MGDA·Na₃ is a biodegradable, high-performance chelating agent used primarily in detergents, cleaning agents, and water treatment. Below are its essential characteristics and uses:
1. Chemical Properties
- IUPAC Name: Trisodium 2-[bis(carboxylatomethyl)amino]acetate
- Molecular Formula: C₇H₇NNa₃O₆
- Structure: A derivative of glycine with three carboxylate groups, forming stable complexes with metal ions.
- Appearance: White crystalline powder
- Solubility: Highly water-soluble (>500 g/L at 20°C)
- pH (1% solution): ~11 (alkaline)
2. Key Features
(1) Strong Chelation Capacity
- Forms stable complexes with Ca²⁺, Mg²⁺, Fe²⁺/³⁺, Cu²⁺, Zn²⁺, even in hard water or alkaline conditions.
- Chelation Stability Constants (log K):
- Ca²⁺: ~6.5
- Fe³⁺: ~12.0
(2) Biodegradability
- Readily biodegradable (OECD 301 standards), eco-friendly alternative to phosphates and EDTA.
(3) Thermal & Chemical Stability
- Stable up to 100°C, effective in hot washing applications (e.g., dishwasher detergents).
- Resists hydrolysis and oxidation.
(4) Low Toxicity
- Safe for household and industrial use (non-irritating at recommended concentrations).
3. Applications
(1) Detergents & Cleaning Agents
- Laundry Detergents: Softens water, prevents scale deposition, and boosts surfactant efficiency.
- Dishwasher Tablets: Reduces lime scale on glassware.
- Industrial Cleaners: Removes metal ion stains (e.g., rust).
(2) Personal Care Products
- Shampoos/Soaps: Prevents hard water effects (e.g., hair dullness).
- Cosmetics: Stabilizes formulations by sequestering metal ions.
(3) Water Treatment
- Cooling Water Systems: Inhibits scale and corrosion.
- Pulp & Paper Industry: Controls metal-induced degradation.
(4) Agriculture
- Fertilizer Additive: Improves micronutrient (e.g., Fe, Zn) availability.
4. Advantages Over Traditional Chelators
| Property | MGDA·Na₃ | EDTA | Phosphates |
|---|---|---|---|
| Biodegradability | High | Poor | Moderate |
| Eco-Toxicity | Low | High (persistent) | Causes eutrophication |
| Ca/Mg Binding | Strong (even at pH 9–12) | Weak at high pH | Strong but banned in many regions |
5. Safety & Handling
- Storage: Keep dry in sealed containers (hygroscopic).
- Handling: Use gloves/goggles to avoid alkaline irritation.
- Regulatory Status: Complies with REACH, USDA BioPreferred®, and EU Ecolabel standards.
Conclusion
MGDA·Na₃ is a sustainable, high-efficiency chelator ideal for applications requiring strong metal ion control without environmental harm. It outperforms EDTA and phosphates in biodegradability and alkaline stability, making it a preferred choice in modern green chemistry.