Introduction
Whiteness is a critical quality indicator for calcium carbonate, especially in high-end applications like plastics, coatings, and papermaking. How to Increase Whiteness of Calcium Carbonate? As a calcium carbonate supplier, mastering techniques to enhance whiteness is essential. This article explores the factors affecting calcium carbonate whiteness and provides actionable solutions for industrial production.
1. Key Factors Affecting Calcium Carbonate Whiteness
1.1 Raw Material Quality: Iron and Manganese Impurities
Iron (Fe³⁺) and manganese (Mn) impurities in limestone directly reduce whiteness.
Acceptable levels: Fe ≤ 0.12%, Mn ≤ 0.006%.
Iron > 0.2% causes yellowing or reddish discoloration.
1.2 Calcination Process: “Nodulation” Issues
Silica (SiO₂) and alumina (Al₂O₃) impurities react with calcium oxide during calcination, forming low-melting-point viscous substances that stick to particle surfaces, reducing whiteness.
1.3 Digestion Equipment
Digestion tanks minimize whiteness loss, while rotary digesters have the worst impact due to uneven mixing.
1.4 Refining Process: Final Barrier Against Impurities
Incomplete removal of yellow/black residues during refining significantly lowers slurry whiteness. Multi-stage filtration or centrifugation is required.
2. Proven Methods to Improve Whiteness
2.1 Strict Raw Material Selection
Use low-iron, low-manganese limestone.
Replace high-impurity ore sources to avoid costly post-treatment.
2.2 Chemical Iron Removal
For Fe > 0.2%, apply reducing agents (e.g., oxalic acid) or chelators (e.g., EDTA) to eliminate Fe³⁺.
Note: Use only when necessary to avoid over-treatment.
2.3 Process Optimization
Calcination control: Prevent impurity melting; clean kilns regularly.
Digestion upgrades: Prioritize digestion tanks over rotary digesters.
Enhanced refining: Use multi-stage screening (e.g., vibrating screens, hydrocyclones).
2.4 Bleaching Techniques
Oxidative bleaching: Sodium hypochlorite or hydrogen peroxide breaks down pigments.
Reductive bleaching: Convert Fe³⁺ to Fe²⁺ using sulfites.
Application: Add bleaching agents during digestion, carbonation, or slurry stages.
2.5 Equipment Maintenance & Monitoring
Inspect pipelines and tanks to prevent rust contamination.
Monitor whiteness with colorimeters and particle size with laser analyzers.
3. Applications of High-Whiteness Calcium Carbonate
Plastics: Replace partial titanium dioxide to reduce costs.
Paper coating: Whiteness ≥94% enhances brightness and ink absorption.
Food/pharma: FDA-grade calcium carbonate requires ultra-low impurities.
4. Jintai factory: Your Trusted Calcium Carbonate Supplier
As a leading calcium carbonate supplier, Jintai factory delivers high-whiteness products (≥94% brightness, 1250 mesh) for plastics, coatings, and paper industries. Our advantages:
Premium raw materials: Iron ≤0.1% in limestone.
Advanced production: Fully automated processes ensure consistency.
Custom solutions: Bleaching, surface modification, and tailored specifications.
Request free high-whiteness calcium carbonate samples today!
