EDTMP•Na₅ is a highly effective phosphonic acid-based scale and corrosion inhibitor, widely used in industrial water treatment due to its strong chelating ability, thermal stability, and excellent metal ion control. Below are its key applications and benefits in the water treatment industry.
1. Key Properties of EDTMP•Na₅
| Parameter | Specification |
|---|---|
| Chemical Name | Ethylenediaminetetra(methylene phosphonic acid) Pentasodium Salt |
| CAS No. | 22042-96-2 |
| Molecular Formula | C₆H₁₂N₂O₁₂P₄Na₅ |
| Appearance | Light yellow to colorless liquid (or crystalline powder) |
| Active Content | ≥ 28–32% (liquid), ≥ 90% (solid) |
| pH (1% solution) | 9.0–11.0 |
| Density (20°C) | 1.3–1.4 g/cm³ (liquid) |
| Solubility | Highly water-soluble |
| Thermal Stability | Stable up to 200°C (superior to HEDP/ATMP) |
2. Major Applications in Water Treatment
(1) Scale Inhibition
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Prevents deposition of:
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Calcium carbonate (CaCO₃)
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Calcium sulfate (CaSO₄)
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Barium sulfate (BaSO₄)
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Iron-based scales (Fe₂O₃, Fe₃O₄)
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Effective in high-hardness & high-TDS water (e.g., cooling towers, boilers).
(2) Corrosion Inhibition
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Forms a protective film on carbon steel, copper, and stainless steel.
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Reduces corrosion rates in closed-loop cooling systems, boilers, and pipelines.
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Often blended with zinc salts or molybdate inhibitors for enhanced protection.
(3) Iron & Manganese Control
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Strong sequestering agent for Fe²⁺/Fe³⁺ and Mn²⁺, preventing fouling in RO membranes and heat exchangers.
(4) Dispersant for Sludge & Particulates
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Prevents clay, silt, and iron oxide deposition in industrial water systems.
(5) High-Temperature Applications
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Used in steam boilers, geothermal plants, and oilfield injection water (due to stability at >150°C).
3. Advantages Over Other Phosphonates
| Feature | EDTMP•Na₅ | HEDP | ATMP |
|---|---|---|---|
| Thermal Stability | Up to 200°C | ≤100°C | ≤120°C |
| Calcium Tolerance | Very high (no precipitation) | Moderate | Low |
| Iron Chelation | Excellent (binds Fe³⁺ strongly) | Good | Fair |
| Chlorine Resistance | Good (better than HEDP) | Poor | Moderate |
4. Recommended Dosage & Application Methods
| Application | Dosage (ppm) | Method |
|---|---|---|
| Cooling Water | 5–20 | Continuous dosing |
| Boiler Water | 10–30 | Feedwater treatment |
| RO Antiscalant | 3–15 | Pre-treatment injection |
| Oilfield Water | 20–50 | Squeeze treatment or continuous injection |
5. Compatibility & Formulation Guidelines
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Works well with:
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Polymeric dispersants (e.g., PAA, HPMA)
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Zinc/molybdate inhibitors
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Non-oxidizing biocides (e.g., DBNPA, THPS)
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Avoid mixing with:
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Strong oxidizers (e.g., chlorine > 1 ppm)
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High doses of cationic polymers (may cause precipitation)
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6. Environmental & Safety Considerations
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Biodegradability: Low (persistent in water, but low toxicity).
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Toxicity (LD50): >2000 mg/kg (practically non-toxic).
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Regulatory Compliance: Meets REACH, EPA, and OSPAR standards.
7. Case Study: EDTMP•Na₅ in Cooling Tower Treatment
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Problem: Severe CaCO₃ scaling & mild steel corrosion in a refinery cooling system.
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Solution: EDTMP•Na₅ (15 ppm) + zinc sulfate (2 ppm) + polyacrylate dispersant.
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Result:
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Scale reduction by 85% in 3 months.
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Corrosion rate dropped from 5 mpy to < 0.5 mpy.
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Conclusion
EDTMP•Na₅ is a high-performance, multi-functional water treatment chemical ideal for:
✔ High-temperature systems (boilers, oilfields)
✔ Hard water scaling control
✔ Iron/manganese stabilization
✔ Corrosion inhibition in mixed-metal systems
Recommendation: Conduct water chemistry analysis before application to optimize dosage and avoid incompatibility issues.