Industrial grade Ammonium iron(III) sulfate CAS 10138-04-2

I. What is ferric ammonium sulfate (CAS 10138-04-2)?

Ferric ammonium sulfate is an inorganic double salt belonging to the alum family. Its structure can be understood as a composite crystal formed by the combination of ferric sulfate [Fe₂(SO₄)₃] and ammonium sulfate [(NH₄)₂SO₄] in a 1:1 ratio.

II . What are the core uses of industrial-grade ferric ammonium sulfate?

If everyday contact with ferric ammonium sulfate is a "chance encounter," then its industrial applications are its true "main battlefield." The following are listed in order of usage scale:

2.1 Water treatment – the largest single-purpose application in terms of tonnage

Urban tap water purification

Compared to traditional aluminum-based flocculants (such as polyaluminum chloride PAC), iron-based flocculants have several important industrial advantages:

Industrial wastewater treatment

Ferrous ammonium sulfate plays multiple roles in wastewater treatment in industries such as printing and dyeing, papermaking, electroplating, and pharmaceuticals:

Decolorization: It has a good flocculation and decolorization effect on reactive dyes and acid dyes in printing and dyeing wastewater.

Chemical phosphorus removal: Fe³⁺ reacts with phosphate ions in wastewater to form insoluble iron phosphate precipitate, making it a powerful tool for upgrading urban wastewater treatment plants (from Class B to Class A).

Heavy metal removal: Removal of heavy metals such as arsenic, chromium, copper, and zinc from wastewater through co-precipitation.

Sludge dewatering: As a conditioner, it improves the dewatering performance of sludge and enhances the dewatering efficiency of filter presses and centrifuges.

Industrial circulating cooling water

Large-scale circulating cooling water systems in the petrochemical, power, and steel industries require the continuous addition of flocculants to remove suspended solids in the water and prevent scaling on heat exchangers and pipes—ferric ammonium sulfate has a stable and large-volume demand in these industries.

2.2 Agriculture – both fertilizer and plant protection product

Iron fertilizer: Corrects iron deficiency chlorosis in plants

Iron is an essential element for chlorophyll synthesis. The most typical symptom of iron deficiency in plants is chlorosis—the leaf tissue of new leaves turns yellow, but the veins remain green (because iron is not easily mobile within the plant, iron deficiency first manifests in new tissues).

Ferrous ammonium sulfate, as a fast-acting iron fertilizer, is widely used in:

Iron deficiency chlorosis correction in northern orchards for apples, pears, peaches, and grapes (northern soils are alkaline with extremely low iron availability).

Iron supplementation for field crops: corn, potatoes, and peanuts

Landscaping: Iron supplementation for lawns (to make lawns greener), iron supplementation for ornamental seedlings.

Flower cultivation: Gardenia, azalea, camellia, and other acid-loving and iron-loving flowers

Application methods include: soil basal application, foliar spraying (0.2%~0.5% solution), and drip irrigation with water.

Sterilization and Plant Protection

Fruit tree rot: Scraping off the lesions and then applying ferric ammonium sulfate solution is one of the classic chemical control methods for apple and pear tree rot.

Moss and lichen removal: Lichens and mosses attached to fruit tree branches and trunks hinder the normal respiration of the bark. Spraying with ferric ammonium sulfate solution can effectively kill them and cause them to fall off.

Seed treatment: Soaking seeds in a low-concentration solution can inhibit seed-borne pathogens.

lawn mowing

Ferrous ammonium sulfate has a selective killing effect on moss and some broadleaf weeds in lawns, but it is relatively safe for grasses (turfgrass) - therefore it is a common ingredient in lawn care products in Europe and America, and China is also following suit.

2.3 Textile Printing and Dyeing—The "Chemical Rivets" Behind Billions of Meters of Fabric

In the dyeing and printing industry, the core role of ferric ammonium sulfate as a metal mordant is:

Improved dye uptake: Iron ions help dye molecules adsorb onto the fabric more efficiently.

Improved color fastness: Iron ions form complexes with dyes and fibers, significantly enhancing resistance to washing and sunlight.

Adjusting the hue: The same dye becomes darker and more muted when mordanted with iron (e.g., indigo → iron gray, madder red → purplish brown). One dye can produce multiple color schemes.

Although most modern synthetic dyes (such as reactive dyes) no longer require mordants, there is still a strong demand in the following market segments:

● Naturally dyed cotton and linen fabrics exported to Europe and America

● High-end handmade plant-dyed clothing and home textiles

● Fabrics for the replication and restoration of museum-grade cultural relics

● Iron mordant dyeing process in traditional crafts (such as Chinese blue calico and Japanese plant dyeing)

2.4 Dye and Pigment Production

Iron oxide pigments: Ferrous ammonium sulfate is one of the iron source raw materials for manufacturing inorganic pigments such as iron oxide red (Fe₂O₃) and iron oxide black (Fe₃O₄, iron black). These pigments are widely used in building exterior wall coatings, colored floor tiles, and cement product coloring.

Blue-black ink: an industrial-scale writing ink production line

Iron tannate pigment: a dark dye used for wood staining and leather dyeing.

2.5 Leathermaking – The chemical transformation from raw hides to leather

In the leather tanning process, the core function of ferric ammonium sulfate is iron tanning:

● Iron ions (Fe³⁺) coordinate with the carboxyl (-COOH) and amino (-NH₂) groups of collagen molecules in raw hides for cross-linking.

● After cross-linking, collagen molecular chains change from a loose structure to a dense network structure.

● Leather → Hide: From perishable "hide" to stable, water-resistant, and resilient "leather"

Historically, iron tanning is older than chrome tanning. Although modern leather tanning is dominated by chrome tanning, iron tanning still has a place in specialty leathers (such as leather for archival restoration, museum-grade leather, and certain vintage-style handmade leather goods). Furthermore, in tanning wastewater treatment, ferric ammonium sulfate can also be used as an auxiliary flocculant to help remove chromium from wastewater.

2.6 Metal Etching – The “Engraving Tool” for PCB Circuit Boards

In printed circuit board (PCB) manufacturing, it is necessary to etch away the non-circuit copper foil on the copper-clad laminate. Ferrous ammonium sulfate is an auxiliary component of acidic copper chloride etching solutions or an iron source for iron-based etching solutions.

● Fe³⁺ + Cu → Fe²⁺ + Cu²⁺ (Copper is oxidized and dissolved)

● Compared to pure ferric chloride etching solution, the ammonium-containing formulation exhibits a more uniform etching rate and less lateral etching.

Ferric ammonium sulfate is also used in precision metal etching (such as the processing of stainless steel mesh and titanium alloy sheets).

2.7 Electronic Grade Applications – High-Purity Iron Source

High-purity ferric ammonium sulfate (electronic grade/ultra-high purity) is used in the following electronic materials fields:

● Iron source precursors for ferrite magnetic materials (such as manganese-zinc ferrite and nickel-zinc ferrite)

● Iron dopants in certain electronic ceramics

● Specific iron sources in semiconductor processes

III . Conclusion

purified water

● It turns muddy river water into clear drinking water in your cup.

Coloring

● —It allows the colors to be firmly preserved in millions of meters of fabric and ancient ink writing.

Planting

● It helps yellow leaves in northern orchards turn green again, and allows fruits to ripen and become plump.

Leather

● —In the unseen chemical tank, it transforms a raw hide into leather that will last for years.

It's not the kind of "star chemical" that makes headlines, but its deep integration into water supply systems, farmland, dyeing plants, and tanneries is enough to secure its place as an "indispensable basic inorganic salt in industrial society."