EDTA Iron(III) Sodium Salt Application 

What Is EDTA Iron(III) Sodium Salt?

EDTA Iron(III) sodium salt — also known as ferric sodium EDTA, sodium iron EDTA, or EDTA-FeNa — is a highly stable, water-soluble iron chelate formed by complexing ferric iron (Fe³⁺) with ethylenediaminetetraacetic acid (EDTA) in the presence of sodium. It is one of the most widely used micronutrient sources in agriculture and a key iron fortificant in the global food industry.

This compound delivers iron in a bioavailable, non-reactive form, preventing the metal from precipitating as insoluble oxides or hydroxides — a critical advantage in alkaline environments where unchelated iron becomes unavailable to plants.

Chemical Identity & Synonyms

This compound appears under numerous trade and systematic names in commerce and literature:

● Ferric sodium edetate

● Sodium ferric ethylenediaminetetraacetate

● Ethylenediaminetetraacetic acid iron(III) sodium salt

● Iron monosodium EDTA

● Sequestrene NaFe

● Komplexon™ II (trade name)

How EDTA Iron(III) Sodium Salt Works: The Chelation Mechanism

EDTA is a hexadentate ligand — it binds to a single ferric ion (Fe³⁺) through six coordination sites (four carboxyl oxygen atoms and two amine nitrogen atoms), forming a stable octahedral cage-like structure. This "claw" (from Greek chele, meaning claw) encapsulates the iron ion and shields it from reaction with other soil or solution components.

The sodium ion balances the residual negative charge of the [Fe-EDTA]⁻ complex, yielding a neutral, water-soluble salt.

Stability Constants & Practical Implications

The stability constant (log K) for the Fe(III)-EDTA complex is approximately 25.1, one of the highest among EDTA-metal complexes. In practical terms, this means:

In soil solutions (pH 5.0–6.5):

● Fe-EDTA remains >95% intact, delivering iron reliably to plant roots

In hydroponic systems (pH 5.5–6.0):

● Near 100% stability — the sweet spot for most crops

At pH 7.0–7.5:

● Dissociation begins; approximately 50% stability at pH 6.8

Above pH 7.5:

● Significant iron loss to precipitation; consider EDDHA or DTPA chelates instead

Key Applications of EDTA Iron(III) Sodium Salt

EDTA Iron(III) sodium salt serves diverse industries where stable, bioavailable iron delivery is essential. Below is an overview of its four primary application domains.

Agricultural Use: EDTA Iron as a Micronutrient Fertilizer

The Problem: Iron Deficiency in Crops

Iron deficiency (iron chlorosis) is one of the most common micronutrient disorders in global agriculture, affecting crop yields on calcareous soils (high pH, high bicarbonate) that cover over 30% of the world's arable land. Symptoms include:

● Interveinal yellowing of young leaves (chlorosis)

● Stunted growth and reduced tillering

● Significant yield losses in sensitive crops (citrus, soybean, grape, peanut)

Free ferric iron (Fe³⁺) in alkaline soils rapidly oxidizes and precipitates as insoluble Fe(OH)₃, making it unavailable to plant roots. EDTA chelation solves this by keeping iron soluble and plant-accessible.

Application Methods

1. Soil Application (Broadcast or Banded)

EDTA-FeNa is applied directly to soil at 5–15 kg/ha, often blended with NPK fertilizers. Best results are achieved in slightly acidic to neutral soils (pH 5.0–6.8). In alkaline soils, higher application rates or switching to EDDHA-chelated iron may be necessary.

2. Foliar Spray

For rapid correction of visible deficiency symptoms, a 0.1–0.5% (w/w) solution is sprayed directly onto leaves. Foliar application bypasses soil chemistry limitations and is effective across all pH ranges. Repeat applications at 10–14 day intervals may be required for severe deficiencies.

3. Fertigation & Hydroponics

EDTA-iron is the most common iron source in hydroponic nutrient solutions operating at pH 5.5–6.5. Typical concentration: 1–5 ppm Fe in the final nutrient solution. It is fully soluble and compatible with most other nutrient salts.

Crops That Benefit Most from EDTA Iron

Food Fortification: Sodium Iron EDTA as a Nutritional Iron Source

Sodium iron EDTA is one of the most effective iron fortificants available for combating iron-deficiency anemia in populations reliant on cereal-based diets. Unlike simpler iron salts (ferrous sulfate, ferrous fumarate), NaFeEDTA remains stable and absorbable even in the presence of phytates — natural compounds in whole grains that strongly inhibit non-heme iron absorption.

