What Is Sodium Molybdate (Na₂MoO₄)? Properties, Uses, Production Methods, and Global Market Trends

1. Introduction to Sodium Molybdate

Sodium molybdate is one of the most widely used water-soluble molybdenum compounds worldwide and serves as an important source of molybdenum in agriculture, industrial water treatment, chemical manufacturing, catalysts, and laboratory applications.

The most common commercial product is Sodium Molybdate Dihydrate, with the chemical formula:

Na₂MoO₄·2H₂O

Although anhydrous sodium molybdate (Na₂MoO₄) is also available, its market share is significantly smaller due to higher production costs and greater hygroscopicity.

As global agriculture places increasing emphasis on micronutrient management and industries seek environmentally friendly corrosion inhibitors, sodium molybdate has become an important product within the global molybdenum chemical value chain.

2. Physical and Chemical Properties

Basic Information

Item	Specification
Product Name	Sodium Molybdate
Common Commercial Grade	Sodium Molybdate Dihydrate
Molecular Formula	Na₂MoO₄·2H₂O
CAS No. (Dihydrate)	10102-40-6
CAS No. (Anhydrous)	7631-95-0
HS Code	28417090
Appearance	White crystalline powder or rhombic crystals
Odor	Odorless
Solubility	Highly soluble in water
Solution Character	Slightly alkaline
pH (1% solution)	8.5-9.5

Physical Characteristics

Sodium molybdate typically appears as white rhombic prismatic crystals with excellent storage stability and high water solubility.

At 20°C:

Water solubility: approximately 65.3 g per 100 mL of water

This high solubility enables rapid dissolution in foliar sprays, fertigation systems, and industrial circulating water applications.

Additional characteristics include:

• Insoluble in ethanol and acetone

• Slightly hygroscopic

• Chemically stable under normal storage conditions

• Dihydrate loses crystallization water at approximately 100°C to form anhydrous sodium molybdate

• Melting point of anhydrous sodium molybdate: approximately 687°C

3. Product Grades

Depending on the application, sodium molybdate is generally classified into the following grades:

Grade	Typical Purity
Agricultural Grade	≥98%
Industrial Grade	≥99%
Reagent Grade	≥99.5%

Agricultural-grade products typically require:

• Mo content ≥39.0-39.5%

• Pb ≤10 ppm

• As ≤15 ppm

• Strict control of Cd and other heavy metals

These specifications comply with micronutrient fertilizer regulations in many international markets.

4. Industrial Production Process

Main Production Route: Roasting and Alkaline Leaching of Molybdenite

The vast majority of global sodium molybdate production originates from molybdenite concentrate (MoS₂).

This process is widely adopted in major molybdenum-producing countries such as China, Chile, and the United States.

Step 1: Oxidative Roasting of Molybdenite

Molybdenite concentrate is oxidized in air at elevated temperatures:

Typical roasting temperature:

500-550°C

This reaction produces molybdenum trioxide (MoO₃) and sulfur dioxide gas.

Step 2: Alkaline Leaching

The resulting molybdenum trioxide reacts with sodium hydroxide:

forming sodium molybdate solution.

Step 3: Purification and Crystallization

The subsequent production process includes:

• Filtration and impurity removal

• Evaporation and concentration

• Cooling crystallization

• Centrifugal dehydration

• Hot-air drying

• Screening and packaging

The final product is then classified according to the desired grade specifications.

5. Agricultural Applications

Molybdenum: An Essential Plant Micronutrient

Molybdenum is one of the 17 essential elements required for plant growth and development.

Although plants require only trace amounts, its physiological functions are irreplaceable.

Plants absorb molybdenum primarily in the form of:

Molybdate ion (MoO₄²⁻)

Sodium molybdate is currently one of the most widely used molybdenum fertilizers globally due to its excellent water solubility and rapid plant availability.

5.1 Promoting Nitrogen Metabolism

Molybdenum is an essential component of key enzymes, including:

• Nitrate reductase

• Nitrite reductase

Nitrate absorbed by plants must be converted into amino acids and proteins through these enzymatic processes.

As a result, molybdenum deficiency often causes:

• Leaf chlorosis

• Stunted growth

• Symptoms similar to nitrogen deficiency

5.2 Enhancing Biological Nitrogen Fixation

In leguminous crops, molybdenum is a critical component of the nitrogenase enzyme system.

Adequate molybdenum supply can:

• Promote root nodule formation

• Improve nodule activity

• Enhance biological nitrogen fixation

• Increase nitrogen-use efficiency

Numerous studies have shown significant improvements in nitrogen utilization in molybdenum-deficient soils following molybdenum fertilization.

