sunscreens for crops reduce heat stress and sunburn while promoting photosynthesis. Seed coatings with kaolin improve handling, planting, germination success, and seedling vigor.

Wastewater Treatment Studies: Research has shown that kaolin is highly effective at removing contaminants from wastewater, including chloride, iron, heavy metal ions (copper, lead, zinc, cadmium), and organic dyes. Kaolin demonstrates excellent adsorption properties and recyclability, remaining effective after multiple regeneration cycles. Its low cost makes it an attractive alternative to traditional wastewater treatment minerals.

Cosmetic Applications: Kaolin is valued in cosmetics for its absorbent, adsorbent, and gentle exfoliating properties. It absorbs excess sebum and impurities without irritating the skin, making it ideal for facial masks, powders, and cleansing products. Its non-swelling property ensures it does not dry or crack on the skin.

Important Disclaimer: This Technical Data Sheet (TDS) is for informational purposes only. For complete safety, handling, storage, and regulatory compliance information, always refer to the official Safety Data Sheet (SDS) provided by the manufacturer/supplier. Kaolin is generally recognized as safe for most applications. However, avoid generating and inhaling dust. Use appropriate dust control measures. Store in a dry environment to prevent caking. This document summarizes information from various sources and is not a substitute for technical expertise or site-specific safety assessments.