Common Fortified Foods

● Wheat flour and maize flour (staple fortification programs in Asia, Africa, Latin America)

● Soy sauce and fish sauce (condiment fortification in East and Southeast Asia)

● Breakfast cereals and infant cereals

● Powdered beverage mixes and nutritional supplements

Industrial & Water Treatment Applications

Water Treatment

EDTA Iron(III) sodium salt functions as a metal ion control agent in industrial water systems:

Boiler water treatment:

● Sequesters hardness ions (Ca²⁺, Mg²⁺) and trace metals that cause scale deposition

Cooling water systems:

● Prevents iron oxide fouling and corrosion by keeping dissolved metals in solution

Industrial cleaning:

● Removes iron stains and rust deposits from equipment surfaces

Molluscicide & Herbicide Applications

Ferric sodium EDTA is registered as a broad-spectrum molluscicide for control of snails and slugs in agricultural and horticultural settings. It also demonstrates herbicidal activity against certain broadleaf weeds (dandelion, creeping buttercup, clovers), offering an iron-based alternative to synthetic chemical herbicides.

Textile & Pulp Industry

In textile processing, EDTA-FeNa serves as a bleaching stabilizer, controlling trace metal ions that would otherwise catalyze the decomposition of hydrogen peroxide bleach. This improves bleaching efficiency and prevents fiber damage.

Photography & Analytical Chemistry

Historically used in photographic processing as a bleaching agent and in analytical chemistry as a complexometric standard for iron.

EDTA Iron vs. Other Iron Chelates: How to Choose

Not all iron chelates are interchangeable. The choice depends primarily on soil/medium pH, application method, and cost considerations.

Quality Specifications

Technical / Agricultural Grade

Food Grade

Packaging & Storage

● Standard packaging: 25 kg net multi-wall paper bags or fiber drums with PE liner

● Store in a cool, dry, well-ventilated area away from strong oxidizing agents

● Shelf life: 24 months from date of manufacture under recommended storage conditions

● Protect from moisture — product is hygroscopic

Frequently Asked Questions (FAQ)

What is the CAS number of EDTA Iron(III) sodium salt?

The CAS number is 15708-41-5. The hydrated form (trihydrate) is sometimes listed under 149022-26-4.

What is the difference between EDTA Iron(III) sodium salt and ferric EDTA?

They refer to the same coordination complex. "Ferric EDTA" (CAS 15275-07-7) is the parent acid form [Fe(EDTA)(H₂O)]⁻, while "EDTA Iron(III) sodium salt" or "ferric sodium EDTA" is the commercially available sodium salt form. The sodium salt is the practical, water-soluble product used in agriculture and food applications.

Is EDTA iron better than ferrous sulfate for plants?

In alkaline or calcareous soils (pH > 7.0), EDTA iron is significantly more effective than ferrous sulfate because the chelate prevents iron from precipitating as insoluble Fe(OH)₃. In acidic soils (pH < 6.0), both can work, but EDTA iron provides more consistent results and is less prone to soil fixation. For foliar application, EDTA iron generally shows faster and more complete leaf absorption.

Can EDTA Iron(III) sodium salt be used in organic farming?

No. Synthetic chelating agents including EDTA are not permitted in certified organic production under USDA NOP, EU Organic, and most other organic standards. Organic growers typically use naturally derived iron sources (iron sulfate with citric acid, amino acid chelates) or cultural practices (organic matter management, pH adjustment).

What is the E number for sodium iron EDTA?

Sodium iron EDTA does not have a specific E number in the EU food additive system. However, it is authorized as a source of iron in food supplements and fortified foods under Regulation (EC) No 1925/2006 and Directive 2002/46/EC. The related EDTA compounds have E numbers: calcium disodium EDTA (E385) and disodium EDTA (E386).

How should I store EDTA Iron(III) sodium salt?

Store in a cool, dry place (below 30°C / 86°F), in tightly sealed containers away from direct sunlight and moisture. The product is hygroscopic — exposure to humidity can cause caking. Keep away from strong oxidizing agents. Under proper conditions, shelf life is typically 24 months.

Is EDTA Iron(III) sodium salt the same as iron EDTA for food fortification?

Yes, but with an important distinction: the food-grade material must meet stricter purity specifications (lower heavy metals, controlled free EDTA content) compared to agricultural or technical grades. Always verify that the product is designated and certified for food use before employing it in food fortification programs.

Conclusion

EDTA Iron(III) sodium salt (CAS 15708-41-5) is a versatile, high-performance iron chelate that serves as a critical input across agriculture, food fortification, water treatment, and industrial processing. Its ability to deliver stable, bioavailable iron in challenging chemical environments — from alkaline soils to phytate-rich foods — makes it indispensable in global crop production and public health nutrition programs.

When selecting an iron chelate, match the product to your specific pH, application method, and purity requirements. For acidic to neutral conditions, EDTA-FeNa offers the best combination of efficacy, iron content, and cost-effectiveness.