5.3 Improving Flowering and Fruiting

Molybdenum is also involved in:

• Flower bud differentiation

• Pollen development

• Pollination and fertilization

• Seed formation

It plays an important role in crops such as rapeseed, citrus, tomatoes, and many vegetable crops.

5.4 Correcting Molybdenum Deficiency in Acidic Soils

Molybdenum is one of the few micronutrients whose availability decreases significantly under acidic soil conditions.

When soil pH falls below 5.5:

• Molybdenum fixation increases

• Plant uptake declines

As a result, the following soils are particularly prone to molybdenum deficiency:

• Red soils

• Lateritic soils

• Tropical acidic soils

These regions represent important markets for molybdenum fertilizers, especially across South America, Southeast Asia, and parts of Africa.

6. Recommended Agricultural Application Methods

Foliar Application

Recommended concentration:

0.05%-0.10% sodium molybdate solution

Application stages:

• Seedling stage

• Pre-flowering stage

• Bud formation stage

Application interval:

7-10 days

Seed Treatment

Recommended dosage:

1-3 g sodium molybdate per kg of seed

Particularly suitable for:

• Soybean

• Peanut

• Alfalfa

• Pea

and other leguminous crops.

Soil Application

Recommended rate:

80-200 g per Chinese mu (approximately 1.2-3.0 kg/ha)

Can be applied together with phosphate fertilizers.

Phosphorus and molybdenum often exhibit synergistic effects that enhance nutrient efficiency.

7. Industrial Applications

7.1 Environmentally Friendly Corrosion Inhibitor

This is one of the most important industrial applications of sodium molybdate.

Sodium molybdate forms a protective passive film on metal surfaces, significantly reducing corrosion.

Compared with traditional chromate-based inhibitors, sodium molybdate offers:

• Lower toxicity

• Better environmental performance

• Easier wastewater treatment

It is widely used in:

• Closed-loop cooling systems

• Industrial boilers

• Heat exchangers

• Central air-conditioning water systems

Modern formulations often combine sodium molybdate with:

• Polyphosphates

• Benzotriazole (BTA)

• Gluconates

to achieve enhanced corrosion protection.

7.2 Fine Chemicals

Sodium molybdate is used in the manufacture of:

• Inorganic pigments

• Molybdenum-based catalysts

• Flame retardants

• Electroplating additives

• Metal surface treatment chemicals

7.3 Laboratory Reagents

In analytical and research laboratories, sodium molybdate is commonly used as:

• A source of molybdenum

• A phosphate analysis reagent

• A component in trace element analytical systems

8. Storage and Transportation

Storage Requirements

Store in:

• Cool and dry environments

• Sealed containers

• Moisture-free conditions

Avoid contact with strong acids, as acidic conditions may cause precipitation of molybdic acid.

Packaging

Common international packaging options include:

• 25 kg woven polypropylene bags

• 25 kg kraft paper bags

• 25 kg fiber drums

typically with inner polyethylene liners for moisture protection.

Transportation

Sodium molybdate is generally classified as:

Non-Hazardous Chemical Product

In most countries and regions, it can be transported via:

• Ocean freight

• Road transport

• Rail transport

without dangerous goods restrictions.

However, packages should be protected from moisture, rain, and prolonged exposure to direct sunlight.

9. Safety and Occupational Health

Sodium molybdate is generally considered a low-toxicity chemical.

Potential Health Effects

Long-term exposure to excessive amounts may cause:

• Respiratory irritation

• Eye irritation

• Skin irritation

Excessive molybdenum intake over extended periods may also affect:

• Copper metabolism

• Nervous system functions

• Joint health

Therefore, appropriate handling procedures should always be followed.

Personal Protective Equipment (PPE)

Recommended protective equipment includes:

• Dust masks or respirators

• Safety goggles

• Nitrile gloves

to minimize dust inhalation and direct skin contact.

10. Market Outlook

Driven by the global expansion of precision agriculture and increasing demand for environmentally friendly industrial water treatment technologies, the sodium molybdate market continues to show stable growth potential.

Current demand is mainly concentrated in three sectors:

1. Micronutrient fertilizers and specialty fertilizers

2. Industrial water treatment and corrosion inhibition

3. Fine chemicals and catalyst manufacturing

Among these sectors, agriculture remains one of the largest consumers of sodium molybdate worldwide. As acidic soils continue to dominate large agricultural regions in South America, Southeast Asia, and Africa, sodium molybdate is expected to maintain strong and sustainable long-term demand as a highly effective and rapidly available source of molybdenum nutrition.

What Is Sodium Molybdate (Na₂MoO₄)? Properties, Uses, Production Methods, and Global Market Trends